Measuring adrenal autoantibody response: Interlaboratory concordance in the first international serum exchange for the determination of 21-hydroxylase autoantibodies

► No assessment of interlaboratory concordance has so far been made for 21OHAb assay. ► Four laboratories showed a good concordance of positive/negative score for 21OHAb. ► Major discrepancies were observed for the quantitation of 21OHAb titer. ► A standardization international program for 21OHAb measurement is strongly needed.