*n=number of visits with an International Classification of Diseases, Ninth Revision (ICD-9) code for each respective condition during each study period. The lists of ICD-9 codes were previously developed by Premera Blue Cross and the Washington State Choosing Wisely Task Force to measure rates of potentially low-value services in visits for which each respective Choosing Wisely recommendation could apply. All lists of ICD-9 codes are shown in online  supplementary appendix table 1.

†The raw percentage of visits with a potential alternate order of questionable value: sinus X-ray, sinus CT or ear, nose and throat referrals for acute sinusitis; opiate prescriptions, or orthopaedics, neurosurgery, spine clinic, neurology or pain clinic referrals for low back pain; or opiate or butalbital prescriptions, or neurology or pain clinic referrals for headaches.

‡Mean absolute differences between the control period and the intervention or follow-up period, respectively, in the percentages of visits with potential alternate orders of questionable value (defined above) as estimated from linear mixed models with random effects for providers nested in practices, adjusted for patient characteristics, time and comorbidities. SEs are robust SEs clustered at the clinic level.

§Composite measure in which the denominator is all visits for one of the three conditions, and the numerator is a potential alternate order of questionable value for that respective condition.