Objective: To retrospectively assess the quality of cardiovascular disease risk factor measurements in routinely collected data and to examine whether there are systematic differences in measurement quality between individuals of different socioeconomic status, and changes in measurement quality over time.
Study design and setting: Comparison of last digit preference in risk factor measurement between a "routine" data set (related to a primary care-based UK cardiovascular risk factor screening programme) and relevant prospective epidemiological surveys (Health Survey for England [HSE] and WHO MONICA). For the routine data set, the records of 37,161 women and 33,977 men aged 35-60 years with a first screening episode during the 11-year period 1989-1999 were analyzed.
Results: Last digits of height, weight, and total cholesterol measurements in the routine data set did not exhibit a digit preference pattern, although the degree of random measurement error was greater compared with epidemiological survey data. The last digits of systolic and diastolic blood pressure (BP) measurements exhibited a strong last digit preference pattern for "0"-comprising 63.1% and 67.3% of all observations in men and women, respectively. Except for diastolic BP in men, last digit distribution patterns were not associated with participant's socioeconomic status and showed no change over time.
Conclusion: It may be feasible to study changes over time in cardiovascular disease risk factor levels in different socioeconomic groups using routine data sets; however, prior critical examination of measurement quality is necessary.