Summary:
Background: Several studies with relatively small size, different design and
endpoints have investigated the diagnostic ability of home blood pressure (HBP)
monitoring. The objective of this study was to investigate the usefulness of
HBP compared to ambulatory monitoring (ABP) in diagnosing sustained
hypertension, white coat phenomenon (WCP) and masked hypertension (MH) in a
large sample of untreated and treated subjects using a blood pressure (BP)
monitoring protocol according to current guidelines. The diagnostic ability of
HBP was also tested in subjects with resistant hypertension (RH), whereas
morning hypertension detected by HBP or ABP, a novel field in hypertension was
also investigated.
Method: A total of 613 subjects attending a hypertension clinic (mean age 53±12.
4 [SD] years, men 57%, untreated 59%) had measurements of clinic BP (3 visits,
triplicate measurements per visit), HBP (6 days, duplicate morning and evening
measurements) and awake ABP (20 min intervals) within 6 weeks. Among subjects
on stable treatment with 3 antihypertensive drugs, clinic RH was defined as
elevated clinic BP and true RH as elevated awake ABP. The diagnostic value of
HBP was assessed by taking ABP as reference method. Threshold for hypertension
diagnosis was 135/85 mmHg for HBP and awake ABP and 140/90 mmHg for clinic
BP. Morning HBP (6 days, duplicate morning readings) was compared with mοrning
ABP (first 1, 2 or 3 h after arising). Morning hypertensives' were defined as
individuals with morning HBP or ABP 135/85 mmHg.
Results: Sustained hypertension was diagnosed in 50% of the participants by ABP
and HBP (agreement 89%, kappa 0.79), WCP in 14% and 15% respectively (agreement
89%, kappa 0.56) and MH in 16% and 15% (agreement 88%, kappa 0.52). The
sensitivity, specificity, positive and negative predictive value of HBP in
detecting sustained hypertension were 90%, 89%, 89% and 90% respectively, WCP
61%, 94%, 64% and 94% and MH 60%, 93%, 60% and 93%. These findings did not
change when treated or untreated subjects were analysed separately. Among 73
subjects on 3 antihypertensive drugs, 44 (60%) had clinic RH and 40 (55%) true
RH. There was agreement between ABP and HBP in diagnosing clinic RH in 82% of
the cases (kappa 0.59). Regarding the diagnosis of true RH, there was agreement
between ABP and HBP in 74% of the cases (kappa 0.46).The sensitivity,
specificity and positive and negative predictive values of HBP in detecting
clinic RH were 93%, 63% and 81% and 83%, respectively and true RH were 90%, 55%
and 71% and 82%, respectively. Morning ABP (2 h) was the closest to morning HBP
(mean difference 0.4±14.0/1.2±8.6 mmHg, p=NS/<0.01, systolic/diastolic) and was
strongly correlated with morning ABP (r=0.60/0.68, p< 0.001). There was
moderate agreement between morning HBP and morning ABP in detecting morning
hypertensives (agreement 72%, kappa 0.44, for systolic BP and 75%, kappa 0.51,
for diastolic). These findings did not change when morning ABP of 1 or 3 h
after arising were used.
Conclusions: HBP appears to be a reliable alternative to ABP in the diagnosis
of hypertension and the detection of WCP and MH in both untreated and treated
subjects. HBP retains the same diagnostic ability in patients with RH and might
therefore, be a useful tool in both uncontrolled and controlled subjects on
triple therapy to detect the WCP and also masked RH. Despite their
methodological differences, there seems to be considerable similarity between
morning HBP and morning ABP, suggesting that these methods are interchangeable
for the assessment of morning hypertension.
Keywords:
ambulatory blood pressure monitoring, home blood pressure monitoring, diagnosic value, masked hypertension, white coat hypertension
