Author Affiliations: Screening and Test Evaluation Program, School of Public Health, The University of Sydney, Sydney, Australia (Drs Hayen, Bell, and Irwig); and Centre for Research in Evidence-Based Practice, Bond University, Gold Coast, Australia (Drs Bell and Glasziou).
We offer an alternative explanation for the conclusion of the recent report by Morrison and colleagues1 that encounter frequency leads to apparent better control of glucose (hemoglobin A1c), blood pressure, and low-density lipoprotein cholesterol in patients with diabetes mellitus. While the authors have acknowledged that several forms of bias (including confounding) may affect their results, another important reason for the association between more frequent consultations and meeting targets is measurement variability. Each marker is subject to considerable random measurement variability.2-4 Because of random “highs,” those with more frequent measurements will more likely be mistakenly labeled as being uncontrolled. The exclusion of patients with “transient” highs partly mitigates this problem. Patients with borderline levels who have more frequent physician encounters are still more likely to be identified as uncontrolled compared with those with less frequent encounters.
Hayen A, Bell K, Glasziou P, Irwig L. A Counterargument to Encounter Frequency and Target Achievement: Measurement Variability. Arch Intern Med. 2012;172(4):374–375. doi:10.1001/archinternmed.2011.807
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