Abstract

The EpiData Center (EDC) has provided routine blood lead level (BLL) surveillance for Department of Defense (DOD) pediatric beneficiaries since 2011. Data for this study were collected and compiled from raw laboratory test records obtained from the Composite Health Care System Health Level 7 (HL7)-formatted chemistry data, allowing an overview of the number of tests performed and the number of elevated results. Between 2010 and 2017, there were 177,061 tests performed among 162,238 pediatric beneficiaries tested. Using only the highest test result per year for each individual, 169,917 tests were retained for analysis, of which 1,334 (0.79%) test results were considered elevated. The percentage of children with elevated BLLs generally decreased over the time period for children of every service affiliation. All tests throughout this time frame were evaluated using current standards and the protocol followed by the Centers for Disease Control and Prevention and the Department of the Navy (DON). The adoption of a standardized BLL surveillance methodology across the DOD supports a cohesive approach to an evolving public health surveillance topic.

What Are the New Findings?

The EDC's BLL surveillance program established a methodology for lead exposure surveillance among DOD pediatric beneficiaries, providing critical data and valuable historical context for the interpretation of findings. Between 2010 and 2017, the percentage of children with elevated BLLs generally remained below 1.2%, and by 2017, the overall percentage was 0.5% for all children tested.

What Is the Impact on Readiness and Force Health Protection?

Blood lead surveillance of DON pediatric beneficiaries is required under Bureau of Medicine and Surgery instruction 6200.14D. The EDC's methodology for BLL surveillance may be leveraged for consistent BLL surveillance across the DOD.

Background

Robust lead exposure surveillance is especially important in pediatric populations. There is no safe blood lead level (BLL) for children; even very low BLLs can increase the risk of harmful hematologic and neurologic effects.¹ The U.S. Preventive Services Task Force concluded there is currently insufficient evidence to recommend BLL screening of asymptomatic children 5 years of age and younger.² The Military Health System (MHS) does not require universal BLL screening for pediatric beneficiaries, but providers are directed to consider assessing the risk of lead exposure among children between 6 months and 6 years of age by parental questionnaire, in accordance with recommendations from the American Academy of Pediatrics.³ Children who screen positive on this questionnaire should have their BLLs tested. Additionally, clinical suspicion of lead exposure or poisoning should prompt a blood lead test. Providers should ensure the performance of follow-up care for any child with an elevated BLL, and retesting is recommended to confirm an initial elevated BLL and to monitor the decline in BLLs following treatment.⁴

Before 2012, a BLL of 10 µg/dL or greater was considered to be an elevated test result.⁵ In 2012, the Centers for Disease Control and Prevention (CDC) updated the guidelines for the blood lead reference value (BLRV) to 5 µg/dL or greater, based on National Health and Nutrition Examination Survey results showing declining BLLs in children.⁶ For an elevated BLL (5 µg/dL or greater) to be considered "confirmed," CDC requires 1 elevated result from a venous blood test or 2 elevated results from capillary blood tests within 12 weeks.⁷ Traditional blood lead laboratory test results are the preferred test for Department of the Navy (DON) BLL surveillance. Rapid testing results, like finger-stick tests obtained by MHS providers at the point of care, were used for BLL surveillance purposes until 30 Aug. 2017 when the Bureau of Medicine and Surgery (BUMED) released an instruction stating point-of-care blood testing devices were no longer authorized for compliance with the childhood lead poisoning prevention program in the DON.⁸

Since 2011, the EpiData Center (EDC) at the Navy and Marine Corps Public Health Center (NMCPHC) has conducted routine BLL surveillance among Department of Defense (DOD) pediatric beneficiaries on a quarterly basis. An annual report based on data at the military treatment facility (MTF) level is also prepared on DON pediatric beneficiaries at the request of the Occupational and Environmental Medicine Department of NMCPHC. All surveillance reports are available to qualified DOD personnel upon request. The EDC's BLL surveillance program provides critical data and valuable historical context for evaluating lead exposure among DOD pediatric beneficiaries.

