Explanations for the 2020 Official Step 3 Practice Questions

Here are my explanations for the November 2020 update of the official practice materials.

My explanations for the 2018/2019 set are here. The one before that, which I explained here, was revised in November 2017.

The asterisks (*) signify one of the 71 new questions.

You can find my thoughts on preparing for Step 3 here. Since writing that post, the only substantive change in the exam has been the ability to schedule CCS on a nonconsecutive day. In short, I think the free materials and UWorld should be enough for most folks. If you want book recs, they’re in that post. If you need another question source, I haven’t tried any of them, but you can get 10% off BoardVitals if you’re interested by using code BW10.

As for this free 137-question practice exam, Blocks 1 and 2 are “Foundations of Independent Practice” (FIP). These should take up to 1 hour each. Blocks 3 and 4 are “Advanced Clinical Medicine” (ACM). These should take up to 45 minutes each. Total practice time should be no more than 3:30 if taken under test-day conditions.

Block 1

  1. E – Rash and arthritis after exposure to a sick kid with a “facial rash” and fever. The kid’s vague description is a perfectly good fit for the slapped cheek of Parvovirus B19. Adults most commonly get polyarthralgia (and sometimes, dangerously, aplastic anemia).*
  2. A – Of the choices, the best explanation for a liver mass in an otherwise healthy female is a hepatic adenoma, a benign lesion for which the patient’s OCPs are a common modifiable risk factor. These do have a tendency to bleed, especially when large, which is an indication to stop her hormonal contraceptive.*
  3. C – She has glomerulonephritis in the setting of what looks like strep throat. Post-strep glomerulonephritis is a type III hypersensitivity, an immune-complex deposition disease that consumes complement (C3).
  4. D – That’s a lot of hyperthyroidism symptoms. Onycholysis (Plummer’s nails) is one of them, but as long as you didn’t somehow let it distract you, the rest of the question info (cold intolerance, anxiety, low BMI) points you in the right direction as well.*
  5. C – Retinitis pigmentosa most commonly has an autosomal dominant inheritance pattern, but the tree we have shows clear X-linked inheritance. In this case, her husband has the disease, meaning his one X copy carries the mutation. However, her son’s X-chromosome must come from her, so her male children have no chance of being affected. Her daughters, however, would be obligate carriers.*
  6. E – First-line therapy for OCD is SSRIs.*
  7. E – Post-hoc subgroup analysis is a form of BS p-hacking. The more subgroups and secondary measures you decide to look at after designing your study and gathering data, the more likely it is for you to find an (often spurious) positive result.
  8. E – I think the answer here is probably intuitive even if you don’t actually know why. But anyway, recall that sickle cell RBCs have a decreased lifespan, so they don’t stick around as long to accumulate glucose as normal RBCs do, which artificially lowers the A1C value.
  9. A – You can’t hold records hostage.*
  10. A – Bleeding in cirrhosis is more complicated and multifactorial than you’d think, but the elevated INR in cirrhosis is primarily secondary to synthetic dysfunction. Recall that elevated PT/INR is related to decreases in Factors II, VII, IX, and X, and the liver makes fibrinogen and factors II, V, VII, IX, X, XI, and XII. Of the choices, Factor VII deficiency is the biggest bleeding risk.*
  11. E – Classic features of scleroderma. Skin-tightening about the mouth can complicate airway management.
  12. C –Number needed to treat (NNT) is 1/(ARR = difference in outcome). There was a 20% difference (35% vs 15%) of recurrent encephalopathy. 1/.2 = 5.
  13. B – This is a well-designed study. The main problem is that EPCS is technically challenging to perform and sclerotherapy is available basically everywhere.
  14. B – B is true (it’s in the table and has an itty-bitty p-value). A confidence interval including 0 (choice A) means the two options are not significantly different.
  15. E – Signs and symptoms of secondary syphilis. It’s usually prudent to keep STIs as a differential for most cases of young-healthy-person-suddenly-develops-a-constellation-of-weird-symptoms.*
