Have you ever wondered whether it’s worth repeating an ANA test? Australian data presented at EULAR congress for rheumatologists in Madrid has finally provided an answer to this clinical conundrum.
Australian rheumatologist Dr Ai Li Yeo, who received a EULAR abstract award for her research, presented her data to hundreds of rheumatologists at the congress’ opening plenary session earlier this month.
She analysed data from around 37,000 ANA tests conducted in Melbourne over a seven-year period.
Around 7,900 of these ANA tests (21.4%) were repeats, with an estimated cost to the health system of around $200,000. She found approximately 6.5% of these results changed from negative to positive.
But there seemed to be little point in ordering these repeat ANA tests, as there was no change in the clinical interpretation in the overwhelming majority of cases.
Out of more than 7,800 repeated ANA tests, there were only five tests that resulted in a new diagnosis (two SLE, one scleroderma and two undifferentiated connective tissue disease).
Repeated ANA testing therefore had a very low positive predictive value of 0.01, Dr Yeo said.
Speaking to The Medical Republic, Dr Yeo said her research “is really reassuring because it really emphasises and backs up what we think in clinical practice,” she said.
“There is no point in repeating an ANA.”
Most of the repeat ANA tests in the study weren’t ordered by rheumatologists, she said.
“They were ordered by non-rheumatological specialties. Only 11% of the time were rheumatologists ordering [repeat] tests.”
For the five patients in the study who received a new diagnosis following a repeat ANA test, that diagnosis wasn’t solely based on the ANA, she said.
“ANA testing is more of a screening test,” she said. “It’s really our clinical decision-making skills that made the biggest difference.”
Instead of repeating an ANA, non-rheumatologists probably should be seeking a reassessment by a rheumatologist to see if anything had changed, she said.
“Having done this research, the times that I would repeat an ANA test would be when there are new clinical feature that would be suggestive of a connective tissue disease … [because] your pretest probability is a lot higher if you’re repeating a test.”