Are Preferences for COX-2 Inhibitors Influenced by the Certainty Effect?

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Journal of Rheumatology

March 2004

Are Preferences for Cyclooxygenase-2 Inhibitors Influenced by the

Certainty Effect?

LIANA FRAENKEL, DICK R. WITTINK, JOHN CONCATO, and TERRI FRIED

ABSTRACT.

Objective. To test whether the widespread use of cyclooxygenase-2

(COX-2) inhibitors may be mediated in part by the certainty effect,

i.e., by a perception that COX-2 inhibitors eliminate the risk of

serious gastrointestinal (GI) events in contrast to merely reduce their

risk.

Methods. Patients' preferences for conventional nonsteroidal

antiinflammatory drugs (NSAID) and COX-2 inhibitors for treatment of

arthritis were predicted across a range of absolute risks of GI events

using an Adaptive Conjoint Analysis survey.

Results. Preferences for COX-2 inhibitors were much stronger when the

risk of serious GI events was eliminated in contrast to reduced, even

though the absolute risk reduction (ARR) was the same. Few patients

(22%) preferred COX-2 inhibitors when the risk associated with NSAID and

COX-2 inhibitors was 4% and 2%, respectively (ARR = 2%). In contrast,

the majority (90%) preferred COX-2 inhibitors when the risk associated

with NSAID and COX-2 inhibitors was 2% and 0%, respectively (ARR = 2%).

We obtained similar findings regardless of the ARR.

Conclusion. The willingness shown by older adults to pay for COX-2

inhibitors may reflect a misperception of the risk of toxicity

associated with these medications. (J Rheumatol 2004;31:591-3)

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