Blood pressure control by home monitoring: meta-analysis of randomised trials

Whilst I accept that the evidence would suggest that ambulatory BP
readings are often lower than clinic readings, I would dispute the
conclusion that BP monitoring at home results in "better BP values and
improved control of hypertension". It may help to distinguish those with
"white coat" hypertension from those with sustained hypertension, and may
reduce overtreatment in some cases
(although the significance of white coat hypertension appears to be
unclear). However, I cannot see that this will "contribute to an important
reduction in vascular complications in the hypertensive population",
particularly in the context of underdiagnosis and undertreatment that the
authors describe.

Competing interests:
Nick Field works a a GP under a PMS contract, and reducing BP readings helps his Quality and Outcome framework payments

In their systematic review (SR) on blood pressure control by home
monitoring Cappucio et al. (1) report on the selection of trials according
to the QUOROM-guidelines (Quality of Reporting of Meta-analyses) (2),
which was advocated by an editorial in BMJ two years ago (3). However, I
found out that the acronym was misspelled (QUORUM). I used the search
option of BMJ (July 23rd, 2004) and found “quorum” in 19 articles, of
which 11 citations were in relation to SRs (1;3-12). It was inaccurately
quoted eight times in the text (of which one time in the related author’s
response)(11), two times in the reference and two times in a figure.
Ironically, it was misspelled in the text of third editorials, of which
two, however, had QUOROM spelled correctly in the reference (3;6;8).
Fortunately, QUOROM was quoted properly 19 times as well (references not
added). JAMA has a better performance, with only one misquotation (in a
reference) and 12 proper quotations.

Acronyms have a widespread use in medical publications. However, if
the acronym, as in QUOROM, does not follow the notation of the original
meaning it leads to citation problems, as I just illustrated.

I am enthusiastic about the free on-line full-text availability of
BMJ. The in-text search option has great advantages and therefore I think
accurate spelling is essential. Since I fully support the use of the
QUOROM guidelines for SRs, I think it is worth paying extra attention to a
correct spelling: QUOROM, not QUORUM.

Reference List

(1) Cappuccio FP, Kerry SM, Forbes L, Donald A. Blood pressure
control by home monitoring: meta-analysis of randomised trials. BMJ 2004;
329(7458):145-0.

(2) Moher D, Cook DJ, Eastwood S, Olkin I, Rennie D, Stroup DF. Improving
the quality of reports of meta-analyses of randomised controlled trials:
the QUOROM statement. Lancet 1999; 354(9193):1896-1900.

(3) Smith R. A plea to authors: ensure your studies comply with
guidelines. BMJ 2002; 324(7333):314.

(4) Brocklebank D, Wright J, Cates C. Systematic review of clinical
effectiveness of pressurised metered dose inhalers versus other hand held
inhaler devices for delivering corticosteroids in asthma. BMJ 2001;
323(7318):896.

(5) Campbell FA, Tramer MR, Carroll D, Reynolds DJ, Moore RA, McQuay HJ.
Are cannabinoids an effective and safe treatment option in the management
of pain? A qualitative systematic review. BMJ 2001; 323(7303):13.

(6) Goldbeck-Wood S, Robinson R. BMJ introduces a fast track system for
papers. BMJ 1999; 318(7184):620.

(7) Holt S, Suder A, Weatherall M, Cheng S, Shirtcliffe P, Beasley R et
al. Dose-response relation of inhaled fluticasone propionate in
adolescents and adults with asthma: meta-analysis Commentary: Dosage needs
systematic and critical. BMJ 2001; 323(7307):253.

(8) Jefferson T, Demicheli V. Quality of economic evaluations in health
care. BMJ 2002; 324(7333):313-314.

(9) Jordan R, Gold L, Cummins C, Hyde C. Systematic review and meta-
analysis of evidence for increasing numbers of drugs in antiretroviral
combination therapy. BMJ 2002; 324(7340):757.

(10) Mann H, Li J, Nathanson LA, Mills TJ, Netland KE, Paula R et al.
Alteplase for stroke. BMJ 2002; 324(7353):1581.

(11) Mitchell E, Sullivan F. A descriptive feast but an evaluative famine:
systematic review of published articles on primary care computing during
1980-97. BMJ 2001; 322(7281):279-282.

(12) Ram FSF, Wright J, Brocklebank D, White JES. Systematic review of
clinical effectiveness of pressurised metered dose inhalers versus other
hand held inhaler devices for delivering beta 2 agonists bronchodilators
in asthma. BMJ 2001; 323(7318):901.

