Differences between clinic blood pressure and morning home blood pressure, as shown by Bland-Altman plots, in a large observational study (HONEST study)

Is the Bland-Altman plot method useful without inferences for accuracy, precision, and agreement?

OBJECTIVE

This study aims to propose a comprehensive alternative to the Bland-Altman plot method, addressing its limitations and providing a statistical framework for evaluating the equivalences of measurement techniques. This involves introducing an innovative three-step approach for assessing accuracy, precision, and agreement between techniques, which enhances objectivity in equivalence assessment. Additionally, the development of an R package that is easy to use enables researchers to efficiently analyze and interpret technique equivalences.

METHODS

Inferential statistics support for equivalence between measurement techniques was proposed in three nested tests. These were based on structural regressions with the goal to assess the equivalence of structural means (accuracy), the equivalence of structural variances (precision), and concordance with the structural bisector line (agreement in measurements obtained from the same subject), using analytical methods and robust approach by bootstrapping. To promote better understanding, graphical outputs following Bland and Altman's principles were also implemented.

RESULTS

The performance of this method was shown and confronted by five data sets from previously published articles that used Bland and Altman's method. One case demonstrated strict equivalence, three cases showed partial equivalence, and one showed poor equivalence. The developed R package containing open codes and data are available for free and with installation instructions at Harvard Dataverse at https://doi.org/10.7910/DVN/AGJPZH.

CONCLUSION

Although easy to communicate, the widely cited and applied Bland and Altman plot method is often misinterpreted, since it lacks suitable inferential statistical support. Common alternatives, such as Pearson's correlation or ordinal least-square linear regression, also fail to locate the weakness of each measurement technique. It may be possible to test whether two techniques have full equivalence by preserving graphical communication, in accordance with Bland and Altman's principles, but also adding robust and suitable inferential statistics. Decomposing equivalence into three features (accuracy, precision, and agreement) helps to locate the sources of the problem when fixing a new technique.

A PPG-Based Calibration-Free Cuffless Blood Pressure Estimation Method Using Cardiovascular Dynamics

Traditional cuff-based sphygmomanometers for measuring blood pressure can be uncomfortable and particularly unsuitable to use during sleep. A proposed alternative method uses dynamic changes in the pulse waveform over short intervals and replaces calibration with information from photoplethysmogram (PPG) morphology to provide a calibration-free approach using a single sensor. Results from 30 patients show a high correlation of 73.64% for systolic blood pressure (SBP) and 77.72% for diastolic blood pressure (DBP) between blood pressure estimated with the PPG morphology features and the calibration method. This suggests that the PPG morphology features could replace the calibration stage for a calibration-free method with similar accuracy. Applying the proposed methodology on 200 patients and testing on 25 new patients resulted in a mean error (ME) of -0.31 mmHg, a standard deviation of error (SDE) of 4.89 mmHg, a mean absolute error (MAE) of 3.32 mmHg for DBP and an ME of -4.02 mmHg, an SDE of 10.40 mmHg, and an MAE of 7.41 mmHg for SBP. These results support the potential for using a PPG signal for calibration-free cuffless blood pressure estimation and improving accuracy by adding information from cardiovascular dynamics to different methods in the cuffless blood pressure monitoring field.

Fimasartan reduces clinic and home pulse pressure in elderly hypertensive patients: A K-MetS study

Background

Angiotensin II receptor blockers (ARBs) are recommended for treating patients with hypertension. However, comparative safety and efficacy of ARB use in elderly patients have not been well established. This study was designed to determine the efficacy of fimasartan, an ARB, in hypertensive elderly patients by measuring clinic and home blood pressures (BPs) and evaluating safety compared to nonelderly patients.

Method

In the K-MetS study, a nationwide prospective observational study of hypertensive patients on fimasartan, elderly patients (60 years and older) who were treated for 1 year with fimasartan were recruited. BP was evaluated in clinic and at home.

Results

Of the 6 399 enrolled patients, 2 363 were elderly (46.9% males, mean age 67.3 ± 5.7 years). Fimasartan reduced systolic and diastolic BP (SBP and DBP) in clinic from 144.1 ± 17.3 to 127.7 ± 12.9 mmHg and from 85.1 ± 10.4 to 76.8 ± 8.4 mmHg, respectively, (all p<0.0001) in 1 year. Similar results were found in home BPs. These BP changes were consistent with those in nonelderly patients. However, pulse pressure, a better predictor of cardiovascular events in the elderly, decreased more in elderly than in nonelderly patients by -8.2 ± 0.3 in elderly and -7.0 ± 0.2 mmHg (p<0.0001), respectively, after adjustment for confounding factors. Adverse events were reported in 1.6% of elderly hypertensives, independent of dose, which was consistent with results in nonelderly patients.

Conclusions

Fimasartan resulted in better pulse pressure reduction with similar BP reduction efficacy and safety in hypertensive elderly patients compared with nonelderly patients.

