Time-resolved immunofluorometric assay for placental protein 14.

A sandwich-type solid phase time-resolved immunofluorometric assay (IFMA) was developed for endometrial protein PP14 (placental protein 14). The assay utilizes affinity-purified polyclonal antibodies for coating the microtiter wells and for labelling with europium (III) chelate. Maintaining specificity, the 0.6 micrograms/l sensitivity of IFMA is over 25 times higher than that of RIA. The immunofluorometric method enables detection and accurate quantitation of PP14 in all those samples in which PP14 is undetectable by RIA. The method is suitable for quantitative measurement of low PP14 levels in serum of postmenopausal and fertile-aged women and men, as well as in follicular fluid. At 14-16 micrograms/l, which is the sensitivity of radioimmunoassay, the intra-assay variation of IFMA is 6.6% and inter-assay variation 11.4%. In postmenopausal women the PP14 levels are 12.7-56.7 micrograms/l, in fertile-aged women 13.7-113.4 micrograms/l, and in men 3.1-53.1 micrograms/l. The levels in preovulatory follicular fluid are 1.2-20.5 micrograms/l. It is concluded that PP14 IFMA is highly sensitive, accurate and suitable for measurement of protein levels undetectable by other currently available methods.