FIG 1.

Performance of each commercial IgM assay kit relative to the CDC IgM ELISA. (A) Absorbance values for samples tested by the CDC IgM ELISA for each commercial kit. The absorbance values of the positive (measles NP antigen) and negative (SF9 control antigen) are shown for each sample used on the comparison for each commercial ELISA. The cutoff criteria for the negative and positive results are indicated by the orange line (P-N = 0.1) and the black line (P/N = 3.0). Black circles indicate CDC IgM results that qualitatively agree with the indicated commercial test. Red squares indicate false-positive results. Blue triangles indicate false-negative results that were confirmed as positive by PCR. (B) Positive and Negative cutoff values for samples tested by the CDC IgM ELISA in comparison for each commercial kit. The cutoff criteria for P/N versus P-N values are indicated by dotted lines. Black circles indicate CDC IgM results that qualitatively agree with the indicated commercial test. Red squares indicate false-positive results. Blue triangles indicate false-negative results that were confirmed as positive by PCR.