Correspondence Address:
Dr. Yashwant Kumar
Department of Immunopathology, PGIMER, Chandigarh
India

Full Text

Sir,

Primary immunoglobulin A deficiency (IgAD) is considered as the most common primary immunodeficiency in the Western world with a prevalence rate of 1/600 in the general population.[1] It is defined as serum IgA levels of ≤70 mg/dl with normal IgM and IgG levels in individuals of 4 years of age or older.[2] The affected patients may be asymptomatic or present with recurrent sinopulmonary and gastrointestinal infections, and sometimes with severe complications such as bronchiectasis or obliterative bronchiolitis. The disease is frequently associated with autoimmune disorders, for example, IgAD is 15–20 times more common in celiac disease (CD), also called gluten-sensitive enteropathy.[3]

In the Indian subcontinent, IgAD is believed to be rare with an unknown prevalence. So far, only two supporting studies are available that report a low incidence of IgAD in Indian population. One done on 3818 healthy blood donors' reported a prevalence of 6.7% in these individuals.[4] The other small study on 134 children of CD incidentally found co-existing IgAD in 6% of these patients.[5] Given its rarity, the patients of CD are investigated for IgAD only when they remain seronegative for CD markers but respond to gluten-free diet.

In our lab, tissue transglutaminase-IgA (tTg-IgA) screening assay for the detection of CD is routinely done. The assay is labeled as positive if the levels of tTg-IgA are >10 Elia U/ml (reference range <7 Elia U/ml). The test is done on an automated immunoassay analyzer (Phadia 100, Thermofisher Scientific, Sweden) using kits from the same manufacturer. While performing the tTg-IgA assay, sometimes, the instrument gives no result and by default shows a peculiar “flag” that is similar to that as if an empty vial has been run. We, therefore, report it as “undetectable tTg-IgA.” Out of curiosity, we measured IgA levels in 30 samples with undetectable tTg-IgA along with 45 samples with negative results (tTg-IgA levels < 0.1 Elia U/ml) by nephelometry (MININEPH, Binding site, Birmingham, UK). To our surprise, we noticed that 76.7% (23/30) of these patients were IgA deficient (<30 mg/dl) compared to those with normal tTg-IgA, in which only 9.7% (4/45) had IgAD. This observation is significant as it suggests that IgAD is much more common in India than expected and a negative tTg-IgA assay does not rule out IgAD. Therefore, all CD suspects rather than only those who are seronegative should be investigated for IgAD irrespective of their results of serological markers, for example, tTg-IgA assay. Pathologists or laboratory personnel can contribute to the detection of IgAD by just being little careful while reporting tTg-IgA assay results. Further, the observation provokes systematic studies on the larger cohort that will clarify the status of IgAD in India and importance of this observation in the detection of IgAD.

Acknowledgment

The author is grateful to Mr. James for providing technical assistance.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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