A modestly elevated CRP threshold of ≥12 mg/dL is equivalent to the previously used ESR of >30 mm/h in the Truelove and Witts criteria (TWC) to define severe ulcerative colitis.
The finding, from a Queensland study published in the Journal of Crohn’s and Colitis, raises questions about whether the current threshold in ECCO guidelines and for PBS-funded access to biologics should be reduced.
The training cohort comprised 204 consecutive admissions at the Royal Brisbane and Women’s Hospital (RBWH) between 1996 and 2020 of adult patients with severe UC satisfying the TWC, and with paired ESR and CRP levels taken within 24 h of admission.
The study found a positive predictive value (PPV) of >85% for a CRP value ≥12 mg/L having a paired ESR of >30 mm/h. The PPV remained about the same but the level of accuracy decreased markedly at increments above a CRP cut-off of ≥12 mg/L.
The CRP threshold was then applied to a validation cohort of 128 presentations to the RBWH and collaborating hospitals from October 2017.
“When applied to the validation cohort, the CRP ≥12 mg/L cut-off produced a sensitivity and PPV of 94% and 83%, respectively,” the study said.
“The new CRP-based criterion did not produce any statistically significant difference in the number of patients experiencing either corticosteroid therapy failure or colectomy-by-discharge.”
“When compared with the classical ESR-based system, it resulted in a net increase of 9% in the number of presentations satisfying the Truelove and Witts inflammatory marker criterion.”
Lead author Dr Anthony Croft from the Royal Brisbane and Women’s Hospital and QIMR Berghofer Medical Research Institute, told the limbic that an evidence-based CRP threshold had been a long time coming.
“The ESR of >30 is the gold standard essentially in addition to the six or more bloody bowel motions per day for acute severe UC who need to come into hospital immediately for at least a week.”
However while ESR was still a popular test in general practice, he said it was not ordered a lot in hospital medicine.
“Everyone just uses the CRP now because it is perceived as a little bit quicker, newer, ….so basically there has been a need to work out what is the commensurate CRP in this patient group.”
“It’s surprising that it [the threshold] is so low because expert opinion was that an ESR of >30 is equal to a CRP of >30 and that’s kind of written into the European guidelines and that’s what is currently the situation with regards to the PBS if we want to access infliximab for these patients.”
“Essentially, in someone who doesn’t meet those criteria and who fails steroids we have to give them infliximab by applying to hospital to pay for it.”
Dr Croft said about one quarter of people presented with severe UC as their first indication of IBD.
“This is the group that will hopefully benefit the most from this paper,” he said. “Various thresholds have been proposed but none to my knowledge have been supported by data.”