Figure 1.

MBT schematic overview and scoring

(A) The MBT strip consists of 12 parallel lines, of which six are test lines (T_n) and six are flow controls (FC_n). Each T_n and FC_n pair measures a single biomarker: αPGL-I IgM, IP-10, CRP, CCL4, S100A12, ApoA1. The up-converting reporter particles (UCP) are incorporated in the sample pad. The strip is read using a portable reader perpendicular to the sample flow. The test readout is a pattern of peaks, showing the signal of each of the 12 lines resulting in a ratio value (R) per biomarker (T_n/FC_n). R values for each biomarker are displayed for plasma samples of a patient with multibacillary leprosy (MB; orange) and an endemic control (EC; green) and an M. leprae antigen-stimulated whole blood assay sample of a patient with paucibacillary leprosy (PB; blue).

(B) Two scores were calculated using the R values, the NUM score and the ALGO score. The NUM score is the sum of positive biomarkers per individual (green; R value above the cutoff). The ALGO score is based on an algorithm that contributes higher weights to R values associated with disease and was calculated using the median R values of the individual biomarkers for the patients with leprosy.