Doctor Potyk raises a concern that although inclusion criteria for studies included in the meta-analysis of deep venous thrombosis prophylaxis were appropriate, some studies using different doses or products of a prophylactic agent were grouped inappropriately. He references data that suggest these differences result in different prophylactic efficacy.
Although we do not dispute that delaying warfarin until the fifth day postoperatively or using 1 mg of warfarin both preoperatively and postoperatively may be inadequate dose schedules, the two warfarin-only studies that we included in our meta-analysis did not use these dose schedules. We, therefore, did not combine studies in which dosing differences are related to differences in efficacy. For external pneumatic compression and low-molecularweight heparin, he states the concern is only theoretic.
Meta-analysis is the systematic overview of individual studies to combine results and integrate the findings to draw conclusions about the effectiveness of therapeutic interventions.1,2 Meta-analysis uses explicit
Mohr DN, Silverstein MD. Meta-analysis Pitfalls: Deep Venous Thrombosis in Patients Undergoing Elective Hip Surgery-Reply. Arch Intern Med. 1994;154(11):1296. doi:10.1001/archinte.1994.00420110143019