  16. C – While there’s overlap between exposure-related/allergic-type symptoms and viral URIs, in this case, RSV is the only virus they gave you, and that’s not going to pan out for this combination cough/coryza/itchy eyes in older kids. As we’ve learned with COVID, viruses travel between people and don’t stay localized to a single physical environment like mold from poorly mitigated water damage.*
  17. A – When someone seems like a truly awful adult, antisocial personality disorder (apparent “charm” is a test-favorite). When under the age of 18, conduct disorder.*
  18. B – You want to nonjudgmentally hear about what happened from the patient in his own words in order to evaluate. I do love that they included truth serum though.
  19. B – Irregular tachycardia? Could she have symptomatic a-fib? Would an ECG provide the diagnosis immediately? Yes and yes and yes.*
  20. B – He is sick leading to decreased PO intake leading to prerenal physiology and hypovolemic hyponatremia. This is very common and the cause of the majority of AKI we see in the hospital when literally anyone is sick. Treat with fluids.*
  21. E – Posterior knee dislocation often results in vascular injury (there is no discrete fracture on the radiographs).*
  22. A – His party foul was cataplexy (the awkward passing out at moments of excitation) and is common in narcolepsy. Decreased sleep latency and the need for frequent (but restorative) naps are also characteristic. See this adorable video.
  23. C – The control group needs to have radiographs in order to prevent a systemic ascertainment bias from unintended differences in the composition of the two groups.
  24. D – We have no reason to doubt the patient’s decision-making capacity, and he doesn’t want treatment. He does, however, have metastatic cancer. Hospice is a very underutilized program that can help patients with terminal illnesses navigate the end of life by prioritizing their care goals and comfort.*
  25. A – Infectious bloody diarrhea is dysentery. Of the choices, only Campylobacter jejuni causes dysentery.
  26. C – Reactive arthritis is associated with HLA-B27. You probably remember this most as the young man with arthritis after an STI (most often chlamydia trachomatis), but bowel infections also do the trick (typically Campylobacter, Salmonella, Shigella, or Yersinia).
  27. A – The most common cause of bloody/black nipple discharge is an intraductal papilloma, which can be diagnosed via ductography. That said, in real life, ultrasound is highly user-dependent and most people would probably at least do another targeted ultrasound to try to find the lesion now that there’s new discharge. For one thing, it’s easiest to biopsy a lesion that is seen on ultrasound.
  28. D – Math.
  29. B – Toxic shock syndrome, caused by exotoxin-producing Staph and Strep. They don’t have to mention the word tampon.*
  30. A – Old man with shoulder girdle pain and/or stiffness, nonspecific somatic complaints, and an elevated ESR? Polymyalgia rheumatica, a disease of exclusively old people.
  31. C – Benzos, like alcohol, suppress respiratory drive. That’s why they’re potentially lethal.
  32. A – Looks a combination of chemo-related side effects and pancytopenia.*
  33. E – Isolated elevated respiratory rate in an otherwise healthy and well-oxygenated baby after a C-section is typically TTN, felt to be a result of retained lung fluid that would normally be squeezed out/resorbed during the normal birthing process.
  34. D – The ulna is fractured, and the radial head is dislocated (way too high). The eponym for this pattern is called a Monteggia fracture-dislocation.*
  35. A – The diagnosis of inflammatory bowel disease can be made with colonoscopy.*
  36. A – She might be doing drugs, but a little coke and MJ don’t cause papilledema (a sign of increased intracranial pressure) and cerebellar signs. A cerebellar tumor could, commonly a medulloblastoma in a patient of this age.*
  37. C – It’s cholangitis because of the stone lodged in and obstructing the common bile duct, which is why the CBD is dilated; you would suspect this clinically before the ultrasound essentially confirmed it due to the combination of upstream liver and pancreatic issues. Only a stone in the distal CBD will affect both organs.
  38. A – Intention tremor that’s improved with alcohol is classic for essential tremor, which can be exacerbated by SSRI therapy.

