The importance of the clinical observer in the development of a white-coat effect in African-American patients with hypertension

Time Sequence of Measurement Affects Blood Pressure Level in an African American Cohort

INTRODUCTION

Uncontrolled hypertension can result in severe clinical conditions such as stroke, chronic kidney disease and congestive heart failure, especially in African American populations. To the knowledge of the authors, the effect of time sequence on blood pressure (BP) using an Automated Office Blood Pressure (AOBP) device has not been documented in an African American cohort. The objective of this study was to investigate the possible influence of time sequence of measurement (pre- and post-physician visit) on BP readings in an African American cohort, in the presence or absence of a Medical Assistant (MA) via AOBP monitoring.

METHODS

A two-phase, single-blinded, non-randomized trial was conducted at MI-based Ascension Providence Hospital with a convenience sample of hypertensive patients. BP readings were taken using both an Omron 907 (Omron Corp., Kyoto, Japan) and a Welch Allyn (WA) Connex Spot Monitor (Welch Allyn, Inc., Skaneateles Falls, NY) AOBP devices. Descriptive statistics were generated, and T-tests were performed.

RESULTS

In Phase 1, (N = 148), the mean systolic/diastolic readings for the pre-physician visits (141/82 mmHg) were statistically significantly higher than the post-visit readings (134/80 mmHg) (p ≤ 0.02). Post-visit physician readings from either AOBP device did not differ statistically (p = 0.72). In Phase 2 (n = 50), the presence of an MA resulted in significantly higher readings than when an MA was absent, however, the results of Phase 2 also supported the trends for lower BP post-physician visit found in Phase 1.

CONCLUSION

Based on the consistency of these results, a post-physician visit AOBP reading, in the presence or absence of an MA, may provide a more accurate BP measurement to determine whether or not to treat hypertension in African American patients.

Genome-wide association study for white coat effect in Japanese middle-aged to elderly people: The HOMED-BP study

BACKGROUND

White coat effect (WCE), the blood pressure (BP) difference between clinical and non-clinical settings, can lead to clinical problems such as misdiagnosis of hypertension. Etiology of WCE has been still unclear, especially from genetic aspects. The present article investigated association between genome-wide single nucleotide polymorphisms (SNPs) and WCE in patients with essential hypertension.

METHODS

The present cross-sectional analyses were based on 295 Japanese essential hypertensive outpatients aged ≧40 years enrolled in randomized control study, Hypertension Objective Treatment Based on Measurement by Electrical Devices of Blood Pressure (HOMED-BP) study, who were not taking antihypertensive medications before the randomization. Home and clinic BP were measured. WCE was defined by subtracting home BP from clinic BP. Genotyping was conducted with 500K DNA microarray chips. Association between genome-wide SNPs and WCE were analyzed. For replication (p < 10^-4), we analyzed participants from Ohasama study who took no antihypertension medications and whose SNPs were collected.

RESULTS

Genome-wide SNPs were not significantly associated with WCE of systolic and diastolic BP after corrections of multiple comparisons (p < 2 × 10^-7). We found suggestive SNPs associated with WCE of systolic and diastolic BP (p < 10^-4). However, the consistent results were not obtained in the replication study.

CONCLUSION

The present article showed no significant association between genome-wide SNPs and WCE. Since there were several suggestive SNPs associated with WCE, the present study warrants a further study with bigger sample size for investigating the genetic influence on WCE.

Nonlinear Conte-Zbilut-Federici (CZF) Method of Computing LF/HF Ratio: A More Reliable Index of Changes in Heart Rate Variability

Objectives:

Acupuncture treatments are safe and effective for a wide variety of diseases involving autonomic dysregulation. Heart rate variability (HRV) is a noninvasive method for assessing sympathovagal balance. The low frequency/high frequency (LF/HF) spectral power ratio is an index of sympathovagal influence on heart rate and of cardiovascular health. This study tests the hypothesis that from rest to 30% to 50% of peak oxygen consumption, the nonlinear Conte-Zbilut-Federici (CZF) method of computing the LF/HF ratio is a more reliable index of changes in the HRV than linear methods are.

Methods:

The subjects of this study were 10 healthy young adults. Electrocardiogram RR intervals were measured during 6-minute periods of rest and aerobic exercise on a cycle ergometer at 30% and 50% of peak oxygen consumption (VO_2peak).

