Pre-precipitated and solid-phase second antibody compared in radioimmunoassay.
We describe simple methods for preparing and determining the titer of pre-precipitated second antibody. We compared the performance of this type of insolubilized second antibody with that of a commercially available solid-phase second antibody (DASP) for separation of reverse triiodothyronine (rT3) and for thyrotropin radioimmunoassays. Equilibrium time for both reagents was about 30 min, considerably briefer than for the usual second-antibody procedure. Within-assay precision was improved and percentages of nonspecific binding (mean and SD) were lower if pre-precipitated second antibody was used in both assays [rT3 pre-precipitate = 1.48 (SD 0.16), rT3 DASP = 3.76 (SD 0.22); thyrotropin pre-precipitate = 1.45 (SD 0.18), thyrotropin DASP = 3.45 (SD 0.26)]. The cost of DASP was three to 10 times that of pre-precipitated second antibody prepared with commercially available products.
D000906:Antibodies / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D005069:Evaluation Studies as Topic; D006801:Humans; D011863:Radioimmunoassay / Q000379:methods*; D013972:Thyrotropin / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*; D014285:Triiodothyronine, Reverse / Q000097:blood*
D000906:Antibodies; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013972:Thyrotropin