Block 2

  1. D – A-fib isn’t ideal, but it’s the giant pleural effusion that’s causing her SOB and hypoxia. Thoracentesis will be diagnostic and therapeutic.
  2. D – Very long question, but we have a combination of post-op severe abdominal pain, fever, and leukocytosis. Of the choices, an ultrasound can (more or less) evaluate the aortic repair and look for free fluid. It would also evaluate for the possibility of acalculous cholecystitis in this old sick patient, which is likely the thrust of this question. In real life, this patient would definitely get a CT scan, but that’s not a choice here.*
  3. E – An ultrasound is used to assess for a tappable joint effusion, particularly in order to exclude septic arthritis. Transient synovitis (aka “toxic synovitis”) is the most common cause of acute hip pain in children aged 3-10 years and is what this child likely has. It frequently occurs after a URI, and a low-grade fever is typical.
  4. E – She has a-fib with rapid ventricular response based on the irregularly irregular rhythm and tachycardia. You don’t really need to know the murmur part to get this question correct, but remember that mitral stenosis results in a diastolic fill murmur loudest at the apex (the snap is the stenotic valve finally and dramatically opening thanks to the increased pressure). Chronic MS predisposes to a-fib due to left atrial enlargement, which stretches and deforms the conduction pathways.
  5. B – Diabetic gastroparesis in a long-standing diabetic.*
  6. E – Vitamin D deficiency is rampant with symptoms including fatigue, muscle aches, and depression, among others. Checking a vitamin D level is also just helpful to make sure we’re treating osteoporosis sufficiently.
  7. D – Gas exchange requires both the ventilation of alveoli and circulation of blood through the capillary bed. Hypoxygenation with a lung infection is usually due to a VQ mismatch and shunt as blood still travels through lung tissue that is poorly ventilated. This is the opposite of a pulmonary embolism, where the perfusion is low to normally ventilated lung.*
  8. C – An intoxicated physician can’t work due to patient safety, obviously, but you also can’t cover for them and try to hide the event.*
  9. D – The first imaging study for any musculoskeletal complaint outside of spine trauma is a radiograph.*
  10. B – You want the first test to be highly sensitive in order to catch most cases of the disease. You want the confirmatory test to be highly specific so that only true positive cases make it through.*
  11. C – You want to make sure she is taking the prescribed medication and confirm she’s not taking anything else on the side.*
  12. A – That isn’t the “opening remark” you might want to use, but it is absolutely the only one that’s appropriate from the list.*
  13. C – Tubal injuries/scarring like those resulting in hydrosalpinx are often secondary to STIs, particularly Chlamydia, and are a common cause of infertility.*
  14. A – Leg claudication in a heavy smoker is concerning for the PAD. The initial test is an ABI.*
  15. D – From the data provided, no one with a negative D-dimer had a PE (high negative predictive value, D), but a positive D-dimer was seen in tons of normal people (low positive predictive value).*
  16. D – The insurance company needs the admitting diagnosis to pay for the visit. They get to hear about everything, and HIPAA doesn’t apply to billing. It would be a HIPAA violation to tell anyone else, though you’d probably try to convince the patient to let you talk to the wife.
  17. C – The p-value column only demonstrates one significant value: HIV co-infection.
  18. C – Ah, the halcyon days before Covid. You’re not done with him yet. But, he could have TB, so mask up.
  19. E – Clear alcohol withdrawal seizures. What else were you hoping to find? If “no further evaluation” is an option, be extra sure you don’t want to pick it.*
  20. A – Only A is true. B is the opposite (hypoxemia was less impactful). As for C, the CI for the odds ratio of lung infiltrates includes 1, meaning that it was not statistically significant (which also means that D is wrong).
  21. C – Spontaneous panic-like sympathetic overload episodes in a person with a family history suggesting MEN2A (comprised by medullary carcinoma of the thyroid, pheochromocytoma, and parathyroid hyperplasia or adenomas). We need to work up a pheo, which we can do laboratorily by measuring serum metanephrines.*
  22. B – You can gently correct incorrect statements, catastrophizing, etc. Denying someone’s feelings (D) is unhelpful, blowing someone off from their story in the middle of evaluation is absurd (C), and just giving advice (A) like an over-credentialed coach isn’t going to work.*
  23. A – Acute-onset LBP and radiculopathy are typically related to a herniated disc.
  24. E – Dementia in the setting of multiple strokes sounds great for vascular dementia. This is especially likely given the rapid course and association with focal neuro deficits, but be aware in real life that dementing processes are not mutually exclusive.
  25. A – Lots of lymph nodes and splenomegaly with weight loss and fevers is concerning for lymphoma. In this case, mediastinal nodes are also causing airway compression.*
  26. D – An uncontrolled seizure disorder and driving don’t mix.*
  27. D – Power is 1 minus the type II error (aka the false-negative threshold).
  28. D – Liver disease was a contraindication in the drug ad (red box at the end), and the patient has cirrhosis.
  29. D – The ad shows that all three doses were similar vs placebo. Remember, when in doubt, the exam loves to test the difference between measurable differences (or even statistical significance) and clinical significance. 
  30. B – Most cases of sinusitis are viral and result in mucosal swelling/edema.
  31. C – Middle-aged female with muscle aches, proximal muscle weakness, and an elevated CK indicating muscle breakdown. The skin cracking is a description of “mechanic’s hands.”
  32. C – Likelihood ratios are often used to judge the performance of a diagnostic test by determining the likelihood that a test result changes the probability of the underlying condition being present. LR = sensitivity / (1 – specificity). In this case that’s (120/336) / (1 – [365/375]). Note that we use 365 because we’re calculating the true negative rate and they provided us with 10 false positives out of the 375 individuals negative for HIV.*
  33. B – This question is actually straight-up bad. There are multiple societal players and guidelines, which complicates things, but the move over the past decade has been to try to biopsy fewer lesions because we’re dramatically overdiagnosing and overtreating thyroid cancer. Basically, a 1 cm nodule should really only be biopsied if it has concerning ultrasound characteristics like microcalcifications. Just saying it’s solid doesn’t really count. The alternative to FNA is observation though, so at least A, C, and D are unworkable.
  34. D – Working outside in the “southwest United States” with nonbacterial pneumonia (no improvement on antibiotics, eosinophilia) is a great setup for coccidiosis.*
  35. D – Sounds like the patient is behaving like a prototypical American. A family meeting would be appropriate because family meetings are basically always appropriate. Legal guardianship for liking fast food and cigarettes is absurd, Down syndrome or not.
  36. E – OTC cold medications often contain decongestants that cause vasoconstriction.*
  37. E – Fever + flank pain + UTI = pyelonephritis. No further workup is needed for a woman’s first episode of pyelo, despite common ER practice. If she fails treatment, then she’ll need imaging.
  38. F – Horner’s syndrome from injury to the superior cervical ganglion reducing sympathetic activity.*
  39. E – Analgesia abuse nephropathy. That’s a lot of Advil.

