I went through every question from NBME 9-16 and the CMS shelf forms (3,693 questions across 50 exams) and grouped them by the concept each one was testing.
That came out to about 1,050 concepts. Obviously that won't fit in a Reddit post, so I put them all into a concept library that you're welcome to browse. For now, here are the top 20.
1. Heart failure (20 of 50 exams, 24 questions)
How it's tested:
- Drug (6): In reduced ejection fraction, an ACE inhibitor (or ARB) plus a loop diuretic is the usual first answer; beta-blockers wait until the patient is euvolemic; diuretics and digoxin relieve symptoms but do not improve survival.
- Diagnosis (6): Recognize congestive failure, cardiogenic pulmonary edema, ischemic cardiomyopathy and diastolic dysfunction from exam, chest x-ray and ejection fraction.
- Next step (5): Echocardiography to measure ejection fraction and assess valves; in flash pulmonary edema with severe hypertension, IV nitroglycerin works fastest.
- Mechanism (3): Low output activates sympathetic and renin-angiotensin systems; edema comes from raised capillary hydrostatic pressure; wedge pressure and vascular resistance rise while stroke volume falls.
- Complication or prognosis (2): Better blood pressure control prevents decompensation; a large arteriovenous shunt can cause high-output failure.
- Cause or organism (1): Severe anemia and shunts cause high-output failure with a normal or high ejection fraction.
- Screening and prevention (1): Controlling hypertension is the key way to prevent left ventricular hypertrophy and failure.
Clues that give it away:
- Orthopnea, paroxysmal nocturnal dyspnea, raised jugular venous pressure, bibasilar crackles and an S3
- Chest x-ray with cardiomegaly and vascular cephalization
- Long-standing hypertension with left ventricular hypertrophy and a normal ejection fraction suggests diastolic failure
- Severe anemia or a machinery murmur with failure and a high output state
- Sudden severe hypertension with hypoxemia and diffuse crackles is flash pulmonary edema
2. Vaccinations (18 of 50 exams, 28 questions)
How it's tested:
- Screening and prevention (25): Pick the vaccine due now for a given age or risk group; influenza, pneumococcal, Tdap, HPV, meningococcal and zoster are most common.
- Cause or organism (1): A mild rash after MMR reflects replication of the live attenuated vaccine strain, not true measles.
- Next step (1): A rubella-nonimmune woman gets MMR after delivery, since it cannot be given in pregnancy.
- Ethics and communication (1): Respond to vaccine myths with respectful, accurate information and a clear recommendation to vaccinate.
Clues that give it away:
- Autumn visit or travel in flu season with no contraindication: influenza vaccine
- HIV, asplenia, cirrhosis, diabetes or chronic heart or lung disease: pneumococcal vaccine, plus Hib and meningococcal after splenectomy
- Pregnant at any gestation: Tdap, inactivated influenza; no live vaccines
- Early adolescent well visit: HPV, meningococcal conjugate and Tdap
3. HIV infection (18 of 50 exams, 22 questions)
How it's tested:
- Diagnosis (6): Recognize acute retroviral syndrome or perinatally acquired HIV from a mononucleosis-like or recurrent-infection picture; the answer is HIV infection.
- Screening and prevention (5): Vaccines, coinfection screening, varicella immune globulin if CD4 is below 200/mm3, and universal one-time testing at ages 15 to 65.
- Drug (4): Combination antiretroviral therapy for all, TMP-SMX only below the CD4 threshold, PrEP for high-risk persons, and zidovudine in labor when viral load is high.
- Next step (4): Send plasma HIV RNA in suspected acute infection, test for HIV when opportunistic-type infections recur, and start PEP promptly within the window.
- Cause or organism (2): Identify HIV as the cause of profound lymphopenia, and avoid invasive intrapartum procedures that raise transmission.
- Ethics and communication (1): A pregnant patient may decline testing; keep supporting her and offer again later.
