Blood pressure measurement and blood pressure control in Veterans Affairs medical centers

Abstract The Veterans Affairs (VA) medical centers provide care for millions of Veterans at high risk of cardiovascular disease and accurate BP measurement in this population is vital for optimal BP control. Few studies have examined terminal digit preference (TDP), a marker of BP measurement bias, clinician perceptions of BP measurement, and BP control in VA medical centers. This mixed methods study examined BP measurements from Veterans aged 18 to 85 years with hypertension and a primary care visit within 8 VA medical centers. TDP for all clinic BP measurements was examined using a goodness of fit test assuming 10% frequency for each digit. Interviews were also conducted with clinicians from 3 VA medical centers to assess perceptions of BP measurement. The mean age of the 98,433 Veterans (93% male) was 68.5 years (SD 12.7). BP was controlled (<140/90 mmHg) in 76.5% and control rates ranged from 72.2% to 81.0% across the 8 VA medical centers. Frequency of terminal digits 0 through 9 differed significantly from 10% for both SBP and DBP within each center (P < .001) but level of TDP differed by center. The highest BP control rates were noted in centers with highest TDP for digits 0 and 8 for both SBP and DBP. Clinicians reported use of semi‐automated oscillometric devices for clinic BP measurement, but elevated BP readings were often confirmed by auscultatory methods. Significant TDP exists for BP measurement in VA medical centers, which reflects continued use of auscultatory methods.


INTRODUCTION & BACKGROUND
Blood pressure (BP) control remains the most effective intervention for primary and secondary cardiovascular disease (CVD) prevention. [1][2][3] Hypertension affects over half of Veterans aged 50 years and older, 4 and CVD prevalence is higher among Veterans compared to the general population 5 and continues to be a major reason for disability and hospitalization. 6,7 Two decades ago, the Veterans Affairs (VA) medical centers, which provides care for millions of Veterans across the U.S., implemented system wide strategies to improve the diagnosis and treatment of hypertension. Interventions to improve BP control included use of BP control as a performance measure, automated provider notification of uncontrolled BP, electronic clinical reminders to address hypertension, and systematic return to clinic schedules. 8 In 2012, Fletcher et al reported that these system wide interventions led to a 3% annual increase in BP control (<140/90 mmHg) across VA medical centers during years 2000−2010. 8 During this timeperiod, BP was measured with the auscultatory method using aneroid sphygmomanometers.
Knowledge regarding optimal BP measurement techniques and hypertension treatment have evolved over the past decade. Hypertension guidelines 1,9 and a scientific statement from the American Heart Association 10 now recommends the oscillatory method using automated or semi-automated devices for BP measurement because this method eliminates terminal digit preference (TDP), the tendency to record a specific digit (e.g., 0) more frequently than others when recording a BP measurement. In addition, automated and semiautomated devices do not require frequent calibration like aneroid sphygmomanometer devices. [11][12][13] We recently reported the presence of strong TDP for BP measurements in Veterans receiving care from a single VA patient aligned care team (PACT) and TDP was eliminated with implementation of a standardized BP measurement protocol using semi-automated oscillometric devices. 14  were identified and 202,781 had at least one PACT clinic visit within 12 months preceding the index visit (see Figure 1). Within this group, over half (n = 107,449) had an ICD-10 diagnosis code of hypertension or their electronic medical record (EMR) problem list included hypertension ( Figure 1). Veterans who died before or within 6 months after the index date (n = 4287), were receiving dialysis (n = 1692), or had no recorded BP value on the index date (n = 3037) were excluded. A total of 98,443 Veterans with hypertension and at least one PACT clinic visit with complete BP data during the study period were included in the analysis ( Figure 1).
Demographics and co-morbidity data were obtained from the CDW.
Race and ethnicity were self-reported and presence of diabetes and CVD (arrhythmias, coronary artery disease, heart failure, valvular heart disease, ischemic or hemorrhagic stroke, peripheral arterial disease, carotid artery disease or aortic aneurysm) were based on ICD-10 diagnosis codes or these diagnoses were included in the EMR problem list. Chronic kidney disease (CKD) was based on an ICD10 CKD diagnosis code, inclusion of CKD in the EMR problem list, or an esti-

Data collection
Each interview was attended by at least two trained members of the study team (AMH, MO, IK). One research team member led the interview with the participant while the other documented notes. The interviewers reviewed field notes scrubbed of identifying information for completeness and accuracy. Two members of the research team (AMH, HK) then reviewed each transcript independently using deductive thematic analysis (DTA) 19,20 to identify and extract emergent themes related to BP measurement according to the MAP framework. [15][16][17][18] Coders were in high agreement (99.9%, Κ = 0.98) and discrepancies were resolved via consensus.

Quantitative analyses
The  Figure S1). Figure 4 shows the BP control rates for each of the 8 centers with their corresponding frequency of terminal digits 0 and 8 for SBP (top) and DBP (bottom). The centers with the highest BP control rates had the highest TDP for 0 and 8.

Qualitative analyses
Thirteen interviews with four LPNs, three nurse managers and six physicians working in PACT clinics were completed. Table 3 provides data on respondent's perceptions of BP measurement

DISCUSSION
In this study, we examined the distribution of terminal digits for both SBP and DBP in hypertensive Veterans across 8 VA medical centers.
For both SBP and DBP, TDP was present in all centers but level of TDP differed by center. All 8 centers showed preference for even numbers when recording BP, which reflects use of auscultatory methods.
Deciles on manometer scales are divided into 2 mm increments so even digits are usually recorded. 13,21,22  The average BP over a prolonged period of time is the most important predictor of long-term CVD events. 25 Clinics measure BP to assess the patient's need for initiation or modification of hypertension treatment to reduce CVD risk. However, a single clinic BP measurement may not provide accurate estimates of long-term average BP and CVD risk due to the beat-to-beat variability in BP. 21 Clinic BP may also be measured with poor technique and then recorded with preference for a certain terminal digit; these sources of error will further lower the correlation of a single clinic BP measurement with a patient's average BP over an entire day. 10