Deka Sangeeta, Kalita Deepjyoti, Rekha Udaykumar Sasi, Mahanta Putul, Rani Diksha, Shankar Ravi, Raj Anusha Krishna, Jha Mithilesh Kumar, Badoni Gaurav, Paul Manisha, Gupta Shailesh Kumar, Negi Shailender, Singh Anshu, Chatterjee Kuhu
All India Institute of Medical Sciences, Rishikesh, India.
Assam Medical College, Dibrugarh, India.
Autoimmune Dis. 2022 Oct 26;2022:1343805. doi: 10.1155/2022/1343805. eCollection 2022.
Indirect immunofluorescence assay (IIFA) based on antineutrophil cytoplasmic antibody (ANCA) testing is a commonly employed test for diagnosing autoimmune vasculitis. Antinuclear antibody (ANA) can give rise to a false interpretation of perinuclear-ANCA (pANCA) in ethanol-fixed granulocyte substrates. Analytical interference could frequently occur in setups where ethanol-fixed substrates are used alone. Here, we intend to investigate this ANA interference in pANCA interpretation.
In this retrospective study, we studied anti-MPO-negative but ANA-positive and pANCA (IIFA based) samples. We also correlated immunoblot results (where data were available) and checked the association between grades of blot positivity (an indicator of the concentration of ANA) and frequency of pANCA interpretation. Data were analyzed by appropriate statistical techniques (Chi-square and kappa statistics).
About 19.2% of ANA blot (ENA-blot) positive samples displayed a pANCA positive pattern in the ethanol-fixed substrate, while this positivity in ENA-blot negatives was 6.5%. In positive ANA-IIFA samples, about 14.7% yielded pANCA patterns (on ethanol fixed substrates). Out of this, nuclear homogenous pattern yielding samples gave the highest frequency pANCA, that is, in 31.5% followed by speckled (11.1%), DFS (10.3%), and centromere (6.7%).The association of the nuclear homogenous pattern was statistically significant.
ANA-positive results may interfere with the interpretation of pANCA as observed in ANA-IIFA and ENA-blot positive samples. ANA-IIFA patterns like nuclear homogenous may strongly associate this pANCA interpretation. This can help laboratories perform ANCA testing more effectively, ruling out ANA interference in ANCA screening.
基于抗中性粒细胞胞浆抗体（ANCA）检测的间接免疫荧光法（IIFA）是诊断自身免疫性血管炎常用的检测方法。在乙醇固定的粒细胞底物中，抗核抗体（ANA）可导致对核周型ANCA（pANCA）的错误解读。在单独使用乙醇固定底物的检测中，经常会出现分析干扰。在此，我们旨在研究ANA对pANCA解读的这种干扰。
在这项回顾性研究中，我们研究了抗髓过氧化物酶（MPO）阴性但ANA阳性且基于IIFA的pANCA样本。我们还对免疫印迹结果（若有数据）进行了相关性分析，并检查了印迹阳性等级（ANA浓度的指标）与pANCA解读频率之间的关联。通过适当的统计技术（卡方检验和kappa统计）对数据进行分析。
约19.2%的ANA印迹（可提取核抗原印迹）阳性样本在乙醇固定底物中显示pANCA阳性模式，而可提取核抗原印迹阴性样本中的这一阳性率为6.5%。在ANA-IIFA阳性样本中，约14.7%呈现pANCA模式（在乙醇固定底物上）。其中，产生核均质型模式的样本出现pANCA的频率最高，即31.5%，其次是斑点型（11.1%）、弥漫性细颗粒型（10.3%）和着丝点型（6.7%）。核均质型模式的关联具有统计学意义。
正如在ANA-IIFA和可提取核抗原印迹阳性样本中所观察到的，ANA阳性结果可能会干扰pANCA的解读。ANA-IIFA模式如核均质型可能与这种pANCA解读密切相关。这有助于实验室更有效地进行ANCA检测，排除ANA在ANCA筛查中的干扰。
