Comparison of different immunoassays for the detection of antibodies against Intrinsic Factor and Parietal Cells

Abstract

Objectives: In the diagnostic work up of autoimmune gastritis several immunological methods are available for the detection of antibodies against Intrinsic Factor (IF) and Parietal Cells (PC). However, there are no recent reports directly comparing all the available assays and methods. The objective of this study was to compare the performance of several commercially available anti-IF and anti-PC antibody assays from different manufacturers in a multi-center multi-cohort setting.

Methods: Sera were used from 5 different cohorts consisting of samples from 25 healthy elderly, 20 HCV or HIV positive patients and 150 patients positive for anti-IF or anti-PC antibodies or in whom these antibodies were requested. These cohorts were tested for anti-IF antibodies with 6 different assays (IIF, ELISA, DIA and EliA) and for anti-PC antibodies with 7 different assays (IIF, ELISA, DIA and EliA). Performance was evaluated by calculating the concordance and relative sensitivity and specificity.

Results: Good concordance was found between the assays for both antibody specificities, ranging from 81 to 100% and 91-100% for anti-IF and anti-PC antibodies, respectively. Highest relative sensitivity was found with the (automated) ELISA based methods. However, all assays had a relative sensitivity between 85 and 100% for anti-IF antibodies and between 95 and 100% for anti-PC antibodies. The relative specificity ranged between 76 and 100% for anti-IF antibodies and between 96 and 100% for anti-PC antibodies.

Conclusions: We conclude that most assays perform well and are concordant to each other, despite the methodological differences and the different sources of antigen used. However, the method used affects the sensitivity and specificity. The (automated) ELISA based assays have the highest relative sensitivity and relative specificity. Care should be taken in the interpretation of positive results by IIF and negative results by the Blue Diver when testing for anti-IF antibodies.

Keywords: Auto antibodies; Auto immune gastritis; Diagnostic laboratory methods; Intrinsic Factor antibodies; Parietal Cell antibodies.