Cholesterol-lowering intervention program. Effect of the step I diet in community office practices

A systematic review of the use of theory in the design of guideline dissemination and implementation strategies and interpretation of the results of rigorous evaluations

BACKGROUND

There is growing interest in the use of cognitive, behavioural, and organisational theories in implementation research. However, the extent of use of theory in implementation research is uncertain.

METHODS

We conducted a systematic review of use of theory in 235 rigorous evaluations of guideline dissemination and implementation studies published between 1966 and 1998. Use of theory was classified according to type of use (explicitly theory based, some conceptual basis, and theoretical construct used) and stage of use (choice/design of intervention, process/mediators/moderators, and post hoc/explanation).

RESULTS

Fifty-three of 235 studies (22.5%) were judged to have employed theories, including 14 studies that explicitly used theory. The majority of studies (n = 42) used only one theory; the maximum number of theories employed by any study was three. Twenty-five different theories were used. A small number of theories accounted for the majority of theory use including PRECEDE (Predisposing, Reinforcing, and Enabling Constructs in Educational Diagnosis and Evaluation), diffusion of innovations, information overload and social marketing (academic detailing).

CONCLUSIONS

There was poor justification of choice of intervention and use of theory in implementation research in the identified studies until at least 1998. Future research should explicitly identify the justification for the interventions. Greater use of explicit theory to understand barriers, design interventions, and explore mediating pathways and moderators is needed to advance the science of implementation research.

Reduced or modified dietary fat for preventing cardiovascular disease

BACKGROUND

Reduction or modification of dietary fat can improve total cholesterol levels, but may also have a variety of effects, both positive and negative, on other cardiovascular risk factors.

OBJECTIVES

The aim of this systematic review was to assess the effect of reduction or modification of dietary fats on total and cardiovascular mortality and cardiovascular morbidity over at least 6 months, using all available randomized clinical trials.

SEARCH STRATEGY

The Cochrane Library, MEDLINE, EMBASE, CAB Abstracts, CVRCT registry and related Cochrane Groups' trial registers were searched through spring 1998, SIGLE to January 1999. Trials known to experts in the field and biographies were included through May 1999.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomized with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) healthy adult humans, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available. Inclusion decisions were duplicated, disagreement resolved by discussion or a third party.

DATA COLLECTION AND ANALYSIS

Rate data were extracted by two independent reviewers and meta-analysis performed using random effects methodology. Meta-regression and funnel plots were used.

MAIN RESULTS

Twenty seven studies were included (40 intervention arms, 30,901 person-years). There was no significant effect on total mortality (rate ratio 0.98, 95% CI 0.86 to 1.12), a trend towards protection form cardiovascular mortality (rate ratio 0.91, 95% CI 0.77 to 1.07), and significant protection from cardiovascular events (rate ratio 0.84, 95% CI 0.72 to 0.99). The latter became non-significant on sensitivity analysis. Trials where participants were involved for more than 2 years showed significant reductions in the rate of cardiovascular events and a suggestion of protection from total mortality. The degree of protection from cardiovascular events appeared similar in high and low risk groups, but was statistically significant only in the former.

REVIEWER'S CONCLUSIONS

The findings are suggestive of a small but potentially important reduction in cardiovascular risk in trials longer than two years. Lifestyle advice to all those at high risk of cardiovascular disease (especially where statins are unavailable or rationed), and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates.

A population-based treat-to-target pharmacoeconomic analysis of HMG-CoA reductase inhibitors in hypercholesterolemia

The 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors have become the drugs of choice for the treatment of patients with hypercholesterolemia. However, one of the major concerns with these drugs is cost. In an attempt to develop a cost-effective treatment strategy for patients referred to our lipid clinic, we conducted a meta-analysis to estimate the lipid-lowering efficacy of the various HMG-CoA reductase inhibitors alone or in combination with niacin or cholestyramine. Based on cholesterol-lowering efficacy estimates derived from a literature-based meta-analysis, we performed a population-based treat-to-target analysis. Fifty-six trials with 101 monotherapy cohorts and 20 trials with 31 combination-therapy cohorts (573 patients) were included in the meta-analysis. Based on reduction in low-density lipoprotein cholesterol (LDL-C), the most effective monotherapy was atorvastatin and the least effective monotherapy was fluvastatin. Combination therapy was more effective in reducing LDL-C than monotherapy with the respective HMG-CoA reductase inhibitor. However, on the basis of dollars spent per percentage of LDL-C reduction, combination therapy was frequently less cost-effective than monotherapy. In addition, combination therapy was associated with a higher rate of noncompliance and a greater risk of drug-drug interactions. As a result, we based our treat-to-target analysis on the use of monotherapy as first-line treatment, with combination therapy reserved for patients failing to achieve the target LDL-C levels of the US National Cholesterol Education Program Adult Treatment Panel II (NCEP ATP-II) with monotherapy. In the population-based treat-to-target analysis, atorvastatin was the most cost-effective drug for high-risk patients (those with coronary heart disease [CHD]), whereas fluvastatin was the most cost-effective agent for low-risk patients (<2 risk factors for CHD) and moderate-risk patients (> or =2 risk factors for CHD). If 1 drug is chosen to treat all patients (i.e., in cases of formulary restriction), atorvastatin would be the most cost-effective agent. In adapting the findings on cholesterol-lowering efficacy from this analysis to our lipid clinic, we concluded that the most cost-effective treatment approach is to individualize the selection of an HMG-CoA reductase inhibitor based on both coronary risk and the LDL-C reduction required to achieve NCEP ATP-II goals. Based on our results, 2 agents--atorvastatin and fluvastatin--should be available on the formulary.