COMPARISON OF RADIOASSAY AND HEMAGGLUTINATION METHODS FOR ANTI-THYROID MICROSOMAL ANTIBODIES

  • 1 January 1978
    • journal article
    • research article
    • Vol. 34  (1) , 118-125
Abstract
Parallel measurements of circulating anti-thyroid microsomal (anti-M) antibodies by radioassay and hemagglutination were performed on subjects with or without thyroid disorders. Of control subjects, 3/4 (75.4%) had undetectable antibody levels (< 10 .mu./ml) by radioassay and only 3.1% had concentrations of .gtoreq. 75 .mu./ml. Abnormally elevated levels (.gtoreq. 75 .mu./ml) were found in most patients with Hashimoto''s thyroiditis (94.1%) or idiopathic myxedema (86.7%), in the majority (75.0%) of those with Graves'' disease and only in a minority of those with other thyroid disorders. The percentage of positive sera by hemagglutination was very similar in all groups to that of abnormal values observed in the radioassay. Direct comparison of parallel tests on 631 sera revealed a highly significant correlation (r = 0.91, P < 0.001) between the 2 methods, but elevated antibody titers by hemagglutination were found in some sera with negative radioassays. All these sera were from a single patient with thyroid carcinoma associated with Hashimoto''s thyroiditis and had elevated levels of anti-thyroglobulin (anti-Tg) antibodies. Evidence that such discrepancies were due to anti-Tg antibodies reacting with microsomal-bound Tg was provided by the demonstration that the hemagglutination produced by these sera could be completely inhibited by the addition of Tg. A similar inhibition was observed with 2 rabbit antisera to human Tg, but not with sera from patients with thyroid autoimmune disorders containing high levels of anti-M antibodies.