A monoclonal antibody-based enzyme-linked immunosorbent assay (antigen elisa) developed for detection of trypanosome antigens in the serum and cerebrospinal fluid (CSF) of patients as a means for diagnosis of Trypanosoma brucei gambiense sleeping sickness was evaluated at the Bureau Central de la Trypanosomiase, Kinshasa, Zaire. Sixty-nine (89·6%) of 77 parasitologically confirmed cases examined at the Daloa clinic had antigens in serum; 35 (45·5%) had antigens in CSF and, in 4 of these, the antigens were detected in CSF only. Taking the serum and CSF results together, 73 (94·8%) of the 77 patients were positive in the assay. In the Kinshasa series, 168 (89·4%) of 188 parasitologically confirmed cases were positive by antigen elisa. The controls, who included 165 blood donors and 40 patients with malaria, 2 with hydatidosis and 12 with leishmaniasis, were negative by antigen elisa. Analysis of CSF results for 35 patients who had antigens in CSF revealed that 34 (97·1%) had elevated CSF white cell counts, 29 (82·9%) had elevated protein levels, and 23 (65·7%) had trypanosomes in their CSF. Moreover, analysis of results for 34 patients whose CSF had been shown to harbour trypanosomes by the double centrifugation technique showed that 24 (70·6%) had antigens in CSF, 28 (82·6%) had elevated protein levels, and 33 (97·1%) had elevated CSF white cell counts. Antigens were rapidly cleared from peripheral circulation following institution of treatment. Antigen clearance was accompanied by a rapid fall in CSF protein levels and white cell counts. These results demonstrate the potential of antigen elisa, not only as a tool for diagnosis, but also for clinical staging and treatment follow-up of patients with T. b. gambiense sleeping sickness.

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