Diagnosis of malaria in the field by fluorescence microscopy of QBC ® capillary tubes

Abstract

The diagnostic performance of commercial capillary tubes containing acridine orange dye (QBC ®) was compared with the standard diagnosis of malaria by microscopical examination of Giemsa-stained thick blood films (GTS) in remote field conditions. The comparison was conducted among 165 volunteers living in north-eastern Irian Jaya, Indonesia, an area having hyperendemic malaria transmission. By GTS, 65 volunteers were positive for malaria, but only 49 were judged positive by QBC ®. Among the 100 blood films found negative by GTS, 5 were considered positive by QBC ®. Thus, relative to a GTS standard, the sensitivity and specificity of the QBC ® was 75% and 95%, respectively. The mean limit of detection for the QBC ® was approximately 60 parasites per μl blood, whereas the limit of detection for GTS was 20 parasites per μl blood. Also, a number of practical difficulties were encountered using the QBC ® at the field site. The QBC ® approach to diagnosis of malaria was less sensitive and more inconvenient than GTS under the conditions in remote Irian Jaya.