Diagnostic Accuracy of Loopamp Trypanosoma brucei Detection Kit for Diagnosis of Human African Trypanosomiasis in Clinical Samples

Abstract

Molecular methods have great potential for sensitive parasite detection in the diagnosis of human African trypanosomiasis (HAT), but the requirements in terms of laboratory infrastructure limit their use to reference centres. A recently developed assay detects the Trypanozoon repetitive insertion mobile element (RIME) DNA under isothermal amplification conditions and has been transformed into a ready-to-use kit format, the Loopamp Trypanosoma brucei. In this study, we have evaluated the diagnostic performance of the Loopamp Trypanosoma brucei assay (hereafter called LAMP) in confirmed T.b. gambiense HAT patients, HAT suspects and healthy endemic controls from the Democratic Republic of the Congo (DRC). 142 T.b. gambiense HAT patients, 111 healthy endemic controls and 97 HAT suspects with unconfirmed status were included in this retrospective evaluation. Reference standard tests were parasite detection in blood, lymph or cerebrospinal fluid. Archived DNA from blood of all study participants was analysed in duplicate with LAMP. Sensitivity of LAMP in parasitologically confirmed cases was 87.3% (95% CI 80.9–91.8%) in the first run and 93.0% (95% CI 87.5–96.1%) in the second run. Specificity in healthy controls was 92.8% (95% CI 86.4–96.3%) in the first run and 96.4% (95% CI 91.1–98.6%) in the second run. Reproducibility was excellent with a kappa value of 0.81. In this laboratory-based study, the Loopamp Trypanosoma brucei Detection Kit showed good diagnostic accuracy and excellent reproducibility. Further studies are needed to assess the feasibility of its routine use for diagnosis of HAT under field conditions. Diagnosis and effective treatment are cornerstones in the control of human African trypanosomiasis (HAT). Molecular tools such as the polymerase chain reaction (PCR) detect the parasite's DNA and are generally very sensitive and specific. However, PCR is not applicable in field settings because it requires a laboratory infrastructure and sophisticated equipment. A recently developed loop-mediated isothermal amplification (LAMP) has emerged as a simpler alternative to conventional molecular methods for the diagnosis of HAT. The test has been transformed into a diagnostic kit for qualitative detection of the parasite's DNA in clinical specimens, the Loopamp Trypanosoma brucei Detection Kit. In this study, we evaluated this kit in laboratory conditions on DNA extracted from blood samples of 142 patients, 97 suspects and 111 healthy endemic controls in the Democratic Republic of the Congo. The test showed good diagnostic accuracy and excellent reproducibility. Given the practical advantages of LAMP over conventional nucleic acid methods these are promising results. Further studies are needed to assess the test's accuracy and feasibility in field conditions.