Monitoring national patterns of hypertension screening, treatment and control is essential to assessing adherence to evidence-based hypertension prevention and treatment guidelines, such as those published by JNC. Whereas previous studies based on NHANES data provided such information for the entire U.S. non-institutionalized civilian population, this study analyzed NAMCS data in the period 2003–2004 and the results specifically assess the care provided in office-based practices across the United States with regard to hypertension screening, treatment and control. The NAMCS is a unique data source for evaluating the quality of care in U.S. ambulatory primary care settings and it has captured BP measurements at the time of a patient visit only since 2003.
According to the latest study of NHANES data, the overall prevalence of hypertension was 29% in 2003–2004, which had not increased significantly since 1999.1
It seems unlikely that, with the aging of the population, the national goal to reduce the proportion of U.S. adults with hypertension to 16%6
can be reach by 2010. Compounding the higher than targeted prevalence of hypertension, approximately one in four hypertensive people in the U.S. were unaware of their hypertension. Awareness of one’s BP is the cornerstone of prevention and control of hypertension through lifestyle modification and, if warranted, pharmacotherapy. To raise awareness of hypertension, concerted efforts are needed for clinicians to routinely screen adults aged 18 and older for high BP.5
However, our analysis of the data from NAMCS 2003–2004 suggests that BP measurements were made in only slightly more than half of all patient visits to physician offices.
Patients who saw a health care provider other than their PCP or a cardiologist were at a notably greater risk of not being screened for hypertension. It is worth noting that BP measurement is important in many specialties beyond primary care and cardiology; for example, these include urology, neurology, endocrinology, obstetrics and gynecology. Also, there is likely value in consistency, even in specialty settings where BP measurement is unlikely to make a difference (e.g., dermatology). This may help raise patients’ expectations about BP measurement during office visits and awareness of its importance. It also could counteract the tendency of some specialists to forget that they need to consider the whole patient. BP measurement also can be an important screening tool in settings where obtaining actionable BP results are less likely. For example, surgeons should be concerned about BP both prior to surgery and immediately post-surgery.
Rates of hypertension pharmacotherapy in our study sample in 2003–2004 (62%) were similar to those reported by the NHANES study for the same period (65%).1
This contrasts with our expectation of a higher percentage of treated hypertensive patients in the NAMCS sample as opposed to the NHANES sample, because the latter is representative of the general population including individuals who may not have access to or use health care services regularly. Yet, it is worth noting that the inaccuracy of clinically measured BP may misclassify patients, particularly patients whose overall cardiovascular risk is low (e.g., younger patients), and lead to unnecessary antihypertensive drug prescription.17
BP measurement is prone to human and equipment error. More sources of measurement error exist in clinical practice that would result in BP overestimation than underestimation, e.g., insufficient prior rest period, use of a single BP measurement, end-digit preference, patient anxiety, improper cuff size, etc. In NAMCS, only one BP reading was recorded, and the method of measurement was not specified but likely varied across physician practices. In NHANES, BP was measured three (sometime four) times manually by a trained operator according to a standard protocol and calculated as the average after excluding the first measurement.
In our study sample, diuretics, particularly thiazide diuretics, were the most commonly prescribed antihypertensive medication. This is consistent with the JNC 7 guidelines recommending diuretics as first-line pharmacotherapy for most patients with uncomplicated hypertension.7
Even among patients receiving combination drug therapy, a diuretic was frequently paired with an ACEI, ARB or β-blocker. These findings are consistent with previous studies12, 18–20
published by the current authors and other researchers who reported a marked increase in prescriptions for thiazide diuretics as monotherapy or polytherapy following the publication of trial evidence on the clinical equivalence of diuretics with CCBs and ACEIs in December 2002.21
The apparently low rates of diet and exercise counseling are not surprising in that voluminous studies have documented many missed opportunities for lifestyle counseling during office visits, even for patients who would clearly benefit for such service.22, 23
Rates of treatment to control were surprisingly low among all treated hypertensive patient visits (39%) and among treated hypertensive patient visits with diabetes or chronic kidney disease (20%), compared with those reported in 2003–2004 NHANES (57% and 38%, respectively). We speculate that this apparent discrepancy in the observed success of treatment is at least partially due to the differences in methodology by which BP was measured and reported in NAMCS vs. NHANES as noted above. Overestimation of BP in clinical practice understandably translates into underestimation of control rates. In addition, control of BP is more difficult to achieve when starting at a higher pre-treatment BP, as is likely the case with the NAMCS population compared with the NHANES population. The latter may also partially explain our finding of no statistical differences in BP control between those on antihypertensive treatment and those not in that treated patients likely include those with the highest pre-treatment BP and therefore the most difficult to control hypertension, whereas untreated patients tend to be less severe and to have borderline BP. This type of bias likely exists in NHANES as well, but would be less prominent because NHANES includes the population of untreated hypertension that has had no contact with the health care system. Furthermore, treatment of hypertensive patients may fail to achieve “optimal” BP goals due to clinical inertia (or the failure to intensify therapy when clinically indicated)24
and poor medication adherence and persistence,25
both commonly observed in patients with chronic diseases, including those with hypertension.
It is prudent to note that dichotomized “optimal” treatment goals alone are rarely sufficient or appropriate to measure the success of treatment.26–28
Despite the definitive evidence of a direct, continuous relationship between BPs and cardiovascular morbidity and mortality, optimal BP goals remain uncertain and could vary by such factors as age and comorbidities as has been suggested for control of diabetes.28
Further, defining BP control using point cut-offs ignores the underlying distribution of what is a continuous variable and minimizes the actual improvement of risk when BP is lowered substantially, yet fails to get below a selected cut-off (e.g., 140/90 mm Hg). NAMCS is a serial, cross-sectional survey of patient visits and thus does not allow for the assessment of intrapersonal changes in BP over time. Nevertheless, we found that over one third of the hypertensive patient visits that were not treated to goal had a near-goal BP measurement, i.e., <150/95 mm Hg. The clinical importance of small deviations from “optimal” treatment targets such as these is unclear without a comprehensive assessment of the overall risk/benefit ratio of the treatment needed to achieve the idealized goals, as well as patient preferences.
Several additional data limitations warrant caution in interpreting the findings of this study. NAMCS is designed to produce nationally representative estimates that are linked to patient visits and not individual patients. Sicker patients, those with difficult to control BP, and those prescribed medications requiring more frequent follow-ups may be oversampled, resulting in an overestimation of the volume of patient visits and actual administration of antihypertensive medications on a per patient basis. Underestimation and omission of clinical data also may be possible due to incomplete reporting of diagnoses, medications prescribed and services rendered to the patient. This may be particularly problematic when a patient’s diagnoses exceed the three spaces allotted for reporting. As a result, hypertension may fail to be reported for some hypertensive patients who had multiple diagnoses leading to exclusion of such patients from our analysis. In addition, the number of medications may exceed the maximum allowed eight spaces for reporting. Furthermore, physician awareness and adherence to practice guidelines is a complex issue that requires careful consideration of a range of factors that can influence physicians’ decision to screen for, treat and control high BP, for some of which we do not have data in this study.
More intervention efforts are needed to further reduce the gaps and variations in routine practice in relation to evidence-based practice guidelines for hypertension screening, treatment and control. Data from recent clinical trials29–31
and epidemiological studies1
suggest the Healthy People 2010 objective to increase the proportion of hypertensive adults with controlled BP to 50%6
can be attained. The United States is leading the way in hypertension treatment and control compared with other westernized countries32
and continues to develop new strategies in pursuit of greater success.33–34