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%; < .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; < .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.