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:10.1177/1759720X221122417

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

Ther Adv Musculoskelet Dis. 2022 Sep 5:14:1759720X221122417. doi: 10.1177/1759720X221122417. eCollection 2022.

Authors

Chrysoula G Gialouri¹, Gerasimos Evangelatos¹, Maria Pappa¹, Anastasios Karamanakos¹, Alexios Iliopoulos², Maria G Tektonidou¹, Petros P Sfikakis¹, George E Fragoulis³

Affiliations

¹ Joint Academic Rheumatology Program, Rheumatology Unit, First Department of Propaedeutic Internal Medicine, Laiko General Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
² Rheumatology Department, 417 Army Shared Fund Hospital NIMTS, Athens, Greece.
³ Joint Academic Rheumatology Program, Rheumatology Unit, First Department of Propaedeutic Internal Medicine, Laiko General Hospital, Medical School, National and Kapodistrian University of Athens, Mikras Asias 75 Str, Athens 11527, Greece.

Abstract

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.

Keywords: CRP; DAPSA; disease activity indices; inflammatory markers; minimal disease activity; psoriatic arthritis.