Use of the Optimality Index-United States in Perinatal Clinical Research: A Validation Study

Authors

  • Lisa Kane Low CNM, PhD,

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    • Lisa Kane Low, CNM, PhD, FACNM, is an assistant professor in the School of Nursing and Women's Studies Department and a lecturer in the Department of Obstetrics and Gynecology at the University of Michigan. She is in clinical practice at the University of Michigan Health System, Ann Arbor, MI.

  • Julia S. Seng CNM, PhD,

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    • Lisa Kane Low, CNM, PhD, FACNM, is an assistant professor in the School of Nursing and Women's Studies Department and a lecturer in the Department of Obstetrics and Gynecology at the University of Michigan. She is in clinical practice at the University of Michigan Health System, Ann Arbor, MI.

    • Julia S. Seng, CNM, PhD, is a research associate professor at the Institute for Research on Women and Gender and the School of Nursing and a research assistant professor in the Department of Obstetrics and Gynecology at the University of Michigan, Ann Arbor, MI.

  • Janis M. Miller RNC, PhD

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  • Janis M. Miller, RNC, PhD, is an assistant professor in the School of Nursing and associate research scientist in both the School of Nursing and the Department of Obstetrics and Gynecology at the University of Michigan, Ann Arbor, MI.

Lisa Kane Low, CNM, PhD, FACNM, assistant professor, University of Michigan, 400 N Ingalls, Rm 3249, School of Nursing, University of Michigan, Ann Arbor, MI 48109. E-mail: kanelow@umich.edu

Abstract

The objective of this study was to assess the validity and observed effect size of a new instrument, the Optimality Index-United States (OI-US), for use in perinatal clinical research. Using a large, hospital-based, midwifery service clinical database that included complete obstetric data for 3425 women, we examined discriminant validity and the effects of two different scoring methods used with the OI-US. Discriminant validity was confirmed by comparing OI scores for women who remained low risk and did not require physician involvement in their care (OI score mean = 84%; standard deviation [SD] = 8%) compared to those whose condition changed to require physician involvement in their care (mean = 71%; SD = 10%; P < .001). Two methods of scoring the OI-US were compared, finding no significant difference and suggesting that the types of data available and the research question can drive this decision. Finally, effect size was calculated by two methods: Cohen's d (–1.4) and the effect size correlation (r = –0.548), the latter of which corresponds to a d of –1.3, both resulting in a similarly large effect size estimation. The OI-US is a new instrument that shows promise for use in perinatal clinical research, particularly when assessing more subtle clinical differences in outcomes between study groups.

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