Sato Masayuki, Nishibata Yuka, Masuda Sakiko, Nagamori Tsunehisa, Ishibazawa Emi, Yoshida Yoichiro, Takahashi Hironori, Ishizu Akihiro, Takahashi Satoru
Department of Pediatrics, Asahikawa Medical University, Asahikawa, Japan.
Department of Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Japan.
Clin Biochem. 2023 Oct;120:110650. doi: 10.1016/j.clinbiochem.2023.110650. Epub 2023 Sep 19.
Anti-glomerular basement membrane (anti-GBM) antibody is essential for the diagnosis of anti-GBM disease. The major epitope consists of the α3 subunits of type IV collagen non-collagenous domain (α 3(IV)NC1). There have been only a few reports of patients false-positive for anti-GBM antibody.
We experienced an 8-year-old boy who presented with asymptomatic hematuria followed by positivity for anti-GBM antibody as evaluated by a commercially available chemiluminescent enzyme immunoassay (CLEIA). While his condition remained stable other than continuing hematuria, his anti-GBM antibody titer increased. Further examination of another anti-GBM antibody assay (fluoroenzyme immunoassay) showed negative results. Thus, evaluation of the accuracy of his positivity for anti-GBM antibody was required. We conducted the following examinations: A) enzyme-linked immunosorbent assay, B) immunoblotting for recombinant α 1-5(IV)NC1, and C) immunohistochemical analysis of normal kidney tissue sections. Specimens used for the analysis were sera in A and IgG from the patient in B and C, respectively. As a result, no anti-GBM antibody was detected in A. In B, no band specific to α 1-5(IV)NC1 was observed. In C, the kidney tissue was not stained. Taken together, these results led us to judge the positive anti-GBM result in CLEIA of our patient to be a non-specific reaction.
The commercial assays for anti-GBM antibody can lead to false-positive results. We recommend confirmation of anti-GBM antibody positivity through the use of multiple assays in patients demonstrating an atypical clinical course for anti-GBM disease.
抗肾小球基底膜（anti-GBM）抗体对于抗GBM病的诊断至关重要。主要表位由IV型胶原非胶原结构域的α3亚基（α3(IV)NC1）组成。抗GBM抗体假阳性的患者报告仅有几例。
我们接诊了一名8岁男孩，他最初表现为无症状血尿，随后通过市售化学发光酶免疫分析（CLEIA）检测抗GBM抗体呈阳性。除持续血尿外，他的病情保持稳定，但抗GBM抗体滴度升高。另一种抗GBM抗体检测方法（荧光酶免疫分析）的进一步检测结果为阴性。因此，需要评估他抗GBM抗体阳性结果的准确性。我们进行了以下检查：A）酶联免疫吸附测定，B）重组α1-5(IV)NC1的免疫印迹分析，以及C）正常肾组织切片的免疫组织化学分析。分析所用标本在A中为血清，在B和C中分别为患者的IgG。结果，在A中未检测到抗GBM抗体。在B中，未观察到α1-5(IV)NC1特异性条带。在C中，肾组织未染色。综合这些结果，我们判断该患者CLEIA检测中抗GBM抗体阳性结果为非特异性反应。
抗GBM抗体的商业检测可能导致假阳性结果。对于临床表现不典型的抗GBM病患者，我们建议通过多种检测方法来确认抗GBM抗体阳性。
