High ANA Titers, Multiple Autoantibodies in ANAs Highly Specific and Suggestive of SLE

The majority of individuals with systemic lupus erythematosus (SLE) have positive antinuculear antibodies (ANAs) and autoantibodies (AAbs) in ANAs, with an ANA titer of at least 2+ and a level of positive AAbs of at least2, supporting the fact that the likelihood of SLE can be assessed with ANA titer and the number of positive AAbs in ANAs. Results of the analysis were published in Scientific Reports.

The researchers sought to assess the association between ANA titer and specificity, along with the association between the number of positive AAbs in ANAs and specificity for SLE.

A retrospective review of the medical records of patients whose ANA spectrum was examined at Fujian Medical University Union Hospital, Fuzhou, China, between August 2012 and August 2013, was conducted. A total of 1297 patients with ANA results were enrolled in the study, with 148 of them with SLE. Receiver-operator characteristic (ROC) curve was used to determine the sensitivity, specificity, titer-sensitive likelihood ratio, and number-specific likelihood ratio of indicators in SLE, following measurement of ANA and AAbs in ANAs (including 13 antibodies) by indirect immunofluorescence and immunoblotting, respectively.

According to the results of ROC analysis, the specificity of ANA titers of at least 1+, 2+, and 3+ for SLE was estimated at 81.29%, 90.69%, and 96.52%, respectively, with an increased titer-specific likelihood ratio of 5.16, 9.29, and 19.60, respectively. In addition, the specificity of the number of positive AAbs of at least 1, 2, and 3 in ANAs for detection of SLE was found to be 80.42%, 94.95%, and 99.30%, respectively, with an increased number-specific likelihood ratio of 4.80, 15.26, and 72.48, respectively.

Although the estimated sensitivity of the number of positive AAbs at least 3, antinucleosome antibody (AnuA), and antiribosome ribonucleoprotein antibody (anti-RNP) was significantly greater than that of antismooth muscle antibody (anti-sm; 50.68%, 41.89%, and 31.76% vs 16.89%, respectively; P <.01), no statistically significant difference in their specificity was reported (99.30%, 99.74%, and 99.56% vs 99.74%, respectively; P >.05).   

The researchers concluded, “The likelihood of SLE can be assessed by ANA titer and the number of positive-AAbs in ANAs.”

Reference

Li H, Zheng Y, Chen L, Lin S. High titers of antinuclear antibody and the presence of multiple autoantibodies are highly suggestive of systemic lupus erythematosus. Sci Rep. Published online February 1, 2022. doi:10.1038/s41598-022-05807-6