This article describes the EDC's methodology for BLL surveillance in DOD pediatric beneficiaries. This methodology represents a potential model for the development of a shared, standardized BLL surveillance method because it could be tailored to meet the unique needs of each DOD service while also maximizing the comparison, replication, and utility of findings. DON blood lead surveillance is modified from the CDC's standard blood lead surveillance definitions and classifications to best meet its needs using current capabilities. For every calendar year (CY), the EDC identifies elevated blood lead tests among DON pediatric beneficiaries and then verifies in the Armed Forces Health Longitudinal Technology Application (AHLTA) whether or not the provider followed up with the pediatric beneficiary. The EDC then provides a list of names of children that have not had follow-up testing to the Occupational and Environmental Medicine Department of NMCPHC.

Methods

Laboratory test records with a sample collection date in CYs 2010–2017 (01 Jan. 2010 through 31 Dec. 2017) were obtained from the Composite Health Care System (CHCS) Health Level 7 (HL7)-formatted chemistry laboratory data. The EDC receives a feed of CHCS HL7-formatted chemistry laboratory data and demographic information daily from the Defense Health Agency. These data include all records from MTFs using the CHCS across the DOD. Records were excluded if the sample was not blood, if the unit of measure or the test result could not be determined, or if the results indicated a test was not performed. For example, before CDC updated its BLRV, 122 test results were recorded as "<10." These results were removed from the final analysis, as it could not be determined if the results were less than the current BLRV of 5 µg/dL. Blood tests with the same sample collection date and date of certified results were excluded from the final sample, as these tests may have been unauthorized point of care tests⁸; moreover, it would have been highly unlikely for the laboratories to have been able to collect, analyze, and certify a sample on the same day. Zinc protoporphyrin (ZPP) tests, which measure the amount of ZPP in the blood (an indicator of chronic lead exposure) rather than BLL, were also excluded. If more than 1 BLL test result was identified for an individual in a single year, the highest BLL test result for that year was retained.

BLL tests administered to beneficiary children aged less than 18 years at the date and time of sample collection were included. Tests could either have been those completed within an MHS laboratory or those completed at an out-of-network laboratory, after which an MHS provider received and entered the results into AHLTA. Records were analyzed by sponsor service affiliation (Army, Air Force, Marine Corps, Navy, Other), age group (=6 years and 7–17 years), BLL value (<5 µg/dL, 5–9 µg/dL, 10–19 µg/dL, and =20 µg/dL), and geographic region (outside of the U.S., New England, Mid-Atlantic, Eastern North Central, Western North Central, South Atlantic, Eastern South Central, Western South Central, Mountain, Pacific). For sponsor service affiliation and geographic region, the percentage of elevated BLL tests per year was determined.

Results

From 01 Jan. 2010 through 31 Dec. 2017, 169,917 BLL records were retained for analysis (Table 1). The Army tested more pediatric beneficiaries than any other service affiliation during the reporting period. The majority of testing occurred among pediatric beneficiaries aged 6 years or younger across all branches of service.

Overall, the percentage of elevated BLLs among pediatric beneficiaries decreased from 2010 to 2017 (Figure). Less than 1% of pediatric BLL tests in any service were elevated in 2016 and 2017, and no children in the "other" category had an elevated BLL test since 2014.

For CYs 2010–2017, 96.2% of all BLL tests among pediatric beneficiaries were performed in the U.S. and 3.8% were performed elsewhere (Table 2). The percentages of elevated tests (0.8%) were equivalent for the 2 regions. Within the U.S., there were no tests performed in 9 states. Of all BLL tests in the U.S., 58.8% (n=96,089) were from the South Atlantic and Western South Central regions, which accounted for 54.8% (n=702) of all elevated BLLs. The New England region had the highest regional percentage of elevated BLLs (1.4%), but that percentage was based on just 22 elevated BLLs out of 1,561 tests, the lowest number of tests for any region. Among the states, Texas had the highest number of tests (n=29,340), followed by Virginia (n=25,852), but the percentages of tests with elevated BLLs were just 0.5% and 0.7%, respectively. The 5 states with the highest percentages of elevated BLLs (Connecticut, Rhode Island, Pennsylvania, New Hampshire, and Tennessee) accounted for just 22 elevated levels out of only 268 tests performed (Table 2). Among the remaining 37 states (including Washington, DC) that performed tests, the mean percentage positive was 0.9% and the values ranged from 0.3% (Arizona and Colorado) to 1.8% (Kansas and Mississippi).

