Therapeutic Advances in Musculoskeletal Disease (Sep 2022)

Normal C-reactive protein in active psoriatic arthritis: results from real-world clinical practice

  • Chrysoula G. Gialouri,
  • Gerasimos Evangelatos,
  • Maria Pappa,
  • Anastasios Karamanakos,
  • Alexios Iliopoulos,
  • Maria G. Tektonidou,
  • Petros P. Sfikakis,
  • George E. Fragoulis

DOI
https://doi.org/10.1177/1759720X221122417
Journal volume & issue
Vol. 14

Abstract

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Background: The value of normal C-reactive protein (CRP) in psoriatic arthritis (PsA) is debatable. Objectives: To test the hypothesis that CRP is frequently normal in contemporary real-world PsA patients, despite active disease. Design: In this cross-sectional study, patients were divided into two groups: CRP ⩽ 0.5 mg/dl (normal) and CRP > 0.5 mg/dl (increased). Having as dependent variable the CRP status, these groups were compared for disease-related features, including composite disease activity indices [clinical Disease Activity in PSoriatic Arthritis (cDAPSA) and minimal disease activity (MDA)] and patient-reported outcomes (PROs). Agreement between CRP status and cDAPSA/MDA scores was calculated (Cohen’s kappa). Methods: Data from consecutive PsA patients attending two outpatient rheumatology clinics (January 2019–June 2021) were analysed. Results: From 128 patients enrolled (51.6% females; mean ± standard deviation age: 53.4 ± 11.7 years; 23.4%, 48.4% and 64.1% treated with glucocorticoids, conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) and biologic DMARDs, respectively), two-thirds (66.4%, n = 85) had normal CRP values. CRP status was not associated with any of the disease-related parameters and PROs, but only with ESR [odds ratio: 1.04 (95% confidence interval: 1.01–1.06), p = 0.005]. Among patients with normal CRP, 45.9% (39/85) were on non-MDA state, while 21.2% (18/85) had cDAPSA-moderate and 5.9% (5/85) had cDAPSA-high disease activities. Conversely, 54.2% (39/72) of patients on non-MDA state and 52.3% (23/44) of those with cDAPSA-moderate or cDAPSA-high disease activity had normal CRP values. Cohen’s kappa between normal CRP and MDA, cDAPSA-remission, and cDAPSA-remission/low disease activity was –0.26, –0.21 and –0.22, respectively, displaying total disagreement. Conclusion: Normal CRP in PsA should not be used as surrogate marker of remission or low/MDA, therefore needs to be interpreted with caution in clinical decision-making.