IngentaConnect Factors associated with the effect-size of thiazolidinedione (TZD...

Abstract:

Objective: To examine factors affecting the size of the HbA_1c response to thiazolidinedione (TZD) therapy.

Research design and methods: Meta-analysis of randomized TZD controlled trials which were identified using PubMed, EBSCO and Sci-lit databases and were published in English. Sociodemographic and clinical data were extracted from each trial. HbA_1c effect size was defined as either a placebo-subtracted change in HbA_1c or a change in HbA_1c from baseline. Weighted multivariable regression was used to examine factors associated with changes in HbA_1c. Bootstrapped smearing estimates were computed to obtain reliable estimates of HbA_1c effect size.

Results: Forty-two trials yielded 60 trial arms which represented 8322 patients treated with thiazolidinediones. Weighted placebo-subtracted change in HbA_1c was −0.99% ± 0.02% with an average baseline HbA_1c of 9.1% ± 1.0%. Weighted bootstrapped smearing estimate of the placebo-subtracted change in HbA_1c was −1.02% ± 0.004%. After controlling for other variables, the baseline HbA_1c level had a significant negative association with placebo-subtracted HbA_1c change (p = 0.004) and also with change in HbA_1c from baseline (p = 0.002). Longer trial duration was associated with greater placebo-subtracted HbA_1c change (p = 0.01) but not with the change in HbA_1c from baseline. The multivariable models explained 72% of the variation in placebo-subtracted HbA_1c change. It was not possible to estimate effects of the run-in period and obesity on TZD effect size.

Conclusion: Baseline HbA_1c and trial duration significantly impacted the effect size of TZD therapy on HbA_1c. Age, gender, duration of diabetes and prior use of anti-diabetic therapy were not associated with the TZD effect size.

Keywords: BASELINE HBA1C; EFFECT-SIZE; PLACEBO-SUBTRACTED CHANGE IN HBA1C; THIAZOLIDINEDIONES

Document Type: Research article

DOI: 10.1185/030079906X148328

Affiliations: 1: Rutgers-Merck Research Associate, Rutgers: The State University of New Jersey, Piscataway, NJ 08854, USA 2: Worldwide Outcomes Research, Merck & Co., Inc., Whitehouse Station, NJ 08889, USA

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Factors associated with the effect-size of thiazolidinedione (TZD) therapy on HbA1c: a meta-analysis of published randomized clinical trials

Factors associated with the effect-size of thiazolidinedione (TZD) therapy on HbA_1c: a meta-analysis of published randomized clinical trials