Referrals for rheumatologic evaluation following a positive antinuclear antibody test result. A cross-sectional single center Brazilian study.

Background: In general, patients are referred for rheumatological evaluation due to isolated laboratory abnormalities, especially antinuclear antibody (ANA) positivity, with the risk of more severe patients remaining on the waiting list for longer than desired. The aim of this study was to analyze the demographic, clinical, and laboratory information of patients referred to a specialized rheumatological care unit because of positive antinuclear antibody.

Methods: This is a retrospective study of 99 out of 1670 patients seen by the same rheumatologist between 01/01/2011 and 01/01/2019. Patients whose referrals were exclusively due to the ANA test result and the specialist's final diagnosis being "abnormal finding of serum immunological test" (ICD-10 R769) were included. Sociodemographic, clinical, and laboratory information were extracted from the consulting rheumatologist's chart. Descriptive statistics were used for data analysis.

Results: A total of 99 patients were included, most of whom were female (84.8%) with a median age of 49 years. At the moment of specialist's appointment, 97 patients (97.9%) repeated the ANA test, and 77 patients remained positive. Of these, only 35 (35.35%) were in a high titer range (greater than or equal to 1:320). Complete blood count for cytopenia's investigation was not performed in a high percentage of patients (22.2%), as well as urinalysis (31.3%). In addition, more than 70% of patients score 0 to 1 classification criteria for Systemic Lupus Erythematosus, according to SLE - ACR 1987 (American College of Rheumatology) and SLICC 2012 (Systemic Lupus International Collaborating Clinics).

Conclusions: Most patients are still referred for specialized evaluation due to the misinterpretation of laboratory tests that were inappropriately requested in patients without clinical evidence of autoimmune rheumatic disease.