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HYPERTENSION/2004/034256 R1
Methods
Study Sample and Procedures
To determine whether patient-centered characteristics are associated with
processes of care for hypertension, we studied patients who had at least one hypertensionrelated outpatient visit to one of twelve general medicine clinics in community health
centers and community practices affiliated with a large urban academic medical center
from July 1, 2001 through June 30, 2002. To determine hypertension-related visits, we
reviewed the electronic medical record (EMR) for all clinic visits with a primary or
secondary diagnostic code of hypertension (HTN) (ICD-9 401- 401.9, 405- 405.99). The
study protocol was approved by the Human Studies Committee at the Brigham and
Women’s Hospital.
Medical Record
Trained abstracters reviewed the EMR of each hypertension-related visit,
collecting: patient race/ethnicity, patient age at time of visit, sex, primary insurer at time
of visit, presence of comorbid disease (diabetes, congestive heart failure (CHF), coronary
artery disease (CAD), or renal failure) listed on the patient problem list, drug allergies,
class of antihypertensive drug on medication list, and any changes made to
antihypertensive drug therapy during visit (decrease or discontinuation of drug, change to
another class of drug, or increase of drug dose or addition of new drug). Patient zip code
was also obtained and linked to 2000 U.S. Census data to obtain the median annual
household income in each patient’s zip code.
JNC Adherence
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To determine adherence to published JNC guidelines, we developed an algorithm
(Figure I) to assess whether patients were receiving the JNC-recommended drug therapy
at the time of each visit. Visits were classified as JNC adherent if the patient had been
receiving a JNC-recommended medication. Visits at which the patient was taking more
than one antihypertensive medication were considered adherent if at least one of the
medications was from a recommended drug class. Visits were considered non-JNC
adherent if a patient was receiving a non-recommended medication, or was not receiving
drug therapy when a clear indication for treatment was found on EMR review. Visits at
which a patient had a documented allergy or contraindication to the JNC recommended
medication were considered adherent if the patient was receiving a different class of antihypertensive medications. Those visits in which no antihypertensive medications were
listed and no comorbid disease indication for drug treatment was documented were
excluded from analysis because of difficulty in determining whether the patient should be
on pharmacologic therapy at their index visit (N=2,641) (however, these visits were
eligible for inclusion for our examination of intensification of therapy). Each reviewer
assessed JNC adherence in a subset of 65 records; we then tested for inter-rater reliability
(kappa=0.98) and found excellent agreement among reviewers.
Blood Pressure Control
To determine BP at time of visit, we obtained BP readings from the encounter
note for each visit. If more than one BP was recorded for the visit, we averaged them to
obtain the mean systolic and diastolic BP at the visit. We also classified each mean BP as
controlled (<130/85 for patients with diabetes or renal failure or <140/90 for other
patients) or uncontrolled for each visit.
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Intensity of Therapy
To determine whether providers intensified drug therapy for hypertension
differentially for racial and ethnic groups, we conducted an EMR review of a random
subset of 1,205 patients who had a minimum of two hypertension-related visits during the
one-year study period (totaling 3,257 visits). Each visit was classified into one of the
following categories according to previously defined changes in medications.1 A
“decrease” was considered a decrease or stop in the dosage of any antihypertensive
medication and no increase in another medication; “no change” was defined as a change
within class (e.g., nifedipine to diltiazem) or no change of BP medications; and an
“increase” was considered an increase in the dosage of any anti-hypertensive medication
or starting a new medication. We further classified each visit into two categories,
intensified (an increase) versus non-intensified (a decrease or no change).
We developed an algorithm to determine whether a patient received at least one
increase in drug therapy in response to a repeatedly elevated BP during the study period
(Figure II). Each patient with fewer than two visits with an elevated BP was excluded
from the algorithm (N=355). Each patient with an uncontrolled BP at more than one visit
was identified as either an intensified case (at least one drug increase) or a non-intensified
case (no drug increases). Each reviewer examined a subset of 30 records; we then tested
for inter-rater reliability and found excellent agreement among reviewers (kappa=0.90).
