title: Non-specific count subtraction in radioimmunoassay (a criticism).
abstract: The radioimmunoassay (RIA) blank (Blk) value (as calssically determined) does not represent the real aspecific portion of the radioactivity because of the lack of both antigen and antiserum and the consequent total availability of free tracer, and is, therefore, unlike the standard and unknown tubes. Gastrin-RIA with bound-free separation by charcoal adsorption was chosen as example for providing evidence that the subtraction of such an empirical constant (Blk) from the dependent variable (the response) of a function (response versus dose) is analytically incorrect. Antigen-recovery and parallelism (serum dilution) tests were carried out, and the results obtained by the so-called "Blk subtraction procedure" (BS values) were compared with the corresponding values without Blk subtraction (BNS values). In the recovery test, the BS values were higher than the BNS values, but the former were higher than the expected values, whereas the latter showed a quantitative recovery. The same result was also found in the serum dilution test: the BNS values gave dilution curves more parallel to the BNS standard curve than did the BS values to the BS standard curve. It is concluded that the Blk subtraction procedure must be avoided in processing RIA results.
mesh_terms: D000328:Adult; D000941:Antigens / Q000032:analysis*; D005755:Gastrins / Q000276:immunology*; D006801:Humans; D008297:Male; D011863:Radioimmunoassay / Q000379:methods*
chemical_list: D000941:Antigens; D005755:Gastrins