Prescription Drugs:

Selected Direct-to-Consumer Advertising Studies Have Methodological Flaws

PEMD-91-20: Published: Jul 22, 1991. Publicly Released: Aug 12, 1991.

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Pursuant to a congressional request, GAO reviewed five technical studies conducted by a marketing research firm which claim that direct-to-consumer prescription drug advertising is increasing among both physicians and consumers, focusing on whether the methodology sufficiently ensured the accuracy and generalizability of its claim.

GAO found that: (1) the physicians' surveys in the marketing firm's studies could not be generalized, since the firm did not make adjustments to ensure that the sample adequately represented physicians included on the American Medical Association's (AMA) Master List and those who had an office practice; (2) the validity of the physician survey findings were questionable, since response rates were only 11 percent or less, far below normal standards for opinion surveys; (3) the consumer surveys did not permit a generalizable measurement of consumer opinions, since the study design did not effectively ensure that the sample's opinions matched the population's opinions about direct-to-consumer advertising; (4) the validity of the consumer survey findings was questionable, since the response rates for the consumer samples were below normal standards, making it impossible to know whether the opinions of the nonrespondents were the same as those of the respondents; and (5) in many cases the studies' analytical interpretations of responses were not consistent with conventional analyses of data used in opinion research.

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