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

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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.