Block 3

  1. A – Trigeminal neuralgia is classically treated with carbamazepine.
  2. C – Pain with passive flexion is a classic exam finding of compartment syndrome. In this case, muscle breakdown (evidenced by the elevated CK) is the source of the swelling that is poised to threaten the limb.
  3. C – Radiofemoral delay and pulse/BP differentials between upper and lower extremities are physical exam findings of aortic coarctation. The stiff/noncompliant narrowed aorta increases afterload and results in hypertension.
  4. E – Pregnancy of unknown location. She doesn’t have a tubal mass to suggest an ectopic pregnancy, so we perform serial HCGs to see if this is an early intrauterine pregnancy, an early ectopic pregnancy, or a failed pregnancy.*
  5. C – Postpartum psychosis is an even bigger risk factor for future peripartum psychiatric issues including depression than run-of-the-mill postpartum depression.*
  6. C – LDL is just above the normal range. In an otherwise healthy adult, the statin treatment threshold is 190. Everyone should have a “heart-healthy diet” and exercise.*
  7. C – ABCs.
  8. C – He’s in as good of shape as he can be. But no one feels comfortable after getting stabbed, receiving a chest tube, getting a thoracotomy, and then keeping a chest tube or two. The tachycardia may or may not be an objective sign of pain here as well.*
  9. E – It would seem he has developed decompensated acute right heart failure in the setting of constrictive pericarditis. An effusion with tamponade is theoretically possible as well, especially keeping in mind that acute effusions often don’t result in the water bottle heart on x-ray that you learned about because it takes some time for the pericardium to stretch, but the X-ray showing a normal size heart is a tip-off here that the pericardium has thickened and hardened, preventing normal heart-filling (and therefore no cardiomegaly as we so often see in heart failure from most causes). Even if the new heart failure was from another cause, an echo would still be the right choice to see what’s going on.*
  10. A – Clear-cut varicose veins. The initial treatment of choice is compression stockings. Venous imaging is really only indicated if there are signs to suggest DVT or pre-procedurally prior to an ablative procedure.*
  11. A – Cat bites on Step exams classically result in infection by Pasteurella multocida. Beta-lactams work just fine, so Ampicillin would be a great choice. Amp has the benefit (unlike a fluoroquinolone) of also covering anaerobes since most bite injuries are actually polymicrobial.
  12. E – Initial cervical cancer treatment is all about staging. Low-stage localized disease gets surgery and higher stages get chemoradiation.
  13. D – He has hypertension.*
  14. D – Trich is often asymptomatic. (Rapid) reinfection is common, and he (and any other occult partners) should be treated empirically even if asymptomatic to prevent reinfecting the girlfriend.*
  15. A – HIV+ with CD4 < 200 means full-blown AIDS, hence the oral hairy leukoplakia (painless, un-scrapable unlike thrush). He needs antiretroviral therapy, which addresses the root cause of his current complaints. He does also need opportunistic infection prophylaxis/treatment, but that’s not an option and would be in addition to antiretroviral therapy.*
  16. A – She has somatic manifestations of a targeted anxiety disorder/phobia. This would best be treated with CBT.
  17. A – Not just pharyngitis or even tonsillitis, the swollen oozing tonsil displacing the palate and uvula and resulting in trismus suggests a peritonsillar abscess, which requires drainage.
  18. C – It would seem he’s a hemophiliac given the bleeding diathesis with an X-linked inheritance. With that inheritance pattern, his daughters will be obligate carriers and his sons will be totally fine. Therefore, the sons of his daughters will have a 50% chance of having the disease.*
  19. E – Smooth small objects like dimes should pass. A rule of thumb is that anything around 1 inch or larger (i.e. quarter or larger) is a problem and should be retrieved if accessible, as well as coin batteries (if still in the esophagus), multiple magnets (which can bind bowel loops together and cause obstruction/perforation), and probably most things with super pointy edges. Once a single smooth object makes it to the stomach, it’ll usually be fine. Some recommend a radiograph if the object hasn’t passed by three days.*
  20. D – Back pain is a way of life for the morbidly obese.
  21. C – Abnormal uterine bleeding in a woman over 45 requires an endometrial biopsy to rule out endometrial cancer. For patients younger than 45, EMB is also recommended for those not responding to medical therapy or who have prolonged periods of unopposed estrogen stimulation.*
  22. C – Smoking is by far the worst modifiable risk factor of all time.
  23. A – You know you want more PEEP, but PEEP isn’t always like cowbell. Sometimes you can have too much. Forcing all that air into noncompliant lungs can raise intrathoracic pressure, which reduces right heart venous return, hence the JVD and systemic hypotension (the latter secondary to the Starling mechanism). Tidal volume and respiratory rate might also be reduced, but the bottom line is that we need to tweak the ventilation settings.*
  24. D – Small anal fissures are treated with a bowel regiment/stool softening. This isn’t a hemorrhoid or perirectal abscess.*
  25. A – Intravenous calcium is used to prevent bad-news cardiac effects of hyperkalemia. Not sure the peaked T-wave on the ECG are really necessary for this question when they give you a serum potassium of 6.4.*
  26. D – Rifampin is meningococcal prophylaxis used for close contacts. You do not want to get meningococcal meningitis.
  27. E – She is severely anemic, which can certainly cause chest pain by itself irrespective of her underlying sickle cell disease, and she needs a blood transfusion. Analgesia is also critical in any potential sickle cell crisis, but that isn’t an option here.*
  28. B – Patients with Parkison’s and other old, weak, and/or demented folks are at high-risk for aspiration. PNA in this population, particularly involving the RLL, could be aspiration pneumonia, and steps should be taken to make sure an appropriate diet plan is in place.
  29. E – IV metoprolol is great for rate-control. It even worked already during this admission; it just doesn’t last very long. Rapid onset, short duration. He’ll need continued IV rate control until oral meds (or other therapy) can treat his RVR or it resolves on its own.
  30. C – Anthracycline-induced (e.g. doxorubicin) cardiomyopathy can occur years after treatment and warrants screening echocardiography.*

