Comparison of agreement between different measures of blood pressure in primary care and daytime ambulatory blood pressure

OBJECTIVE: To assess alternatives to measuring ambulatory pressure, which best predicts response to treatment and adverse outcome. SETTING: Three general practices in England. DESIGN: Validation study. PARTICIPANTS: Patients with newly diagnosed high or borderline high blood pressure; patients receiving treatment for hypertension but with poor control. MAIN OUTCOME MEASURES: Overall agreement with ambulatory pressure; prediction of high ambulatory pressure (>135/85 mm Hg) and treatment thresholds. RESULTS: Readings made by doctors were much higher than ambulatory systolic pressure (difference 18.9 mm Hg, 95% confidence interval 16.1 to 21.7), as were recent readings made in the clinic outside research settings (19.9 mm Hg,17.6 to 22.1). This applied equally to treated patients with poor control (doctor v ambulatory 21.4 mm Hg, 17.3 to 25.4). Doctors' and recent clinic readings ranked systolic pressure poorly compared with ambulatory pressure and other measurements (doctor r=0.46; clinic 0.47; repeated readings by nurse 0.60; repeated self measurement 0.73; home readings 0.75) and were not specific at predicting high blood pressure (doctor 26%; recent clinic 15%; nurse 72%; patient in surgery 81%; home 60%), with poor likelihood ratios for a positive test (doctor 1.2; clinic 1.1; nurse 2.1, patient in surgery 4.7; home 2.2). Nor were doctor or recent clinic measures specific in predicting treatment thresholds. CONCLUSION: The “white coat” effect is important in diagnosing and assessing control of hypertension in primary care and is not a research artefact. If ambulatory or home measurements are not available, repeated measurements by the nurse or patient should result in considerably less unnecessary monitoring, initiation, or changing of treatment. It is time to stop using high blood pressure readings documented by general practitioners to make treatment decisions.

研究目的：评估动态血压（ambulatory pressure）测量的替代方案，该方案可最优预测治疗响应与不良预后。
研究场景：英格兰的三家全科诊所。
研究设计：验证性研究。
研究对象：新诊断为高血压或临界高血压的患者；正在接受高血压治疗但血压控制不佳的患者。
主要结局指标：与动态血压的整体一致性；预测动态血压升高（>135/85 mmHg）及治疗阈值的情况。
研究结果：医生测量的读数显著高于动态收缩压（差值为18.9 mmHg，95%置信区间16.1~21.7 mmHg），非研究场景下近期的门诊测量读数亦是如此（差值19.9 mmHg，95%置信区间17.6~22.1 mmHg）。该差异在血压控制不佳的接受治疗患者中同样存在（医生测量值与动态血压差值为21.4 mmHg，95%置信区间17.3~25.4 mmHg）。相较于动态血压及其他测量方式，医生测量与近期门诊测量的收缩压排序相关性较差（医生组r=0.46；门诊组r=0.47；护士重复测量组r=0.60；患者自我重复测量组r=0.73；家庭测量组r=0.75），且二者在预测高血压时特异性不足（医生组26%；近期门诊组15%；护士组72%；诊室患者测量组81%；家庭测量组60%），阳性检测似然比亦较差（医生组1.2；门诊组1.1；护士组2.1；诊室患者组4.7；家庭组2.2）。医生测量与近期门诊测量同样无法特异性预测治疗阈值。
研究结论：“白大衣效应”在基层医疗的高血压诊断与疗效评估中具有重要意义，并非仅存在于研究场景中的人为现象。若无法获取动态血压或家庭测量数据，采用护士或患者的重复测量方式，可大幅减少不必要的监测、治疗启动或治疗方案调整。如今应停止使用全科医生记录的高血压读数来制定治疗决策。