JMC Human Medicine Exam common mistakes
JMC Human Medicine Exam · Understand the traps and how to avoid them.
When asked to trace a nerve or vessel through a limb or the neck, the candidate names the structures in the correct order but attaches each to the wrong neighbouring landmark (e.g., describing the axillary artery's parts by the wrong muscle, or placing the median nerve medial to the axillary artery throughout).
Candidates memorise the sequence of structures as a list and never anchor each item to a bony or muscular landmark, so under exam pressure the list survives but the spatial relationships collapse. Surface anatomy is under-practised relative to written facts.
What to do instead
For every relation you learn, force a two-point link: structure plus a named landmark ("axillary artery part 1 lies medial to pectoralis minor"). Redraw each region from a blank outline three times, labelling only landmarks first, then adding nerves and vessels. Test yourself by asking "what is immediately lateral/medial/anterior to X?" rather than reciting lists.
On acid-base and respiratory physiology items, the candidate calculates a value correctly but then interprets it using the wrong reference range or forgets to check compensation, concluding 'normal' when a mixed disorder is present.
Formulas are memorised in isolation from the clinical reasoning step. Candidates also default to the arterial pH range for venous samples or forget that a normal pH can hide a combined metabolic and respiratory derangement.
What to do instead
Adopt a fixed four-step routine for every blood gas: identify the primary disorder from pH and CO2/HCO3, check whether compensation is appropriate (use Winter's formula for metabolic acidosis), calculate the anion gap and delta ratio when a metabolic acidosis exists, then state the final combined diagnosis. Practise on 20 gases with mixed disorders until the routine is automatic.
In biochemistry, the candidate answers enzyme-deficiency and pathway questions by recalling the disease name but misplaces the defective step, so they give the wrong accumulating metabolite or the wrong missing product (e.g., confusing the block in phenylketonuria with that in alkaptonuria, or misplacing the rate-limiting enzyme of glycolysis).
Pathways are studied as names of enzymes in order without linking each step to its cofactor, its regulation, and the clinical consequence of its failure. The clinical vignette then triggers a remembered disease label rather than a step-by-step reconstruction.
What to do instead
Rebuild each high-yield pathway (glycolysis, TCA, urea cycle, heme synthesis, glycogen storage) on one page with three columns: enzyme, cofactor/regulated step, and disease plus accumulating metabolite. For each disorder, state the missing product and the resulting laboratory pattern. Rehearse by covering the enzyme column and naming it from the metabolite.
On pathology items the candidate labels a lesion by its morphological pattern (e.g., 'granuloma', 'crescent') without matching it to the mechanism and the clinical context, so they pick a diagnosis that fits the picture but not the stem (e.g., sarcoidosis for a case of tuberculosis, or a non-caseating answer where caseation is described).
Histology is revised as image-recognition and buzzwords, while the causal chain from aetiology to cellular injury to tissue appearance is skipped. Exam stems deliberately include discriminating context that pattern-matching ignores.
What to do instead
For each major pattern, write a short causal chain: cause, mechanism of injury, cell type involved, tissue appearance, and clinical correlate. When answering, underline the discriminating phrase in the stem (caseating vs non-caseating, neutrophil vs lymphocyte infiltrate) before choosing. Build a comparison table of look-alike lesions with the single feature that separates them.
In pharmacology, the candidate selects a drug class that is correct in principle but ignores the patient-specific contraindication or interaction in the stem (e.g., choosing a beta-blocker in a patient with asthma, an NSAID in renal impairment, or a drug that inhibits the enzyme responsible for metabolising a co-prescribed medicine).
Drugs are learned as indication-to-drug pairs, with adverse effects and interactions stored separately. The stem's comorbidity or co-medication is read as background rather than as the deciding constraint.
What to do instead
For every drug you revise, write four lines: mechanism, main indication, absolute contraindication, and clinically important interaction (especially CYP inhibitors/inducers and QT prolongation). Before choosing an option, list the stem's constraints (organ function, pregnancy, age, co-medications) and eliminate any drug that violates one. Practise 'which drug is contraindicated here?' questions as well as 'which drug treats this?'.
On microbiology items, the candidate identifies the organism from the vignette but then picks the wrong diagnostic test, culture medium, or first-line antimicrobial because they conflate similar organisms (e.g., confusing the testing approach for streptococcal vs staphylococcal infection, or the treatment of typical vs atypical pneumonia).
