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

Patrick Mitashi,Veerle Lejon,Philippe Büscher,Pati Patient Pyana,Epco Hasker,Marleen Boelaert,Pascal Lutumba,Stijn Deborggraeve,Dieudonné Mumba Ngoyi,Wim Van Der Veken

doi:10.1371/journal.pntd.0002504

Abstract

BackgroundMolecular 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).Methodology/Principal findings142 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.Conclusions/SignificanceIn 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.

Highlights

Human African trypanosomiasis (HAT) is a protozoan disease caused by the Trypanosoma brucei species, which are cyclically transmitted by tsetse flies
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. 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 sensitivity of the commercial loop-mediated isothermal amplification (LAMP) kit tested here was equivalent to that of the 18S polymerase chain reaction (PCR) test, which showed a sensitivity between 87.3% and 90.1% on the same DNA extracts

Summary

Introduction

Human African trypanosomiasis (HAT) is a protozoan disease caused by the Trypanosoma brucei species, which are cyclically transmitted by tsetse flies. Diagnostic algorithms for T.b. gambiense HAT generally start using the Card Agglutination Test for Trypanosomiasis (CATT) as initial screening for the presence of antibodies. Those testing positive in CATT are subjected to parasitological tests for confirmation of the infection [3]. 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. 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)

Methods

Results

Conclusion