Block 4

  1. D – He has toxo from eating cat feces in the dirt (oops). That doesn’t address the why of his pica (geophagia, in his case). I don’t know about you, but I don’t think managing dirt-eating in five-year-olds is part of most people’s practice, even in “Advanced Clinical Medicine.”
  2. D – We should be worried about cord compression, possibly from spinal metastasis in the setting of breast cancer. Recall that the spinothalamic tract crosses in the spinal cord unlike the main sensory and motor tracts, which cross in the brainstem, which is why a right-sided lesion would affect right-sided strength, sensation, and reflexes but left-sided pain/temperature. The inguinal ligament is the T12 sensory level, but you might remember that the fibers travel 1-2 segments before crossing, so the sensory level will often be below the lesion level (i.e. our lesion could be at T10).*
  3. C – The combination of fever and back pain is concerning for osteomyelitis. MRI is the test of choice.*
  4. E – You might recall that children with sickle cell disease are at risk for salmonella osteomyelitis in addition to the more common bugs like MRSA. Empiric treatment should cover both: vanc for MRSA and a third-gen cephalosporin like cefotaxime for the salmonella.*
  5. D – Pain control is always a priority. Obviously, you’re going to get an imaging study and give antibiotics, but the question here is getting at how to address his symptomatic misery.*
  6. C – Lactic acid lotions are used for exfoliating and moisturizing super dry skin. There is no evidence for an infection or inflammatory condition.*
  7. D – It’s all from outlet obstruction. We need to drain that bladder, so if a foley can’t be passed, then it’s time for a suprapubic catheter.*
  8. A – Abscesses get drained.
  9. E – She has cerebral edema, which is the leading cause of death in DKA. Signs, in this case, were somnolence, lethargy, headache, n/v, and incontinence. Seizures, bradycardia, and eventually respiratory arrest are also bad news. Mannitol decreases ICP.
  10. B – Hormonal therapy with estrogen is the most effective treatment for the symptoms of menopause like hot flashes. Nonhormonal therapies like gabapentin and certain antidepressants carry lower risks but are not as effective and therefore not “most likely to alleviate” her symptoms. She has evidence of prior TB, but that’s a distractor.*
  11. E – Thinking psoriasis with the raised red, scaly plaques, and even some nail involvement, but every rash can be treated with steroids right? (kidding not kidding.) I presume the episode of joint pain is a toss-out to suggest psoriatic arthritis.
  12. D – Try not to fight “normal patient just needs a high five” questions.
  13. D – Cocaine can cause chest pain and even MI due to alpha-mediated coronary artery vasoconstriction and spasm. He hasn’t responded to the first-line treatments of ASA, NTG, and BZD, so next up is phentolamine, an alpha-blocker that can loosen things up.
  14. D – He has the four-liner description of hypovolemia. You treat hypovolemia with saline. Remember your ABCs.
  15. C – Thrush is common in newborns and young infants and is almost always initially treated with topical nystatin. Difficult cases can be treated with oral (systemic) fluconazole. In a newborn, the two most common sources of a white tongue are milk residue and thrush. Milk residue comes off easily. You of course can scrape thrush off, but not necessarily with “gentle” scraping, and doing so will often leave red, inflamed areas underneath.
  16. B – MDD is treated first-line with SSRIs. He has complicated depression (with hallucinations), not bipolar disorder.
  17. D – That late systolic murmur is concerning for aortic stenosis. Untreated aortic stenosis is a rapid killer of old people, especially if it’s already symptomatic.
  18. E – Super common safe combination.
  19. C – Most patients with Bell’s palsy have a complete recovery.*
  20. E – Asthma exacerbations are treated with steroids. Even though her flow rates aren’t that bad, she is not getting relief with her rescue inhaler.*
  21. A – Gestational diabetes is pretty likely in this overweight patient with a history of a large baby delivery and now measuring greater than dates.*
  22. E – Immediate and most effective pharmacotherapy to help firm up the uterus and stop postpartum hemorrhage is oxytocin.*
  23. A – This is an example of cold urticaria, a rash that forms on cold-exposed skin and typically worsens as the skin warms (hence why it happened after she returned home). Mild reactions don’t require treatment (such as antihistamines or an EpiPen), but avoiding cold exposure will allow the reaction to fade and prevent future occurrences. Anaphylaxis can occur.*
  24. B – Community-acquired pneumonia (possibly with an atypical pathogen suggested by the addition of diarrhea) in a pregnant patient. Patients with comorbidities (e.g. COPD, alcoholism, diabetes) should get levoflox, moxiflox, or a combination of a beta-lactam like amoxicillin or third-gen cephalosporin like ceftriaxone PLUS a macrolide (e.g. azithromycin). Fluoroquinolones are generally avoided in pregnancy when effective alternatives are available, making B a better answer than C.*
  25. D – Lovenox is the DVT prophylaxis of choice in patients with reasonable renal function. Recent knee surgery isn’t a contraindication; orthopedic surgery is a huge risk factor!
  26. C – Addison’s disease presenting with Addisonian crisis–indicated by the combination of skin bronzing, generalized weakness/failure to thrive, and salt wasting with hyponatremia and hypotension–will immediately need fluids and steroids. This is a commonly fatal condition when insufficiently untreated.*
  27. D – Super duper classic gout. Big angry MTP joint full of white cells but no organism (Podagra). Treatment of an acute attack would be indomethacin. Prophylaxis is allopurinol.
  28. D – The AAFP actually recommends a single dose of oral steroid (usually dexamethasone) in all (even mild) cases of croup to help with airway edema. Croup is viral, so no antibiotics.
  29. B – The diagnosis of shingles here is clinical and does not require any further testing itself. However, given multiple sexual partners and a case of shingles way younger than typical, HIV testing is prudent. HIV significantly increases the risk of reactivation diseases like shingles.*
  30. B – Condyloma acuminatum (genital warts) can be treated with imiquimod, a topic immune-response modifier.

