Thirty-Minute Office Blood Pressure Monitoring in Primary Care

Michiel J. Bos; Sylvia Buis

doi:10.1370/afm.2041

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Table 1

Mean Difference Between OBP30 and OBP Stratified by Reason to Request OBP30

Reasons to request OBP30	N^b	Difference Between OBP and OBP30^a
Reasons to request OBP30	N^b	Systolic (mm Hg)	Diastolic (mm Hg)
Suspected white-coat hypertension	75	29.6 (25.1–34.7)	14.4 (11.8–16.9)
New diagnosis of hypertension	42	19.7 (14.6–24.8)	10.8 (7.5–14.2)
Inconsistent office readings	23	22.3 (14.5–30.4)	11.4 (7.2–15.2)
To monitor medication effect	62	20.1 (15.0–25.8)	9.9 (7.6–12.4)
Suspected therapy resistance	13	28.4 (15.5–40.4)	8.2 (4.1–12.2)
Suspected episodes of hypotension	4	21.8 (11.5–37.0)	16.8 (13.5–21.5)
Other	7	13.7 (4.3–24.0)	7.7 (0.1–13.9)

OBP30 = automated office blood pressure monitoring during 30 minutes; OBP = office blood pressure.
↵a OBP minus OBP30.
↵b Multiple reasons may apply for a single patient.

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Table 2

Mean Blood Pressure: OBP30 Compared With OBP

Patient Group	N	Systolic OBP (95% CI), mm Hg	Systolic OBP30 (95% CI), mm Hg	Systolic Difference (95% CI), mm Hg	Diastolic OBP (95% CI), mm Hg	Diastolic OBP30 (95% CI), mm Hg	Diastolic Difference (95% CI), mm Hg
All patients	201	163.8 (161.5–166.2)	140.9 (138.4–143.5)	22.8 (19.8–26.1)	88.9 (87.4–90.4)	77.3 (75.7–78.9)	11.6 (10.2–13.1)
Men	87	162.5 (159.6–165.5)	141.9 (138.6–145.5)	20.6 (16.8–24.4)	90.0 (87.8–92.0)	80.1 (77.5–82.7)	9.9 (7.7–12.0)
Women	114	164.7 (161.5–167.8)	140.2 (136.8–143.5)	24.5 (20.7–28.7)	88.1 (86.1–90.0)	75.2 (72.9–77.5)	12.9 (10.9–14.8)
Aged <70 yrs	100	157.8 (155.4–160.0)	142.7 (139.5–146.1)	15.1 (11.5–18.2)	91.7 (89.8–93.7)	83.2 (81.0–85.5)	8.5 (6.7–10.5)
Aged >70 yrs	101	169.7 (166.1–173.4)	139.2 (135.8–142.8)	30.5 (26.5–34.7)	86.2 (84.1–88.4)	71.5 (69.6–73.6)	14.7 (12.6–16.7)
Without CVD or DM	132	162.0 (159.1–164.8)	140.1 (136.9–143.1)	21.9 (18.5–25.8)	89.5 (87.7–91.3)	77.6 (75.5–79.8)	11.8 (10.0–13.6)
With CVD or DM	69	167.2 (163.2–171.1)	142.6 (138.7–146.7)	24.6 (19.6–29.4)	87.8 (85.6–90.5)	76.8 (74.0–79.8)	11.1 (8.6–13.8)

CVD = cardiovascular disease (myocardial infarction, angina pectoris, stroke, transient ischemic attack); DM = diabetes mellitus; OBP30 = automated office blood pressure monitoring during 30 minutes; OBP = office blood pressure.

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Table 3

Physicians’ Treatment Advice Based on All Available Information Including OBP, but Ignoring OBP30 Results, and Based on All Available Information Including OBP30 Results

Medication Decision^a	Treatment Advice Ignoring OBP30 Results		Treatment Advice Including OBP30 Results		Difference % (95% CI)

	N	% (95% CI)	N	% (95% CI)
Intensified	159	79.1 (73.6–84.6)	50	24.9 (18.9–30.9)	−54.2 (−61.7 to −46.8)
Unchanged	34	16.9 (11.4–22.4)	134	66.7 (59.7–72.6)	49.8 (41.3–58.2)
Reduced	3	1.5 (0.0–3.5)	15	7.5 (4.0–11.4)	6.0 (3.0–9.5)
Other	5	2.5 (0.5–4.5)	2	1.0 (0.0–2.5)	−1.5 (−3.5–0.5)

OBP30 = automated office blood pressure monitoring during 30 minutes; OBP = office blood pressure.
↵a Intensified = medication was added or the dosage was increased. Unchanged = includes patients who continued on the same dosage and patients who were not on antihypertensive medication. Reduced = medication was stopped or the dosage was decreased.

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The Article in Brief

Thirty-Minute Office Blood Pressure Monitoring in Primary Health Care

Michiel J. Bos , and colleagues

Background Automated office blood pressure monitoring for a period of 30 minutes (OBP30) has been proposed as an alternative method for assessing sustained hypertension, since it yields almost the same results as daytime ambulatory blood pressure monitoring and is much more convenient. This study compares OBP30 with routine office blood pressure (OBP) readings in primary care and evaluates how OBP30 influences medications prescribed by family doctors.

What This Study Found In-office automated blood pressure monitoring over 30 minutes (OBP30) yields considerably lower blood pressure readings than office blood pressure in all patient groups studied. It also reduces the number of patients who meet the criteria for intensification of antihypertensive medication regimes. The differences between office blood pressure and OBP30 were larger for patients aged 70 years or older. Based on OBP alone, physicians said they would have started or intensified hypertension medication in 79 percent of studied cases, but with the results of OBP30 available, this number was only 25 percent.

Implications

OBP30 yields lower blood pressure readings than routine OBP in primary care and leads to an important reduction in medication prescriptions.