Multicentre Comparative Study of Theophylline Concentration Estimations in Serum: (4 RIAs and 1 EMIT-Assay)

Serum concentrations of theophylline were measured in 108 serum samples in four different clinical laboratories. The commercially available RIA kits GAMMA-DABR (Clinical Assays) and RIA-MATR (Byk-Mallinckrodt) and the enzyme immunoassay EMIT-SYVAR (Merck) were used. Serum samples were collected from 12 healthy volunteers after administration of 3 different single doses of various theophylline formulations: 15, 60, 120 min after 360 mg EuphyllinR intravenouslz, 60, 120, 360 min after 350 mg EuphyllinR retard Drg. orally or 350 mg EuphyllinR Tbl. In all tests repeated analyses of reference standards indicated an intraassay variation of 10 % or less and the results indicate that the analyses are reliable. Statistical analysis, however, indicated significant differences between determinations which could be due to either laboratory or methodological differences. All determinations made showed that subtherapeutic serum concentrations of Theophylline were attained after administration of commonly used doses of EuphyllinR.