Organisms are learned as a list of features rather than as a decision tree from specimen to stain to culture to treatment. The candidate recognises the name but has not stored which test actually confirms it.
What to do instead
Build organism cards with five fields: Gram stain/morphology, key virulence factor, specimen and confirmatory test, first-line treatment, and classic clinical syndrome. Group organisms by the test that identifies them (e.g., optochin, bile solubility, coagulase, oxidase) so the test becomes the retrieval cue. Revise by starting from the test and naming the organism.
In community medicine, the candidate computes a rate, ratio, or screening measure with the wrong denominator or numerator (e.g., mixing incidence and prevalence, using total population instead of the at-risk group, or miscomputing sensitivity and positive predictive value), or designs a study without stating the comparison group.
Epidemiological formulas are memorised as symbols without a defined population base. Candidates also overlook that predictive value depends on prevalence, and treat study design as a vocabulary list rather than a set of decisions about sampling and comparison.
What to do instead
For every measure, write the numerator and denominator in words before substituting numbers, and state the population at risk explicitly. Work through ten calculations covering incidence, prevalence, relative risk, attributable risk, sensitivity, specificity, and predictive values, then repeat with prevalence changed to see how predictive value moves. For study design, always name the exposure, the outcome, the comparison group, and the timing.
In internal medicine long cases, the candidate jumps from a single striking finding to a diagnosis and then lists investigations without a structured problem list, missing a second active problem or an important comorbidity described in the stem.
Pattern recognition is rewarded in revision and candidates practise single-diagnosis vignettes. Under time pressure, the first plausible diagnosis anchors subsequent reasoning, and the habit of summarising problems before investigating is under-developed.
What to do instead
Use a fixed written structure: problem list, differential with the feature that favours or opposes each option, then investigations grouped as confirmatory, baseline, and to exclude serious alternatives. Deliberately practise multi-problem stems and always ask 'what else is described here?'. Review each answer to confirm every abnormal finding in the stem has been addressed.
In surgery items, the candidate chooses definitive management when the question asks for the immediate next step, or the reverse, and omits resuscitation and investigation sequencing (e.g., selecting laparotomy for a stable patient who needs imaging first, or choosing an operation before fluid resuscitation in a shocked patient).
Management is learned as a final diagnosis-to-operation map, without the staged sequence of resuscitation, investigation, and definitive treatment. Candidates also misread 'next step' as 'best treatment'.
What to do instead
For each acute surgical presentation, write the sequence as numbered stages: resuscitate, investigate, decide, definitive management. Note explicitly which stage the question is asking about by circling the phrase 'next step' or 'definitive'. Include the stability criteria that change the pathway, and revise by covering the stages and reconstructing the order.
In obstetrics and gynaecology, the candidate manages the fetal or maternal problem without first establishing gestational age and maternal stability, or applies a non-pregnant reference range and drug list to a pregnant patient (e.g., ordering an unsafe imaging modality or drug, or misinterpreting a value that is normal in pregnancy).
Obstetric content is studied as separate conditions rather than as a framework in which gestational age and maternal condition determine every subsequent decision. Pregnancy-specific physiology and safe-medication lists are under-revised.
What to do instead
Begin every obstetric answer by stating gestational age, maternal stability, and fetal status, then reason from there. Keep a one-page list of physiological changes in pregnancy with their effect on common laboratory values, and a list of drugs and investigations that are safe versus avoided in pregnancy. Apply this framework to ten stems until it becomes the first step.
In paediatrics, the candidate assesses a child using adult thresholds and adult drug dosing, or omits weight-based calculation and age-specific normal ranges (e.g., calling a respiratory rate normal that is tachypnoea for the child's age, or missing dehydration percentage because adult vital-sign cut-offs are used).
Adult medicine is revised more heavily, and paediatric normal values vary by age band, so adult defaults are applied unconsciously. Candidates also treat children as small adults rather than as a group with different physiology and dosing.
What to do instead
Memorise age-banded normal ranges for respiratory rate, heart rate, and blood pressure, plus the weight-based dosing formula for emergency drugs. In every paediatric stem, state the child's age and weight first, classify the findings against the age-appropriate range, and grade dehydration and severity explicitly before choosing management.