Correlation between trough serum levels of adalimumab and absolute PASI score in a series of patients with psoriasis.

BACKGROUND: The possibility of monitoring serum drug levels has opened the door to optimising biologic therapy. To consolidate this advance, it is imperative to demonstrate an adequate correlation between serum drug levels and clinical course.

OBJECTIVES: To investigate whether a correlation exists between adalimumab levels and clinical response measured as absolute PASI.

METHODS: In a prospective cohort study, we enrolled 51 patients with psoriasis treated with adalimumab for at least 16 s. Patients received approved doses of adalimumab, but after 52  s the dosing interval could be modified according to clinical criteria. Excellent response was defined as PASI ≤3, appropriate response as PASI >3 and ≤5 and inappropriate response as PASI> 5. Correlations were calculated using Spearman's correlation test.

RESULTS: A total of 92 serum samples from 51 patients were analysed. Significant differences were found in serum trough levels between patients achieving an excellent response (6.46 μg/mL), versus an appropriate (2.5 μg/mL) and an inappropriate response (2 μg/mL). The therapeutic range for adalimumab serum levels was from 3.30 to 7.30 μg/mL.

CONCLUSIONS: We found an adequate correlation between drug serum levels and PASI scores. Monitoring of absolute PASI and serum levels can provide a personalised and cost-effective evaluation.