Physician’s prescribing preference as an instrumental variable: exploring assumptions using survey data.
Open accessAbstract
BACKGROUND: Physician's prescribing preference is increasingly used as an instrumental variable in studies of therapeutic effects. However, differences in prescribing patterns among physicians may reflect differences in preferences or in case-mix. Furthermore, there is debate regarding the possible assumptions for point estimation using physician's preference as an instrument. METHODS: A survey was sent to general practitioners (GPs) in The Netherlands, the United Kingdom, New Zealand, Ireland, Switzerland, and Germany, asking whether they would prescribe levothyroxine to eight fictitious patients with subclinical hypothyroidism. We investigated (1) whether variation in physician's preference was observable and to what extent it was explained by characteristics of GPs and their patient populations and (2) whether the data were compatible with deterministic and stochastic monotonicity assumptions. RESULTS: Levothyroxine prescriptions varied substantially among the 526 responding GPs. Between-GP variance in levothyroxine prescriptions (logit scale) was 9.9 (95% confidence interval: 8.0, 12) in the initial mixed effects logistic model, 8.3 (6.7, 10) after adding a fixed effect for country and 8.2 (6.6, 10) after adding GP characteristics. The occurring prescription patterns falsified the deterministic monotonicity assumption. All cases in all countries were more likely to receive levothyroxine if a different case of the same GP received levothyroxine, which is compatible with the stochastic monotonicity assumption. The data were incompatible with this assumption for a different definition of the instrument. CONCLUSIONS: Our study supports the existence of physician's preference as a determinant in treatment decisions. Deterministic monotonicity will generally not be plausible for physician's preference as an instrument. Depending on the definition of the instrument, stochastic monotonicity may be plausible.
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Unexplained variation in practice patterns has been shown for other thyroid disorders, such as thyroid cancer and subclinical hypothyroidism.
“Unexplained variation in practice patterns has been shown for other thyroid disorders, such as thyroid cancer (37) and subclinical hypothyroidism (38,39).”
From Short-Term Time Trends in Prescribing Therapy for Hypothyroidism: Results of a Survey of American Thyroid Association Members (2019) · cites this paper as [38]
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Commentary: How to Report Instrumental Variable Analyses (Suggestions Welcome)
Swanson, S. A., & Hernán, M. A. (2013) · Epidemiology · doi:10.1097/ede.0b013e31828d0590 · Cited by 197 · cited 3× · see citing works
“Our aims are twofold, (1) to establish whether variation in physician’s preference regarding treatment of subclinical hypothyroidism is observable when gPs are presented with the same set of patients and to what extent this variation is explained by characteristics of the gPs and (2) to establish to what extent the da…”
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- Hernán MA, Robins JM. Instruments for causal inference: an epidemiologist's dream? Epidemiology 2006;17:360-372.
- Imbens GW, Angrist JD. Identification and Estimation of Local Average Treatment Effects. Econometrica 1994;62:467-475.
- Small DS, Tan Z, Lorch SA, Brookhart MA. Instrumental variable estimation when compliance is not deterministic: the stochastic monotonicity assumption. 2014. arXiv: 1407.7308v2 · arXiv
- den Elzen WP, Lefebre-van de Fliert AA, Virgini V et al. International variation in GP treatment strategies for subclinical hypothyroidism in older adults: a case-based survey. Br J Gen Pract 2015;65:e121-e132.
- Angrist JD, Imbens GW, Rubin DB. Identification of Causal Effects Using Instrumental Variables. Journal of the American Statistical Association 1996;91:444-455.
- Brookhart MA, Rassen JA, Schneeweiss S. Instrumental variable methods in comparative safety and effectiveness research. Pharmacoepidemiol Drug Saf 2010;19:537-554.
- Swanson SA, Hernán MA. Think globally, act globally: An epidemiologist's perspective on instrumental variable estimation. Stat Sci 2014;29:371-374.
- Imbens GW. Instrumental Variables: An Econometrician's Perspective. Stat Sci 2014;29:323-358.
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Prescribing Therapy for Hypothyroidism: Influence of Physician Characteristics
Jonklaas, J., Tefera, E., & Shara, N. (2019) · Thyroid · doi:10.1089/thy.2018.0369 · Cited by 31 · see citing works
Jonklaas, J., Tefera, E., & Shara, N. (2019) · Frontiers in Endocrinology · doi:10.3389/fendo.2019.00031 · Cited by 23 · see citing works
- Authors
- Boef, A. G. C., le Cessie, S., Dekkers, O. M., Frey, P., Kearney, P. M., Kerse, N., Mallen, C. D., McCarthy, V. J. C., Mooijaart, S. P., Muth, C., Rodondi, N., Rosemann, T., Russell, A., Schers, H., Virgini, V., de Waal, M. W. M., Warner, A., Gussekloo, J., & den Elzen, W. P. J.
- Affiliations
- Goethe University Frankfurt (DE)
- Leiden University Medical Center (NL)
- University of Bern (CH)
- University College Cork (IE)
- University of Auckland (NZ)
- Arthritis Research UK (GB)
- University Hospital of Bern (CH)
- University of Zurich (CH)
- Radboud University Medical Center (NL)
- University College London (GB)
- Leiden University (NL)
- ORCID
- Venue
- Epidemiology
- Published
- 2015-11
- Volume
- 27
- Issue
- 2
- Pages
- 1
- ISSN
- 1044-3983 (ISSN-L)
- OpenAlex
- W2178166217
- Cited by
- 13
- References
- 1
- Citations by year
- 2026: 1 · 2025: 2 · 2021: 1 · 2020: 2 · 2019: 2 · 2018: 2 · 2017: 3
- FWCI
- 1.48
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Epidemiology (publishedVersion)
- PubMed (publishedVersion)
- Zurich Open Repository and Archive (University of Zurich) (acceptedVersion, other-oa)
- Keele Research Repository (Keele University) (submittedVersion)
- Data Archiving and Networked Services (DANS) (submittedVersion)
- Leiden Repository (Leiden University) (submittedVersion)
- BORIS (University Library Bern) (submittedVersion, other-oa)
- Pure Amsterdam UMC (submittedVersion)
- Radboud Repository (Radboud University) (submittedVersion)
- Zurich Open Repository and Archive (University of Zurich) (submittedVersion, other-oa)
- Zurich Open Repository and Archive (University of Zurich)
- Funders
- National Science Foundation
- National Institute for Health and Care Research (WMCLAHRC-2014-1, RP_2014-04-026)
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (320 030-150 025, 150025, 320030)
- ZonMw (152002040)
- NIHR School for Primary Care Research
- Topics
- Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Keywords
- instrumental variable validity, stochastic monotonicity, levothyroxine, subclinical hypothyroidism, general practitioners, case mix, treatment decision-making
- MeSH terms
- Female, Germany, United Kingdom, Humans, Hypothyroidism, Ireland, Male, Netherlands, New Zealand, Practice Patterns, Physicians', Surveys and Questionnaires, Switzerland, Thyroxine, Logistic Models, General Practitioners
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