Data Analysis
To examine the demographic and clinical characteristics of our cohort, we used
chi-square tests for categorical variables and Student's t-tests for continuous variables to
compare patient characteristics by race/ethnicity and to compare demographic and
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clinical characteristics by visit type (JNC adherent vs. non-adherent). We report twotailed P values with statistical significance set at P0.05.
We also estimated the association of BP control at a visit with JNC adherence and
with the demographic and clinical characteristics obtained from EMR review. Since the
JNC VI cutoff for uncontrolled BP is different for patients with diabetes or renal failure
than for the general population, we also compared mean systolic and diastolic BP levels
in patients with diabetes and/or renal failure and those without, using Student's t-test.
Using logistic regression and adjusting for all measured confounders, we assessed
whether race/ethnicity was associated with JNC adherence or BP control. Data were
available on every variable for 12,790 of the 13,127 visits (97.4%) for multivariate
analyses. We report adjusted odds ratios with 95% confidence intervals for JNCadherent visits and for BP control by patient race/ethnicity. All analyses used SUDAAN
statistical software (Research Triangle Institute, Research Triangle Park, North Carolina)
to adjust for within-patient correlation of visits and within-provider correlation of visits.2
For each of the 1,205 patients with multiple hypertension-related visits, we estimated the
association of intensifying therapy (intensified case versus non-intensified case) during
the study period with race/ethnicity using chi-square tests. We also estimated the
association between intensifying therapy at a visit and obtaining BP control at a
subsequent visit, adjusting for race/ethnicity and baseline systolic and diastolic BP using
repeated measures logistic regression. In a secondary analysis, we included interaction
terms for race/ethnicity and intensity of therapy to determine whether the association of
intensity of therapy with subsequent BP control differed by race. All non-significant
interaction terms were removed from the final model. Data were available on every
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variable for 1,926 of the 3,257 visits (59.1%) for multivariate analyses. Models were
estimated with the SAS procedures Proc GenMod and Proc Mixed.
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References:
1. Berlowitz DR, Ash AS, Hickey EC, Friedman RH, Glickman M, Kader B,
Moskowitz MA. Inadequate management of blood pressure in a hypertensive
population. N Engl J Med. 1998; 339:1957-1963.
2. Frane J. SUDAAN: Professional Software for Survey Data Analysis. Research
Triangle Park, NC: Research Triangle Institute; 1989.
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LEGEND FOR FIGURES
Figure I:
Flow diagram of algorithm for determining JNC adherence. Inter-rater reliability was
high (kappa 0.98). We identified a total of 13,127 visits as either “guideline adherent”
(N=10,653) or a “non-adherent” (N=2474).
Figure II:
Flow diagram of algorithm for determining an “intensified case.” Inter-rater reliability
was high (kappa 0.90). We identified a total of 850 cases as either an “intensified case
(N=671) or a “non-intensified case” (N=179).
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Figure I: Algorithm for determining adherence to JNC VI guidelines
History of hypertension
or elevated blood
pressure?
No
Yes
Diabetes or Targetorgan damage?
No
Excluded from
analysis
Yes
Yes
Diabetes?
Blood pressure
medications listed?
No
Yes
ACE inhibitor
or
A-II blocker
Age  60 or Black?
Yes
Diuretic or Calcium
channel blocker
No
Myocardial infarction,
or coronary artery
disease?
Yes
Beta blocker
No
No
Renal insufficiency?
Yes
ACE inhibitor
or A-II blocker
Yes
ACE inhibitor or
A-II blocker
No
Congestive heart failure
or left ventricular
hypertrophy?
No
Age  60 or Black?
Diuretic or Beta
Blocker
No
Yes
Diuretic or Calcium
channel blocker
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Figure II: Algorithm for determining intensified case
BP uncontrolled at any
visit?
Yes
No
Patient excluded from
Therapy
intensified 1st
uncontrolled visit
analyses
No
Yes
BP controlled at a
second visit following
an uncontrolled visit?
BP controlled at
all subsequent
visits?
Yes
Yes
No
No
Therapy intensified at
an uncontrolled
follow-up visit?
Yes
Intensified
case
No
Non-intensified
case
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