Abstract-This study assessed trends from 1980 to 1995 in ambulatory patients' antihypertensive drug therapy by US office-based physicians for visits in which hypertension was the principal diagnosis and compared these trends with the respective guidelines given in 5 Joint National Committee (JNC) Reports on Detection, Evaluation, and Treatment of High Blood Pressure published around the same time period. Data from the National Center for Health Statistics' National Ambulatory Medical Care Surveys for 1980, 1990 were used. From 1980 1 In 1995, it accounted for 3.2% of these visits. The purpose of this study was to (1) assess NAMCS trends from 1980 to 1995 in ambulatory patients' antihypertensive drug therapy by US office-based physicians at visits in which hypertension was the principal diagnosis and (2) compare these trends with the respective guidelines given in the 5 Joint National Committee (JNC) reports 2-6 published around the same time period. These were 1975 to 1976 1980, JNC II; 1984, JNC III; 1988, JNC IV;, JNC V. The most recent, JNC VI, was published in 1997. 7 There have been other national surveys that have evaluated antihypertensive drug prescribing trends. 8 -10 However, NAMCS data have the advantages of methodological and analytical consistencies, coverage of the time periods necessary to measure the effects of the first 5 JNC reports, and the ability to assess antihypertensive drug pattern characteristics during patient visits.
MethodsNAMCS is a national, probability-sample survey conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention. It collects data on medical care services provided by office-based physicians during ambulatory patient visits. To assess a 15-year trend in antihypertensive drug therapy, 1980, 1985, 1990, and 1995 NAMCS data were used. NAMCS medication data were first collected in 1980. Detailed information on NAMCS sampling and data collection is given in other NAMCS references. [11][12][13][14] Only patient visits having a principal (first-listed) diagnosis of essential hypertension (ICD-9-CM code 401 15 ) were included for this study. The JNC reports 2-6 were used to identify and classify the antihypertensive drugs. To analyze antihypertensive drug prescribing, the following coding procedures were performed. Each hypertension visit in which at least 1 antihypertensive drug was mentioned was counted as an antihypertensive drug visit. On the NAMCS data collection forms, physicians could record the antihypertensive drugs prescribed during the visit by using either generic drug names or brand names. Where brand names were listed, each generic name (active ingredient) component of the drug product was coded separately. Then, each occurrence of an antihypertensive generic name was categorized to its major antihypertensive drug class. If a particular antihypertensive drug class occurred more than once for a visit, it was counted only once. For the first analysis, antihypertensive drug class occurrences, the frequency of occurrence for e...