Investigation of End-Digit Preference in Blood Pressure Records of Hospitalized Chinese Patients and Analysis of Risk Factors

Abstract

Objective: End–digit preference is common in blood pressure (BP) measurement, but there are no data available on end–digit preference in China. The purpose of this study was to investigate the frequency of end–digit preference in Chinese hospitalized patients and to explore its risk factors. Methods: We used systematic sampling to investigate the BP values and related characteristics in records from Chinese patients hospitalized at a university–affiliated hospital in Shanghai, China. Data were collected from January to December 2010. Logistic regression models were created to analyze the relationship between potential risk factors and zero end digit in recorded BP values. Results: Of all 4511 patient records, 57.1% of patients were male. The mean age was 55.1 years (standard deviation [SD], 15.4 years). When admitted, the mean BP values were 124.6 mm Hg (SD, 14.3 mm Hg) for systolic blood pressure (SBP) and 77.5 mm Hg (SD, 8.6 mm Hg) for diastolic blood pressure (DBP). 81.8% and 81.2% of SBP and DBP values had an end digit of zero. 7.7% and 9.6% of SBP and DBP values had an end digit of “5.” In the logistic regression analyses, female sex (odds ratio [OR], 1.34 for SBP, 1.24 for DBP), admission to a surgical department (OR, 2.04 for SBP, 1.88 for DBP), admission heart rate of ≥ 80 bpm (OR, 1.41 for SBP, 1.61 for DBP), and not having a history of hypertension (OR, 1.41 for SBP, 1.33 for DBP) were related to a high risk of having SBP and DBP values with a zero end digit. Patients with SBP values of ≥ 140 mm Hg had a high risk of having a zero end digit in SBP values (OR, 1.33) and a low risk of having a zero end digit in DBP values (OR, 0.67). Patients whose DBP values were ≥ 90 mm Hg had a high risk of having a zero end digit in DBP values (OR, 2.49). Conclusion: The zero end–digit preference in recorded BP values of hospitalized patients in China was strong. Patients' sex, admission to a surgical department, admission heart rate, history of hypertension, and SBP and DBP values were risk factors that influenced the preference for zero as the end–digit BP value.