Objective To examine whether the number of very low birthweight (VLBW) infants treated annually in neonatal intensive care units (NICUs) (hospital volume) has an effect on their in-hospital mortality under the regulatory conditions in Germany.
Setting The study included VLBW infants with <33 weeks of gestational age and birth weight below 1500 g admitted to NICUs in the state of Baden-Wüerttemberg, Germany, from 2003 to 2008. Cases were extracted from the compulsory German neonatal quality assurance programme with variables essential for calculation of the Clinical Risk Index for Babies (CRIB) and PREM birth model (PREM(bm)) scores. The cohort was divided into four subgroups corresponding to their disease severity (low, intermediate, high and very high) according to each score. Low-volume NICUs (LV-NICUs) were defined as treating up to 50 cases per year, while high-volume NICUs >50 cases.
Results After exclusion of infants with lethal malformations, 5340 cases from 32 units were analysed. While raw mortality was comparable, infants in LV-NICUs had an increased mortality after risk adjustment with the CRIB and PREM(bm) scores (OR 1.48 (95% CI 1.16 to 1.90), p=0.002 with CRIB; and OR 1.39 (95% CI 1.11 to 1.76), p=0.005 with PREM(bm)). In a subgroup analysis mortality was significantly higher for LV-NICUs in the intermediate disease severity group (OR 1.49 (95% CI 1.02 to 2.17), p=0.037 with CRIB) and in the high-risk group (OR 1.70 (95% CI 1.16 to 1.90), p=0.002 with CRIB; and OR 1.39 (95% CI 1.11 to 1.76), p=0.005 with PREM(bm)), but not in the low-risk and very high-risk subgroups.
Conclusion Depending on the severity of the disease, the risk-adjusted mortality in German NICUs with 50 or less annual cases of VLBW infants may be significantly increased.
- vlbw infant
- crib score
- prem score
- case load
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RH and KG contributed equally.
Contributors RH conceived the study, supervised the progress and wrote the manuscript with the help of KG. KG developed the mathematical model, collected and analysed the data, calculated the statistics, and designed the tables and the figure. WV gave advice for the statistical analysis, supervised the calculations and gave significant input in the interpretation of data. IB supplied the raw data, prepared them for statistical analysis and gave advice in the analysis and interpretation of data. All authors discussed the results and contributed to the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Ethics approval The study was approved by the ethics committee of the State Medical Council of Baden-Wuerttemberg, Stuttgart, Germany.
Provenance and peer review Not commissioned; externally peer reviewed.