GPs request unnecessary RF tests
medwireNews: General practitioners (GPs) may be requesting inappropriate tests for rheumatoid factor (RF), and inflating the costs associated with diagnosis of rheumatoid arthritis (RA), say UK researchers.
Between 2003 and 2009, 252 RF tests were performed at a single laboratory in the UK for 235 primary care patients attending two GP practices, say Anne Miller (Nuffield Orthopaedic Centre, Oxford) and co-authors.
But just 20% of the patients tested were suspected of having RA, while 32% of patients were suspected of having inflammatory arthritis that was not recorded as RA.
Of concern, 42.6% of patients were tested for RF in the absence of signs and symptoms for RA, inflammatory arthritis, or other connective tissue disease, including 34 patients with a diagnosis of osteoarthritis and 31 patients with known back pain.
Overall, 69% of the 48 patients suspected of having RA had one or more American College of Rheumatology (ACR) criteria for RA, such as synovitis in at least one joint, no alternative diagnosis to explain synovitis, and the minimum score for duration of symptoms, number and severity of joints affected, elevated acute-phase response, and serologic abnormalities.
However, 63.8% of patients did not meet any ACR criteria, the researchers report in Clinical Rheumatology.
Seven (3%) patients had a positive RF test, four of whom were suspected of having RA. However, RF testing did not result in a diagnosis of RA or other inflammatory arthritis in any patient without a previous suspicion of the condition.
Just five of 33 patients referred to a rheumatologist had a positive RF test; 17 patients were diagnosed with inflammatory arthritis, including 10 cases of RA. The area under the receiver operating characterstic curve for RF was just 0.82 compared with 0.98 for number of ACR criteria met.
The RF tests cost £ 405 (€ 475; US$ 621) per positive result, and £ 709 (€ 831; US$ 1087) was spent per case of seropositive RA.
"Our results demonstrate the overuse of RF in primary care and support the current guidelines on referral of patients with suspected RA on the basis of clinical features rather than on RF result," say Miller et al.
The authors suggest that some GPs in their study may have used the RF test to reassure anxious patients but believe that RF testing increased diagnosis costs in patients without suspicion of RA.
"Further studies are required to establish whether RF has value in diagnosing or excluding RA in patients with various clinical presentations in primary care and whether [anti-citrullinated protein antibodies] has better utility in the primary care setting," the authors conclude.
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