TABLE 3.

California Health Benefits Review Program (CHBRP) Hierarchy of Evidence of Medical Effectiveness

1. High-quality meta-analysesa

2. Systematic reviews

3. Well-implemented randomized controlled trials (RCTs) and cluster RCTsb

4. RCTs and cluster RCTs with major weaknesses

5. Nonrandomized studies with comparison groups and time series analyses

6. Case series and case reports

7. Narrative reviews and clinical guidelines based on consensus or opinion

Notes:

^a“High-quality” meta-analyses are meta-analyses that have clear objectives and hypotheses, apply appropriate inclusion/exclusion criteria, assess meaningful outcomes, and use sound methods to find, select, and evaluate studies and to generate pooled estimates of an intervention's effects.

^b“Well-implemented” RCTs and cluster RCTs are defined as studies that have (1) sample sizes that are sufficiently large to detect statistically significant differences between the intervention and control groups, (2) low attrition rates (less than 20 percent) or use intent-to-treat methods, and (3) intervention and control groups that are statistically equivalent before the intervention with respect to baseline measures of the outcome and important factors associated with the outcome. To be considered well implemented, a cluster RCT must also use appropriate statistical methods to take into account the clustering of observations at the level at which randomization occurs.

Source:CHBRP 2008d.