A consensus means that everyone agrees to say collectively what no one believes individually.—Abba Eban
Congratulations are in order to the American Society of Hypertension (ASH) and the International Society of Hypertension (ISH) for publishing Clinical Practice Guidelines for the Management of Hypertension in the Community. This publication comes at a propitious time as the National Heart, Lung and Blood Institute (NHLBI) of the US National Institutes of Health (NIH) have now proposed that organizations such as ASH and ISH be responsible for preparing clinical guidelines while using the work product of NHLBI as an evidentiary review.[2, 3] This puts the NHLBI work product in proper perspective since the NHLBI reviews, ie, JNC reports, were not all-inclusive of the available evidence but relied almost entirely on the results of randomized clinical trials.
Hypertension is a global health problem of enormous magnitude. Approximately 1 billion individuals have hypertension worldwide. Globally. cardiovascular disease accounts for approximately 17 million deaths a year, nearly one third of the total. Of these, complications of hypertension account for 9.4 million deaths worldwide every year. These numbers eclipse those of other communicable and noncommunicable diseases.
Why have efforts to control hypertension been less than satisfactory? One answer probably lies in overly complicated approaches to diagnosis and treatment. This likely explains why the greatest failure to control hypertension occurs in underdeveloped countries and in areas of developed countries that do not have advanced medical personnel and institutions to administer care. Part of the difficulty in starting up a community program is the lack of a simple guide.
There is an overabundance of guidelines for the diagnosis and management of hypertension. The most recent and comprehensive hypertension guidelines were published this year by the European Society of Cardiology and the European Society of Hypertension (ESH/ESC). This publication is an excellent resource document for hypertension specialists and those wishing to attain the status of an expert in hypertension. However, at 76 pages long and containing 735 references, it is unlikely that the document will be read by the usual practitioner. On the contrary, the ASH/ISH guidelines are succinct and intended to be useful on a day-to-day basis.
There are a few issues that the ASH/ISH group will have to consider in the future:
- The definition of hypertension and the role of ambulatory blood pressure monitoring (ABPM).
- The adverse effects of antihypertensive drugs and persistence of therapy.
Hypertension is a disease and blood pressure is a biomarker. The authors have chosen rightly to utilize blood pressure as the means for defining the presence and severity of hypertension. However, there must be greater recognition that using blood pressure alone to detect hypertension has about a 20% false-positive rate due to the white-coat effect.[7, 8] Imagine that the term “cancer” was substituted for “hypertension” and one had a biomarker for the cancer that had a 20% false-positive rate. It is hard to believe that one would label all people with the abnormal biomarker as having cancer if simple further testing would clarify the diagnosis. Hypertension, the “silent killer,” is as threatening to an individual as many cancers and usually involves a lifetime of drug therapy. Thus, a good use of resources is the practice of ABPM to establish the diagnosis of hypertension, particularly in an individual with increased blood pressure but no evidence of target organ damage. This not only protects the individual from an erroneous diagnosis with all the consequences, but it also makes good economic sense as well. Eliminating 20% of the 1 billion individuals currently labeled as having hypertension, ie, 200 million persons, from a lifetime of therapy would be a great economic and social benefit. The use of ABPM to establish the diagnosis of hypertension is now part of the National Institute for Health and Clinical Excellence (NICE) guidelines from the United Kingdom and should be part of the data gathered from populations for planning purposes, eg, the National Health and Nutritional Evaluation Survey (NHANES) conducted in the United States.
All drugs labeled as antihypertensive by the US Food and Drug Administration lower elevated blood pressure. This observation is the basis for the recommendation by the ESH/ESC guidelines that any class of drug(s) may be used to initiate therapy. However, the ASH/ISH authors have chosen to be more prescriptive and suggest certain drug classes for various groups. The authors do recognize that certain comorbid conditions should influence therapy, but little discussion is given to the wide diversity of side effects of the various drug classes and the effect on persistence of therapy. For example, the drug class with the greatest number of side effects is the thiazide-type diuretics. It is well-known that many persons with hypertension will not take these medications for the long-term because of these side effects. In particular, among younger patients, the adverse effect on sexual function markedly influences the quality of life such that some patients, particularly young men, may not take them at all. It appears that there are no significant differences between hydrochlorothiazide and chlorthalidone and the issue of sudden cardiac death associated with thiazides therapy remains a concern.
Despite the concerns discussed above, and others as well, the document published by the ASH/ISH group serves as a blueprint for those needing guidance to deal with the tremendous worldwide problem of hypertension, particularly groups with limited resources. The ASH/ISH guidelines are useful at any level of medical training including medical students. No generic guidelines are perfect and are all associated with vested interests, be it from government, industry, or even clinicians themselves wanting validation of their wishes to access new technology or therapies. Also, the ASH/ISH authors acknowledge that the guidelines will be modified by local circumstances. These factors may include ethnicity, lifestyle, urbanization, access to care, vested interests, prevalence of disease, and complications.
It is refreshing and important that the ASH/ISH authors included various types of evidence, including expert opinion and experience, when deciding on guideline recommendations. Rather than apologize for this approach, the authors should take proud responsibility for introducing a Bayesian approach to hypertension guideline development. While many scientists recoil at the concept of “scientific belief,” it is clear that one's assumptions or beliefs about the relationship between observations and a hypothesis will affect whether that person takes the observations as evidence. Rather than ignoring prior data and beliefs, the analysis would embrace these marvelous evidentiary contributions to understanding and is needed urgently to assist the development of future policy.[14-16] The Bayesian approach is philosophically uninhibited regarding the ability to analyze all of the available external evidence regarding a particular problem, eg, hypertension.
The institution of the ASH/ISH guidelines worldwide would result in a remarkable reduction in morbidity and mortality, rivaling the control of any of the other world major health issues. There is no longer any excuse for responsible parties to delay the implementation of the recommendations provided by these guidelines. As of now, the ASH/ISH guidelines are Hypertension 101.