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Utility of Birth Certificate Data for Evaluating Hospital Variation in Admissions to NICUs.

OBJECTIVES
Efforts to study potential overuse of NICU admissions and hospital variation in practice are often hindered by a lack of an appropriate data source. We examined the concordance of hospital-level NICU admission rates between birth certificate data and California Children's Services (CCS) data to inform the utility of birth certificate data in studying hospital variation in NICU admissions.


METHODS
We analyzed birth certificate data from California in 2012 and hospital-specific summary data from CCS regarding NICU admissions. NICU admission rates were calculated for both data sets while using CCS data as the gold standard. The difference between birth certificate-based and CCS-based NICU admission rates was assessed by using the Wilcoxon signed rank test, and concordance between the 2 rates was evaluated by using Lin's concordance correlation coefficient and Kendall's W concordance coefficient.


RESULTS
Among a total of 103 hospitals that were linked between the 2 data sets, birth certificate data generally underreported NICU admission rates compared with CCS data (median = 7.72% vs 11.51%; P < .001). However, in a subset of 35 hospitals where the difference in NICU admission rates between the 2 data sets was small, the birth certificate-based NICU admission rate showed good concordance with the rate from CCS data (Lin's concordance correlation coefficient = 0.91; 95% confidence interval: 0.84-0.95; Kendall's W concordance coefficient = 0.99; P < .001). Hospitals with good-concordance data did not differ from other hospitals in the institutional characteristics assessed.


CONCLUSIONS
For a selected subset of hospitals, birth certificate data may offer a reasonable means to investigate hospital variation in NICU admissions.