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Survival rates in extremely low birthweight infants depend on the denominator: avoiding potential for bias by

Ursula Guillen1, Sara DeMauro, Li Ma

  • 1Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.

American Journal of Obstetrics and Gynecology
|July 12, 2011
PubMed

Insights

Survival rates for preterm infants vary due to inconsistent reporting denominators. Using different denominators like all births, live births, or NICU admissions significantly impacts reported survival rates for extremely low-birthweight infants.

Area of Science:

  • Neonatalogy
  • Medical Statistics
  • Public Health

Background:

  • Accurate reporting of survival rates for preterm infants is crucial for clinical decision-making and resource allocation.
  • Previous studies on extremely low-birthweight (<1000 g) and extremely low-gestational-age (<28 weeks) infants have shown wide variations in survival outcomes.
  • The use of inconsistent denominators in calculating survival rates may introduce bias and hinder accurate comparisons.

Purpose of the Study:

  • To evaluate whether recent data on preterm infant survival is biased by the use of varying denominators.
  • To identify the specific denominators used in reporting survival rates for extremely low-birthweight and extremely low-gestational-age infants.
  • To quantify the impact of different denominators on reported hospital survival rates.

Main Methods:

  • A systematic review was conducted on publications reporting hospital survival of infants weighing less than 1000 g or born at less than 28 weeks gestation.
  • Included studies were those that explicitly specified the denominator used for calculating survival rates.
  • Data extraction focused on the denominator type (all births, live births, NICU admissions) and reported survival rates.

Main Results:

  • Out of 111 eligible publications, only 51 (46%) clearly stated the denominator used for survival calculations.
  • Commonly used denominators included all births (6 publications), live births (25 publications), and neonatal intensive care unit admissions (20 publications).
  • Mean survival rates varied significantly based on the denominator: 45.0% for all births, 60.7% for live births, and 71.6% for NICU admissions (P ≤ .009).

Conclusions:

  • The wide range in reported survival rates for extremely low-birthweight and extremely low-gestational-age infants is partly due to denominator bias.
  • Inconsistent use of denominators significantly affects the interpretation and comparability of survival data in neonatal research.
  • Standardization of denominator reporting is essential for accurate assessment of preterm infant survival outcomes.
Abstract

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