I’m a fallible human being. Questions/thoughts are welcome in the comments as always.


Alexander Hamilton 04.08.21 Reply

Absolute legend, cheers mate

Megan Fox 05.21.21 Reply

Super helpful. Thank you for taking the time to put this together. Helped me out big time 2 days before my step 3 exam.

rick 05.21.21 Reply

Can someone explain why number 5 is C? Why can’t the mom be a carrier and thus the answer be B?

Ben 05.22.21 Reply

This is a very rare disease. We know it’s X-linked from the tree, the father has it, and it’s the prediction based on the inheritance pattern that we are evaluating in this question. It would be a stretch to assume his wife coincidentally is also a carrier for this rare condition without her own supporting family history.

Zatia 02.19.22

If this is the case then why does the maternal uncle have the disease? It seems they made a mistake in the question. If men don’t pass it down to their sons then how would the uncle get it from the grandfather?

Ben 02.22.22

He doesn’t, that is not stated nor in the tree.

zara 06.23.21 Reply

thanks for this, i think the question about the likelihood ratio, the specificity should be calculated as 10/375?

Ben 06.23.21 Reply

I don’t believe so conceptually or mathematically. 10 is the number of false positives using that serum threshold, not the true negatives needed to calculate specificity.

Using 10 also gives an answer less than 1, not the correct answer of 13 (which you get by using 365/375 as I described above).

Peri Peri 06.28.21 Reply

For question, 131 is it legionella ?

Ben 06.30.21 Reply

Quite possibly.

Daniel 01.12.22

Legionella also causes thrombocytopenia, hyponatremia, AKI and diarrhea. It can be treated with a macrolide or fluoroquinolone (which wouldn’t work in this case due to the patient being pregnant)

Frank 01.13.22

For number 122, I get that thrush is common in infants. But when we are taught and see in every day clinical practice that thrush does tend to be scraped off without much effort, the examiner purposefully throwing out “not easily scraped off” (especially knowing that this is all we have to go off of), it does seem a bit deceitful on their part. It’s not asking much to not give us presentations specifically and purposefully the opposite of what we have been taught and see in practice.
This kind of deception paired with extremely relative modifier terms like “easily” is problematic. Easily compared to what? Unless this particular physician is incredibly weak, then this question comes off as nothing more than a query designed to challenge the tester’s ability to read the examiner’s mind rather than investigate their clinical knowledge. I thought we were training to be physicians, not paralegals? Cheers

Ben 01.13.22

This was also discussed in the comments of the prior set, which you may or may not enjoy: https://www.benwhite.com/medicine/explanations-for-the-2018-official-step-3-practice-questions/

Peri peri 06.28.21 Reply

118. Psoriatric arthritis: isn’t it systemic therapy like MTX (according to UW)

Ben 06.30.21 Reply

I would be surprised if UW actually said to treat plaque psoriasis with systemic oral therapy only and ignore topical steroids. That’s not per the guidelines such as https://emedicine.medscape.com/article/1943419-guidelines

Peri Peri 06.28.21 Reply

67. P value is more than .05. Is this study statistically significant? So why not C? any explanation?
68. Why not Eustachian tube dysfuction?
100. Why not chest tube? Can MVentilation cause Pneumothorax?
Thank you so much for your help.

Ben 06.30.21 Reply

67. No it’s not. No point giving a higher dose when none of the doses did anything.

68. Eustachian tubes drain the middle ears, not the sinuses.

100. Yes, ventilation-related barotrauma can indeed cause a pneumothorax. But he does not have a PTX with his symmetric breath sounds and midline trachea. Putting a chest tube in someone without a drainable pleural effusion or pneumothorax would be poor form.

Esha 08.14.21 Reply

you are the happiness in my dreary USMLE studying soul.
Thank you for this :)

Ben 08.15.21 Reply

You’re welcome, thanks for taking the time to comment.

Luke 08.25.21 Reply

Been using your explanations for other questions on past Steps. Explanations are succinct and very understandable this time around too. Thank you again as always! :)

Ray 08.31.21 Reply

32. My answer is also A but I thought of post-chemo pancytopenia. I can’t see why TLS. Am I missing something?

Ben 08.31.21 Reply

Yeah, it’s probably all chemo.

Ray 08.31.21 Reply

40. Do you think this is acalculous cholecystitis (RUQ abdominal tenderness), hence US is the answer?

Ben 08.31.21 Reply

Good thought, definitely feasible.

Ray 08.31.21 Reply

92. Isn’t the tongue lesion leukoplakia (non-scrapable — haha is this a word?)

Ben 08.31.21 Reply

I don’t think so. Leukoplakia is a completely separate process, typically seen in adults and predisposing to oral cancer.

Gab 09.05.21 Reply

Am I the only one that didn’t why the 71 questions marked with an asterisk? do you mind explaining what you meant? is it even important?

Ben 09.06.21 Reply

Third paragraph from the top. They signify new questions from last year’s set. Every year, some questions are new and some are old. Some people like to do multiple years’ worth of these sets, in which case I’m making it easier to only do the new ones if you start from the older sets and work your way forward.

Vinny 10.19.21 Reply

Once again, I find peace, comfort, and solace in your explanations for the third time here, now finally as a resident :)

On 19, why would we not do TSH first? They even said “thin woman”, and I thought hyperthyroid could cause Afib? When they said she had SOB at the end of her last pregnancy, I was thinking maybe a history of postpartum thyroiditis.

