UK guidelines call for routine 24-hour ambulatory blood pressure monitoring in all patients to make the diagnosis of hypertension--not ready for prime time in the United States.

In May 2011, the UK National Clinical Guideline Centre (NCGC) published their most recent guideline for the clinical management of primary hypertension in adults. As an update to the National Institute for Clinical Excellence (NICE) guideline report, this 332page document covers a wide range of issues worthy of discussion. However, the main subject that caught our attention was the recommendation calling for routine use of ambulatory blood pressure monitoring (ABPM) to make the initial diagnosis of hypertension. According to these guidelines, clinic blood pressure (BP) measurement is recommended as a screening tool, and if the mean clinic BP is 140 ⁄90 mm Hg, the clinician is instructed to ‘‘offer ABPM to confirm the diagnosis of hypertension.’’ Specifically, the guidelines recommend that ABPM be performed by measuring at least 2 readings per hour during usual waking hours and that a minimum of 14 readings be obtained. A diagnosis of hypertension is thereby made in patients with mean daytime ambulatory BP of at least 135 ⁄85 mm Hg. Of note, this means that patients do not necessarily need to wear the ABPM monitor for a full 24 hours or in the evenings. Home BP self-monitoring is only recommended as an alternative method for making the diagnosis of hypertension when ABPM is not tolerated. In the setting of ‘‘severe’’ clinic hypertension, antihypertensive medications can be started while waiting for the results of ABPM, but in other cases, the clinician is instructed to await the results of ABPM (as well as screening for target organ damage) prior to initiating antihypertensive therapy. ABPM is not widely available in primary care practice and in the United States is usually offered only by centers that specialize in hypertension or cardiovascular medicine. Advantages of ABPM include the ability to detect white-coat or masked hypertension, determine the presence or absence of normal nocturnal dipping status, and assess the adequacy BP control in patients taking complex antihypertensive medication regimens. While it makes intuitive sense to use ABPM in these situations, it has been hard to obtain evidence of improved clinical outcome to support these indications. While numerous observational studies have demonstrated ABPM to be superior to clinic measurements in predicting target organ damage and other clinical outcomes associated with hypertension, definitive evidence that this is a superior management strategy is still lacking. To date, ABPM is most commonly used to determine the presence or absence of an exaggerated alerting response (white-coat effect), and this is generally the only indication for which it is covered by payers in the United States. Now, the NCGC is recommending ABPM in all patients suspected of having hypertension. As part of the basis for its recommendation, the NCGC performed a rigorous cost-effective analysis that demonstrated that ABPM would not only be a more effective means of making the diagnosis of hypertension, but also would provide a more costeffective approach than either the current approach (clinic BP) or use of home BP monitoring. Compared with making the diagnosis with clinic or home BP monitoring, not only was ABPM determined to be the most cost-effective approach in all age and sex subgroups, it also led to an improvement in quality health outcomes and was cost-saving when long-term costs were taken into account. The key driver of cost savings in this analysis was the cost of hypertension treatment that would be avoided due to improved specificity in making an accurate diagnosis with ABPM. The model suggested that antihypertensive therapy would be required in about 25% fewer patients than if the diagnosis was made based on clinic BPs alone. The pharmacy cost savings overwhelmed the cost increases associated with ABPM itself. According to the NICE publication, the conclusions of this analysis were generally stable regardless of a wide range of sensitivity analyses that were performed. But, cost-effective analyses require that the investigators make important assumptions about the future. Even with the best of intentions, these assumptions may prove inaccurate. We believe that while such analyses may play a supportive role in developing guidelines, they should not be the primary driver in determining clinical utility. Unfortunately, it can be very difficult for outside observers to confirm the methodology of a costeffective analysis, and they are probably most helpful when they can be independently externally validated. In any event, the assumptions made in the NCGC costeffective analysis are based on the UK model of health care delivery and should not be considered valid for use in the United States or other countries. Regardless of the validity of the UK cost-effective analysis, the requirement for routine ABPM in order From the Department of Internal Medicine, University of Nevada School of Medicine, Medical Director, Risk Reduction Center, Saint Mary’s Regional Medical Center, Reno, NV; and The Seinsheimer Cardiovascular Health Program, Division of General Internal Medicine ⁄Geriatrics, Medical University of South Carolina, Ralph H. Johnson VA Medical Center, Charleston, SC