Hegewald M J, Schoenfeld S L, McCulloch D K, Greenbaum C J, Klaff L J, Palmer J P
Veterans Affairs Medical Center, Seattle, WA 98108.
J Immunol Methods. 1992 Sep 18;154(1):61-8. doi: 10.1016/0022-1759(92)90213-d.
Insulin autoantibodies (IAA), a marker for insulin-dependent diabetes mellitus (IDDM), have been reported in other diseases such as thyroid disease and after treatment with sulfhydryl containing medications. Reported prevalences of IAA in non-diabetics vary widely, probably due in part to methodological differences between laboratories. In addition, certain sera may have a high non-specific binding to insulin. We compared a radioimmunoassay (RIA) for IAA which included non-specific binding with an RIA that incorporated a competitive displacement with cold insulin to remove non-specific binding. Using the RIA which measured specific plus non-specific binding, IAA positivity was found in 22/92 (23.9%) of sera from thyroid disease patients, 16/124 (12.9%) of random masked sera from a hospital laboratory, 27/335 (8.1%) of first degree relatives of IDDM patients, 63/178 (35.4%) of subjects with newly diagnosed IDDM, and 0/92 (0%) of normal controls. Insulin antibodies (IA) were found in 80/99 (80.8%) of insulin-treated diabetic subjects. In contrast, using the displacement assay which allowed measurement of specific binding, the frequency of IAA positivity was lower for subjects with thyroid disease (7/92 (7.6%)), random hospital sera (12/124 (9.8%)), and for first degree relatives of IDDM patients (8/335 (2.4%)), while higher for subjects with newly diagnosed IDDM (71/178 (39.9%)). Subjects with insulin-treated diabetes (78/99 (78.8%)) and normal subjects (1/92 (1.1%)) showed little change. Strikingly, three of the eight (37.5%) relatives of IDDM patients that were positive in the RIA measuring specific binding were detected only because cold displacement was utilized. We conclude: (1) subjects with thyroid disease and first degree relatives of IDDM patients frequently have high non-specific binding for IAA in an RIA not employing a cold displacement step, (2) in some newly diagnosed IDDM patients and first degree relatives of IDDM patients, IAA may be missed by an assay not optimized to measure specific binding, and (3) displacement with cold insulin increases both the specificity and sensitivity of RIAs measuring insulin autoantibodies.
胰岛素自身抗体（IAA）是胰岛素依赖型糖尿病（IDDM）的一个标志物，已在其他疾病如甲状腺疾病以及使用含巯基药物治疗后被报道。非糖尿病患者中IAA的报道患病率差异很大，这可能部分归因于各实验室方法学上的差异。此外，某些血清可能与胰岛素有较高的非特异性结合。我们比较了一种用于检测IAA的放射免疫分析（RIA）方法，该方法包括非特异性结合，与一种采用冷胰岛素竞争性置换以去除非特异性结合的RIA方法。使用测量特异性加非特异性结合的RIA方法，在甲状腺疾病患者的92份血清中有22份（23.9%）呈IAA阳性，医院实验室的124份随机盲法血清中有16份（12.9%）呈阳性，IDDM患者的一级亲属335份血清中有27份（8.1%）呈阳性，新诊断的IDDM患者178份血清中有63份（35.4%）呈阳性，正常对照者92份血清中无阳性（0%）。在接受胰岛素治疗的糖尿病患者中，99份血清中有80份（80.8%）检测到胰岛素抗体（IA）。相比之下，使用允许测量特异性结合的置换分析方法，甲状腺疾病患者（92份血清中有7份（7.6%））、医院随机血清（124份血清中有12份（9.8%））以及IDDM患者的一级亲属（335份血清中有8份（2.4%））中IAA阳性的频率较低，而新诊断的IDDM患者（178份血清中有71份（39.9%））中IAA阳性的频率较高。接受胰岛素治疗的糖尿病患者（99份血清中有78份（78.8%））和正常受试者（92份血清中有1份（1.1%））的结果变化不大。引人注目的是，在测量特异性结合的RIA中呈阳性的8名IDDM患者亲属中，有3名（37.5%）仅因为采用了冷置换才被检测到。我们得出结论：（1）在未采用冷置换步骤的RIA中，甲状腺疾病患者和IDDM患者的一级亲属对IAA常常有较高的非特异性结合；（2）在一些新诊断的IDDM患者和IDDM患者的一级亲属中，未优化用于测量特异性结合的检测方法可能会漏检IAA；（3）用冷胰岛素进行置换可提高测量胰岛素自身抗体的RIA的特异性和敏感性。
