300 Abstracts

Logistics of Double-Blinding a Randomized Trial of Intravenous vs. Subcutaneous Heparin for the Treatment of Venous T h r o m b o s i s G. Raskob, R. Hull , D. Rosenbloom, J. Leclerc, R. Jay, M. David, M. Thomas , M. Johns ton , A.G. Turpie , M. Gent , and J. Hi rsh McMaster University, Hamilton, Canada (32) The use of a double-blind design may be made difficult by the nature of the interventions. We have developed a technique to double blind a randomized clinical trial of continuous intravenous (IV) vs. 12-hourly subcutaneous (s.c.) heparin. Patients receive either IV heparin + s.c. saline or s.c. heparin + IV saline. Unblinding by monitoring of heparin clearance is avoided by re- stricting anticoagulant monitoring to the daily mid-interval activated partial thromboplastin time (AIYIT). Both the IV infusion rate and s.c. injection volume are simultaneously adjusted daily in each patient by a dosage nomogram established a priori. The nomogram indicates specific changes in IV infusion rate (saline or heparin) and s.c. injection volume (saline or heparin) corresponding to specific ranges in the mid-interval APTT. This process has been used success- fully for maintaining a double-blind design in our ongoing clinical trial to determine the effec- tiveness of s.c. heparin for the initial therapy of proximal venous thrombosis.

Clinical Trials and Medical Practice: Methodological Considerations Joerg Has fo rd and Wol fgang Koepcke Department of Medical Statistics (ISB), University of Munich, Munich, West Germany (33) The diffusion of knowledge generated by clinical trials can be remarkably slow. Attempting to analyze the reasons, we have to consider at least three factors: firstly, the patients and their influence on the selection of the individual therapy; secondly, the sodo-economic frame in which the patient and the physician meet; thirdly, the physician who treats the patient. An adequate explanatory model of his behavior, i.e., a kind of "Physician Belief Model" exists only in fragments if at all. Regarding the physician as a "homo sdentificus" we concentrate our presentation on research design and analysis features of clinical trials, stressing the aspects of transferability. Among these are (1) What is the methodological basis for transferring results of clinical trials? (2) How do placebo-controlled trials influence the acceptance of the results? (3) Does the common negligence of adverse effects, "quality of life" aspects and of the complexity of therapy favor the implementation of a new therapeutic regimen?

Clinical Trials and Medical Technologies Assessment. The Experience of the C E D I T Pierre Dur ieux, C laud ine Blum, Sylvie Chante reau , Jacques Fermanian , and D o m i n i q u e Jolly Direction du Plan, Assistance Publique de Paris, France (34) Medical technologies assessment is a regulation strategy for controlling hospital costs widely discussed today. The aim of the CEDIT (Comit~ d'~valuation de la diffusion des innovations technoiogiques) is to rationalize the diffusion of new technologies within the Assistance Publique of Paris, a health care institution that consists of 38 hospitals. The first subject studied in 1982 was plasmapheresis (PL). A scientific committee was set up to give recommendations about indications of PL. A consensus was obtained with physicians to develop clinical trials when no proof of the utility of PL for a specific disease was found in the literature. Thus multicenter clinical trials were set up. We think that development of clinical trials within our institution improves quality of care and reinforces the interest of physicians for medical technologies as- sessment.

Competency-Based Survey Method for Assessing Physician Clinical THai Knowledge and Ski l l s Michael L. Russell , Jeffrey L. Probstf ield, and Mar tyn O. H o t v e d t Baylor College of Medicine, Houston, TX (35) The physician community has inadequate awareness of the results of major clinical trials (CT). Moreover, traditional norm-referenced survey methods cannot determine the impact of CT results on clinical abilities used in patient care. Reported here is the development and application of a