A diagnostic accuracy study to evaluate standard rapid diagnostic test (RDT) alone to safely rule out imported malaria in children presenting to UK emergency departments.

BACKGROUND: Microscopy is the gold standard for malaria diagnosis but is dependent on trained personnel. Rapid diagnostic tests (RDT) form the mainstay of diagnosis in endemic areas without access to high quality microscopy. We aimed to evaluate whether RDT alone could rule out imported malaria in children presenting to UK Emergency Departments (EDs).

METHODS: UK-based, multi-centre, retrospective, diagnostic accuracy study. Included: any child <16 years presenting to ED with history of fever and travel to a malaria-endemic country, between 01/01/2016 and 31/12/2017. Diagnosis: microscopy for malarial parasites (clinical reference standard) and RDT (index test). UK Health Research Authority approval: 20/HRA/1341.

RESULTS: There were 47 cases of malaria out of 1,414 eligible cases (prevalence 3·3%) in a cohort of children whose median age was 4 years (IQR 2-9), of whom 43% were female. Cases of Plasmodium falciparum totalled 36 (77%, prevalence 2·5% ).The sensitivity of RDT alone to detect malaria infection due to any Plasmodium species was 93·6% (95% CI 82·5% to 98·7%), specificity 99·4% (95% CI 98·9% to 99·7%), positive predictive value 84·6% (95% CI 71·9% to 93·1%) and negative predictive value 99·8% (95% CI 99·4% to 100·0%). Sensitivity of RDT to detect P. falciparum infection was 100% (90·3% to 100%), specificity 98·8% (98·1% to 99·3%), positive predictive value 69·2% (54·9% to 81·2%, n=46/52) and negative predictive value 100% (99·7% to 100%, n=1362/1362).

CONCLUSIONS: RDTs were 100% sensitive in detecting P. falciparum malaria. However, lower sensitivity for other malaria species and the rise of pfhrp2 and pfhrp3 (pfhrp2/3) gene deletions in the P. falciparum parasite mandate the continued use of microscopy for diagnosing malaria.