Antibody test ‘inappropriate’ without connective tissue symptoms

By Lynda Williams, Senior medwireNews Reporter

The positive antinuclear antibody (ANA) test is often used inappropriately in patients without indications of connective tissue disease, real-world research suggests.

The study showed that over 90% of patients referred to a rheumatology clinic following a positive ANA test had no evidence of ANA-associated rheumatic disease.

The team reviewed medical records from 232 patients and found that ANA testing was ordered most commonly for widespread pain and tenderness (23.2%), hand pain (9.1%), knee pain (3.9%), and chronic lower back pain (3.4%). Eighty-five percent of referrals came from primary care providers.

The positive predictive value (PPV) for a positive ANA test result, using an ANA titer threshold of 1:160 or above, was just 2.1% for the diagnosis of lupus and 9.1% for the diagnosis of any ANA-associated rheumatic disease.

No patient with a titer below 1:160 had an ANA-associated rheumatic disease, the researchers note, and 85.7% of the 21 patients diagnosed had a level of 1:640 or above. However, even using this threshold, the PPV was low, at 26.9% for any diagnosis and 6.0% for lupus.

"Although we do not discourage primary care physicians from ordering the ANA test, we would encourage careful consideration before ordering the screen as to whether an [ANA]-associated disease seems likely," say Aryeh Abeles and Micha Abeles, both from the University of Connecticut Health Center in Farmington, USA.

"For cases that do not suggest an [ANA]-associated disease (eg, chronic widespread pain), the test should not be ordered," they advise in the American Journal of Medicine.

The researchers recommend that physicians explain to patients that serologic testing is only one aspect of diagnosis and should not be considered to show definite or even likely presence of disease, given the high background positivity for ANA in the general population.

"These simple interventions would likely not only improve the utility of the test for providers and patients but also help to reduce health costs spurred by unnecessary testing and its consequences," the authors conclude.

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