Evaluation of the Colorimetric Malachite Green Loop-Mediated Isothermal Amplification (MG-LAMP) Assay for the Detection of Plasmodium Species at Two Different Health Facilities in a Malaria Endemic Area of Western Kenya

Abstract

Prompt diagnosis and effective malaria treatment are key strategies in the control of malaria. However, the recommended routine diagnostic methods, particularly microscopy and rapid diagnostic tests (RDTs), do not have robust quality assurance systems in malaria endemic areas. This study aimed at comparing the performance of routine RDTs and smear microscopy with a simple molecular-based colorimetric loop-mediated isothermal amplification (LAMP) at two different levels of the health care system in a malaria-endemic area of western Kenya. Patients presenting with clinical symptoms of malaria at Rota Dispensary (level II) and Siaya County Referral Hospital (level IV) were enrolled into the study after obtaining written informed consent. Capillary blood was collected to test for malaria by RDT and microscopy at the dispensary and county hospital, and for preparation of blood smears and dried blood spots (DBS) for expert microscopy and quantitative real-time polymerase chain reaction (qPCR). Results of the routine diagnostic tests were compared with those of malachite green loop-mediated isothermal amplification (MG-LAMP) performed at the two facilities. The feasibility of using MG-LAMP for routine diagnosis was assessed using structured-questionnaire administered to health workers and study participants. A total of 264 participants were enrolled into the study. At the dispensary level, the positivity rate by RDT, expert microscopy, MG-LAMP and RT-PCR was 37%, 30%, 44% and 42%, respectively, while the county referral rates were 42%, 43%, 57% and 43%, respectively. Using qPCR as the reference test, the sensitivity of RDT and MG-LAMP was 78.1% (CI 67.5–86.4) and 82.9% (CI 73.0–90.3) at Rota dispensary. At Siaya hospital the sensitivity of routine microscopy and MG-LAMP was 83.3% (CI 65.3–94.4) and 93.3% (CI 77.9–99.2), respectively. Compared to MG-LAMP, there were 14 false positives and 29 false negatives by RDT at Rota dispensary and 3 false positives and 13 false negatives by routine microscopy at Siaya Hospital. Majority (64%) of study participants in both facilities disagreed that MG-LAMP can be used for malaria diagnosis in a health facility. MG-LAMP had a higher sensitivity than RDTs and microscopy in the detection of Plasmodium at the public health facilities and might be a useful quality control tool in resource-limited settings. The MG-LAMP assay had a shorter turn-around time compared to qPCR and can be easily used in a health facility.