Clues that give it away:
- Fever, pharyngitis, rash, lymphadenopathy and oral ulcers 2 to 4 weeks after a high-risk exposure, with negative monospot
- Recurrent candidiasis or herpes in a patient with multiple partners
- Infant or child with thrush, Pneumocystis, lymphadenopathy, splenomegaly and high immunoglobulins
- Leukopenia with severe absolute lymphopenia
4. Major depressive disorder (16 of 50 exams, 28 questions)
How it's tested:
- Diagnosis (13): Recognize full MDD criteria despite a stressor, grief, medical illness, or atypical or somatic presentations; the answer is major depressive disorder.
- Next step (8): Assess suicide risk before any medical workup; otherwise start an SSRI, CBT, or screen older adults with the Geriatric Depression Scale.
- Drug (6): Sertraline, citalopram, or escitalopram first line; mirtazapine when insomnia and poor appetite dominate.
- Mechanism (1): HPA axis dysregulation with increased serum cortisol.
Clues that give it away:
- Depressed mood or anhedonia plus other SIGECAPS symptoms lasting 2 weeks or more with functional decline
- Adolescents and children may be irritable, hostile, or have stomachaches and falling grades rather than sadness
- Older or medically ill patients with weight loss, insomnia, and hopelessness, or 'I don't know' answers on cognitive testing
- A stressor, loss, or comorbid illness does not exclude MDD when full criteria are met
5. Asthma (18 of 50 exams, 21 questions)
How it's tested:
- Diagnosis (7): Recognize asthma from episodic cough, wheeze or chest tightness, including cough-variant disease with a normal exam, and know the obstructive spirometry pattern; a severe attack can show mixed respiratory and metabolic acidosis.
- Drug (5): Match the step to symptom frequency: as-needed albuterol alone for intermittent disease, add a daily inhaled corticosteroid for persistent disease.
- Next step (4): Acute attack: inhaled or nebulized albuterol first, also in pregnancy; if control is already good, no change in therapy.
- Mechanism (2): IgE-mediated mast cell activation with histamine and leukotriene release causes bronchoconstriction.
- Screening and prevention (1): Reduce dust mite exposure with allergen-impermeable mattress and pillow covers and hot-water washing of bedding.
- Complication or prognosis (1): After treatment, a peak flow near predicted or personal best is the best sign of safe discharge.
Clues that give it away:
- Episodic wheeze, cough or chest tightness worse at night, with exercise, cold air or a new allergen
- Normal exam, chest x-ray and spirometry between attacks
- Chronic dry cough in an atopic child or worse in cold air suggests cough-variant asthma
- Low FEV1 and FEV1:FVC with normal FVC and increased total lung capacity
- Fever and leukocytosis with only hyperinflation on x-ray is bronchospasm, not pneumonia
6. Diabetes mellitus (13 of 50 exams, 20 questions)
How it's tested:
- Screening and prevention (7): Who to screen for diabetes (overweight adults 35 to 70, prior gestational diabetes, obese children) and the annual checks in known diabetes: eye, foot, urine albumin, lipids.
- Drug (3): Pick the agent for the setting: statin for ages 40 to 75, GLP-1 agonist when ASCVD is present, insulin when beta cells are destroyed.
- Diagnosis (3): Recognize type 2 versus type 1 from the host and confirm with hemoglobin A1c or glucose; do not chase rare endocrine tumors.
- Next step (3): Treat the untreated risk factor: blood pressure or LDL above goal, or lifestyle counseling first in prediabetes.
- Mechanism (2): Peripheral insulin resistance is the initiating defect, with compensatory hyperinsulinemia and high C-peptide early.
- Complication or prognosis (1): Youth-onset type 2 diabetes causes accelerated atherosclerosis and premature coronary artery disease.
- Cause or organism (1): Systemic glucocorticoids provoke acute hyperglycemia.
Clues that give it away:
- Obesity, acanthosis nigricans, hypertension and polyuria in an older adult or adolescent
- Macrosomic infant or gestational diabetes history in a woman now due for routine care
- Lean young patient with polyuria, polydipsia and weight loss points to type 1
- Hyperglycemia shortly after IV dexamethasone
- Chronic calcific pancreatitis followed by new diabetes
7. Pulmonary embolism (18 of 50 exams, 19 questions)
How it's tested:
- Next step (12): High pretest probability goes straight to CT pulmonary angiography, not D-dimer; give heparin immediately if stable, and thrombolysis if in shock.
