Related Experiment Videos
Evidence of selection bias in preterm survival studies: a systematic review
1Centre for Reproduction, Growth and Development, University of Leeds, D Floor Clarendon Wing, The General Infirmary at Leeds, Leeds LS2 9NS, UK. evans_d@southmead.swest.nhs.uk
Insights
Selection bias in preterm infant studies significantly overestimates survival rates, especially at the limits of viability. Future research must include all pregnancy outcomes to ensure accurate survival data for premature infants.
Area of Science:
- Neonatal research
- Perinatal epidemiology
- Biostatistics
Background:
- Accurate survival data for preterm infants is crucial for clinical decision-making and resource allocation.
- Cohort studies on infant survival are susceptible to selection bias, potentially skewing results.
Purpose of the Study:
- To quantify the extent to which selection bias in preterm infant cohort studies leads to an overestimation of survival rates.
- To assess the impact of different study methodologies on reported survival figures.
Main Methods:
- A systematic review was conducted on studies published between 1978 and 1998, focusing on infants born before 28 weeks of gestation.
- Studies were categorized into three grades (A, B, C) based on cohort definition, ranging from all pregnancy outcomes to neonatal unit admissions.
- Survival proportions to discharge were calculated for each week of gestation.
Main Results:
- Sixty-seven studies comprising 55 cohorts were analyzed.
- More selective study designs (Grade C) reported significantly higher survival rates compared to less selective ones (Grade B and A) between 23 and 26 weeks of gestation (p < 0.01).
- Survival was overestimated by 100% at 23 weeks and 56% at 24 weeks due to selection bias.
Conclusions:
- Selection bias can substantially inflate survival estimates in preterm infant studies, particularly around the limits of viability.
- To improve accuracy, future studies should aim to report outcomes for all pregnancies, including terminations, miscarriages, stillbirths, and all live births.
- Standardizing reporting to include all outcomes is essential for minimizing overestimation and providing reliable data on preterm infant survival.
Objective:
To determine by how much selection bias in preterm infant cohort studies results in an overestimate of survival.
Design:
Systematic review of studies reporting survival in infants less than 28 weeks of gestation published 1978-1998. Studies were graded according to cohort definition: A, stillbirths and live births; B, live births; C, neonatal unit admissions. Proportions of infants surviving to discharge were calculated for each week of gestation.
Results:
Sixty seven studies report data on 55 cohorts (16 grade A, 23 grade B, 16 grade C). Studies that are more selective report significantly higher survival between 23 and 26 weeks of gestation (grade C > grade B > grade A, p < 0.01), exaggerating survival by 100% and 56% at 23 and 24 weeks respectively.
Conclusion:
To minimise the potential for overestimating survival around the limits of viability, future studies should endeavour to report the outcome of all pregnancies for each week of gestation (terminations, miscarriages, stillbirths, and all live births).