Hypertension Management: The Care Gap Between Clinical Guidelines and Clinical Practice

Published Online: July 01, 2004
Susan E. Andrade, ScD; Jerry H. Gurwitz, MD; Terry S. Field, DSc; Michael Kelleher, MD; Sumit R. Majumdar, MD, MPH; George Reed, PhD; and Robert Black, MD

Objective: To evaluate how well hypertension is managed in HMO patients and to assess opportunities for improvement.

Study Design: Retrospective cohort study.

Patients and Methods: The study population included HMO members (age 45-84 years) who had at least 1 ambulatory encounter with an ICD-9-CM diagnosis code of essential hypertension during the first 6 months of 1999. Medical records were reviewed to obtain information on blood pressure measurements, sex, age, coexisting medical conditions, smoking status, and changes made to the antihypertensive drug regimen.

Results: We identified 681 members with 3347 encounters related to hypertension management during 1999. Overall, 74 (11%) patients were at target blood pressure for all visits and 260 (38%) were at target blood pressure for at least 50% of the visits; 222 (33%) patients were not at target blood pressure for any visit. A history of coronary artery disease or cerebrovascular disease was associated with better blood pressure control (defined as being at goal levels during at least 50% of visits), while being older (age ≥75) or having diabetes mellitus was associated with poorer control. Medication regimen intensifications occurred in 10% of visits with systolic blood pressure levels of 140-149 mm Hg, compared with 45% of visits with levels of ≥180 mm Hg. Medication regimen intensifications occurred in 21% of visits with diastolic blood pressure levels of 90-99 mm Hg and 43% of visits with levels of ≥100 mm Hg.

Conclusion: Efforts are required to reduce "therapeutic inertia," particularly in patients with modestly elevated systolic blood pressure levels.

(Am J Manag Care. 2004;10:481-486)

Hypertension is among the most common outpatient diagnoses in the United States.1 The accumulated evidence establishing the benefits of treating hypertension far exceeds that which exists for the treatment of most medical conditions managed in the ambulatory setting. Although primary care physicians may be aware of the existence of treatment guidelines for hypertension,2 these physicians' blood pressure thresholds for the diagnosis and treatment of hypertension reportedly are often substantially higher than recommended.3 Data from the most recent National Health and Nutrition Examination Survey (NHANES 1999-2000) indicate that hypertension prevalence is increasing in the United States, and hypertension control rates are unacceptably low.4 In 1999-2000, 28.7% of NHANES participants had hypertension, a 3.7% increase compared with 1988-1991.4

Control of high blood pressure has been included as a Health Plan Employer Data and Information Set (HEDIS®) measure by the National Committee for Quality Assurance as part of its program to compare the performances of managed health care plans.5 Alexander and colleagues previously demonstrated that it is feasible to assess blood pressure control as a quality measure through review of medical records in an HMO population.6 In the present study, we evaluated the quality of hypertension management in patients followed in a managed care setting in order to assess the opportunities that exist for improvement.

METHODS

Study Population and Design

A retrospective study was conducted among patients enrolled in a mixed-model, not-for-profit HMO operating in New England. The study population included a random sample of 770 HMO members who were 45-84 years old as of January 1, 1999; had continuous plan enrollment in 1999; and had at least 1 ambulatory encounter with a diagnosis of essential hypertension (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code 401.xx) during the first 6 months of 1999 documented in the HMO administrative databases. The age characteristics for study subjects related to the HEDIS® 2000 measure "Controlling High Blood Pressure." Medical records of these members were reviewed by trained nurse abstractors for all ambulatory visits to any healthcare provider that were related to the management of hypertension from January 1, 1998, through December 31, 1999. Information was obtained on blood pressure measurements, demographic characteristics (sex and age), coexisting medical conditions (diabetes mellitus, coronary artery disease, cerebrovascular disease, peripheral arterial disease, and hypercholesterolemia), smoking status, and changes made to the antihypertensive drug regimen because of the patient's blood pressure level.

For the purpose of this study, diabetes mellitus was defined by use of a hypoglycemic agent, a documented plasma glucose level of >200 mg/dL, or a glycosylated hemoglobin level of >6%. Coronary artery disease was considered to be present based on a diagnosis documented in the medical record or a history of myocardial infarction, angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, or prescription of nitrate therapy. Cerebrovascular disease was determined based on a diagnosis in the medical record, or documentation of a history of stroke or transient ischemic attack. Peripheral arterial disease was considered present based on a diagnosis in the medical record. Hyperlipidemia was defined by use of a lipid-lowering agent or a total cholesterol level of ≥240 mg/dL.

