POST TREATMENT SENSITIVITY STUDIES WITH THE PARASIGHT(R)-F TEST FOR MALARIA DIAGNOSIS IN ZIMBABWE

The post-treatment diagnostic performance of the Plasmodium frrlcipnil rin histidine-rich protein (HRP-II) antigen detection test, ParaSight( R)-F test, was assessed on 55 falciparum malaria cases treated with ch loroquine during in vivo drug sensitivity studies. The post-treatment sensitivity of the test remained high, except for an insignificant dec line on day 1. However specificity dropped sharply by day 1, subsequen tly increasing linearly with time to satisfactory values by day 10. As expected, from its inverse relationship to specificity, the false pos itive rate was high on day 1 and decreased linearly to low level by da y 10. The temporary increase in false positive rate following treatmen t was due to persistent parasite antigen, rather than subpatent parasi taemia. Thus findings showed that positive readings by the test within 10 days post-treatment may occur in cured cases and will not necessar ily imply treatment failure. Furthermore, it will be important to rake patient antimalarial history into consideration during routine usage of the test for malaria diagnosis. The trend of Youden's J-index for t he ParaSight(R)-F test showed that from 10 days post-treatment, the te st was generally reliable, with positive readings indicating active in fection. Tt was concluded that the ParaSight(R)-F test was not only va luable at confirming malaria diagnosis on clinical cases in seasonal t ransmission areas, but had potential for application to detect recrude scent infections within 2 weeks of chloroquine treatment. (C) 1997 Els evier Science B.V.