Results:

The frequency domain CZF computations of the LF/HF ratio and the time domain computations of the standard deviation of normal-to-normal intervals (SDNN) decreased sequentially from rest to 30% VO_2peak (P < 0.001) to 50% VO_2peak (P < 0.05). The SDNN and the CZF computations of the LF/HF ratio were positively correlated (Pearson’s r = 0.75, P < 0.001). fast Fourier transform (FFT), autoregressive (AR) and Lomb periodogram computations of the LF/HF ratio increased only from rest to 50% VO_2peak.

Conclusion:

Computations of the LF/HF ratio by using the nonlinear CZF method appear to be more sensitive to changes in physical activity than computations of the LF/HF ratio by using linear methods. Future studies should determine whether the CZF computation of the LF/HF ratio improves evaluations of pharmacopuncture and other treatment modalities.

Doctors record higher blood pressures than nurses: systematic review and meta-analysis

BACKGROUND

The magnitude of the 'white coat effect', the alerting rise in blood pressure, is greater for doctors than nurses. This could bias interpretation of studies on nurse-led care in hypertension, and risks overestimating or overtreating high blood pressure by doctors in clinical practice.

AIM

To quantify differences between blood pressure measurements made by doctors and nurses.

DESIGN AND SETTING

Systematic review and meta-analysis using searches of MEDLINE, CENTRAL, CINAHL, Embase, journal collections, and conference abstracts.

METHOD

Studies in adults reporting mean blood pressures measured by doctors and nurses at the same visit were selected, and mean blood pressures extracted, by two reviewers. Study risk of bias was assessed using modified Cochrane criteria. Outcomes were pooled across studies using random effects meta-analysis.

RESULTS

In total, 15 studies (11 hypertensive; four mixed hypertensive and normotensive populations) were included from 1899 unique citations. Compared with doctors' measurements, nurse-measured blood pressures were lower (weighted mean differences: systolic -7.0 [95% confidence interval {CI} = -4.7 to -9.2] mmHg, diastolic -3.8 [95% CI = -2.2 to -5.4] mmHg). For studies at low risk of bias, differences were lower: systolic -4.6 (95% CI = -1.9 to -7.3) mmHg; diastolic -1.7 (95% CI = -0.1 to -3.2) mmHg. White coat hypertension was diagnosed more frequently based on doctors' than on nurses' readings: relative risk 1.6 (95% CI =1.2 to 2.1).

CONCLUSIONS

The white coat effect is smaller for blood pressure measurements made by nurses than by doctors. This systematic difference has implications for hypertension diagnosis and management. Caution is required in pooling data from studies using both nurse- and doctor-measured blood pressures.

Elevated Baseline Anxiety Among African Americans in Laboratory Research Settings

We tested the hypothesis that African Americans would show greater anxiety than their European American counterparts when entering laboratory research settings. We examined subjective and physiological anxiety measures obtained both inside and outside the research laboratory from 126 African Americans and 147 European Americans in three separate studies. Consistent with our hypotheses, African Americans reported experiencing significantly more baseline anxiety and showed greater baseline physiological arousal consistent with anxiety than European Americans. These differences were evident when controlling for anxiety observed outside of the research setting as well as baseline differences in overall emotional experience. Our findings highlight the need to consider laboratory-induced anxiety as a potential confound in studies involving African Americans. This may be especially important in race comparison studies in which undetected baseline anxiety could alter the interpretation of subsequent race comparisons.

Diagnosis and management of patients with white-coat and masked hypertension

White-coat hypertension is characterized by an elevation in clinic blood pressure but normal home or ambulatory blood-pressure values, whereas patients with masked hypertension have normal clinic blood pressure and elevated ambulatory or home blood-pressure load. Both white-coat and masked hypertension are frequent clinical entities that need appropriate recognition and a close diagnostic follow-up. White-coat and masked hypertension seem to be associated with organ damage and increased cardiovascular risk, although not invariably. In addition, patients with masked or white-coat hypertension have an increased risk of abnormalities affecting their glucose and lipid profiles. Therefore, the diagnosis of these conditions should be accurate and include the assessment of cardiovascular as well as of metabolic risk. Once diagnosed, first-line therapeutic interventions should be nonpharmacological and aim at lifestyle changes, but drug treatment can be indicated, particularly when the patient's cardiovascular risk profile is elevated or when target-organ damage is detected.