Abstract
This prospective study explored the link between values of C-reactive protein (CRP) in patients with SpA (ankylosing spondylitis, psoriatic arthritis, reactive arthritis, or arthritis-related inflammatory bowel disease) and functional disability in order to derive an algorithm that may predict functional disability based on disease activity. Patients diagnosed with Spa were classified into five groups based on the type of therapy and they were followed up for 3 years. Group 1: Symptomatic medication alone; Group 2: Disease-modifying antirheumatic drugs (DMARDs); Group 3: DMARDs and 30 rehabilitation sessions twice a year; Group 4: Group 3 therapy and biologic anti-tumor necrosis factor-alpha (anti-TNF-α) drugs; and Group 5: Group 4 therapy and, in addition, a daily home-adapted kinesiotherapy program. CRP, modified Health Assessment Questionnaire (mHAQ-S), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and T-score of the patients were recorded. Correlation and multivariate regression analyses were conducted using demographic data, CRP, and mHAQ-S scores to derive the CRP-mHAQ-S correlation algorithm. Statistical analysis included the chi-square, Mann-Whitney, and multiple regression tests and repeated measures analysis of variance. A total of 144 patients were enrolled, all of whom completed the study. The best predictive model (P<0.001) provided the algorithm mHAQ-S(36)=17.14+0.12xCRP(0)-0.24xCRP(12)-0.15xCRP(36) (CRP(0), CRP(12), and CRP(36) correspond to CRP levels at baseline, 12, and 36 months, respectively, and mHAQ-S(36) to mHAQ-S score at 36 months). This derived algorithm based on objective CRP assessment may have implications in the prediction of functional disability evolution in patients with SpA.