The relation between methods and recommendations in clinical practice guidelines for hypertension and hyperlipidemia

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Original Research

The relation between methods and recommendations in clinical practice guidelines for hypertension and hyperlipidemia

J Fam Pract. 2002 November;51(11):963-968

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References

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Aggressiveness of recommendations

To grade the aggressiveness of the treatment recommendations, we evaluated the threshold for initiating pharmacologic treatment of hypertension (low = aggressive), threshold for initiating pharmacologic treatment of hyperlipidemia (low = aggressive), first-line antihypertensive drug (all drugs = aggressive), and the number of persons eligible for cholesterol screening (high = aggressive).

The thresholds for treatment of hypertension and hyperlipidemia were categorized with 4 clinical scenarios. By applying the scenarios we could determine the recommended thresholds for drug treatment among the various guidelines. We chose these specific scenarios to illustrate the existing variation in recommendations among the guidelines:

A 50-year-old man without a high-risk profile of cardiovascular disease.
A 50-year-old man with a high-risk profile of cardiovascular disease.
A 70-year-old man without a high-risk profile of cardiovascular disease.
A 70-year-old man with a high-risk profile of cardiovascular disease.

High-risk profile was defined separately for treatment of hypertension and treatment of hyperlipidemia. For hypertension, the high-risk scenario was a patient who smoked and was hyperlipidemic (total cholesterol > 310 mg/dL). For hyperlipidemia, the high-risk scenario was a patient who smoked and was hypertensive (blood pressure > 160/100 mm Hg). We assumed that lifestyle interventions had been attempted. For simplicity we used only the systolic value for blood pressure. We dichotomized the aggressiveness of thresholds for lipid-lowering treatment rather than calculating averages because many guidelines gave recommendations other than actual cholesterol values; eg, no treatment or familial hypercholesterolemia. Guidelines were considered nonaggressive if, for 2 or more of the scenarios, the threshold was set at 310 mg/dL or higher or was specified as familial hypercholesterolemia.

Guidelines recommending all common antihypertensive drugs were considered aggressive, and the ones suggesting more restrictive recommendations were considered nonaggressive. In a few guidelines this recommendation depended on the patient’s age. For simplicity we examined the recommendations for 50-year-olds. We graded aggressiveness of recommendations on cholesterol screening by estimating the proportion of the general adult population (in Norway) who would be candidates for screening or by case finding per year, if the guidelines were fully implemented.

Analysis

We qualitatively and quantitatively examined the relation between fulfillment of a methodologic criterion and the aggressiveness of recommendations. The power of our statistical analyses was limited by the available sample size. For hypertension, we averaged the treatment threshold for the 4 clinical scenarios within each guideline and compared the overall mean between guidelines meeting and not meeting the criterion. For the threshold to treat hyperlipidemia and for first-line therapy for hypertension, the degree of aggressiveness was dichotomized. We used the Fisher exact test to calculate P values for the association between the proportion of guidelines fulfilling a methodologic criterion and whether the recommendation was classified as aggressive. For cholesterol screening we found the mean yearly proportion of the adult population eligible for screening among guidelines fulfilling a methodologic criterion, and compared this with the mean for guidelines that did not fulfill the criterion. In addition to examining the association between methods and recommendations, we examined whether the level of stakeholder involvement or sponsorship by specialty societies was associated with fulfillment of the methodologic criteria. We included generalist physicians, specialists, and methodologists as “essential stakeholders” and patients, policy makers/health administrators, nurses, pharmacists, economists, and other physicians as “optional stakeholders.”

Results

We found 12 clinical guidelines for managing hypertension, 12 for hyperlipidemia, 5 for cholesterol screening, and 4 general guidelines for the prevention of coronary heart disease that met our inclusion criteria (references are available from the authors). Because each guideline was appraised according to the 8 methodologic criteria, we ended up with 264 appraisals (8 criteria applied to each of the 33 guidelines). There were 28 disagreements (11%), all of which were easily resolved by discussion. As expected, there was variation among the guidelines regarding fulfillment of methodologic criteria and the aggressiveness of recommendations.

Most guidelines did not meet the majority of the methodologic criteria (Table 2). Only 6 of the 33 guidelines met 5 or more of the 8 criteria. The threshold to start antihypertensive treatment varied in systolic blood pressure from 140 to 180 mm Hg for each of the 4 clinical scenarios we applied to the guidelines (Table 3). For 3 of the scenarios, the threshold to treat hyperlipidemia ranged from a total cholesterol value of 190 mg/dL to more than 310 mg/dL (Table 3). Fifteen guidelines gave recommendations for first-line therapy for hypertension. Three recommended thiazides only; 6 recommended thiazides and β-blockers; 1 recommended thiazides, β-blockers, and angiotensinconverting enzyme inhibitors; and 5 recommended all commonly used drugs. Recommendations for cholesterol screening ranged from no screening to testing the entire adult population every 2 to 5 years.