Quality control aspects of blood pressure measurements in the Multiple Risk Factor Intervention Trial.

Quality control of an ongoing study of blood pressure must be an active, dynamic process in which attempts are continually made to reduce error and bias and maintain comparability among clinics. Training is an important means of initiating and maintaining proper procedures. In addition, changes in procedures during the trial must be properly evaluated so that their impact upon the conduct of the trial is known and, if necessary, quantifiable. The monitoring of quality measurement of blood pressure in a large clinical trial such as MRFIT must be a two-pronged effort that considers observation and evaluation of methods of measuring blood pressure in actual clinical practice and evaluation of data resulting from these procedures.