Examining the effectiveness of telemonitoring with routinely acquired blood pressure data in primary care: challenges in the statistical analysis

Divergent confidence intervals among pre-specified analyses in the HiSTORIC stepped wedge trial: An exploratory post-hoc investigation

BACKGROUND

The high-sensitivity cardiac troponin on presentation to rule out myocardial infarction (HiSTORIC) study was a stepped-wedge cluster randomised trial with long before-and-after periods, involving seven hospitals across Scotland. Results were divergent for the binary safety endpoint (type 1 or type 4b myocardial infarction or cardiac death) across certain pre-specified analyses, which warranted further investigation. In particular, the calendar-matched analysis produced an odds ratio in the opposite direction to the primary logistic mixed-effects model analysis.

METHODS

Several post-hoc statistical models were fitted to each of the co-primary outcomes of length of hospital stay and safety events, which included adjusting for exposure time, incorporating splines, and fitting a random time effect. We improved control of patient characteristics over time by adjusting for multiple additional covariates using different methods: direct inclusion, regression adjustment for propensity score, and weighting. A data augmentation approach was also conducted aiming to reduce the effect of sparse data bias. Finally, the raw data was examined.

RESULTS

The new statistical models confirmed the results of the pre-specified trial analysis. In particular, the observed divergence between the calendar-matched and other analyses remained, even after performing the covariate adjustment methods, and after using data augmentation. Divergence was particularly acute for the safety endpoint, which had an event rate of 0.36% overall. Examining the raw data was particularly helpful to assess the sensitivity of the results to small changes in event rates and identify patterns in the data.

CONCLUSIONS

Our experience reveals the importance of conducting multiple pre-specified sensitivity analyses and examining the raw data, particularly for stepped wedge trials with low event rates or with a small number of sites. Before-and-after analytical approaches that adjust for differences in patient populations but avoid direct modelling of the time trend should be considered in future stepped wedge trials with similar designs.

Clinical Practice Changes in Monitoring Hypertension Early in the COVID-19 Pandemic

BACKGROUND

Clinical practices can use telemedicine and other strategies (e.g., self-measured blood pressure [SMBP]) for remote monitoring of hypertension to promote control while decreasing risk of exposure to SARS-CoV-2, the virus that causes COVID-19.

METHODS

The DocStyles survey collected data from primary care providers (PCPs), obstetricians-gynecologists (OB/GYNs), and nurse practitioners/physician assistants (NP/PAs) in fall 2020 (n = 1,502). We investigated clinical practice changes for monitoring hypertension that were implemented early in the COVID-19 pandemic and examined differences by clinician and practice characteristics (P < 0.05).

RESULTS

Overall, 369 (24.6%) of clinicians reported their clinical practices made no changes in monitoring hypertension early in the pandemic, 884 (58.9%) advised patients to monitor blood pressure at home or a pharmacy, 699 (46.5%) implemented or increased use of telemedicine for blood pressure monitoring visits, and 545 (36.3%) reduced the frequency of office visits for blood pressure monitoring. Compared with NP/PAs, PCPs were more likely to advise SMBP monitoring (adjusted prevalence ratios [aPR] 1.28, 95% confidence intervals [CI] 1.11-1.47), implement or increase use of telemedicine (aPR 1.23, 95% CI 1.04-1.46), and reduce the frequency of office visits (aPR 1.37, 95% CI 1.11-1.70) for blood pressure monitoring, and less likely to report making no practice changes (aPR 0.63, 95% CI 0.51-0.77).

CONCLUSIONS

We noted variation in clinical practice changes by clinician type and practice characteristics. Clinical practices may need additional support and resources to fully maximize telemedicine and other strategies for remote monitoring of hypertension during pandemics and other emergencies that can disrupt routine health care.