How expert opinion influences P&T decisions

Pharmacy and therapeutics committee members say that expert opinion has very little effect on formulary decisions, but a new study suggests otherwise. Mark Oremus, PhD, an assistant professor of clinical epidemiology and biostatistics at McMaster University and lead author of a new study says that “people who run formulary committees need to think about whether expert opinion can be useful to help interpret evidence.”

Oremus surveyed formulary committee members who were considering hypothetical Alzheimer’s disease (AD) medications for insurance coverage. Formulary committees review efficacy data based primarily on changes in the score of outcome measures such as the Alzheimer’s Disease Assessment Scale-cognitive subscale (ADAS-cog). These scales are used because AD is a syndrome without definite clinical measures.

In the study, formulary members were provided two sets of scenarios involving symptomatic drugs (i.e., drugs that don’t slow the progress of the disease) and disease-modifying drugs (i.e., drugs that stabilize patients or slow down their decline). In the first set of scenarios, the researchers provided committee members with scale scores and information on statistical significance.

In the second set, the researchers added an element of clinical judgment. The judgments indicated whether or not the observed change in scale score was clinically significant. Formulary members were asked whether they would be likely to recommend that the drug be covered by insurance.

“In the case of a medication that modified disease, the addition of clinician judgment to the body of evidence would increase formulary committee members’ likelihood of recommending the new drug for insurability,” he says. “This is relevant because the next generation of AD medications will have the ability to modify disease.”

In the case of medications that symptomatically treated disease, the committee members indicated that the addition of clinician judgment would not influence their decision making.


A disease-modifying medication was more likely to to gain insurance coverage if, in addition to efficacy evidence, clinician judgment was a factor in decision making. The numbers in the chart represent the mean likelihood that a decision maker would recommend a medication for insurance coverage.

Source: Oremus M, Raina P, Eva K, Lavis J, et al. Impact of clinician judgment on formulary committees’ recommendations in Canada. 2010. J Health Serv Res & Pol;15(2):98-105.