Diagnostic value of blood count derived inflammatory biomarkers in differentiating occult psoriatic arthritis from psoriasis

Abstract Background Psoriatic arthritis (PsA) is a long-term immune mediated condition. That can develop in individuals with psoriasis, often before any obvious symptoms appear. These asymptomatic individuals, classified as having occult PsA, may already have joint involvement detectable only through imaging, making early diagnosis difficult. Timely identification is essential to avoid permanent structural damage. This study investigates the possible use of hematological inflammatory markers in identifying hidden or undiagnosed PsA. Methods A case–control study involved 60 patients with psoriasis. were divided into two groups: 30 with imaging-confirmed occult psoriatic arthritis (PsA) and 30 with psoriasis only, all without clinical arthritis. Hematological inflammatory biomarkers including neutrophil-to-lymphocyte ratio (NLR), derived NLR (dNLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), and aggregate index of systemic inflammation (AISI), and platelet-to-monocyte ratio (PMR) were assessed from venous blood samples. Musculoskeletal ultrasonography was performed to detect subclinical joint involvement. Results Patients with occult PsA showed significantly elevated levels of white blood cells, neutrophils, and monocytes. In addition, inflammatory markers such as the NLR, dNLR, MLR, SII, SIRI, and AISI were also notably increased, while PMR was decreased (all p < 0.001). NLR and dNLR demonstrated perfect diagnostic accuracy (AUC = 1.000). WBC > 6.7, MLR > 0.17, and PMR ≤ 503 were independently associated with occult PsA. Conclusion Hematological markers, especially NLR, dNLR, and MLR, may serve as effective, low-cost tools for early identification of occult PsA in psoriasis patients, enabling earlier intervention and improved outcomes.