Evaluating serum procollagen type III N-terminal peptide use as a liver fibrosis screening test in patients with psoriasis receiving methotrexate: a retrospective service evaluation in comparison with the Fibrosis-4 (FIB-4) index.

Whilst procollagen type III N-terminal peptide (PIIINP) is recommended as a marker of liver fibrosis in patients with psoriasis on methotrexate, its efficacy is increasingly questioned. PIIINP is not specific as a marker of liver fibrosis, is expensive and has a lengthy turnaround time. There is growing evidence that methotrexate is not a direct cause of liver disease. Fibrosis-4 (FIB-4) is a validated screening score of liver fibrosis that has a substantial weight of evidence. FIB-4 scores are quick to calculate, minimally invasive and cost-effective. Our study reviews PIIINP use versus FIB-4 use in patients with psoriasis about to start or taking methotrexate therapy. This service evaluation demonstrates poor real-world adherence to PIIINP monitoring guidance and a lack of correlation between PIIINP and FIB-4 referral thresholds.