Instantaneous preference was a stronger instrumental variable than 3- and 6-month prescribing preference for NSAIDs.

@article{citeulike:2943669, abstract = {OBJECTIVE: Prescriber preference has been used as an instrumental variable (IV) in a prior study of nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) vs. selective cyclooxygenase-2 (COX-2) inhibitors, with preference expressed as the drug constituting the immediately preceding prescription by the same prescriber (instantaneous preference). We sought to compare the correlations between different IV measures with exposure. STUDY DESIGN AND SETTING: In an ambulatory electronic medical record database of university-based physicians, we compared correlations with exposure among three measures of prescriber preference: instantaneous preference, and the proportion of that prescriber's prescriptions in the past 3 and 6 months that were for an NSAID. RESULTS: We identified 37,934 initial NSAID/COX-2 prescriptions. The correlation with exposure was 0.283 (95\% confidence interval 0.274-0.292) for instantaneous preference, 0.197 (0.187-0.206) for 3-month preference, and 0.170 (0.160-0.180) for 6-month preference. CONCLUSION: Instantaneous NSAID/COX-2 prescribing preference was most strongly correlated, and therefore the strongest IV. Future research should focus on the robustness of IV methods to violations of underlying assumptions, extension of IV methods to more than two groups, ratio measures of association, second and subsequent prescriptions per person, and time-varying exposures.}, address = {Center for Clinical Epidemiology \& Biostatistics, Department of Biostatistics \& Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA; Center for Education and Research on Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.}, author = {Hennessy, Sean and Leonard, Charles E E. and Palumbo, Cristin M M. and Shi, Xiaoli and Ten Have, Thomas R R. }, citeulike-article-id = {2943669}, doi = {http://dx.doi.org/10.1016/j.jclinepi.2008.01.003}, issn = {0895-4356}, journal = {Journal of clinical epidemiology}, keywords = {analgesics, iv}, month = {May}, posted-at = {2008-06-30 11:54:57}, priority = {2}, title = {Instantaneous preference was a stronger instrumental variable than 3- and 6-month prescribing preference for NSAIDs.}, url = {http://dx.doi.org/10.1016/j.jclinepi.2008.01.003}, year = {2008} }

TY - JOUR ID - citeulike:2943669 L3 - citeulike-article-id:2943669 TI - Instantaneous preference was a stronger instrumental variable than 3- and 6-month prescribing preference for NSAIDs. JF - Journal of clinical epidemiology AD - Center for Clinical Epidemiology & Biostatistics, Department of Biostatistics & Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA; Center for Education and Research on Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. SN - 0895-4356 N2 - OBJECTIVE: Prescriber preference has been used as an instrumental variable (IV) in a prior study of nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) vs. selective cyclooxygenase-2 (COX-2) inhibitors, with preference expressed as the drug constituting the immediately preceding prescription by the same prescriber (instantaneous preference). We sought to compare the correlations between different IV measures with exposure. STUDY DESIGN AND SETTING: In an ambulatory electronic medical record database of university-based physicians, we compared correlations with exposure among three measures of prescriber preference: instantaneous preference, and the proportion of that prescriber's prescriptions in the past 3 and 6 months that were for an NSAID. RESULTS: We identified 37,934 initial NSAID/COX-2 prescriptions. The correlation with exposure was 0.283 (95% confidence interval 0.274-0.292) for instantaneous preference, 0.197 (0.187-0.206) for 3-month preference, and 0.170 (0.160-0.180) for 6-month preference. CONCLUSION: Instantaneous NSAID/COX-2 prescribing preference was most strongly correlated, and therefore the strongest IV. Future research should focus on the robustness of IV methods to violations of underlying assumptions, extension of IV methods to more than two groups, ratio measures of association, second and subsequent prescriptions per person, and time-varying exposures. KW - analgesics KW - iv AU - Hennessy, Sean AU - Leonard, Charles E AU - Palumbo, Cristin M AU - Shi, Xiaoli AU - Ten Have, Thomas R PY - 2008/05/19/ UR - http://dx.doi.org/10.1016/j.jclinepi.2008.01.003 ER -