Editorial Comment

Across the DOD, there were 177,061 tests performed between 2010 and 2017 among 162,238 pediatric beneficiaries. Some children may have had multiple tests occurring within the same year or during the totality of the reporting time frame because they had a positive lead questionnaire screen during a doctor's visit, exhibited clinical symptoms of lead poisoning per the provider's discretion, or had a prior elevated BLL test. For surveillance purposes, the highest BLL result per year per pediatric beneficiary was kept for analysis, leading to a final observation count of 169,917 BLL tests.

While the percentage of elevated BLL tests varied by sponsor service affiliation, the overall percentage of elevated BLL tests decreased from 2010 to 2017. The number of BLL tests among pediatric beneficiaries varied by state because of the location of fixed MTFs; however, in general, the percentage of elevated BLL tests did not differ between regions inside and outside of the U.S. The number of children tested within each branch of service likely varied because of the difference in the size of the service populations. Percentages of children with elevated BLLs could potentially be affected by the number of children tested within a branch of service or geographic region, whether the children tested were at a lower or higher risk of lead exposure, and the screening recommendations of the MHS.

To adequately identify and address lead exposure risks in their active duty and beneficiary populations, the DON and other DOD services might consider the adoption of a single, standardized method for BLL surveillance. A shared methodology would facilitate comparisons and reduce duplicative effort across the services. Ideally, a shared methodology would also be flexible and responsive to accommodate the challenges related to BLL surveillance in the DOD.

HL7-formatted data are routinely generated within the CHCS at fixed MTFs. HL7-formatted data do not include records from BLL tests without certified results. This may include specimens collected at an MTF that were sent to an out-of-network laboratory for testing. Data from purchased care providers also were not included. Records from MHS GENESIS, a new electronic health record that launched in Feb. 2017 at select MHS facilities, were unavailable. Therefore, records from the following MTFs throughout the Pacific Northwest region were not included in this analysis after the launch of MHS GENESIS at their facilities: Fairchild Air Force Base, Madigan Army Medical Center, Naval Health Clinic Oak Harbor, and Naval Hospital Bremerton. Changes in civilian and military testing policies, updates to exposure thresholds, population- or service-specific practices, and data limitations complicate comparisons over time and across services and limit the generalizability of findings.

The HL7-formatted chemistry database consists of nonculture laboratory test results (e.g., polymerase chain reaction and antigen testing). Providers may order a panel when patients present with nonspecific symptoms. If the test name or test results within a panel are not disease-specific, these results may not be captured in search terms used to query the chemistry data. Classifying chemistry tests involves extensive searching of free-text test result fields. It is possible that some test results were misclassified, though validation steps were included to reduce error. Venous and capillary BLL specimen samples are unable to be distinguished in the HL7-formatted chemistry data. Capillary specimen samples for lead testing are generally viewed as less reliable than venous samples because of the potential for lead contamination of specimens during collection that could result in false positives. For surveillance purposes, the EDC reports the highest BLL result per year per pediatric beneficiary and ensures that there is follow-up regarding that elevated test regardless of specimen sample type.

Universal BLL screening is not required in the MHS but is based on the discretion of health care practitioners. As a result, the proportion of pediatric beneficiaries with high BLLs may not be a true representation of the BLLs in the pediatric beneficiary population. However, the EDC's pediatric BLL surveillance methods may provide a starting point for discussions on the value of developing a standardized blood lead surveillance program across all DOD services.

Author affiliations: EpiData Center, Navy and Marine Corps Public Health Center, Portsmouth, VA (Ms. Kotas, Ms. Madden, Ms. Luse, and Ms. Carroll).

Acknowledgments: The authors thank Ashleigh McCabe and Angela Schlein for their support of this analysis and manuscript.

Disclaimers: The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the U.S. Government. The authors are employees of the U.S. Government. This work was prepared as part of their official duties. Title 17, U.S.C., §105 provides that copyright protection under this title is not available for any work of the U.S. Government. Title 17, U.S.C., §101 defines a U.S. Government work as a work prepared by a military service member or employee of the U.S. Government as part of that person's official duties. This research was supported in part by an appointment to the Postgraduate Research Participation Program at the Navy and Marine Corps Public Health Center administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the Navy and Marine Corps Public Health Center.

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