Competing interests:
None declared

The primary objection to these review efforts, by Cappuccio et al.,
of a multiplicity of work in metaänalytical form is fundamental.
Objectivity and at least some validity are being sought now in this paper
for parts of studies for which the designs were never originally
undertaken; there is properly no natural indication for the aggregation of
work done for many different purposes, by different people, over a range
of time – here from 2 to 36 months but undertaken up to 25 years before.
The hope no doubt is that the parts, even taken out of context, are in
fact amalgamable, comparable and contrastable. Because of the degrees of
uncertainty there is no conclusion which may be made with such reliability
that it may be safely acted on. Forty years ago it was standard teaching
that reports in the form of metaänalysis were worse than useless; there
was always this risk that the implied and concluded findings would be
acted on at face-value. Nothing has changed.

In the work, the two objectives given are deceptively simple. What
was the effect of home blood pressure monitoring on (1) (clinic) blood
pressure levels and (2) on the proportion of people achieving set targets?
In this paper we read of references to eighteen other papers chosen for
review involving the 2417 people participating. All eighteen papers deal
with the use of home or self-monitoring of essential hypertension with a
(form of) sphygmomanometer. The comparability of all the targets is not
established.

The titles of the eighteen studies do reveal though the specific
secondary objections to a tutti-frutti approach. The described purposes of
the studies numbered 12 to 29 are in sequence as follows: the effects of
self monitoring, medication compliance, none (for reference 14), family
involvement, health education, effects on long term control, compliance
techniques, none (for 19), services and costs, teaching,
telecommunications and medication adherence, management strategy,
treatment, pharmacist intervention, losartan responder rates, African
American responses, the elderly, and blood pressure control. This is
therefore a quite unholy mix.

There are also other obvious and immediate secondary practical
differences, incompatibilities and inconsistencies likely to be present in
this form of analysis. In the present work for instance, these might be,

1. The BP machines were not all standardised. In Stahl the home
machine was not automatic.

2. The technique used in each case was too variable, from two
resting measurements one minute apart to an averaging of 6 months'
readings (Stahl).

3. Were the BPs taken lying, standing or sitting? It is not stated
in 16 trials.

4. Were they singleton or multiple readings? Usually this is
omitted.

5. Were all patients treated on-going and if so well, or badly?

6. Were the records sufficiently comparable – in one case (Stahl at
report 19) one definition of diastolic hypertension was put at 120 mmHg?
In another it was 85.
7. What were the proportions of male, female, adult or child?

8. Is one recording a sufficient entry criterion to this or any such
trial?

9. Why were ambulatory measurements said to be excluded? And why
should they be? In appendix A the authors state that the Broege and Rogers
trials were in fact ambulatory and are included.

10. Were there any unacceptable contradictions in the results and
findings of any two or more of the works? One notes the Artinian study
(27) is particularly atypical in favouring intervention, when its
interventions were far too rare.

11. Which doctors were paid? Payment always influences an outcome.

12. Which patients were paid?

13. The frequency range of the intervention recordings was too wide,
varying from twice a day to once a week. All the trials suffer from this
defect; the readings should be hourly or two hourly, as often as possible.
That gets the baseline. Compliance is no problem, with life at stake.
Constant reiteration provides the same information.

14. They were also all too long: the benefits of self-monitoring can
be assessed in a few days. Daily self observations over three years
(Stahl, report 19) is entirely misconceived. It repeatedly reconfirms
itself.

15. The 2714 patients did not all have isolated essential HT.

16. The patients were in too diverse age groupings even where
stated; one trial had a maximum age for inclusion of 18, another 35 and
only one went above 80.

Unless all the readings and observations are made in the same
conditions for the tight purpose of the objectives to be proved or
disproved they simply have no bearing on consolidated interpretations. The
wide variations in the trials in base, treatment and methods and other
design aspects, are admitted on page 146, in terms of wide degrees of
heterogeneity. The statistical analyses used are too hypothetical applied
to this highly practical subject. Thus the authors do accept there are
severe limitations to the study and these must effectively declare the
work as inconsequential. It is difficult to know why it was done, but it
is obviously cheap. The investigation and the conclusions are well known
in practice, and might in any event have been easily obtained again in any
BP clinic over the course of a relatively short time and have given much
more instructive contemporary information, and without the need to
introduce the dubious concept of “publication bias”. The authors might
also have included some rationale as to why any potentially consistent
effect should (only) have been underestimated.

