Automated continuous-flow radioimmunoassay for salivary estriol

We have automated a radioimmunoassay for salivary estriol by using the "Southmead" continuous-flow system. The assay, based on a well-validated manual assay, involves a Sepharose-coupled antiserum and an 125I-radioligand. The antibody-bound and free radioligand fractions are separated by on-line filtration. Performance of the automated assay has been reliable during six months of regular use, and compares favorably with that of the manual assay. Drift (0.5 nmol/L per 100 samples) and sample carryover (3%) are acceptable, and the throughput rate is 55 samples per hour. The system is suitable for the assay of the large numbers of samples generated by daily saliva specimen collection in the third trimester of pregnancy.