The study population was further restricted to include members who had at least 1 ambulatory encounter associated with the prescription of an antihypertensive medication or a blood pressure measurement above a specified target level documented in the medical chart in both 1998 and 1999. Target blood pressure control levels were defined as a systolic blood pressure of <140 mm Hg and a diastolic blood pressure of <90 mm Hg for nondiabetic patients, and a systolic blood pressure of <130 mm Hg and a diastolic blood pressure of <85 mm Hg for diabetic patients, consistent with guidelines in effect at the time of the study.7

When multiple blood pressure readings were documented for the same visit, the blood pressure reading with the lowest systolic blood pressure level during the visit was used in our analyses, regardless of the level of the diastolic blood pressure. For each visit, an intensification of the antihypertensive regimen was considered to have occurred if the dose of an antihypertensive medication had been increased, or a new agent was prescribed.

Statistical Analysis

The numbers and proportions of patients with blood pressure control for at least 50% of visits during calendar year 1999 were determined–both overall and by patient demographic characteristics (sex and age), coexisting medical conditions (diabetes mellitus, coronary artery disease, cerebrovascular disease, peripheral arterial disease, and hypercholesterolemia), smoking status, history of blood pressure control (percentage of visits in the previous year with blood pressure at target level), and history of antihypertensive medication intensification (percentage of visits in the previous year with a medication intensification). Based on the distribution of the data, the percentages of visits in the previous year with blood pressure at target level were categorized as 0%, 1%-25%, 26%-50%, 51%-75%, and >75%; the percentages of visits in the previous year with medication intensification were categorized as 0%, 1%-20%, and >20%. Statistical significance of differences was tested by using the Pearson chi-square statistic and the Mantel-Haenszel test for linear association. Logistic regression was used to estimate the strength of the association between selected patient characteristics and blood pressure at target level for at least 50% of the visits. Stepwise logistic regression was used to identify the multivariate predictors of blood pressure at target level, with the criterion for entry into the models being a probability value of <.05.

Using data from all visits for which the patient's blood pressure was not at target level during calendar year 1999, random effects logistic regression8 was used to evaluate the associations between patient characteristics and intensification of the antihypertensive regimen. Models were constructed that included variables for patient sex, age (<55 years, 55-64 years, 65-74 years, and ≥75 years of age), coexisting medical conditions (diabetes mellitus, coronary artery disease, cerebrovascular disease, peripheral arterial disease, and hypercholesterolemia), smoking status (current, past or nonsmoker), history of blood pressure control (control at previous visit and the percentage of visits in the previous year with blood pressure at target level), history of antihypertensive medication intensification (intensification at previous visit and the percentage of visits in the previous year with a medication intensification), the number of days since the last ambulatory visit related to management of high blood pressure, systolic blood pressure level (<130, 130-139, 140-149, 150-159, and ≥160 mm Hg), and diastolic blood pressure level (<80, 80-84, 85-89, 90-99, and ≥100 mm Hg).

RESULTS

Medical records were located for 758 (98%) of the 770 patients selected for study. Of these, 10 patients had no documentation of hypertension or use of antihypertensive agents in the medical chart during 1998 and 1999, and an additional 67 patients did not have an ambulatory visit potentially related to hypertension in both calendar years. Thus, 681 members, with 3347 encounters related to the management of hypertension during the calendar year 1999, met the criteria for inclusion in the study. The mean number of visits per member was 4.9 (range 1 to 24) during 1999, and 4.6 (range 1 to 24) during 1998. Among eligible patients, 637 (94%) had more than 1 visit and 519 (76%) had more than 2 visits in 1999, and 606 (89%) had more than 1 visit and 485 (71%) had more than 2 visits in 1998. The mean age of the study population was 66 years and 55% (n = 373) were female.

Overall, 74 (11%) patients were at target blood pressure for all visits and 260 (38%) were at target blood pressure for at least 50% of visits during 1999; 222 (33%) patients were not at target blood pressure for any visit during 1999. The relationship between patient characteristics and having been at target blood pressure for at least 50% of visits during 1999 is shown in Table 1. As detailed in Table 2, older patients were less likely to be at target blood pressure (adjusted odds ratio [OR] = 0.49, 95% confidence interval [CI] = 0.29, 0.84 among those age 75 years or older compared with those less than 55 years of age), as were patients with a diagnosis of diabetes mellitus (adjusted OR = 0.32, 95% CI = 0.18, 0.56). Patients with a diagnosis of coronary artery disease and those with a diagnosis of cerebrovascular disease were more likely to be at target blood pressure for at least 50% of visits, as were patients with a prior history of blood pressure control. Patient sex, a diagnosis of hypercholesterolemia, peripheral arterial disease, smoking status, and prior medication change history were not significantly associated with blood pressure control.

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