Systematic analysis of serum peptidase inhibitor 3 in psoriasis diagnosis and treatment.

Background: Psoriasis is a chronic inflammatory skin disease. To date, there are no serum biomarkers for psoriasis that have been validated to diagnose or treat psoriasis.

Methods: Peptidase inhibitor 3 (PI3) levels in serum were measured using chemiluminescence immunoassay (CLIA) in two independent cohorts including healthy controls (HC) and patients diagnosed with chronic urticaria (CU), chronic eczema (CE), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), psoriatic arthritis (PsA), or psoriasis vulgaris (PV). Receiver operating characteristic (ROC) curve analysis determined the diagnostic performance of PI3 in patients with psoriasis. The correlation between PI3 levels and the Psoriasis Area Severity Index (PASI) score was analyzed using the Spearman correlation method. Additionally, the study evaluated PI3 expression and treatment response of PV patients 12 weeks before and after topical treatment with calcipotriol betamethasone and calcipotriol ointment (T#1) or topical therapy plus PSORI-CM01 granules (T#2).

Results: In cohort #1, PI3 levels effectively discriminate PV patients from HC and CU patients, with AUCs of 0.909 and 0.840, respectively. In cohort #2, AUCs for detecting PV patients among HC, CU, CE, SLE, and RA patients were 0.940, 0.926, 0.802, 0.989, and 0.951, respectively. For PsA patients, AUCs were 0.989, 0.986, 0.910, 1.000, and 0.984 compared to HC, CU, CE, SLE, and RA patients, respectively. In both cohorts, PI3 levels correlated significantly with PASI scores in PV patients (cohort #1, r = 0.433; cohort #2, r = 0.634) and PsA patients (cohort #2, r = 0.718). Moreover, univariate logistic regression analyses revealed that PV patients with higher PI3 expression had a significantly higher risk of treatment resistance, with an odds ratio of 3.45 [95% confidence interval (CI) 1.54, 7.74, p = 0.003]. Finally, PI3 levels decreased nearly 35-fold more in the responder than in the non-responder group before and after treatment.

Conclusions: Serological PI3 is a reliable biomarker for PV diagnosis and may have the potential to predict and monitor the progression of PV before and after treatment. Key Points • This study validated PI3's diagnostic performance in two independent psoriasis cohorts using CLIA. • PI3 expression is significantly correlated with the psoriasis severity and with patients who benefited from the treatments. • Serological PI3 is a reliable biomarker for psoriasis diagnosis and may have the potential to monitor the psoriasis progression with and without treatments.