Background  Guidelines concerning biological treatment of patients with psoriasis recommend different pretreatment and monitoring laboratory panels in variable frequencies to monitor treatment.

Objectives  To investigate the relevance of laboratory investigations in monitoring patients with psoriasis on etanercept or adalimumab.

Methods  A prospective cohort study over 5 years was conducted in all consecutive patients with psoriasis on etanercept or adalimumab. All laboratory investigations performed for monitoring treatment were analysed. Laboratory abnormalities were graded according to the Common Terminology Criteria for Adverse Events v4.03. The primary endpoint was the percentage of patients with a grade 3 or grade 4 laboratory abnormality. The secondary endpoints were defined as: (i) significant changes in laboratory parameters during etanercept or adalimumab treatment and (ii) the percentage of patients having a laboratory abnormality requiring discontinuation of etanercept or adalimumab treatment.

Results  Laboratory parameters were available for 162 patients treated with etanercept and/or adalimumab. The number of treatment episodes was 155 for etanercept and 58 for adalimumab. Follow-up was 316 patient-years for etanercept and 54 patient-years for adalimumab. Thirty-eight of 146 patients treated with etanercept (26%) had one or more grade 3 and/or grade 4 laboratory abnormalities. For adalimumab, this was eight of 58 (14%). These were predominantly considered unrelated to biologic therapy. For both biologics, significant changes were observed in mean laboratory parameters during treatment compared with pretreatment as well as significant trends. However, mean values during treatment remained within normal ranges. Laboratory abnormalities did not lead to permanent discontinuation of biologic treatment in any patient.

Conclusions  In this cohort, the incidence of biologic therapy-related serious laboratory abnormalities was low. Our findings do not support a need for routine laboratory testing in patients with psoriasis on etanercept or adalimumab beyond the laboratory testing required for concomitant therapies or comorbidities.