The data collection and quality control system for the Collaborative Study of Coronary Artery Surgery (CASS) is described. A special feature of the CASS system is that data at the sixteen clinics are keyed directly into a programmable terminal and later transmitted over telephone lines to the data collection center. This system is compared with the traditional data collection system of mailed paper forms.
I. INTR~DLJCTI~N
The Coronary Artery Surgery Study (CASS) has as its major goal the determination of the efficacy of coronary artery surgery in prolonging life. A secondary goal is assessing the success of this surgery at preventing myocardial infarction and its effect on lessening angina1 pain. It is a collaborative study involving 16 clinical sites and a coordinating center.
All patients seen at the clinics who undergo coronary arteriography for the purpose of evaluating the causes of suspected coronary artery disease are enrolled in a registry. The enrollment in the registry is presently 13 000 patients and will reach more than 20 000 before the enrollment period ends in July 1978. From the registry patients, a special subgroup of patients with significant coronary artery disease who have relatively minor functional impairment due to angina are enrolled in a randomized clinical trial in which half of the individuals are allocated to medical therapy and the other half to surgical therapy (I ).
This report describes the methods used to collect and edit the data and to convert it to computer readable form. The unique feature of the data collection for the CASS study is the use of distributed data processing in which much of the preliminary data entry, error checking, and conversion is done remotely at each of the clinical sites, rather than centrally at the study data processing center (the coordinating center). In addition, the computer requirements for the study are discussed with various alternatives.