93 A SENSITIVE ELISA FOR THE MEASUREMENT OF CH IN SERUM, BLOOD AND URINE

A sensitive sandwich ELISA for GH was developed using guinea-pig (CP) polyclonal IgG to coat microtitre plates (which can be stored for up to 3 months). The standard was 22K biosynthetic hGH (2.97U/mg). Assay volume was 100μl which could include up to 20μl of serum, plasma or blood in buffer, (0.04mol/l sodium phosphate, pH7.4, containing human serum albumin 6g/l), or 100μl of dialysed urine. Total assay time was 16hrs. The conjugate was a peroxidase labelled Fab'-fragment of GP anti-hCH with O-phenylenediamine as the substrate for the enzymatic reaction. Optical density was read at 490nm. The detection limit was 0.5 nanounits/well. The working assay range using 20μl of serum was 0.05-15mU/l. The inter assay coefficients of variation were 6.8% at 0.15mU/l, 2.4% at 2.2mU/l and 6.9% at 11.6mU/l. The assay was compared to an 1RMA (Pharmacia); the regression equation was Y (ELISA) = 0.967X (IRMA) - 0.84 with r = 0.996 for 18 samples ranging from 1 to 60mU/l.