Seroprevalence for SIC and DRS antibodies in PSGN, pyoderma and control groups. Recombinant SIC and DRS proteins with a thioredoxin tag were used as the streptococcal antigens for ELISA. Background optical density (OD450) readings to thioredoxin were subtracted from all ODs. OD values for control 1 and PSGN cases (n = 25 each) are shown in panel A and for control 2 (n = 50), GAS pyoderma (n = 150) and non-GAS pyoderma (n = 50) cases in panel C. The box-whisker plots show median (cross bar in the box), quartiles, and range. The mean OD values for control 1 are 0.081 and 0.042 for SIC and DRS respectively; and those for control 2 are 0.12 and 0.076 respectively. These means and those for non-GAS pyoderma cases (0.14 and 0.09 for SIC and DRS respectively) are not significantly different. The means for PSGN and GAS pyoderma cohorts are significantly higher than their controls for both SIC and DRS (p < 0.05, >0.01 for PSGN; and p < 0.0001 for GAS pyoderma). The calculated cutoff values (mean + 2x Standard deviation for the corresponding control) is shown as dotted line across. Samples scoring equal to or above the cutoff values were scored as positive. Panels B and D show per cent seropositive samples for SIC antibodies (black bars) or DRS antibodies (shaded bars) in each group and compared with respective controls. Lines with asterisks indicate statistically significant differences (** = 0.05 ≤ p > 0.0001; *** = p ≤ 0.0001) between the means in 1A and 1C, and between proportion of seropositives in 1B and 1D. Lack of such lines means there is no significant differences between groups (eg; control 2 and non-GAS pyoderma groups in 1C and 1D).