The Diagnostic Role of Antinuclear Antibody: A Study of Clinical Utility in a Tertiary Hospital

Abstract

Introduction: Various studies reported unnecessary and inappropriate serology testing of rheumatic diseases leading to a significant waste in healthcare utilization. The purpose of this study is to evaluate the clinical utility of antinuclear antibody (ANA) testing in a real-world setting within a tertiary hospital for systemic lupus erythematosus (SLE) and other ANA-associated rheumatic diseases (AARDs), as well as to identify patient characteristics and test results that predict rheumatic disease association. Subjects and Methods: This is a retrospective study of patients aged 15 years or older who underwent ANA testing at Aseer Central Hospital from January 2018 to December 2022. Data collected included patient demographics, clinical presentations, referral physician type, ANA test results, and final diagnoses. Descriptive statistics characterized patient demographics and ANA test results. Sensitivity, specificity, and predictive values of ANA testing were calculated for SLE and AARD diagnoses. Chi-squared test was used to identify the predictive values of AARDs. Results: Of the 2141 patients tested for ANA at Aseer Central Hospital, 583 (27.2%) tested positive, with a higher proportion of females (80.8%). Notably, 85.1% of patients who tested ANA positive were under 55 years old. The highest ANA test-positive proportion was noticed by rheumatologist physician’s referral (67.6%), referral symptoms including joint symptoms (38.3%), mucocutaneous symptoms (19.7%), renal disease symptoms (14.4%), and hematological abnormalities (14.2%). The sensitivity and specificity of ANA for diagnosing SLE were 86.4% and 79.3%, respectively, with a positive predictive value (PPV) of 31.7% and a negative predictive value (NPV) of 98.1%. The sensitivity and specificity of other AARDs were 85.4% and 73.9%, respectively, with a PPV of 6% and an NPV of 99.6%. Significant associated factors with AARDs included younger age (<55 years), female patients, higher ANA titer, rheumatologist referral, and clinical indications such as sicca symptoms, myopathy, mucocutaneous symptoms, and hematological abnormalities (P < 0.001). Conclusion: In this study, ANA testing showed a good sensitivity and NPV in ruling out AARDs; however, its poor specificity and PPV suggest that positive ANA findings should be interpreted cautiously. Younger age, female gender, higher ANA titer, rheumatologist referral, and specific clinical indications were significantly associated with AARDs, suggesting the importance of targeted ANA testing in clinical practice.