Clinical, hematologic, and inflammatory factors associated with psoriatic arthritis in a Chinese hospital-based study

Psoriatic arthritis (PsA) develops in up to approximately 30% of patients with psoriasis (PsO) and can cause irreversible joint damage. For dermatologists, identifying factors independently associated with PsA may help identify patients who may benefit from earlier musculoskeletal monitoring and specialist referral.

To identify demographic, clinical, and laboratory factors independently associated with clinical and subclinical PsA in patients with psoriasis.

This retrospective study at Shandong Provincial Hospital included 75 clinical PsA, 22 subclinical PsA, and 95 PsO patients. Subclinical PsA was applied as an operational label only: 21 of these 22 patients met the symptom-based criterion alone and 1 met both the symptom-based and imaging-based criteria. Separate multivariable logistic regression models were fitted for clinical PsA versus PsO and subclinical PsA versus PsO, checked for multicollinearity, with C-reactive protein (CRP) log-transformed and platelet (PLT) count expressed per 50×10⁹/L. Age and sex were force-entered but were not retained after backward elimination, so each estimate is adjusted for the other variables retained in the same model. Model performance was assessed by the Hosmer-Lemeshow test, area under the receiver operating characteristic curve (AUC), and Nagelkerke R².

In clinical PsA, lower hemoglobin (adjusted OR 0.75 per 10 g/L increment), higher PLT count (adjusted OR 1.39 per 50×10⁹/L increment), and higher CRP (adjusted OR 1.78 per doubling) were independently associated with PsA (all p < 0.01; AUC 0.859). In subclinical PsA, hemoglobin and CRP showed comparable independent associations (AUC 0.878); PLT count could not be reliably assessed given the small subgroup (n = 22). Clinical PsA showed more frequent tenosynovitis, synovitis, synovial thickening, and joint effusion on ultrasound than subclinical PsA (p < 0.05).

Lower hemoglobin and elevated CRP were consistently associated with PsA across both subgroups. Routine hematologic and inflammatory markers, combined with musculoskeletal ultrasound (MSUS), may help dermatologists identify psoriasis patients warranting earlier rheumatological referral; prospective studies are needed to confirm predictive value.