ABPS Internal Medicine common mistakes
ABPS Internal Medicine · Understand the traps and how to avoid them.
Committing to a non-cardiac cause of chest pain after a single normal troponin and a non-diagnostic ECG in a woman, an older adult, or a patient with diabetes, then discharging without serial troponins or any provocative testing.
Candidates carry textbook templates built on classic male presentations; once the history looks 'atypical' the mind anchors early and stops looking for ischemia. Time pressure reinforces the first plausible label.
What to do instead
Document a structured risk score (for example a HEART score) before any disposition decision, require serial high-sensitivity troponins at the protocol intervals, and write down the specific alternative diagnosis plus the follow-up plan that makes the discharge safe.
Reading an arterial blood gas as a single primary disorder, missing a mixed acid-base picture, and accepting a low PaO2 as 'hypoxia' without calculating the alveolar-arterial gradient or the expected respiratory compensation.
Under time pressure candidates stop at the first plausible label instead of running the arithmetic; the formulas are learned but rarely rehearsed under exam timing.
What to do instead
Use a fixed sequence every time: pH, then PaCO2, then the expected compensation (Winter's formula for metabolic acidosis, expected PaCO2 rise for metabolic alkalosis), then the A-a gradient and delta ratio before selecting an answer.
Starting levothyroxine because a panel drawn during acute illness shows a low free T4 with a low or normal TSH, or treating an isolated low free T3.
Nonthyroidal illness produces a laboratory pattern that mimics central hypothyroidism, and candidates do not account for how illness and recovery distort TSH over weeks.
What to do instead
In the hospitalized patient, treat the illness and repeat TSH with free T4 six to eight weeks after recovery; only commit to replacement when a confirmed TSH elevation pairs with a low free T4, or when central hypothyroidism is documented with pituitary imaging and other pituitary axes.
Escalating to broad-spectrum antibiotics and then continuing the full planned course without review, treating asymptomatic bacteriuria, or never obtaining cultures before the first dose.
Fear of undertreatment plus ambiguous duration guidance pushes candidates toward maximum coverage; de-escalation is not reinforced in the way escalation is.
What to do instead
Draw cultures before antibiotics, schedule an explicit 48-to-72-hour antibiotic time-out, match duration to the syndrome (shorter courses for uncomplicated cystitis and community-acquired pneumonia), and do not treat pyuria without symptoms in the absence of pregnancy or instrumentation.
Labeling acute kidney injury as prerenal purely from a blood urea nitrogen to creatinine ratio above 20, giving fluids, and never reassessing; or interpreting a fractional excretion of sodium in a patient who is already on diuretics.
The ratio heuristic is taught as a shortcut and is easy to apply under exam conditions, and the caveats about diuretics, chronic kidney disease, and contrast are forgotten.
What to do instead
Combine urine microscopy, bedside volume assessment, and response of creatinine and urine output to a fluid challenge; when diuretics are on board, use the fractional excretion of urea rather than sodium, and reassess rather than assume.
Attributing a falling platelet count in a hospitalized patient on heparin to chemotherapy, sepsis, or dilution without calculating a 4T score or considering heparin-induced thrombocytopenia.
Heparin-induced thrombocytopenia is rare, so it is unconsciously down-weighted against common causes, and the paradox that thrombosis accompanies the low platelets is easily overlooked.
What to do instead
On any platelet drop of roughly 50 percent or any new thrombosis appearing five to ten days after heparin exposure, calculate the 4T score, stop heparin pending results if the score is intermediate or high, and send PF4 antibodies rather than waiting for the count to recover.
Applying the same A1c and blood pressure targets used for middle-aged adults to a frail 85-year-old with falls, and adding new medications before reviewing the existing list for deprescribing.
Guideline targets come from trials that exclude frail elderly patients; candidates study one disease at a time and never weigh competing mortality, fall risk, and treatment burden.
What to do instead
Set individualized targets (for example A1c around 7.5 to 8.5 percent in limited life expectancy, relaxed blood pressure when orthostasis is present), screen the medication list against explicit criteria for potentially inappropriate drugs, and document goals of care in the plan.
Ordering an antinuclear antibody test as a screen for nonspecific fatigue or vague arthralgia and then diagnosing systemic lupus erythematosus from a low-titer positive result without clinical criteria.
The antinuclear antibody is sensitive but not specific, so a positive result in a low-probability patient feels confirmatory; candidates confuse a sensitive test with a diagnostic one.
What to do instead
Estimate pretest probability first, then require a compatible clinical picture plus classification criteria and specific antibodies (double-stranded DNA, Smith, complement consumption) before making the diagnosis; a positive antinuclear antibody alone is not a disease.
Excluding stroke after a negative non-contrast head CT in a patient with acute vertigo, diplopia, dysarthria, or ataxia and sending them home with a vestibular label.
A negative imaging result feels definitive, and the posterior fossa is exactly the region where early CT is least sensitive; vertigo is also the most common stroke mimic in either direction.
What to do instead
Treat the presentation as time-critical: document onset, perform the HINTS oculomotor exam and truncal ataxia testing, and pursue MRI with diffusion weighting or vascular imaging when suspicion persists despite a negative CT.
Accepting a new psychiatric label such as anxiety, agitation, or noncompliance in a patient with an acute behavioral change without screening for delirium, substance withdrawal, hypoglycemia, hypoxia, or a new medication effect.
Psychiatric framing is fast and satisfying, and delirium is missed in a large fraction of cases because it fluctuates and can look like a mood or personality problem.
What to do instead
Before recording a psychiatric diagnosis, apply a delirium screen (for example the confusion assessment method), check glucose, pulse oximetry, and vital signs, review recent medication changes, and use a withdrawal scale when alcohol or sedative use is possible.