Related Experiment Videos
Terminal digit preference and single-number preference in the Syst-Eur trial: influence of quality control
David Wingfield1, Jonathan Cooke, Lut Thijs
1Department of Primary Health Care and General Practice, Charing Cross Campus, Imperial College, Faculty of Medicine, London, UK. david@hammerpcg.org.uk
Insights
Terminal digit preference in blood pressure measurements can lead to biased results. Data quality monitoring and feedback significantly reduced this bias in the Syst-Eur trial.
Area of Science:
- Clinical Trials
- Hypertension Management
- Data Quality Assurance
Background:
- Terminal digit preference and single-number preference can introduce inaccuracies and bias in blood pressure measurements.
- These biases can compromise the integrity of clinical trial data and treatment efficacy assessments.
Purpose of the Study:
- To describe terminal digit and single-number preference in blood pressure readings within the Syst-Eur trial.
- To detail the methods used to identify and mitigate these measurement biases.
Main Methods:
- The Syst-Eur trial's Data Monitoring Committee conducted annual quality control meetings and site visits.
- These meetings focused on identifying terminal digit preference, enhancing blood pressure control, and improving patient recruitment.
Main Results:
- The prevalence of terminal digit zero preference in systolic blood pressure readings decreased from 42.4% to 22% over 6 years.
- This reduction was attributed to data quality monitoring and feedback, independent of trial entry year.
- A single-number preference bias (148 mmHg) was observed in active treatment groups, linked to the target of reducing systolic blood pressure below 150 mmHg.
Conclusions:
- Continuous monitoring and feedback of data quality are essential to minimize digit and number preference in blood pressure measurements.
- Utilizing validated and regularly serviced automatic blood pressure devices can help avoid these issues, provided readings are not rejected and repeated.
Background:
Terminal digit and single-number preference may produce inaccuracy and biased results when measuring blood pressure. We describe these preferences in the Syst-Eur randomized placebo-controlled trial of the treatment of isolated systolic hypertension and describe how we sought to eliminate these problems.
Methods:
The Data Monitoring Committee of the trial conducted yearly quality control meetings in Belgium and visited the participating centres to check their adherence to the protocol. These meetings involved identifying terminal digit preference, improving blood pressure control and boosting recruitment.
Results:
The prevalence of use of terminal digit zero when measuring sitting systolic blood pressure (first readings) reduced from an average of 42.4% in the year prior to the date when a centre first randomized a patient to 31.5, 25, 22.3, 26.3, 23.2 and 22% in the subsequent 6 years. This trend was independent of the calendar year during which a centre entered the trial and supports the hypothesis that data-quality monitoring, including the feedback of digit preference to centres, led to a reduction in terminal digit zero preference. In addition, a higher than expected prevalence of the systolic blood pressure value of 148 mmHg was found in the active treatment groups in the double-blind phase. Selection for 148 mmHg persisted over time and constituted a single-number preference bias. This arose from the instruction to investigators to reduce systolic blood pressure to below 150 mmHg.
Conclusion:
Monitoring and feedback of data quality should be undertaken to minimize digit and number preference. Automatic devices should ideally be employed to help to avoid these problems as long as the devices are fully validated and regularly serviced, and providing that readings are not rejected and repeated.