Also, what could the statement “I was always sick as a child” be trying to hint us toward? Or does it mean nothing? Thank you!

Ben 10.19.21 Reply

The way I see it is that we have someone in our office with symptomatic irregular tachycardia–first things first is to know what she has going on with her rhythm (ECG). Takes a few minutes, definitive answer.

Then, we can consider the why, such as laboratory work like a TSH.

Vinny 10.19.21

Got it, thank you so much!

Nathan 11.01.22 Reply

I thought the diastolic rumble meant they were hinting at rheumatic heart disease with mitral stenosis, which might predispose to AFib. The “always sick as a child” might be hinting that one of these episodes might have actually been a GAS infection that was untreated, hence leading to rheumatic heart disease. This makes sense also given that one of the other answer choices is an ASO titre.

MJ 10.27.21 Reply

122. I was 99% sure that this was thrush but chose E because it couldn’t be scraped off.

Brit 12.05.21 Reply

Question about Number 3, its not IGa nephropathy because of the short time frame? I know c is the answer. But c fits more it PSGN? The time frame is only 1 week out from the URI

MS 09.04.22 Reply

Same question.

Ripu 12.24.21 Reply

Step 1, CK and now 3. Thank you for giving the best explanations I wished for right before my exams.
Cheers doc

Ben 12.27.21 Reply

<3 <3

Brandy 12.27.21 Reply

Taking my Day 2 later today- you’ve been an absolute godsend for Step 1, 2CK and looks like you’ve saved me once more. Cheers!

Ben 12.30.21 Reply

Hope it went well! And good luck to everyone else as well.

Rick James 01.13.22 Reply

For Q 106, I understand that the metoprolol worked to reduce the HR in the stem, but realistically I don’t think that this, in and of itself, is enough explanation to rely upon once taking the actual exam. I mean, what if they don’t tell you that the patient first received metoprolol that worked to slow the heart down?
As such, when thinking on the question a bit more, would it not be prudent to try adenosine first, in order to rule out a more serious underlying issue like WPW syndrome? No one is saying just give adenosine and walk away never to see the pt again. Just that the adenosine would temporarily slow conduction through the AV node in order to determine whether or not there are hidden P waves, or even eliminate the tachycardia altogether if it is an AV node dependent arrhythmia like AVNRT or orthodromic AVRT. This would still slow the HR down and, even better, help get to the root of the problem. Thoughts?

Ben 01.13.22 Reply

A fib with RVR, which is what the patient has by history and what the ECG showed, is typically treated with rate control by beta blocker. (“ECG obtained in the emergency department showed atrial fibrillation with narrow QRS
complex.”) So what justification would you have for thinking they have an SVT requiring adenosine?

Rick James 01.16.22

“Paroxysmal supraventricular tachycardia (PSVT) usually presents as a sudden-onset, regular, and narrow-complex tachycardia. Adenosine slows atrioventricular nodal conduction to interrupt the reentry pathway and terminate PSVT…Adenosine or carotid sinus massage can cause transient atrioventricular block and slow ventricular rates in AF, but they are not effective for long-term rate control.”

IIRC, it asked for can be given to slow the patient’s HR down in the moment, not what the best long term treatment would be for him. I agree otherwise. I don’t think anyone is arguing that metoprolol isn’t the best long-term option. But I appreciate you taking the time to respond.

Rick James 01.16.22

Is it not fair to say that A. fib is a type of SVT?

Ben 01.16.22

It is, SVT is a broad umbrella. The point I was trying to make is that adenosine is primarily used to slow AV conduction down for the purpose of breaking the reentry loop in AVNRT. Just slowing down the rate for a few minutes in a fib or flutter isn’t particularly helpful. When it’s an unknown SVT and the rate is so fast you can’t tell, then then you give adenosine because it will potentially fix it (and sure, potentially slow it down enough transiently that you can see what the underlying problem is).

In this case, we know it’s atrial tachycardia and not ANVRT, so there’s really isn’t a good role for adenosine (it’s also very unpleasant for patients).

Rick James 01.16.22

I think the main benefit I got from that Q is that despite A fib being a type of SVT, test examiners use SVT to mean any supraventricular tachy that is not obviously Afib or A flutter. I wish they would change the nomenclature a bit to avoid this confusion, as forcing testers to compare “SVT vs A. fib” is a bit like asking someone to explain the difference between “weather vs thunderstorm”. Anyways, I appreciate your taking the time to respond. Thank you very much for doing this for us.

Rick Astley 01.13.22 Reply

For 38, it says her tremor got worse over the past MONTH, but that she’s only been taking the SSRI for the past three weeks? How would an SSRI that she hasn’t even started taking explain her worsening tremor that first week predating the addition of fluoxetine? Cheers

Ben 01.13.22 Reply

“During the past month” does not mean the same thing as “for 1 month.” It means it’s happened within the past month, not that it started exactly 4 weeks ago.

Rick Astley 01.16.22

Geez. You’d think a test that expects us to know medical facts to such minute detail (as we should) could be a bit more precise with their wording knowing that we are hanging on to every syllable to help elicit the answer from the text.

Ray 01.25.22 Reply

absolute gold mine here, just wanted to voice my appreciation. thanks!

Ben 01.26.22 Reply


Zheng Song 02.17.22 Reply

First of all, thank you so much for doing this Dr. White. I used your explanation for STEP 1, 2 and now 3.

