ORIGINAL ARTICLE: PDF OnlyComparison of Radioimmunoassay with Homogeneous Enzyme Immunoassay for the Determination of Theophylline Concentration in SerumForrester, Roger L.; Worrall, Jacqueline; Robertson, William R.; Wataji, Lester J.; Wilhelm, DavidAuthor Information Mercy San Juan Hospital, Clinical Chemistry Laboratory, Carmichael, California Therapeutic Drug Monitoring: Volume 1 - Issue 3 - p 381-386 Buy Abstract The homogeneous enzyme immunoassay (EMIT®) and radioimmunoassay (RIA) procedures for the quantitation of theophyl-line concentrations in serum were evaluated and compared. Both methods exhibited curves linear over the therapeutic range (range of concentration, 2.0–33.0 μg/ml). Precision was acceptable for both methods with the coefficient of variation being less than 8.3%. The RIA procedure was found to be slightly more precise. The correlation between the EMIT and RIA procedures was found to be sufficient to allow the procedures to be used interchangeably. This would facilitate the test availability on a 24 hr, 7 day basis. © Lippincott-Raven Publishers.