Faculty Bibliography

In any clinical trial, the use of imperfect diagnostic procedures or laboratory techniques may lead to misclassification and measurement error in the primary outcome. Although the effects of non-differential outcome misclassification and measurement error on conventional superiority trials have been extensively investigated, less is known about the impact of these errors on the results and interpretation of therapeutic equivalence trials. In this paper we formally investigate the effects of outcome misclassification and measurement error on the estimates of treatment effects, type I error rate, and power of equivalence trials. Our results indicate that, contrary to what one may expect based on the well known attenuating effects of non-differential error in conventional studies, these errors do not always favour the goal of demonstrating equivalence. The magnitude and direction of the influence depend on a number of factors including the nature of the outcome variable, specific formulation of equivalence, size of the error rates, and assumptions regarding the true treatment effect.

OBJECTIVES: To examine the incidence, effectiveness of intervention, effect on continence, and factors predisposing to the occurrence of anastomotic strictures following radical retropubic prostatectomy. METHODS: Between January 1994 and June 1999, 753 radical retropubic prostatectomies were performed by a single surgeon. Anastomotic strictures were managed by dilatation followed by a self-catheterization regimen. Dilatations were repeated unless more than three dilatations were required over a 9-month interval. A control group representing a randomly selected group of men who did not develop anastomotic strictures was identified. The largest width of the midline vertical abdominal scar was measured. RESULTS: Of the 753 radical retropubic prostatectomies, 36 (4.8%) developed an anastomotic stricture. The mean time interval between the surgical procedure and diagnosis of the stricture was 4.22 months. Of the 26 cases of anastomotic strictures with at least 1-year follow-up, 24 (92.3%) were managed successfully by dilatations alone. No baseline characteristics before surgery were associated with the development of a stricture. The maximal scar width was the only factor that was associated with the development of a stricture in this study. Men with a maximal scar of greater than 10 mm were eight times more likely to develop strictures than men with smaller scars. The percentage of men who required protective pads 1 year following radical retropubic prostatectomy in the control and stricture groups was 12.5% and 46.2%, respectively. CONCLUSIONS: Anastomotic strictures are relatively rare following radical prostatectomy and have a negative effect on the development of continence. Most men are successfully managed with dilatations alone. The development of anastomotic strictures in some men appears to be related to a generalized hypertrophic wound-healing mechanism

BACKGROUND: The safety and effectiveness of different dosages and combinations of antihypertensive agents can be efficiently studied using a multifactorial trial design. In consultation with the Cardio-Renal Division of the Food and Drug Administration, we conducted a randomized, double-blind, placebo-controlled, 3 x 4 factorial trial of bisoprolol, a beta 1-selective adrenergic blocking agent, and hydrochlorothiazide. METHODS: A total of 512 patients with mild to moderate essential hypertension were randomized to once-daily treatment with bisoprolol (0, 2.5, 10, or 40 mg), hydrochlorothiazide (0, 6.25, or 25 mg), and all possible combinations. Diastolic and systolic blood pressures were monitored during this 12-week trial. RESULTS: The effects of bisoprolol and hydrochlorothiazide were additive with respect to reductions in diastolic and systolic blood pressures over the dosage ranges studied. The addition of hydrochlorothiazide (or bisoprolol) to therapy with bisoprolol (or hydrochlorothiazide) produced an incremental reduction in blood pressure. Dosages of hydrochlorothiazide as low as 6.25 mg/d contributed a significant antihypertensive effect. A hydrochlorothiazide dosage of 6.25 mg/d produced significantly less hypokalemia and less of an increase in uric acid levels than a dosage of 25 mg/d. The low-dose combination of bisoprolol, 2.5 mg/d, and hydrochlorothiazide, 6.25 mg/d, reduced diastolic blood pressure to lower than 90 mm Hg in 61% of patients and demonstrated a safety profile that compared favorably with that of placebo. CONCLUSIONS: The utility of factorial design trials to characterize dose-response relationships and to test the potential interactions between various antihypertensive agents has been demonstrated. The combination of low dosages of bisoprolol and hydrochlorothiazide may be a rational alternative to conventional stepped-care therapy for the initial treatment of patients with mild to moderate hypertension

We consider design, analysis and regulatory issues relating to clinical trials in periodontal disease and identify complications commonly associated with such studies. Alternative statistical procedures that can be used for the analyses of data from periodontal research are reviewed and a case study of the analysis of a Phase II periodontal disease clinical trial is provided to illustrate the use of one of these procedures