automated office BP as good as ABPM

automated office BP as good as ABPM

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You forwarded this message on Mon 2/25/2019 7:28 AM

G

Geoff A. Modest, M.D.

Mon 2/25/2019 7:25 AM

Geoff A. Modest, M.D.

A recent systematic review and meta-analysis found that automated office blood pressure (AOBP) measurements are as accurate as awake ambulatory blood pressure (ABP) measurements, and both are significantly different from the routine office blood pressure measurement (see htn automated office bp good as abpm jamaintmed2019 in dropbox, or doi:10.1001/jamainternmed.2018.6551).

Details:

-- 31 articles including 9279 people (4736 men and 4543 women), with possible hypertension

-- mean age 56 years, mean systolic AOBP >130 mmHg in ½ the studies

-- all of the studies except one used one of the 3 following AOBP monitors (all studies used fully automated devices that did not require involvement of the patient or office staff at the time of the measurement):

    -- BpTRU:  6 blood pressure measurement one minute apart, discarding the first and averaging the remaining 5. No antecedent rest

    -- Omron 907: averages 3 readings at 1-minute intervals, with 5 minutes of antecedent rest

    -- WatchBP Office: averages 3 readings at 1-minute intervals after 1 minute delay

--they compared the routine office blood pressure, the AOBP and the ABP, looking separately at those patients with initial systolic BP >130 vs <130 mmHg by AOBP

Results:

-- overall, the pooled mean difference between routine clinic BP and awake ABP was 13.4/5.9 mmHg.

--in patients with AOBP systolic blood pressure >130mmHg:

    --comparing AOBP and routine office BP: routine office SBP was 14.5 mmHg higher

    --comparing AOBP and ABP: no difference (2 of the studies had a difference of >5 mmHg)

    --similar pattern for diastolic BP

--in patients with normal AOBP SBP:

    --mean AOBP was about 5.4 mmHg lower than the awake ABP, with one study finding a higher difference

Commentary:

-- This study was not a clinical outcome study. It just showed the equivalence of automated office blood pressure (AOBP) with the daytime ambulatory blood pressure (ABP)

-- prior studies are quite consistent that 24-hour ambulatory blood pressure monitoring (ABPM) is a much better predictor of actual clinical cardiovascular outcomes than office-based blood pressure, leading to international organizations promoting this as the gold standard for diagnosis (see http://gmodestmedblogs.blogspot.com/2015/01/uspstf-recs-on-ambulatory-blood.html. There is some variability in the studies regarding whether daytime (ie, the ABP in the study above) or nighttime monitoring alone was more predictive of clinical cardiovascular events. However, the formal USPSTF recommendations at https://www.uspreventiveservicestaskforce.org/Page/Document/evidence-summary19/high-blood-pressure-in-adults-screening , noted that “On the basis of the prognostic evidence, we selected ABPM as the reference standard for BP measurement and for evaluating the diagnostic accuracy of other measurement methods. We regarded daytime, nighttime, or 24-hour ABPM protocols as acceptable”

--one important background issue is that several other studies have looked at patients with stage 1 hypertension measured in the clinic, finding that 30% do NOT have hypertension by ABPM. Relying solely on the clinic blood pressure would therefore lead to over-medicalization, over-treatment, and over-exposure to adverse effects/further blood work or other testing, etc in many patients. 

-- automated office blood pressure measurements have the advantage of decreasing whitecoat hypertension both by having the patient rest for several minutes as well as not having a nurse or medical assistant in the room at the time of blood pressure measurement. it should be noted that the research studies assessing the clinical value of treating "routine" office-based hypertension, such as the SPRINT trial (see http://gmodestmedblogs.blogspot.com/2017/02/blood-pressure-guidelines-for-older.html ) did have the patients wait in a quiet room for several minutes prior to checking the blood pressure. But even within the SPRINT study, they found that ABPM was much more accurate than their meticulous office-based approach (seehttps://blogs.bmj.com/bmjebmspotlight/2017/06/14/primary-care-corner-with-geoffrey-modest-md-monitor-bp-effects-by-abpm-sprint-trial/ ). 

    --even though waiting 5 minutes before checking the blood pressure is much more accurate than having the patient walk into a room and checking the pressure right away, 

--it is striking in this meta-analysis that overall there was quite close approximation of AOBP with daytime ABP readings. In fact, assessing the highest quality studies (no added rest for the patient, patient completely alone, results not based on chart review, at least 3 readings for AOBP), the Forest Plot was quite narrow: ie, there was marked coherence in outcomes betweent the individual studies, with only 1 study of 12 finding a bit more than 5mmHg higher for the AOBP

(see http://gmodestmedblogs.blogspot.com/2017/02/blood-pressure-guidelines-for-older.html

-- one concern is that there is no standard way to check AOBP, given that the current models all use different algorithms. it is somewhat reassuring that subgroup analysis in the above meta-analysis did not find much difference between the different AOBP devices used, suggesting that probably it is not necessary to follow the strict guideline of waiting 5 minutes before checking the blood pressure (ie, it is likely sufficient to have the patient relax, the AOBP machine automatically record the blood pressures without the patient or staff doing anything, and having multiple recordings) 

--AOBP is the preferred approach in Canada since their 2016 guidelines (seehttps://www.onlinecjc.ca/article/S0828-282X(16)00192-6/abstract ) and is now more routinely used in primary care settings.

So, bottom line: it is really important to have an accurate blood pressure on which clinical decisions are based…. And AOBP provides a potentially much easier way to get more accurate blood pressure determinations in the office, one not necessitating that the patient have a 24-hour ambulatory monitor that they have to make a special trip to have put on, then another 1 day later to remove.

My guess, though not formally tested, is that the most accurate and really practicable approach to getting a reliable blood pressure is to put the patient in a quiet room by themselves with dimmed lighting, and have  the AOBP automatically measure the blood pressure at least 3 times and discard the first measurement, without the patient doing anything or there being a clinical person in the room.  And use the regular 24-hour ambulatory blood pressure monitor a few times initially to validate the accuracy of the AOBP, as well as when there are questions about the AOBP results (eg, if very discordant from what would be expected given the individual clinical situation of the patient)

geoff​

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