Plasmodium vivax relapse prevention — DTM&H MCQ

Instant feedback + full explanation. One question, done properly.

ModerateMalariaPlasmodium vivax relapse preventionDTM&H

A 28-year-old aid worker returns from Ethiopia with fever every 48 hours and mild thrombocytopenia. A thin film identifies Plasmodium vivax and he improves after chloroquine-sensitive blood-stage treatment, but he has not had G6PD testing. What is the most appropriate next step to prevent relapse?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Check G6PD status before giving primaquine radical cure

The correct answer is B, check G6PD status before giving primaquine radical cure. Plasmodium vivax forms dormant liver-stage hypnozoites that survive standard blood-stage chloroquine treatment and cause relapse in over a quarter of patients if untreated; primaquine is the only currently effective drug for hypnozoite eradication, but it is an oxidant drug that can precipitate severe haemolysis in G6PD-deficient individuals. UK guidance therefore mandates measuring G6PD activity before starting primaquine so that dosing and monitoring (or an alternative weekly regimen) can be tailored to the patient's enzyme status. This sequencing, acute blood-stage cure first, then G6PD-guided radical cure, is the accepted safe pathway and the discriminating teaching point of this stem. Why the other options are wrong: A. Give primaquine immediately without enzyme testing: this risks acute intravascular haemolysis and severe anaemia in an undiagnosed G6PD-deficient patient, which is precisely what guidelines warn against. D. Repeat chloroquine monthly for 6 months: chloroquine is a blood-stage schizonticide only and has no activity against liver hypnozoites, so repeated dosing cannot prevent relapse. E. Use doxycycline as radical cure: doxycycline has no hypnozoiticidal activity and is not used for radical cure of vivax or ovale malaria. C. Give mefloquine after the acute episode: mefloquine is another blood-stage agent with no liver-stage activity, so it does not address the hypnozoite reservoir causing relapse. Key point: In P. vivax or P. ovale malaria, G6PD status must be checked before primaquine radical cure because primaquine is the only hypnozoiticidal drug but carries a real risk of severe haemolysis in G6PD deficiency.

Reference: Lalloo DG, Shingadia D, Bell DJ, et al. UK malaria treatment guidelines 2016. Journal of Infection 2016;72(6):635-649 (statements 19-21 on G6PD testing and primaquine radical cure). https://www.journalofinfection.com/article/S0163-4453(16)00047-5/fulltext