Early detection of BA permits surgical repair by the Kasai portoenterostomy. In the industrial world, the median age at Kasai operation is between 54 and 69 days of age 
. Unfortunately, even with a successful Kasai, more than 70% of children eventually develop cirrhosis and require liver transplantation prior to adulthood, but much of this depends on age of surgery 
. In a retrospective analysis of 349 Canadian patients treated with the Kasai procedure, those who had surgery at<than 30 days of age had a 52% survival of the native liver vs. a 21% survival rate for those who underwent surgery at>90 days of age 
For the primary care clinician, improving the age of diagnosis is akin to improving the prognosis of the Kasai. To this aim, parent education on the signs and symptoms of BA, particularly acholic stools, has been a major focus in many countries 
. In Taiwan, an infant stool color card is sent home with every neonate to educate parents on the importance of acholic stools and increase the rate of early self-referral. A recent study credits this card program for increasing the rate of detection before 60 days of age to 72.5% in 2004 (start of program) and 97.1% in 2005, with subsequent age at Kasai before 60 days of age improving from 23.3% (1976–1989 historical data) to 60% in 2004 and 74.3% in 2005 
. What’s not mentioned in this study is Taiwan’s establishment of National Health Insurance (NHI) in 1995, prior to which 41% of the population was uninsured 
. With a concomitant dramatic increase in childhood immunizations since NHI implementation 
, one must wonder if greater access to care in this population has also strongly contributed to the increased rate of BA detection from pre to post–NHI years.
In the MHS, where all active duty members and their families have access to medical care, two-thirds of infants with biliary atresia were diagnosed prior to 60 days of life. Despite the economic differences in receiving primary care at a civilian facility versus a military treatment facility, there was no difference in median age at BA diagnosis by access to care models, with timely diagnoses of biliary atresia made at equivalent rates. The median age of diagnosis of BA in the MHS was 40 days of age, ranging from 1 to 189 days, with no significant change in age of diagnosis from 2004 to 2008. Comparing this age of diagnosis to data from the US purchased care system may help uncover any influence healthcare access has on age of diagnosis within this country.
Median age at diagnosis has been recently reported for the 55 patients who underwent a Kasai Procedure for BA at the St Louis Children’s Hospital from 1990–2004 
. The overall median age at diagnosis was 60 days, with the breakdown by 5-year time period demonstrating a worsening trend toward increasing age. Median age at diagnosis from 1990 to 1994 was 48.5 days, increasing to 60 days from 1995 to 19999 and 69 days from 2000 to 2004. The difference in median age was significant (p<0.1) comparing those diagnosed from the 1990–1994 period to the more recent 2000–2004 subjects. In 2006, The Biliary Atresia Research Consortium (BARC) studied 104 infants who underwent Kasai Procedure between 1997 and 2000 at 9 clinical centers and demonstrated a mean age at initial evaluation of 53 days, with mean age at surgery of 61 days 
Comparing our data to that from within the U.S. purchased care system implies that BA is diagnosed at an earlier age in the MHS. However, there are a number of differences between these studies that make a direct comparison difficult. For example, the St Louis study defines age at diagnosis as the age that subjects underwent Kasai. In our study, age at diagnosis was set as the first date that an inpatient or outpatient encounter was coded as BA, allowing for the possibility of BA diagnosis before Kasai Procedure (if performed). This may lead to a comparative earlier median age in our study when compared to the St Louis study. On the other hand, both the St Louis study and BARC study looked only at that subset of patients who underwent Kasai. Not all patients with BA get this procedure, particularly those who are diagnosed at an advanced age. As our study includes all patients, regardless of Kasai Procedure, the median age could easily be advanced when compared to studies that exclude non-Kasai patients.
There were several limitations to our study. We relied on health claims data and not direct chart review to identify infants with biliary atresia. We minimized ascertainment bias by using a validated algorithm for the identification of infants with congenital conditions in these health claims data. Despite the relative large size of the identified sample compared with other studies of biliary atresia, the sample size was limited to only detect a significant determinant of an early diagnosis of biliary atresia if the effect size was twice or one-half of the comparison group. There is the possibility that primary care model and the other factors considered in our analysis did significantly impact diagnosis at a level less than the minimum detectable difference.
As the importance of early age at Kasai Procedure has been well-established, age at Kasai Procedure was not the focus of this study. However, a limitation of our study is that the M2 database inpatient procedure codes were significantly lacking, making further analysis of our data by presence or absence of Kasai Procedure not possible. There were other limitations secondary to the M2 database data-mining process. Whereas the BARC study found differences in age at Kasai by race and ethnicity, with non-Hispanic whites being more likely to undergo Kasai by 60 days of life 
, the significant absence of race data in our subject population precluded comparison of age at diagnosis by this variable.
Gender, prematurity or presence of additional anomalies did not affect the timing of BA diagnosis in the MHS. In the BARC study, 26 of the total 104 patients (25%) had additional congenital anomalies identified, 11 of which were identified as having Biliary Atresia Splenic Malformation Syndrome (BASM) 
. Those with BASM were found to undergo evaluation and Kasai at an earlier age, although the great majority of them had a poor outcome. None of our patients had ICD-9 diagnostic codes for spleen anomalies (i.e. polysplenia or other splenic malformations), implying that there were no cases of BASM in our study population; however this could be the result of incomplete coding. We did not examine mortality data and cannot establish whether or not patients with additional anomalies have a worse prognosis than those without.
We were unable to reliably determine the total number of births within the MHS during our study period, making any attempt at annual incidence or overall incidence inaccurate. The Department of Defense Birth and Infant Health Registry 
published their total five year rate of BA for 2001–2005 as 1.37 per 10,000, with a total of 65 BA patients over this five year period. Unfortunately, there is no distribution by year in this report. Our data is drawn from FY 2004–2008, with a total of 64 BA subjects. Examining the distribution by FY in , there is a decreasing number of BA diagnoses with subsequent years, yet we cannot determine if this is a change in overall incidence or a reflection of decreased total births during this time period.
Our study design was not able to make causal inferences about the effect of the determinants considered on timely BA diagnosis. Primary care systems in the U.S. are complex systems with national, family, and individual patient level contributors to outcomes. As such, our study was designed to detect associations only to provide insight into possible causal determinants.
The strengths of this study derive from the large study population in an open access health care system that minimizes economic health care disparities. The population also has the option of having their medical care in 2 parallel systems – one provided by civilian providers and one provided by military providers – that allows additional comparisons by type of access model.
Timely diagnoses of biliary atresia (BA) are made in an open access medical system with a fully insured population. The majority of infants with biliary atresia are diagnosed prior to 60 days of age, when the success of a Kasai procedure is highest. Military and civilian primary care providers make timely BA diagnoses at equivalent rates within the same open-access system. Presence of prematurity, co-existent congenital anomalies, and gender do not influence the timing of BA diagnoses. Fully insured infants in open-access health care systems appear to be diagnosed approximately 2 weeks earlier than in traditional health care systems. Nevertheless, a sizeable portion of our study population (20%) had diagnosis beyond 90 days of age. Efforts must continue to be made to eliminate delayed diagnosis in order to improve success of Kasai and reduce the necessity of liver transplantation. Further studies directly comparing infants in competing health-care delivery systems should be conducted and efforts made to identify factors that may be contributing to delayed diagnosis in subjects with advanced age at BA diagnosis.