The Combination of IL-6, PLR and Nail Psoriasis : Screen for the Early Diagnosis of Psoriatic Arthritis

Background: Early screening or timely prediction of psoriatic arthritis (PsA) are crucial. The study aimed to compare the clinical characteristics, cytokines and inflammation index between plaque psoriasis and PsA to explore their values in the early diagnosis of PsA. Methods: This was a case-control study in a single center from January 2021 to February 2023. The differences in clinical characteristics and laboratory examinations between PsA and plaque psoriasis were conducted. Patients with rheumatoid arthritis (RA) were used as a positive control. The correlation between variables were analyzed and multivariable logistic regression were performed by using the 10-fold cross-validation to find independently risk factors of plaque psoriasis that are developing PsA. Results: A total of 109 patients with plaque psoriasis (without joint damage), 47 patients with PsA and 41 patients with RA were enrolled in this study. The study found that the proportion of patients with elevated serum IL-6 levels, as well as the value of platelet to lymphocyte ratio (PLR) and systemic immune-inflammation index (SII), were significantly higher in patients with PsA and early PsA (PsA course & LE;2 years) compared to those with plaque psoriasis (p<0.05). After adjusting for age, gender, severity of skin lesions, and comorbidities (diabetes, hypertension, hyperlipidemia, hyperuricemia, and overweight/obesity), the study identified nail psoriasis (OR=4.35, 95% CI 1.67-11.29, p<0.002), elevated serum IL-6 (OR=6.78, 95% CI 2.34-19.67, p<0.001), and PLR (OR=8.37, 95% CI 2.97-23.61, p<0.001) as independent risk factors for PsA. A multivariable logistic regression analysis employing 10-fold cross -validation assessing the predictive association between the diagnosis of early PsA and the combination of IL-6, PLR, and nail psoriasis demonstrated that the area under the curve (AUC) was 0.84 (95% CI 0.77-0.90) and the F1-score was 0.67 (95% CI 0.54-0.80). Conclusion: The combination of elevated serum IL-6, PLR, and nail psoriasis can help to predict and screen the early stage of PsA.

Automated summary

This study aimed to compare the clinical characteristics, cytokines, and inflammation index between plaque psoriasis and psoriatic arthritis (PsA) to explore their values in the early diagnosis of PsA. The results showed that elevated serum IL-6 levels, as well as the value of platelet to lymphocyte ratio (PLR) and systemic immune-inflammation index (SII), were significantly higher in patients with PsA and early PsA compared to those with plaque psoriasis. Nail psoriasis, elevated serum IL-6, and PLR were identified as independent risk factors for PsA. The combination of elevated serum IL-6, PLR, and nail psoriasis can help predict and screen the early stage of PsA.