FIG 1.

Categorization for SD RDT band intensity, based on a standard color scale provided by SD Biosensor. A score of 0 indicates no signal; 1 indicates barely visible but present (corresponding to R1 to R6 on the standard scale); 2 indicates low intensity (i.e., faint but definitively positive, corresponding to R7 to R12 on the standard scale); and 3 indicates medium to high intensity (corresponding to R13 to R21 on the standard scale). The upper row shows the standard color scale provided by the manufacturer. The lower row shows actual RDTs used in the present study, photographed on the same day under standardized lighting conditions. The illustrative test line is shown in the dashed rectangle.