Evaluation of the immunochromatographic assay for HTLV-1/2 detection in Gabon: genotype-specific limitations in Central Africa.

The human T lymphotropic virus types 1 and 2 (HTLV-1/2) are highly endemic in sub-Saharan Africa but are largely unreported. This is due to limited knowledge of HTLV-1/2 infections and a lack of suitable facilities for systematic screening. To address this, the flow immunochromatographic assay (IC) was developed for the rapid, point-of-care detection of anti-HTLV-I/II antibodies in blood samples, offering a convenient tool for improving healthcare in low-income countries. Previous reports on the IC assay have noted high specificity (up to 99.42%) and sensitivity (100%) for certain HTLV-1 strains. In this study, we assessed the performance of the IC assay using HTLV-1/2 samples from Gabon and compared its results with those obtained using two reference serological methods: enzyme-linked immunosorbent assay (ELISA) and western blot (WB). Our findings indicate that the overall performance of the IC assay was lower with Gabon-related strains, showing a sensitivity of 66.7% (95% CI, 58.5%-74.3%) and a specificity of 99.1% (95% CI, 96.7%-99.8%). A notable variation in sensitivity was observed across different HTLV-1 genotypes: B-genotype with 73.7% sensitivity (95% CI, 61.0%-83.3%), D-genotype with 25% sensitivity (95% CI, 0.04%-0.7%), and A-genotype with 100% sensitivity (95% CI, 0.7%-100%). The IC assay also showed a positive reaction with samples of the rare F-genotype and correctly detected all eight samples related to HTLV-1-associated diseases that were tested. These results suggest that while the IC assay appears suitable for detecting A-genotypes, it has relatively lower sensitivity for the B- and D-genotypes that are common in Central Africa. Therefore, IC test outcomes, especially negative results, should be interpreted with caution in this region. IMPORTANCE: Over 5 million people in Africa are living with HTLV-1 without knowing their serological status or the potential risks of associated diseases. Contrary to other industrialized countries, where systematic HTLV-1/2 screening is implemented, HTLV-1 antibody screening appears to be totally absent in low-income countries of the African continent. Such conditions are undoubtedly due to the high cost of current HTLV-1/2 reagents and laboratory equipment needed for retrovirus screening. In this context, the newly developed lateral flow immunochromatographic assay (IC), specifically the MP Diagnostics ASSURE HTLV-I/II Rapid Test, could help not only to gain a better understanding of HTLV-1/2 epidemiology but also to improve the health care system of low-income countries. Thus, in this study, we aimed to assess the performance of this IC assay with HTLV-1/2 African genotypes.