Positive correlation between etanercept concentration and the decrease in Psoriasis Area and Severity Index scale value

Background In the case of psoriatic patients, only a limited number of studies have related serum biological therapies and antidrug antibodies levels to clinical response. With respect to etanercept, the available evidence has not shown any relationship yet. Objective The aim of this study was to determine if there is any correlation among etanercept serum levels, the presence of anti-etanercept antibodies and clinical response to this treatment in psoriatic patients. Setting A 1500-bed hospital (A Coruña University Hospital Complex). Method A retrospective observational study in psoriatic patients treated with etanercept (50 mg once weekly) was carried out. Psoriasis Area and Severity Index scale and adverse reactions were recorded at the time of the extraction sample. The pharmacokinetic monitoring was evaluated at the previous time points by extracting peripheral blood samples before the dose administration. Etanercept and anti-etanercept antibodies concentrations were quantified by two sandwich-type ELISA immunoassays. The patients were classified into three groups (good, partial and nonresponders) in accordance with the treatment efficacy at the blood assessment moments. The Kruskall-Wallis test and Spearman correlation assay were used to assess the efficacy and incidence of adverse effects according to the etanercept concentration and anti-etanercept antibodies, considering p values of <0.05 as statistically significant. This statistical analysis was conducted using SPSS software (version19.0). Main outcome measures Etanercept and anti-etanercept antibodies trough serum levels and clinical response. Results 38 patients were included. 26 patients (68.4 %) were good, 5 (13.2 %) were partial and 7 (18.4 %) were non-responders. There was no significant difference with respect to etanercept levels: 2.7 μg/mL (range 0.7-5.6) versus 2.2 μg/mL (range 1.0-3.5) versus 1.73 μg/mL (range 0.1-2.3), respectively (p = 0.085). Nevertheless, a positive correlation between percentage decrease in the Psoriasis Area and Severity Index scale value with respect to the baseline value and etanercept concentration was found (p = 0.011). No anti-etanercept antibodies were detected; nor was there a significant difference in the incidence of adverse effects (p = 0.8523). Conclusions Our results showed a positive correlated between etanercept concentration and the percentage decrease in the Psoriasis Area and Severity Index scale value. The incidence of anti-etanercept antibodies in psoriatic patients was low.