Clinical evaluation of the EMIT salicylic acid assay.

Salicylic acid was measured by a homogeneous enzyme immunoassay technique (EMIT). Replicate analyses of samples in the therapeutic range gave a within-day coefficient of variation (CV) of 5.1% and day-to-day CV of less than 5.0%. Quantitative results obtained by immunoassay on serum samples from patients receiving acetylsalicylic acid were compared with the results obtained by the colorimetric procedure of Trinder. Regression analysis of 100 specimens analyzed by immunoassay (y) and the reference procedure (x) gave the equation y = 0.99x - 1.18 (r = 0.995, Sy.x = 1.23). Clinical evaluation of the results indicates that the enzyme immunoassay procedure is highly sensitive and specific for salicylic acid.