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Development of the optimality index-NL2015, an instrument to measure outcomes of maternity care.

Hermus, M., Boesveld, I., Pal-de Bruin, K.M. van der, Wiegers, T. Development of the optimality index-NL2015, an instrument to measure outcomes of maternity care. Journal of Midwifery & Women's Health: 2017, 62(5), 580-588
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Introduction
An optimality index is a composite tool to measure maximum outcome with minimal intervention. It focuses on optimality instead of on normality and is useful in comparing differences in processes and perinatal outcomes for women at low risk of complications. The latest Dutch version dates from 2 decades ago, and international versions of the optimality index are not directly applicable to the Dutch maternity system. Most data for perinatal research in the Netherlands are derived from a national perinatal database: the Netherlands Perinatal Registry.

Aim
The aim of this study was to develop a new Dutch version of the optimality index (OI-NL2015) that could be calculated from data derived from this national perinatal database and to assess the reliability of these data for use in the index.

Methods
Potential items were collected by a thorough comparison of earlier (inter)national optimality indexes and the current data collection of the national database. All items were reviewed by 2 experts in maternity care and assessed for importance, relevance for the Dutch maternity care system, and feasibility to retrieve information on these items. For each item a criterion for optimality was formulated based on evidence-based or consensus-based effectiveness of care in pregnancy and childbirth. All selected items were scored on potential problems, with reliability by 20 randomly selected community midwives. The level of agreement was calculated comparing these 2 data sets, which included data of the same women.

Results
The final OI-NL2015 consists of 31 items in 3 different components: 22 intrapartum, 7 neonatal, and 2 postpartum. Of the 7 items that were examined because of expected potential problems with reliability, in 6 items a level of 90% agreement was found.

Discussion
An optimality index is not a standard measurement instrument but must be validated and adapted to local circumstances and available data.