Passive surveillance of human African trypanosomiasis in Côte d'Ivoire: Understanding prevalence, clinical symptoms and signs, and diagnostic test characteristics

Background Little is known about the diagnostic performance of rapid diagnostic tests (RDTs) for passive screening of human African trypanosomiasis (HAT) in Côte d’Ivoire. We determined HAT prevalence among clinical suspects, identified clinical symptoms and signs associated with HAT RDT positivity, and assessed the diagnostic tests’ specificity, positive predictive value and agreement. Methods Clinical suspects were screened with SD Bioline HAT, HAT Sero-K-Set and rHAT Sero-Strip. Seropositives were parasitologically examined, and their dried blood spots tested in trypanolysis, ELISA/Tbg, m18S-qPCR and LAMP. The HAT prevalence in the study population was calculated based on RDT positivity followed by parasitological confirmation. The association between clinical symptoms and signs and RDT positivity was determined using multivariable logistic regression. The tests’ Positive Predictive Value (PPV), specificity and agreement were determined. Results Over 29 months, 3433 clinical suspects were tested. The RDT positivity rate was 2.83%, HAT prevalence 0.06%. Individuals with sleep disturbances (p
Author summary As human African trypanosomiasis (HAT) or sleeping sickness is approaching elimination, case management is progressively transferred from specialized teams to front line health care centres. This approach raises practical questions. What clinical symptoms and signs should trigger HAT testing? What rapid diagnostic tests (RDT) are suitable for screening? Which unconfirmed serological suspects should be examined further? During this study conducted in Côte d’Ivoire, individuals with sleep disturbances, motor disorders, convulsions, severe weight loss, or psychiatric problems were more often positive in RDTs. These symptoms and signs should trigger referral for HAT screening. Our results confirm appropriateness of the existing HAT screening strategy with SD Bioline HAT or HAT Sero-K-Set having specificities of 97.8% and 98.9%. Subsequent tests on dried blood spots from RDT positives were 93.3% to 98.9% specific, and increased the positive predictive value from below 15% up to 67%. For selection of RDT seropositives for additional parasitological examinations, trypanolysis on dried blood spots is suitable, but could be replaced by ELISA, which can be performed locally. The optimal diagnostic test algorithm for Côte d’Ivoire, in terms of cost-effectiveness, remains to be determined.