GPs should avoid ordering multiple inflammatory markers, says study
GPs should not order multiple inflammatory marker tests when investigating possible infection or cancer and instead use only CRP due to its 'superior diagnostic accuracy', researchers have warned.
Using multiple inflammatory tests at once, including CRP, ESR and plasma viscosity, does not increase the ability to rule out disease and GPs should use CRP alone as a first-line test, they said.
This approach would also reduce GP workload and save the NHS money, due to CRP being a cheaper test, noted the researchers from the University of Bristol.
The study adds to the evidence about when GPs should use inflammmatory markers, depending on the specificity of the patient's symptoms.
Research published recently by the same team found that using inflammatory markers as a non-specific way of ruling out disease in patients with vague symptoms was not effective and should be avoided - but this latest study says CRP should be used for patients with specific symptoms.
The study, presented last week at the Society for Academic Primary Care annual conference, looked at just under 140,000 patients who had inflammatory marker testing in 2014.
The researchers found the area under the curve (AUC) value, which is a measure of how well a test discriminates between those who do and those who do not have the disease, was similar between CRP, ESR and plasma viscosity testing.
While adding in ESR to CRP testing did increase the AUC value to 0.69 - up from 0.68 when using CRP alone - the researchers said this was of ‘debatable clinical significance’.
They found the likelihood of patients with a negative result from a single inflammatory marker test truly not having an underlying condition was 94%, which increased to only 94.1% when other tests were done concurrently.
Lead researcher and GP Dr Jessica Watson, said: ‘GPs sometimes opt for multiple tests "just in case" to try to avoid missing something; our analysis shows that testing multiple inflammatory markers together does not improve ability to rule out serious disease.’
The study authors said: ‘CRP has superior diagnostic accuracy for infections and is equivalent for autoimmune conditions and cancers; we therefore suggest this should generally be the first-line test.
'As CRP is also cheaper, we expect that implementation of these findings could generate significant cost savings for the NHS as well as reductions in GP workload.’
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.
The team's previous research published in June - also led by Dr Watson - warned that GPs should stop using inflammatory markers as non-specific tests for ruling out underlying disease after finding that only 15% of patients with raised inflammatory markers actually had an underlying pathology.