Quite variable. With >2 measurements at each visit, the standard deviation between visits is 5–12 mmHg
systolic and 6–8 diastolic. Between-visits variability is greater than within-visit fluctuation. Hence, more visits
are needed to ensure diagnostic precision. That is why the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommends repeat measurements within 1 month for initial values in the range of 160–179 mmHg systolic or 100–109 mmHg diastolic (stage 2 hypertension), within 2 months for stage 1, within 1 week for stage 3, and immediate evaluation for stage 4. Arrhythmias (especially atrial fibrillation) also may cause beat-tobeat variations in cardiac output and thus increase interobserver variation in blood pressure measurements. Averaging several readings may help
systolic and 6–8 diastolic. Between-visits variability is greater than within-visit fluctuation. Hence, more visits
are needed to ensure diagnostic precision. That is why the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommends repeat measurements within 1 month for initial values in the range of 160–179 mmHg systolic or 100–109 mmHg diastolic (stage 2 hypertension), within 2 months for stage 1, within 1 week for stage 3, and immediate evaluation for stage 4. Arrhythmias (especially atrial fibrillation) also may cause beat-tobeat variations in cardiac output and thus increase interobserver variation in blood pressure measurements. Averaging several readings may help