Comparison of three antigen detection methods for diagnosis and therapeutic monitoring of malaria: a field study from southern Vietnam
Huong, N.Mai.; Davis, T.M.E.; Hewitt, S.; Huong, N.Van.; Uyen, T.Thi.; Nhan, D.Hanh.; Cong, L.Dinh.
Tropical Medicine and International Health Tm and Ih 7(4): 304-308
2002
ISSN/ISBN: 1360-2276 PMID: 11952945 DOI: 10.1046/j.1365-3156.2002.00869.xDocument Number: 242237
OBJECTIVES: To compare the sensitivity, specificity and post-treatment persistence of three commonly used rapid antigen detection methods. METHOD: We studied 252 Vietnamese patients aged from 4 to 60 years, 157 with falciparum and 95 with vivax malaria and 160 healthy volunteers. An initial blood sample was taken for microscopy, and OptiMAL(R), immunochromatographic test (ICT) malaria P.f./P.v.(R) and Paracheck-Pf(R) tests. Patients with falciparum malaria were treated with an artesunate-based combination regimen and those with vivax malaria received chloroquine. Eighty-seven patients with falciparum malaria who were initially positive for one of the antigen tests and who remained blood smear-negative underwent follow-up testing over 28 days. RESULTS: Paracheck-Pf(R) was the most sensitive test for Plasmodium falciparum (95.8% vs. 82.6% for ICT malaria P.f./P.v.(R) and 49.7% for OptiMAL(R)). Specificities were all 100%. For vivax malaria, OptiMAL(R) performed better than ICT malaria P.f./P.v.(R) (sensitivities 73.7% and 20.0%, respectively), with 100% specificity in both cases. All tests had low sensitivities (ltoreq75.0%) at parasitaemias <1000/mul regardless of malaria species. During follow-up, Paracheck-Pf(R) remained positive in the greatest proportion of patients, especially at higher parasitaemias (>10 000/mul). Residual OptiMAL(R) positivity occurred only in a relatively small proportion of patients (<10%) with parasitaemias >10 000/mul during the first 2 weeks after treatment. CONCLUSIONS: Although microscopy remains the gold standard for malaria diagnosis, Paracheck-Pf(R) may prove a useful adjunctive test in uncomplicated falciparum malaria in southern Vietnam. OptiMAL(R) had the lowest sensitivity for P. falciparum but it might have a use in the diagnosis of vivax malaria and perhaps to monitor efficacy of treatment for falciparum malaria where microscopy is unavailable.