The results are too specific in any event. Describing BPs to one
decimal point is too punctilious. Whether a clinic manual reading could be
regularly identically repeated to an accuracy of 1.5 mm Hg is also highly
doubtful, even if sufficient consecutive beats were of the same pressure.
Too much emphasis is placed on the significance of decimalised readings.

The reasons that clinic BP control and target achievement are both
increased as formulated in the first conclusion are important, if true.
The authors say the reasons for this are unknown; the money used on this
study might rather have been profitably used to elucidate this.

The setting of interventions at home is almost certainly too
exclusive. This is mentioned because of the doubt concerning the second
conclusion. Haemorrhagic cerebral and cardiac events are typically diurnal
and after exercise; the structural integrity of the vessel wall is
overcome. It is a specific single event in each episode, a normally
flexible artery, able to resist considerable BP elevations, fails, and the
explanation usually offered is that exceptional pressure is the cause.
White coat elevations and anxiogenic activity do therefore need normally
to be protected against and home readings are not enough. Ambulatory
readings are useful in high-risk cases. When the size of the standard, and
even more so the “attenuated”, benefits are considered, as the authors
conclude them, they are not likely to contribute much to any extra
reduction in vascular complications in the labile mild to moderate
hypertensive (unless with persistent diastolics greater than 120!). Home
recordings are clearly good for continual control in undemanding
circumstances, and as a corollary, all schools ought to teach BP recording
to all children.

Where responsibility for the prevention of the outcome of blood
pressure treatment is taken by physicians in general and where the only
risk factor for stroke and MI is that BP, then failure to control such BP
properly, where stroke or MI does occur, would be reckless or negligent
especially if regard were only to be paid to and decisions based on this
sort of tacked together work. (For their £80,000 pa in the UK, doctors
ought to be responsible for something. The authors do state that high BP
is one of the most readily preventable causes of stroke, easily detected,
and effectively the way to reduce risk is to reduce the BP. They say it is
undertreated, and that nowadays must be culpable.)

The time and effort spent dutifully trawling through this sort of
work is quite disproportionate to any benefit which may be obtained from
it. There is no adequate substitute for doing the real work oneself.

Hopefully the new BMJ editor will pay more attention to minimising
this kind of report (i.e. metaänalyses) appearing in the rational sections
of the journal where practitioners of the future really ought only to be
exposed to useful and truly paradigmatic material. If it is merely
descriptive and reflective it wastes time, money and effort. The effort is
in particular of having to read as here 18 or more opportune reports the
abstractions from which are to be the source of new fact, while bearing in
mind all 38 reports required to set the background.
David Barnes LLB(Hons)

Competing interests:
None declared

Carpuccio and colleagues found that home monitoring of blood pressure
clearly contributes to better control, but remark that "the reasons for
this are not clear". This is not surprising since randomised controlled
trials themselves rarely help to explain their results. Narrative
interviews of people with hypertension can however do so. Interviews of
18 such patients conducted in the UK in 2000 are summarised on the DIPEx
(Database of Personal Experiences) website (www.dipex.org/hypertension);
video or audio clips from the interviews illustrate the summary.

Benefits of self-monitoring that patients mentioned included gaining
reassurance, and understanding more about how the blood pressure
fluctuates. It helped the patient to take responsibility for the
condition, and to check if stress is affecting it. Home monitoring also
made it much easier to cope with the the blood pressure, which could be
very stressful precisely because it causes no symptoms. It can also
convince the patient that the high blood pressure is real and that
medication is necessary. This may be particularly important for patients
who suspect that they may only have 'white coat hypertension' where the
blood pressure is normal away from the doctor's surgery.

The interviews also revealed people's doubts and hesitations about
using a home blood pressure monitor. Some found the machines too
expensive, or worried that the results may not be reliable, although those
who had been able to check them against their practice machines had been
reassured.

Some of the people we saw suspected that their doctors and nurses
disapproved of home monitors - one man had wondered about getting one but
thought his doctor might laugh at him. We believe that self-monitoring
leads to better control because it involves people much more in the
management of their hypertension and motivates them to take part in it.

The clear benefits identified by the meta-analysis now justify a
general policy of encouraging and supporting home monitoring as part of
the efforts to promote concordance.

Competing interests:
None declared