Accuracy of a rapid immunochromatographic card test for Plasmodium falciparum in a malaria control programme in South Africa

The Lowveld Region of Mpumalanga Province, South Africa, nestles between Mozambique in the east and Swaziland in the south. The predominantly non-immune population, of approximately 850 000 inhabitants, is at risk of seasonal malaria. Plasmodium falciparum infection accounts for more than 90% of all malaria cases diagnosed in the area (ANONYMOUS, 1996). A corner-stone of the World Health Organization (WHO) global malaria control strategy is prompt diagnosis of malaria so that effective therapy can be initiated without delay (WHO, 1993). Malaria treatment is usually initiated in Mpumalanga Province only after detection of malaria parasites in the peripheral blood, as other rickettsial and viral febrile illnesses mimic malaria in the area. The Mpumalanga Province Malaria Control Programme has relied on light microscopy of Giemsastained thick blood films (GTF) at 4 large laboratories located on the fringe of the malarious area for malaria diagnosis. However, a recent random sample of 42% (30/72) of Lowveld clinics found that only 20 were still preparing thick blood films and, of these, only 3 (15%) received results within 24 h (DURRHEIM et al., 1997a). Three clinics (15%) received their patients' GTF results after a week, 3 (15%) waited for 2 weeks or longer, and the remaining 11 clinics (55%) reported never receiving results of the blood films they submitted. Even more perplexing were the discordant GTF results from the 4 laboratories responsible for examining the majority of malaria blood films in the Province (DURRHEIM et al., 1997b). The summary Kappa value of 0.11 (95% confidence interval [95% CI] 0-0.23) found signified minimal agreement beyond the chance level among participating laboratories (LANDIS & KOCH, 1977). These disturbing findings and the prediction of an impending large-scale malaria epidemic in 1996 provided the impetus for the introduction of a rapid immunochromatographic card test (ICT) for P. falciparum diagnosis at all clinics in the Lowveld Region early in 1996.