Rational test selection in immunology laboratory: Investigating the utility of repeated antinuclear antibody tests

The primary reason for increased lab use is inappropriate or needless test requests. Our study examined the benefits of repeated antinuclear antibody (ANA) testing and the reasons for ANA test requests in accordance with reasonable test selection and inappropriate scenarios.

We examined 2.5 years of data from a Turkish tertiary hospital in this retrospective cohort analysis. ANA and other autoimmune test data and clinical information of all patients whose ANA result changed from negative to positive on repeat testing were gathered from the hospital record system.

44,341 individuals had 51,959 ANA tests between February 2019 and June 2021. ANA tests were positive in 7551 (17 %) of 44,341 patients and 9303 (17.9 %) of 51,959 tests. On 14.6 % (7618 out of 51,959) of tests requested and 13.2 % (5891 out of 44,341) of patients, repeat tests were performed. Of the 5891 patients retested, 171 were initially negative but later positive. A minority (3.7 %) of initially negative ANA patients experienced a change to a titer of ≥1:100 in our 2.5-year investigation. A novel ANA associated rheumatic disease (AARD) was detected in 17 patients. The new positive ANA test had a positive predictive value of 15.1 % following an initially negative ANA test.

It is common to repeat ANA testing. ANA tests that yielded negative results in the beginning frequently repeat without change. Repetition had no effect on clinical prediction of AARD. Repeat ANA testing in hospital patients is ineffective rather than useful.