[Meta-analysis of efficacy of anti-TNF alpha therapy in ankylosing spondylitis patients].

Introduction: Tumor necrosis factor (TNF) plays an important role in the pathology of ankylosing spondylitis (AS). Therefore, anti-TNF antibody based therapies could hopefuly be a treatment in AS patients without response to current drugs, mainly non-steroidal antiinflammatory drugs (NSAIDs).

Objective: To assess the evidence from clinical trials on the efficacy of anti-TNF alpha for the treatment of AS by performing a meta-analysis to derive estimates of responses occurring in randomized trials employing anti-TNF therapy.

Methods: A systematic literature search of EMBASE, PubMed, Cochrane Library and electronic abstract databases of the annual scientific meetings of both the European League Against Rheumatism and the American College of Rheumatology was conducted through August 2006. To be selected, the studies had to fulfil all of the followings conditions: a) randomized controlled trial comparing one therapy anti-TNF alpha (infliximab, etanercept or adalimumab) versus placebo. Used between 6 and 24 weeks in patients with AS; b) diagnosis based on the New York modified criteria for AS; c) the primary end point had to be the proportion of patients with a 20% improvement response according to the criteria of the Assessment in Ankylosing Spondylitis (ASAS) International Working Group (ASAS20 responders).

Results: Seven trials met our inclusion criteria and were selected for meta-analysis and were considered of high methodological quality with a total of 1,094 patients, 660 patients in treatment group and 434 patients in control-placebo group. In anti-TNF alpha treatment group, the ASAS20 response rate improvement was 60.4% and 22.1% in placebo group at 6-24 weeks period. The relative risk was 2.78 (95% CI, 2.3-3.4), favourable to treatment group. The number needed to treat was 3 (95% CI, 2-4).

Conclusions: There is evidence of an increased relative benefit of improved clinical outcomes in patients with AS, treated with anti-TNF antibody therapy with two assessment criteria ASAS20 at short term (6 to 24 weeks) treatment periods; with an evidence level I and recommendation level A.