Title Long term healthcare costs of infants who survived neonatal necrotizing enterocolitis : a retrospective longitudinal study among infants enrolled in Texas Medicaid Permalink

Background: Infants who survive advanced necrotizing enterocolitis (NEC) at the time of birth are at increased risk of having poor long term physiological and neurodevelopmental growth. The economic implications of the long term morbidity in these children have not been studied to date. This paper compares the long term healthcare costs beyond the initial hospitalization period incurred by medical and surgical NEC survivors with that of matched controls without a diagnosis of NEC during birth hospitalization. Methods: The longitudinal healthcare utilization claim files of infants born between January 2002 and December 2003 and enrolled in the Texas Medicaid fee-for-service program were used for this research. Propensity scoring was used to match infants diagnosed with NEC during birth hospitalization to infants without a diagnosis of NEC on the basis of gender, race, prematurity, extremely low birth weight status and presence of any major birth defects. The Medicaid paid all-inclusive healthcare costs for the period from 6 months to 3 years of age among children in the medical NEC, surgical NEC and matched control groups were evaluated descriptively, and in a generalized linear regression framework in order to model the impact of NEC over time and by birth weight. Results: Two hundred fifty NEC survivors (73 with surgical NEC) and 2,909 matched controls were available for follow-up. Medical NEC infants incurred significantly higher healthcare costs than matched controls between 6–12 months of age (mean incremental cost = US$ 5,112 per infant). No significant difference in healthcare costs between medical NEC infants and matched controls was seen after 12 months. Surgical NEC survivors incurred healthcare costs that were consistently higher than that of matched controls through 36 months of age. The mean incremental healthcare costs of surgical NEC infants compared to matched controls between 6–12, 12–24 and 24–36 months of age were US$ 18,274, 14,067 (p < 0.01) and 8,501 (p = 0.06) per infant per six month period, respectively. These incremental costs were found to vary between sub-groups of infants born with birth weight < 1,000g versus ≥ 1,000g (p < 0.05). Conclusions: The all-inclusive healthcare costs of surgical NEC survivors continued to be substantially higher than that of matched controls through the early childhood development period. These results can have important treatment and policy implications. Further research in this topic is needed. * Correspondence: jhay@usc.edu Equal contributors Department of Clinical Pharmacy and Pharmaceutical Economics & Policy, University of Southern California, 3335 S Figueroa Street, Unit A, Los Angeles, CA 90089-7273, USA Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles, CA 90089-7273, USA Full list of author information is available at the end of the article © 2013 Ganapathy et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Table 1 Procedures and ICD-9-CM codes used to define infants with surgical NEC Surgical procedures ICD-9-CM Codes Intestinal resection procedures 45.02-3, 45.1, 45.29, 45.3-4, 45.41, 45.49, 45.50-2, 45.60-3, 45.70-9, 45.8, 46.99 Procedures related to stoma creation 46.0 – 46.64 Intestinal anastomosis 45.9 – 94, 46.73-79, 46.93-4 Exploratory laparotomy 45.0, 45.00, 54.11 Percutaneous abdominal drainage 54.91 Ganapathy et al. BMC Pediatrics 2013, 13:127 Page 2 of 11 http://www.biomedcentral. com/1471-2431/13/127 Background Neonatal necrotizing enterocolitis (NEC) is a gastrointestinal inflammatory condition in neonates that has a detrimental effect on the survival and long term development of affected infants. The disease is most commonly seen in premature infants, although up to 25% of NEC cases have been observed among full-term babies [1,2]. The overall incidence of necrotizing enterocolitis in the United States among infants born with birth weights < 1500 grams is estimated to be 7 – 12% [3-7]. The etiology of NEC is understood to be multi-factorial; ischemic injury and aberrant microbial colonization, among other factors, have been found to play a very important role in the disease process [1]. Initial management of NEC is often highly complicated and resource intensive. About 44-70% of neonates diagnosed with NEC show signs of advanced disease (commonly categorized as Bell’s stage III) that requires surgical management [3,8,9]. The economic burden of NEC has been estimated to be approximately 500 million to 1 billion US dollars annually [1,10]. These estimates are probably conservative given the strong evidence to support the many adverse consequences of surgical NEC beyond the initial hospitalization period. In particular, the outcomes of bowel resection among survivors of the procedure has been well studied and has been found to be associated with complications such as short gut syndrome and prolonged administration of parenteral nutrition [9,11,12]. There also is growing evidence for a possible link between surgical NEC and growth and neurodevelopmental impairment, leading to poor health outcomes in the long term [9,13-17]. The long term economic outcomes, such as healthcare or special education costs, of NEC survivors have not been well studied and there are very few published studies on this topic. There is a clear need for research on this topic to understand the full spectrum of disease burden, and also to evaluate the costeffectiveness of novel therapeutic strategies that can mitigate the risk of developing NEC or reduce its impact on infant growth and development in the long term. The primary goal of this study is to compare the healthcare costs between 6 and 36 months of chronological age, among survivors of medical and surgical NEC to that of matched infants without a diagnosis of NEC during birth hospitalization. This study was driven by the hypothesis that NEC survivors on average will continue to have greater demand for healthcare services throughout the early developmental period due to the increased risk of long term complications in these children as compared to similar infants without a diagnosis of NEC. Furthermore, the incremental demand for healthcare services will vary depending on the type of NEC (medical or surgical). Methods This is a retrospective cohort study using claims database analyses. Infants enrolled in the Texas Medicaid fee-for-service program, born between January 2002 and December 2003, were selected for this study. Greater than 50% of live births in Texas were covered by Medicaid [18]. Also, unlike in other large states such as California, Illinois or New York, a significant proportion of Texas Medicaid clients were managed under traditional fee-for-service arrangements during the study period (2002 to 2006), making this data source ideal for our research [19]. Infants with NEC diagnoses were identified using a primary or secondary ICD-9-CM code of 777.50-53 in the hospital or physician claims at the time of initial hospitalization. NEC infants who had undergone procedures such as exploratory laparotomy involving bowel resection, peritoneal drainage, enterostomy with creation of stoma, etc. were defined as having “surgical NEC” (Table 1). NEC infants without claims for any of these surgical procedures were defined as having “medical NEC”. Based on the theoretical work of Rosenbaum & Rubin (1985) [20] and Imbens & Rubin [21] on the role of propensity score matching in the design of observational studies, each NEC infant was matched to infants without NEC diagnoses at a 1:10 ratio without replacement. Propensity scores were obtained from a stepwise logistic regression of NEC on infant demographic and birth characteristics at baseline including black race, gender, prematurity, born with extremely low birth weight (ELBW; defined as birth weight <1,000 g using the 5th digit of ICD-9 codes: 765.0x – 765.1x), and presence of any major birth defects, which was defined as having one or more of the following conditions: congenital heart disease (CHD) including patent ductus arteriosus (PDA), neural tube defects (NTD), hereditary CNS conditions and cleft lip or palate. The matching technique was implemented using the PSMatching algorithm in SAS 9.2. [22]. The longitudinal inpatient, outpatient, physician and prescription claim files of all infants were followed from 6 months up to 3 years after birth. Follow-up beyond this