Delayed malaria diagnosis — DTM&H MCQ

Correct answer: B — Failure to request thick film examination and repeat films at 12-24 hour intervals

The correct answer is B, failure to request thick film examination and repeat films at 12 to 24 hour intervals. A single negative blood film never excludes malaria because early parasitaemia can be cyclical, low-level, or sequestered, so falciparum infection can be missed on the first film even by a competent microscopist. UK guidance is explicit that where malaria is suspected, blood films should be examined daily (with repeats typically at 12 to 24 hour intervals) for three days before the diagnosis is stood down, and expert advice sought if suspicion remains despite three negative films. This patient was discharged after only one negative film and re-presented deteriorating with a 9% parasitaemia, cerebral involvement (confusion) and jaundice, features of severe falciparum malaria that could have been caught earlier had serial films been mandated as per protocol. The error was therefore diagnostic follow-up, not the initial film-negative result itself, which is an accepted and expected occurrence. Why the other options are wrong: D. Failure to prescribe empirical antimalarials at first presentation: empirical treatment without parasitological confirmation is not standard UK practice and is only considered in convincing exposure history with severe features after expert advice, not simply because a first film is negative. C. Failure to perform a rapid diagnostic test before discharge: RDTs are a useful adjunct alongside microscopy but are not a substitute for it in UK practice, so omitting one is not the defining error when serial films were never arranged. A. Failure to admit for observation regardless of the initial film result: admission is not mandated purely because of travel history if the patient is clinically well; the failing was not arranging follow-up testing, not the discharge decision per se. E. Failure to prescribe chemoprophylaxis post-travel: this is irrelevant retrospectively once the patient is already unwell with an acute illness; prophylaxis errors relate to pre-travel advice, not to management of an established febrile presentation. Key point: one negative blood film never excludes malaria; UK protocol requires repeat thick and thin films at 12 to 24 hour intervals (to a total of three) before the diagnosis can be safely discounted.

Reference: GOV.UK, Malaria prevention guidelines for travellers from the UK 2026, Diagnosis section (UK Malaria Expert Advisory Group, UKHSA): 'Where malaria is suspected, blood films should be examined daily for 3 days while other diagnoses are also considered' and 'RDTs are not a substitute for microscopy in UK practice.' https://www.gov.uk/government/publications/malaria-prevention-guidelines-for-travellers-from-the-uk-2026/diagnosis