The facilities to detect antinuclear antibodies (ANA) patterns in patients with systemic rheumatic diseases/connective tissue disorders (CTD) using indirect immunofluorescence (IIF) technique (the gold standard) are sparse; the technique is technically difficult and expensive. A simpler technique, such as the indirect immunoenzyme (IIE) which uses light microscopy, ought to be evaluated for widespread use in our setting.
To study the feasibility and relevance of IIE in demonstrating ANA patterns, both from serum and filter paper blood clots (FPBC), in patients with CTD.
In this pilot study, ANA were detected from sera and FPBC of 21 patients with proven CTD using IIE; paired FPBC and serum samples were simultaneously collected in 10 patients. All samples, coded randomly, were tested by IIE and IIF, along with positive and negative controls.
Using IIE, the results of the ANA patterns obtained from FPBC eluates and sera were similar; homogenous (SLE-6, PSS-1, RA-4), speckled (SLE-8, PSS-2, Overlap CTD-1) and centromere (PSS-1). Four SLE patients showed mixed pattern; sensitivity of IIE for lupus was hundred percent. On comparing the results with the serum IIF, the Kappa statistic of agreement was 1 (perfect) and 0.4 (fair) for FPBC-IIF and FPBC-IIE respectively; the results matched between serum IIF and FPBC-IIE in 8 of the 10 paired samples tested.
IIE can demonstrate ANA both from sera and FPBC. This pilot study besides demonstrating positive trends for further probe also creates an awareness for such a feasible technique. However a larger sample size would be required to carry out its evaluation as an alternative to IIF and as a screening technique.