– Repeated antinuclear antibody testing after a negative result has limited use for the diagnosis of ANA-associated rheumatologic conditions, according to data from a multicenter, retrospective analysis that considered a 7-year period.

Dr. Ai Li Yeo, a PhD candidate, rheumatologist, and infectious disease fellow at Monash University, Melbourne Sara Freeman/MDEdge News

Dr. Ai Li Yeo

Considering more than 7,875 repeated ANA tests in 4,887 patients, “the vast majority of results didn’t change,” Ai Li Yeo, MBBS, a PhD candidate, rheumatologist, and infectious disease fellow at Monash University, Melbourne, reported at the European Congress of Rheumatology.

ANA tests were repeated between 2 and as many as 45 times in individual patients, she reported, but the results of 79% of these tests remained unchanged – 45% of tests were persistently negative and 34% persistently positive using a cutoff titer of 1:160.

“Our study showed that there was a very low yield in repeating an ANA test for the diagnosis of ANA-associated rheumatological conditions unless there was evidence of evolving multisystem clinical features,” Dr. Yeo said.

Indeed, the positive predictive value was just 0.01. “So for a hundred patients staring off with a negative ANA results that on repeat testing became positive, the probability is that one patient will have a new ANA-associated rheumatological condition diagnosis,” Dr. Yeo said.

“ANA testing is frequently performed and is part of the classification criteria for autoimmune conditions such as lupus and scleroderma,” she observed. However, the test provides no information on the severity or activity of the disease, and the value of serial monitoring for such conditions is unclear.

“Minimizing unnecessary tests is a global health economic priority,” Dr. Yeo said. She noted that there are multiple initiatives in place to try to open a dialog about using health care resources most effectively, such as ‘Choosing Wisely’ set up by the American Board of Internal Medicine (ABIM) Foundation.

The aim of the present analysis was to calculate the cost of repeated ANA testing and to see if any change in the ANA result was associated with new diagnoses of ANA-associated rheumatological conditions.

The analysis considered more than 36,700 tests that were performed on samples from more than 28,800 patients within the Monash Health tertiary health network between 2011 and 2018. Of these, 22,657 (62%) had given a negative result and 14,058 (38%) had given a positive result.

“Not surprisingly, the age of those who tested positive was significantly higher than those who tested negative,” Dr. Yeo said (52.6 vs. 48.9 years; P less than .001). There was also a higher number of women than men tested, and women more often tested positive.

Around one-fifth of tests performed were repeat tests, of which 511 (6.5%) changed from being negative to positive over a median of 1.71 years.

“A small percentage of people alternated between results,” Dr. Yeo acknowledged, with 9.4% of people going from a positive to a negative result; 10.5% moving from a negative to a positive result, and 1.9% going from positive to negative to positive.

With repeated tests, just five new diagnoses of ANA-associated rheumatologic conditions were made: two cases of systemic lupus erythematosus (SLE), one case of scleroderma, and two cases of undifferentiated connective tissue disease. There was a range of ANA titers and patterns and evolving clinical features of a multisystem disease.

Based on the direct costs of ANA testing in her health care system, not performing repeated tests could yield significant savings, Dr. Yeo said, a 21.4% reduction, in fact, based on this analysis. The cost of an ANA test in Australia ranges from 15 to 46 euros, making the cost of all tests in this analysis 564,745 euros. Taking away the cost of all the single ANA tests performed (443,209 euros) gives a potential cost saving of more than 121,000 euros, she said.

“We now have an opportunity to prevent unnecessary ANA testing, Dr. Yeo said. “Ultimately, our aim is to change behavior at the start of the ordering cycle by educating medical students and doctors about inappropriate test ordering.”

The majority of repeated tests had been ordered by nonrheumatologists (82% of cases), and Dr. Yeo said that rheumatologists ordered repeat tests in 11% of cases. However, there was little information available in this retrospective analysis as to why the tests had been repeated.

The research was picked as one of the six best clinical abstracts at the meeting, out of a total of almost 5,000 submitted abstracts.

Dr. Yeo reported having no conflicts of interest.

SOURCE: Yeo AL et al. Ann Rheum Dis. Jun 2019;78(suppl 2):76-7, Abstract OP0020. doi: 10.1136/annrheumdis-2019-eular.4517.