Question 92, the lesions are not thrush but Hairy leukoplakia: irregular, white, painless plaques on lateral tongue that cannot be scraped off. EBV mediated. Occurs in patients living with HIV, organ transplant recipients. Contrast with thrush (scrapable) and leukoplakia (precancerous). (Quoted from STEP 1 First Aid 2021, page 493).

Thank you again! Some your explanation are hilarious, and I learned the truth serum.

Ben 02.17.22 Reply

Good pick up!

Zheng Song 02.17.22 Reply

98. the age cut-off for biopsy is >45 not 35.

For women who are 6 months, or on tamoxifen treatment). Quoted from UWORLD STEP 2 QBANK question explanation.

Thank you.

Zheng Song 02.17.22 Reply

It didn’t come out right for whatever reason. Sorry about that. So, biopsy is for women age >45 or <45 who are high risk. High risk means having AUB for 6 months, obesity, failed treatment for AUB (e.g. OCP), or on tamoxifen treatment.

Ben 02.17.22

(You’re right, the guidelines changed a few years ago. In older versions of this question, the patient was 42 because 35 was the standard cutoff.)

Zheng Song 02.17.22 Reply

Q102, yes they still have to show the ECG change because potassium of 6.4 by itself is still not sufficient enough to justify emergent therapy in peds patients.

Reference: Management of hyperkalemia in children UPTODATE

Zheng Song 02.17.22 Reply

Q134. I don’t think it’s a fair question. I picked vanco. Yes, the question is a perfect setup for gouty arthritis. However, neither being afebrile nor a negative gram stain can rule out a septic joint. Gram stain sensitivity is less than 50% in septic joint. Plus, this guy is diabetic which increases his chance for infection. The only thing I can say is indomethacin may be a better choice because vanco by itself may not be sufficient for this patient due to him being immunocompromised (he should be on vanco and a cephalosporin).

Ben 02.17.22 Reply

I agree if there’s bad diabetic neuropathy and/or a wound, otherwise with that history and involving that specific joint? I think it’s probably okay overall. With these it’s single best answer, it doesn’t mean the other choices are necessarily entirely wrong or unreasonable.

Curiosity 03.06.22 Reply

Thank you. Explanations are golden.

syed 03.07.22 Reply

for Q 16 can u explain why is the answer Molds spores ? that was very weird .
Also why not Mycoplasma pneumniae ?

Tabby 09.23.22 Reply

Same question!

Ben 09.23.22 Reply

Allergic symptoms in a whole bunch of otherwise disparate people all linked to a specific location. Nothing in the community, just a bunch of people sharing the same space.

A virus or walking pneumonia in a whole bunch of people at the same time with allergic sxs including itchy eyes but not a single fever–and all after this water-damage event?

syed 03.07.22 Reply

Confused here
for Q 23. why is not confounding ?
Ascertainment bias definition they gave in uworl was : study population differ from target population due to non-random selection methods .
But in Q we did randomized selection . so selcting a population with same variable ( ex: Xray) dosent it reduce confounding ?

M 04.01.22 Reply

Thank you for this. Still helpful a year later!

MS 09.04.22 Reply

#3 Why PSGN? And not IgA nephropathy. PSGN usually takes 3 weeks after streptococcal throat infection while IgA nephropathy occurs can occur from 2 -7days.
The question mentioned the girl had throat infection a week prior to the bleeding form urine.

Ben 09.06.22 Reply

Commonly 1-2 weeks after strep throat, within 6 weeks of step skin infection: https://www.ncbi.nlm.nih.gov/books/NBK538255/. So the timecourse is reasonable.

IgA is often even faster. Same source: “Usually occurs after an upper respiratory tract or gastrointestinal infection, but it differs from PSGN in the shorter latency period it takes to appear after the episode of infection. It can also be described as synpharyngitic hematuria-hematuria and infection coincide.”

BUT perhaps most importantly, IgA nephropathy typically has normal serum IgA levels. It’s not a serologic diagnosis, so D is not an optimal answer.

JB 09.24.22 Reply

Number 70. I am having a hard time understanding why 10 is the FP rate. I know the math makes sense, but was hoping you could explain why we should have assumed 10 is the FP rate in this question? Thank you so much again for doing all this!

JT 10.16.22 Reply

Thanks a ton for these explanations!

Keerthi Renjith 11.02.22 Reply

Thank you, you’re the best.

ZP 11.12.22 Reply

thanks mate!

JN 11.27.22 Reply

Thanks! Still relevant in 2022.

Omar 01.01.23 Reply

28. A physician is conducting a retrospective review of a trial involving the use of Drug X in patients with a specific disease. It is known that Drug X is associated with an increased probability of cancer in patients who use the drug. A total of 600 individuals with a specific disease were included in the trial. Of the participants, 200 individuals received Drug X and 400 individuals did not receive it. One hundred individuals who received Drug X died of a particular type of cancer and 100 individuals who did not receive the drug died of the same type of cancer. Based on these data, which of the following is the relative risk of death from this type of cancer in individuals who take Drug X as compared with individuals who do not take Drug X?

Can someone please do the calculation? 🙏

Cristina 03.24.23 Reply


Mahmoud Mohi 02.15.24 Reply

I was wondering where can i find the questions for this key answer? Thank you very much

Ben 02.19.24 Reply

Link in the first sentence.

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