The objective of this retrospective study is to assess neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) as inflammatory markers in patients with psoriasis and psoriatic arthritis (PsA). A hundred and eleven psoriasis patients and 25 PsA patients were compared with 94 healthy controls. Demographic, clinical and laboratory information were collected and analyzed. NLR and PLR were calculated. White blood cell (WBC), neutrophils, eosinophils and NLR were increased in psoriasis patients compared with controls. WBC, neutrophils, NLR, monocytes, platelets and PLR were increased in PsA patients compared with both controls and psoriasis patients. Erythrocyte sedimentation rate (ESR) and C-reactive protein were significantly higher in PsA patients compared with psoriasis patients. Among psoriasis patients, Psoriasis Area and Severity Index (PASI) score correlated positively with platelets, NLR and PLR. These parameters were all significantly higher in moderate to severe psoriasis patients (PASI ≥ 10) compared with mild patients (PASI < 10). Elevated platelets, NLR and PLR were significantly associated with the increased PASI scores in multivariate analysis. NLR, PLR and ESR were statistically significant predictors for the presence of PsA in psoriasis patients. NLR was the strongest predictor (odds ratio = 3.351, P = 0.005). In conclusion, elevated NLR and PLR were significantly associated with psoriasis and PsA. Both NLR and PLR were strong predictors for the presence of PsA among psoriasis patients.
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