GPs should stop using CRP and other inflammatory markers as non-specific tests to rule out serious underlying conditions, researchers have recommended.
The authors of a study published in the British Journal of General Practice called for a review of NICE guidelines for chronic fatigue and irritable bowel syndrome after finding that only 15% of patients with raised inflammatory markers actually had an underlying pathology.
The researchers from Bristol Medical School calculated that per 1,000 inflammatory marker tests performed, 236 false-positive results could be expected, leading to an additional 710 GP appointments being needed, and 24 referrals.
The study looked at just under 137,000 patients who had had an inflammatory marker test in 2014.
They found that in patients with raised inflammatory markers, only 15% had an underlying condition such as an infection, autoimmune condition or cancer. The remaining 85% were classed as false-positives.
Patients who had false-positive results had around 10 GP appointments in the six months following the test, compared with seven in patients who had true-negative results. The false-positive patients also had around 24 further tests requested, compared with 14 in the true-negatives.
Due to the low sensitivity of inflammatory marker tests, they are ‘not suitable’ for ruling out underlying disease in primary care, the researchers concluded.
They said in the paper: ‘Though the unit cost of inflammatory marker tests is relatively low, the total costs, including follow-on consultations, investigations, and referrals, are likely to be substantial. As well as financial costs, patient anxiety and GP workload may be generated. Further studies, including health economic evaluations, may be useful to inform clinical guidelines and recommendations for GPs about when (and when not) to use inflammatory marker tests.’
Dr Jessica Watson, a GP and lead author of the study, said: ‘We recommend that GPs stop using inflammatory markers as a non-specific test to rule out serious underlying disease. We would also like to see a review of NICE guidelines for chronic fatigue and irritable bowel syndrome, which currently promote the use of inflammatory markers to exclude other diagnoses.’
NHS England announced plans in 2018 to require point-of-care CRP testing in primary care before GPs could prescribe antibiotics, in a bid to curb antibiotic prescribing.