British guidelines on managing hypertensionBMJ 1999; 319 doi: https://doi.org/10.1136/bmj.319.7210.589 (Published 04 September 1999) Cite this as: BMJ 1999;319:589
- Bruce M Psaty, professor (, )
- Curt D Furberg, professor
- Cardiovascular Health Research Unit, University of Washington, Seattle, WA 88101, USA
- Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, USA
Provide evidence, progress, and an occasional missed opportunity
Education and debate p 630
This issue of the BMJ includes a summary of the new British Hypertension Society guidelines for managing hypertension.1 Recently, one of the authors of these guidelines commented on the strengths of the fifth and sixth reports of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC): “The JNC reports score highly on two counts—they took note of important new evidence, and unlike the others, delivered a clear message.”2 The same can be said of this version of the British guidelines, which represent an outstanding summary of the existing evidence about the diagnosis and treatment of hypertension. In contrast to the World Health Organisation-International Society of Hypertension3 and the Joint National Committee VI guidelines,4 the brevity of this version will make the British Hypertension Society guidelines especially usefulto clinicians.
The authors aimed to produce an evidence based document, and in the full version (reference 1 in 1) they applied the North of England Group criteria to grade the evidence for most recommendations. For instance, a low dose thiazide diuretic is listed as the first line treatment for patients with uncomplicated hypertension. This evidence based recommendation, appropriately, received a grade A rating, which signifies evidence from at least one randomised trial or from a meta-analysis of randomised trials.
Implicit in the recommendations about drug choice is a distinction not often made in the traditional evidence based grading systems. For the main drug treatment recommendation the authors have relied on the results of randomised clinical trials that assess major disease end points rather than surrogate end points such as level of blood pressure.5 All drugs approved for treating hypertension lower blood pressure. But the purpose of treatment is to reduce the risk of devastating hypertensive complications such as myocardial infarction, stroke, and heart failure. Few antihypertensive drugs, only low dose diuretics and β blockers, have consistently passed this higher standard of evidence—one which is appropriate for publichealth recommendations. Trials such as ALLHAT6 that directly compare active therapies in terms of their effects on major disease end points will provide the bestevidence for future treatment recommendations.
Unfortunately, the recommendations for drug therapies according to various “compelling” and “possible” indications in table 2 (p 632) are consensus rather than evidence based. The World Health Organisation-International Society of Hypertension and Joint National Committee VI guidelines have similar tables.3 4 All three guidelines fail to define explicit criteria for “special” indications, and in the absence of a careful evaluation of the evidence, it is difficult to judge their merit, especially for the “possible” indications. The variation among the special indications tables is striking and sometimes looks like the result of special pleading. The Joint National Committee VI, but not the British Hypertension Society, lists heart failure as a compelling indication for diuretics; the British Hypertension Society, but not the Joint National Committee VI, lists angina as a compelling indication for non-dihydropyridine calcium antagonists. In contrast, evidence based guidelines for chronic stable angina recommend β blockers.7 If one were to favour the proliferation of items in special indications tables, surely diabetes would have been a compelling or possible contraindication to calcium antagonists.8–10
This elaborate special indications approach has been criticised as an attempt to circumvent the evidence from clinical trials on major disease endpoints.11 Compelling indications—four in Joint National Committee VI but eight in the British Hypertension Society guidelines—should be defined in terms of health benefits shown in the large clinical trials. Is cough induced by angiotension converting enzyme inhibitors a compelling indication for an angiotensisn II antagonist? Rather, it may be a contraindication to angiotension converting enzyme inhibitors Indeed, there are no large long term clinical trials showing a benefit of angiotensin II antagonists on morbidity and mortality. In failing to apply evidence based criteria consistently and focus on compelling indications alone, the British missed an opportunity to set a higher standard here.
One of the more controversial issues is the notion of initiating treatment on the basis of the level of risk rather than level of blood pressure Among patients without diabetes, cardiovascular disease, or target organ damage, the Joint National Committee VI recommends drug treatment if blood pressures are sustained in the 140-59/90-9 mm Hg range. The British Hypertension Society guidelines have incorporated an important innovation. Among patients without diabetes, cardiovascular disease, or target organ damage, the decision to treat or not depends on the level of cardiovascular risk if the blood pressure is in the 140-59/90-9 mm Hg range. Though there are potential problems with estimating absolute levels of risk, the effort to incorporate risk stratification into the treatment algorithms represents an important new direction, one that will need to be evaluated.
The risk stratified decision to treat is still forced to be a binary one according to whether the 10 year risk of coronary heart disease risk is 15% or more. People with a 10 year risk of 14.9% need not be treated. This boundary problem can perhaps be solved by incorporating patient preferences. For patients with uncomplicated hypertension and blood pressure of 140-59/90-9 mm Hg physicians can use the estimated risk of coronary heart disease as an opportunity to discuss the risks and benefits of drug therapies and, thus, involve the patient in decision making about treatments.
Finally, there is no disclosure of potential conflicts of interest. The authors did not feel that it was necessary and the BMJ did not insist (personal communication, BMJ). To maintain credibility with the public, disclosure is essential for authors of guidelines It was omitted by the Joint National Committee VI12 and the World Health Organisation-International Society of Hypertension. It is a preventive measure: full disclosure simply precludes the possibility that some potential conflict may eventually be revealed and discredit the profession. It would have been nice to see the British set a new standard here.
The research reported in this article was supported in part by grants from the National Heart, Lung, and Blood Institute and the National Institute on Aging. BMP is a Merck/SER clinical epidemiology fellow (sponsored by Merck Co Foundation and the Society for Epidemiologic Research, Baltimore). He has served on the events committee for a trial funded by Wyeth Ayerst. CDF receives research funding from Pfizer and Wyeth Ayerst and is consultant to Bristol Myers Squibb.