To the Editor,

I have read with interests the systematic review by Gómez Outes et al, about the efficacy of new anticoagulants. I believe that they are serious pitfalls in the assessment of risk of bias of the clinical trials. Authors use Jadad scale that is explicitly discouraged by the Cochrane Collaboration [1]. For example, the RECORD studies obtain the maximum score (the lowest risk of bias). In contrast, in a FDA review of these studies conclusions are quite different:

“The resubmission confirms serious monitoring and reporting problems within the RECORD studies, particularly for RECORD 4 to the extent that data from RECORD 4 cannot be considered reliable. For the remaining RECORD studies, though each had serious problems necessitating exclusion of data from one or more audited sites, overall the result for the studies appear sufficiently robust to support that rivaroxaban is efficacious for the proposed use.
…..
Quantitatively, because of the issues with the quality of the data collection for the studies, conclusions regarding relative efficacy of rivaroxaban and enoxaparin for these uses should not be drawn from the studies.”[2].

In conclusion, Jadad scale is not a useful tool to assess the risk of bias. Assessments of drug regulatory agencies should be incorporated to systematic reviews.

References

1. Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org.
2. Robie-Suh, KM. Xarelto (rivaroxaban) 10 mg immediate release tablets. Medical Review. Silver Spring (MD): U.S. Food and Drugs Administration; 2011 Jun. Application No.: 022406. Available from www.fda.gov

Competing interests: None declared