Blood pressure differences between home monitoring and daytime ambulatory values and their reproducibility in treated hypertensive stroke and TIA patients

BACKGROUND

Guidelines recommend ambulatory or home blood pressure monitoring to improve hypertension diagnosis and monitoring. Both these methods are ascribed the same threshold values, but whether they produce similar results has not been established in certain patient groups.

METHODS

Adults with mild/moderate stroke or transient ischemic attack (N = 80) completed 2 sets of ambulatory and home blood pressure monitoring. Systolic and diastolic blood pressure values from contemporaneous measurements were compared, and the limits of agreement were assessed. Exploratory analyses for predictive factors of any difference were conducted.

RESULTS

Daytime ambulatory blood pressure values were consistently lower than home values, the mean difference in systolic blood pressure for initial ambulatory versus first home monitoring was -6.6 ± 13.5 mm Hg (P≤.001), and final ambulatory versus second home monitoring was -7.1 ± 11.0mm Hg (P≤.001). Mean diastolic blood pressure differences were -2.1 ± 8.5mm Hg (P=.03) and -2.0 ± 7.2mm Hg (P=.02). Limits of agreement for systolic blood pressure were -33.0 to 19.9mm Hg and -28.7 to 14.5mm Hg for the 2 comparisons and for DBP were -18.8 to 14.5mm Hg and -16.1 to 12.2mm Hg, respectively. The individual mean change in systolic blood pressure difference was 11.0 ± 8.3mm Hg across the 2 comparisons. No predictive factors for these differences were identified.

CONCLUSIONS

Daytime ambulatory systolic and diastolic blood pressure values were significantly lower than home monitored values at both time points. Differences between the 2 methods were not reproducible for individuals. Using the same threshold value for both out-of-office measurement methods may not be appropriate in patients with cerebrovascular disease.

Home blood pressure and cardiovascular risk in treated hypertensive patients: the prognostic value of the first and second measurements and the difference between them in the HONEST study

Hypertension guidelines recommend using the average of two home blood pressure (HBP) measurements obtained on one occasion to monitor blood pressure. We studied the prognostic value of the first and second measurements or their average value during the follow-up period, as well as the relationships among the difference between the first and second HBP measurements and the prognosis using data from the HONEST (HBP measurement with Olmesartan-Naive patients to Establish Standard Target blood pressure) study. During the mean 2.02 years follow-up, 280 patients had cardiovascular events. Hazard ratios (HRs) for cardiovascular events for each 1 mm Hg increase in the first, second and averaged morning home systolic blood pressure (MHSBP) were similar. Hazards were significantly higher in patients with a large difference between the first and second MHSBP (ΔMHSBP) of <-5 mm Hg (HR: 2.12) or ⩾5 mm Hg (HR: 1.44) compared with those with a small ΔMHSBP of ⩾-5 to <5 mm Hg using the Cox proportional hazards model adjusted for the averaged MHSBP during the follow-up and other risk factors. Hazards in patients with an averaged MHSBP ⩾145 mmHg and a small ΔMHSBP (HR: 3.11), those with an averaged MHSBP ⩾125 to <145 mm Hg and a large ΔMHSBP (HR: 1.91) and those with an averaged MHSBP ⩾145 mm Hg and a large ΔMHSBP (HR: 4.63) were higher compared with those with an averaged MHSBP <125 mm Hg and a small ΔMHSBP. In conclusion, the first, second and averaged MHSBP measurements have similar prognostic values. Prognosis is worse for patients with a large ΔMHSBP. In clinical practice, it would be prudent to measure the HBP two times and use the average HBP of two measurements obtained on one occasion with particular attention to patients with a large ΔMHSBP.

Administration time-dependent effects of combination therapy on ambulatory blood pressure in hypertensive subjects

The aim of this study was to explore the influence of combination therapy in different administration time on antihypertensive efficacy and blood pressure variability in patients with essential hypertension. A total of 86 patients with stage II to III essential hypertension were randomly divided into 4 groups: taking indapamide and losartan potassium together in the morning or in the evening 2 to 4 hours before sleep, indapamide in the morning and losartan potassium in the evening, losartan potassium in the morning and indapamide in the evening. Ambulatory blood pressure monitoring was performed before and 12 weeks after the medication. The result showed that statistically significant reductions from baseline of systolic blood pressure/diastolic blood pressure occurred in all treatment groups. There was no significant difference of the reductions or SI among the four groups, neither the rate of decline of BP in the night or the circadian rhythm. In group B, the numbers of rapid rise in BP in the morning hours were significantly less after the medication, while not in the other groups. It is concluded that independent of the administration time, both once-daily treatment and component-based dual therapy had significant antihypertensive effect, but the night taken-together combination resulted in reductions of BP, SI and morning blood pressure peak that may have advantages over the other combinations, without the increased incidence of hypotension at night. Medicines should be taken 2 to 4 hours before sleep.