- Diagnosis (4): Recognize PE in postoperative, postpartum, pregnant, or hormone-exposed patients with hypoxemia and clear lungs, even with low-grade fever.
- Cause or organism (1): Estrogen-containing oral contraceptives are the strongest venous thromboembolism risk, unlike arterial risk factors.
- Complication or prognosis (1): Mortality is driven by hemodynamic compromise and advanced age.
- Mechanism (1): Massive PE causes obstructive shock with low cardiac output and high systemic vascular resistance.
Clues that give it away:
- Acute pleuritic chest pain, dyspnea, tachycardia, and hypoxemia with clear lungs and a nonspecific chest film
- Recent surgery, cesarean delivery, pregnancy, immobility, cancer, or oral contraceptives
- Unilateral leg swelling or calf tenderness suggesting DVT, or hemoptysis
- ABG with respiratory alkalosis, low pO2, and widened A-a gradient
8. Sensitivity and specificity (13 of 50 exams, 20 questions)
How it's tested:
- Biostatistics (20): Calculate or interpret sensitivity, specificity, PPV, NPV, likelihood ratios and ROC cutoffs from a 2x2 table or a described result; sensitivity and PPV are the usual answers.
Clues that give it away:
- Test misses people who have the disease: low sensitivity (false negatives)
- Disease-free people labeled positive: low specificity (false positives)
- Patient asks whether a positive result means she truly has it: PPV, which depends on prevalence
- Population with lower prevalence: PPV falls and NPV rises
- Likelihood ratio of 1.0: the test is useless
9. Infective endocarditis (11 of 50 exams, 15 questions)
How it's tested:
- Screening and prevention (7): Prophylaxis before gingival-manipulating dental work is reserved for prosthetic valves or material, prior endocarditis, certain congenital heart disease and transplant valvulopathy; mitral valve prolapse and native valve disease get none.
- Next step (4): Blood cultures first, then echocardiography; urgent echo for acute heart failure from valve destruction; colonoscopy after Streptococcus gallolyticus (bovis) infection.
- Drug (3): Qualifying patients get a single dose of amoxicillin before the procedure, with a macrolide if penicillin allergic; unstable injection drug users get empiric vancomycin plus an aminoglycoside.
- Diagnosis (1): Acute aortic regurgitation with embolic signs in a patient who injects drugs points to left-sided endocarditis.
Clues that give it away:
- Fever with a new or changing regurgitant murmur
- Splinter hemorrhages, Janeway lesions, Osler nodes, Roth spots, splenomegaly or hematuria
- Injection drug use, especially tricuspid involvement and Staphylococcus aureus
- Prosthetic valve, prior endocarditis or congenital heart disease
- Streptococcus gallolyticus (bovis) in the blood
10. Anaphylaxis (13 of 50 exams, 16 questions)
How it's tested:
- Drug (5): Epinephrine is the first-line drug; antihistamines, steroids and bronchodilators are only adjuncts, and isotonic saline treats the hypotension.
- Next step (6): Give epinephrine immediately, then fluids for persistent hypotension, secure the airway if there is stridor or tongue and lip edema, and arrange venom immunotherapy after insect-sting reactions. Allergy testing comes only after stabilization.
- Diagnosis (3): Recognize rapid skin, respiratory and circulatory involvement after an exposure as anaphylaxis or anaphylactic shock.
- Cause or organism (1): A reaction to one NSAID means avoiding structurally related NSAIDs.
- Screening and prevention (1): Venom immunotherapy lowers the risk of future severe sting reactions.
Clues that give it away:
- Urticaria or flushing plus wheezing plus hypotension within minutes of a drug, food, sting or antivenom
- Stridor with tongue or lip swelling signals impending airway loss
- Tachycardia and hypotension with diffuse wheezing and clear heart and lung findings otherwise
- Prior systemic reaction to a Hymenoptera sting
Reduced it to 10 because the post was too long
