To the Editor.
—We believe that the conclusions reached by Weinberg et al1 in the May issue of the Archives are misleading. The authors found two instances of major perioperative bleeding in a retrospective review of 59 hypothyroid patients. The patients were successfully treated, with no grossly bad outcomes, such as those reported in the two frequently cited "anecdotal case reports." The authors retrospectively reviewed charts for 59 matched euthyroid control patients and found no bleeding complications. From such data, they reasoned that "it is safe to proceed with anesthesia and surgery" for hypothyroid patients and that the incidence of perioperative complications is no greater for hypothyroid patients than for euthyroid patients.The authors failed to appreciate limitations resulting from the inadequate size of their sample population. One point crucial to the investigation is the incidence of the complication being studied. Suppose that a particular complication occurs in 0.1%