Design: Systematic review of 96 studies, 35 with genotype-linked clearance or ring-stage survival data
Population: Plasmodium falciparum infections across southeast Asia and Africa
Primary outcome: Parasite clearance half-life and ring-stage survival by kelch13 genotype, compared between continents
Effect: Southeast Asia: canonical kelch13 mutations showed prolonged clearance concordant with raised ring-stage survival. East Africa and the Horn of Africa: independently emergent kelch13 mutations generally cleared faster despite raised ring-stage survival

Artemisinin partial resistance is defined for surveillance by how long parasites take to clear after treatment — a threshold set from southeast Asian data, where kelch13 mutations reliably produce slow clearance. This review, published in May 2026, examined 96 studies across southeast Asia and Africa, 35 of which linked genotype to parasite clearance half-life or to ring-stage survival assay results.

The two continents behaved differently. In southeast Asia the expected pattern held: canonical kelch13 mutations gave prolonged clearance half-lives, closely concordant with ring-stage survival. In east Africa and the Horn of Africa, kelch13 mutations that emerged independently generally showed faster clearance kinetics despite raised ring-stage survival — the laboratory marker of resistance was up while the clinical marker used for surveillance was not.

If that holds, surveillance built on clearance half-life alone will keep reporting African settings as sensitive while resistance spreads, exactly as happened in the Greater Mekong Subregion before the mutation became fixed. The authors call for region-specific criteria combining clearance half-life, ring-stage survival, molecular markers and partner-drug susceptibility. For clinicians the message is narrower but worth holding: treatment failure in an imported or local falciparum case should not be dismissed because national surveillance reports no resistance.

Take a persistently parasitaemic patient after a full artemisinin combination course seriously and report it
Send molecular typing where available rather than relying on clearance time alone
Note that the partner drug matters as much as the artemisinin in combination failure
Read national resistance surveillance as a lower bound, not a clean bill of health
Keep day 3 parasitaemia in the record — it is the surveillance signal

Why it matters

A surveillance definition that under-detects resistance does not just delay the response; it produces reassurance while the problem fixes itself in the population.

The statistics, in plain English

This is a narrative synthesis of heterogeneous studies rather than a pooled estimate, so there is no single effect size to quote and none should be invented. The important comparison is not between numbers but between two markers of the same thing: ring-stage survival, measured in the laboratory, and clearance half-life, measured in the patient. Where those two disagree, the one used for surveillance decides what gets reported.