Correlation of ANA Characteristics with pANCA IFA Interference.

Abstract

BACKGROUND:

Antineutrophil cytoplasmic antibody (ANCA) testing by the indirect immunofluorescence assay (IFA) is important for the diagnosis of autoimmune vasculitis. A common analytical interference for ANCA-IFA is the presence of an antinuclear antibody (ANA), which can cause an apparent perinuclear ANCA (pANCA) result on ethanol-fixed neutrophils. Here, the association of ANA patterns, titers, and concentrations with pANCA interference is investigated.

METHODS:

Samples positive for ANA by IFA with homogeneous, speckled, dense fine speckled (DFS), and centromere patterns were tested for ANA by enzyme immunoassay (EIA)] and for ANCA by IFA on ethanol-fixed neutrophils. Titers and concentrations were determined for the ANA-IFA and EIA, respectively, and correlated with the frequency of pANCA interpretations.

RESULTS:

For ANA-EIA positive samples (≥1.1U), 20.0% led to a pANCA interpretation compared to 5.1% for negative samples (≤1.0U). For samples positive by ANA-IFA, 12.9% resulted in a pANCA interpretation. Interference on pANCA correlated with ANA-IFA titer, with ANA titers ≥1:1280 identified as pANCA positive in 20.9% of samples compared to 9.7% for titers <1:1280. There was also a correlation with ANA pattern, as homogeneous samples were most likely to be called positive for pANCA (31.7%), followed by speckled (8.8%), DFS (6.8%), and centromere (3.6%).

CONCLUSIONS:

Positivity for ANA by EIA is associated with increased prevalence of pANCA interpretation. Samples positive for ANA by IFA also demonstrated this association, particularly with higher-titer, homogeneous patterns. Laboratories can use this information to determine an optimal workflow for when investigating potential pANCA interferences.

• Authors: Nicholas E Larkey, Ashley M Denome, Melissa R Snyder
• Journal: The journal of applied laboratory medicine (J Appl Lab Med) Vol. 7 Issue 1 Pg. 75-80 (01 05 2022) ISSN: 2576-9456 [Print] England
• PMID: 34996078 (Publication Type: Journal Article)
• Copyright: © American Association for Clinical Chemistry 2021. All rights reserved. For permissions, please email: [email protected].

Chemical References

• Antibodies, Antinuclear

Topics

• Antibodies, Antinuclear
• Fluorescent Antibody Technique, Indirect
• Humans
• Immunoenzyme Techniques
• Neutrophils