RESUMO
Confirmatory diagnosis of African trypanosomiasis relies on demonstration of parasites in body fluids by bright field microscopy. The parasitaemia in infected patients and animals is usually low, and concentration methods are used to try and increase the chances of seeing parasites. Recently, fluorescence microscopes using light-emitting diodes (LED) have been developed. Since they emit strong light, their use does not require a dark room, making field application a possibility. We have combined LED fluorescence microscopy with lysis of red blood cells (RBC) to improve the sensitivity and speed of detecting trypanosomes. In studies conducted at four centers in Uganda and the Democratic Republic of the Congo, parasitaemic blood was serially diluted and the RBCs lysed using commercial buffer. Samples were then concentrated by centrifugation, and different volumes of the sediment used to make thin and thick smears. Next, these were stained with acridine orange or Giemsa, and examined using an LED microscope under fluorescence or bright light, respectively. Detection of parasites was significantly improved by RBC lysis and concentration, regardless of the staining and microscopy method used. Further improvements were made when smears were prepared using larger volumes of sediment. The best results were obtained with thin smears prepared using 20 µl of sediment and stained with acridine orange. The time taken to see the first parasite was dramatically reduced when smears were examined by LED fluorescence microscopy, compared to bright light. LED fluorescence microscopy was found to be easier and requiring less visual effort than bright field microscopy. These studies demonstrate the potential for incremental improvement in detection of Trypanosoma brucei by combining LED fluorescence microscopy with RBC lysis and concentration. The lysis and concentration method may also be useful in sample preparation for other diagnostic tests for trypanosomiasis.