GPs do not need to use rheumatoid factor testing as all patients with rheumatoid arthritis are able to be identified on the basis of clinical features alone, claim specialists.
Their study found that, in two UK practices, GPs requested over 250 rheumatoid factor tests during a three-year period, but that all of the patients subsequently diagnosed with rheumatoid arthritis could have been referred on the basis of their clinical features alone.
But GP experts criticised the conclusions of the study - carried out by specialists in Oxford - saying patients often did not present with the classic symptoms of rheumatoid arthritis and were not ordering test unnecessarily.
Currently NICE recommends referral of patients with persistent synovitis of undetermined cause, and does not require a positive rheumatoid factor test for early referral.
The study, published in Clinical Rheumatology, identified 235 patients from two general practices who between them had 252 RF test requests made between April 2005 and March 2008. The GP suspected rheumatoid arthritis in 48 (20%) of these patients, while inflammatory arthritis was suspected but not specifically recorded as rheumatoid arthritis in 76 (32%).
Ten (4%) of the patients were diagnosed with rheumatoid arthritis, all of whom had a pretest diagnosis of rheumatoid arthritis or suspected inflammatory arthritis on the basis of clinical features suggestive of rheumatoid arthritis.
The analysis confirmed that the number of American College of Rheumatology (ACR) clinical criteria recorded at the time of rheumatoid factor testing was more accurate than the rheumatoid factor test itself at predicting rheumatoid arthritis.
The team also found that of 36,191 requests for rheumatoid factor tests at one immunology lab over a 7-year period, which cost around £60,000 each year, two-thirds were from GPs – compared with a quarter from hospital departments and less than 10% from rheumatologists.
The authors said their findings demonstrated ‘overuse’ of rheumatoid factor tests in primary care that ‘significantly increases the overall cost of testing’.
But Dr Louise Warburton, a GPSI in musculoskeletal medicine and president of the Primary Care Rheumatology Society, said GPs should not be put off ordering rheumatoid factor tests in order to pick up rheumatoid arthritis early in the disease course.
‘GPs need to be alert to any possibility of presentation and I think this is why a lot of RF tests are negative,’ she said.
‘Rheumatoid arthritis can start in many varied and disparate ways, sometimes not following any previously seen pattern.
‘It is not wasteful use of resources, it is just GPs being thorough and making sure no stones are left unturned in their assessment.’
Dr Warburton also cautioned that the ACR criteria used in the study tend to be positive for RA only quite late in the disease process, however. She explained that ‘newer, much more sensitive criteria’ for RA diagnosis, developed jointly by the ACR and European League Against Rheumatism, are able to detect the disease much earlier and involve RF testing.
Clin Rheumatol 2013; online 21 March
