Low specificities of HIV diagnostic tests caused by Trypanosoma brucei gambiense sleeping sickness

BACKGROUND: Accuracy of HIV diagnostic tests in tropical infections is poorly documented. Human African trypanosomiasis (HAT) is characterized by a polyclonal B-cell activation, constituting a risk for false positive reactions in diagnostic tests, including HIV tests. METHODS: A retrospective HIV diagnostic test accuracy study was performed on 360 human African trypanosomiasis (HAT) patients infected with T.b. gambiense before treatment, and 163 patients 2 years after successful treatment in Mbuji Mayi, East Kasai, DR Congo. Sensitivity, specificity and positive predictive value (PPV) of individual tests and algorithms consisting of 3 rapid tests were determined. RESULTS: Sensitivity for all tests was 100% (11/11). Low specificity (96.3%, 335/348) and PPV (45.8%, 11/24) of a classical seroconfirmation strategy (Vironostika ELISA followed by Line Immunoassay) complicated determination of the HIV status, which had to be determined by PCR. Specificities of rapid diagnostic tests were 39.1% for Determine (136/348), 85.3-92.8% (297/348-323/348) for VIKIA, Immunoflow, Doublecheck and Bioline, and 96.6-98.3% (336/348-342/348) for UniGold, Oraquick and STAT-PAK. Specificity for Vironostika was 67.5% (235/348). PPVs ranged between 4.9 and 64.7%. Combining 3 different rapid tests resulted in specificities of 98.3-100% (342-348/348) and PPVs of 64.7-100% (11/17-11/11). In cured HAT patients, specificities were significantly higher for Vironostika, Determine, Unigold and Immunoflow. CONCLUSIONS: T.b. gambiense infection decreases the specificity of antibody detection tests for HIV diagnosis. Unless tests have been validated for interference with HAT, HIV diagnosis in untreated HAT using classical algorithms should be avoided. Specific, validated combinations of 3 HIV rapid tests can increase specificity