Background Autoantibody and laboratory testing is essential for SLE diagnosis. ANA by indirect immunofluorescence (ANA IIF) remains the gold standard to screen for lupus and studies demonstrate preclinical phase during which autoantibodies accumulate. Prevalence of ANA IIF alone without more specific autoantibodies and the accompanying clinical phenotype of these patients uncertain.

Methods Queried 602 patients in the NYU Lupus Registry with 4 or more ACR or SLICC criteria as adjudicated by the authors for prevalence of ANA IIF, dsDNA, Sm, Ro, La, RNP, aPL, C3, C4. Compared clinical features of isolated ANA (ANA IIF alone) with the ANA IIF plus one or more lupus associated abnormalities (ANA IIF +).

Results 590/602 (98%) ANA IIF positive. 548/590 (93%) patients at least one of associated tests compared to only 42/590 (7%) ANA IIF alone. SLE nephritis significantly more prevalent in ANA IIF+254/548 (46%), compared to 13/42 (31%) recorded with renal criteria ANA IIF alone. ANA IIF +, 158/254 (62%) biopsy proven nephritis (LN), rather than relying on proteinuria for diagnosis, compared to 5/13 (38%) of ANA IIF alone biopsy proven LN. Remaining 8 ANA IIF alone, uPCR exceeded 0.5 g in 1 of 44 (2%) encounters. Low incidence of proteinuria explained by complete renal response or prior proteinuria misconstrued as evidence of LN. In comparison, uPCR >0.5 g was present in 694 of 1157 (60%) encounters in ANA IIF +, casting doubt on validity of LN diagnosis in 8 ANA IIF alone without biopsy. Leucopenia, lymphocytopenia, AITP, AIHA statistically less ANA IIF alone compared to ANA IIF + ; 24% vs 36%, 29% vs 40%, 7% vs 15% and 0% vs 7%, respectively. 42 patients with ANA IIF alone prevalence of potentially misattributed (e.g. not result of IMID) clinical criteria such as photosensitivity (64%) and malar rash (60%) greater compared to ANA IIF +, 38% and 44%, respectively. Prevalence oral ulcers, DLE, arthritis, serositis, seizures and psychosis equivalent in both.

Conclusions ANA IIF alone rare and patients infrequently develop nephritis, leucopenia, lymphocytopenia, AITP, AIHA. In patients ANA IIF alone attribution of ACR/SLICC clinical criteria needs to be point of emphasis and unless biopsy proven, alternative explanation for proteinuria should be considered. Data argues inclusion criteria for clinical trials, rather than allowing ANA IIF alone or dsDNA, may need to require ANA IIF and at least one of the following (dsDNA, Sm, Ro, La, aPL, or hypocomplementemia) to avoid enrolling patients that do not have SLE.

Funding Source(s): None