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Frans E S Tan

Publications and source records attributed to Frans E S Tan.

2 recordsLinked to original sources

Maximin D-optimal designs for longitudinal mixed effects models.

In this article, the optimal selection and allocation of time points in repeated measures experiments is considered. D-optimal cohort designs are computed numerically for the first- and second-degree polynomial models with random intercept, random slope, and first-order autoregressive serial correlations. Because the optimal designs are locally optimal, it is proposed to use a maximin criterion. It is shown that, for a large class of symmetric designs, the smallest relative efficiency over the model parameter space is substantial.

Child↗

Improving test ordering in primary care: the added value of a small-group quality improvement strategy compared with classic feedback only.

PURPOSE: We wanted to evaluate the added value of small peer-group quality improvement meetings compared with simple feedback as a strategy to improve test-ordering behavior. Numbers of tests ordered by primary care physicians are increasing, and many of these tests seem to be unnecessary according to established, evidence-based guidelines. METHODS: We enrolled 194 primary care physicians from 27 local primary care practice groups in 5 health care regions (5 diagnostic centers). The study was a cluster randomized trial with randomization at the local physician group level. We evaluated an innovative, multifaceted strategy, combining written comparative feedback, group education on national guidelines, and social influence by peers in quality improvement sessions in small groups. The strategy was aimed at 3 specific clinical topics: cardiovascular issues, upper abdominal complaints, and lower abdominal complaints. The mean number of tests per physician per 6 months at baseline and the physicians' region were used as independent variables, and the mean number of tests per physician per 6 months was the dependent variable. RESULTS: The new strategy was executed in 13 primary care groups, whereas 14 groups received feedback only. For all 3 clinical topics, the decrease in mean total number of tests ordered by physicians in the intervention arm was far more substantial (on average 51 fewer tests per physician per half-year) than the decrease in mean number of tests ordered by physicians in the feedback arm (P = .005). Five tests considered to be inappropriate for the clinical problem of upper abdominal complaints decreased in the intervention arm, with physicians in the feedback arm ordering 13 more tests per 6 months (P = .002). Interdoctor variation in test ordering decreased more in the intervention arm. CONCLUSION: Compared with only disseminating comparative feedback reports to primary care physicians, the new strategy of involving peer interaction and social influence improved the physicians' test-ordering behavior. To be effective, feedback needs to be integrated in an interactive, educational environment.

Abdominal Pain↗