Appropriateness of laboratory tests in the diagnosis of inflammatory rheumatic diseases among patients newly referred to rheumatologists.

INTRODUCTION: Autoantibody tests are commonly ordered when screening for rheumatic diseases. Rheumatoid factor (RF) and antinuclear antibody (ANA) have low positive predictive values in general practice. Overuse of diagnostic tests can result in an increase in unnecessary referrals, patient anxiety, and further costs.

OBJECTIVE: The objective was to evaluate the utilization patterns, appropriateness, and associated costs of tests including ANA, extractable nuclear antibodies (ENA), anti-double stranded DNA (anti-dsDNA), RF, and HLA-B27 in patients referred to rheumatologists.

METHODS: A review was conducted of consecutive referrals (accepted and rejected) using university rheumatologists' practices over one year. Inappropriate investigations, and associated costs were analyzed. Tests were considered appropriate if at least one criterion for a specific disease was provided.

RESULTS: Of 638 referrals the most common reported reasons for referral were: spondyloarthropathies (SpA), rheumatoid arthritis (RA), and lupus (SLE). Prior to referral: 61% had undergone ANA testing at least once, ANA was repeated in one third; 19% had ENA and 21% had anti-dsDNA. 20% had ANA testing with no clinical indication. Half of ENA and anti-dsDNA testing was in the context of a negative ANA. RF was requested in 65% and in close to one third, there was no clinical suspicion of inflammatory arthritis.

CONCLUSION: Despite the recommendations by CRA Choosing Wisely Campaign, at least 50% of laboratory investigations, including RF, ANA, ENA, and anti-dsDNA, are inappropriately ordered. More selective ordering of the above tests would lead to marked cost reduction.