RESUMEN
BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.