ABSTRACT
Home-made enzyme-linked immunosorbent assays (ELISA) for protein C (PC) and protein S (PS) antigenic assays, using commercial antibodies, were set up in our laboratory. The latter can be used for the measurement of total PS and also free PS, after the precipitation of bound form. Here we describe the procedure for both PC and PS ELISA's, and their quality evaluation and cost. Intra- and inter-assay variation (n = 20) were calculated to be 7.3% and 8.1% for the PC ELISA and 10.2% and 10.1% for free PS ELISA. The accuracy of the tests assessed by external quality assurance of WHO International External Quality Assessment Scheme in Blood Coagulation (IEQAS) was satisfactory. The level of PC antigen in 50 healthy volunteers was 89 ฑ 18% and that of free protein S was 94 ฑ 16%. In conclusion the quality of the home-made ELISA's was acceptable while the cost was much cheaper than that of commercial ELISA kits.