The National Tracking Network’s Lead Team has developed new indicators for childhood lead exposure, prompted by the CDC’s new reference level. An elevated blood lead level (EBLL) is now defined as a result above 5 micrograms of lead per deciliter of blood (mcg/dL), lower than the previous threshold of 10 mcg/dL. The new indicators use the lower EBLL threshold and include other major differences, such as prioritizing venous results as the gold standard and choosing the highest capillary test to confirm an EBLL.
Minnesota piloted these methods to develop new nationally-consistent indicators for childhood lead exposure, using surveillance data from MN’s Blood Lead Information System (BLIS). Minnesota is unique in that it also lowered its definition of an EBLL to 5 mcg/dL in state statute and Minnesota’s Tracking Program & Childhood Lead Poisoning Prevention Program have recently collaborated on several lead surveillance projects that apply the lower threshold.
METHODS:
We piloted the proposed indicators using Minnesota’s 2010 birth cohort, which uses multiple test years and better highlights improvements to the indicator. About 56,000 children born in 2010 were tested before the age of three (approximately 82% of the birth cohort). We compared the current indicators to the proposed indicators using Minnesota lead surveillance data by calculating the number and percentage of children reclassified between blood lead level categories and examining blood lead test results in detail.
RESULTS:
Out of the 56,355 children tested, 437 (1%) were reclassified using the new indicators. The majority of children (430 children, 98% of those that changed categories) reclassified from the unelevated category (<5 mcg/dL). Many of those 430 children reclassified up only one category to the lowest elevated category (5-<10 mcg/dL) and remained unconfirmed. The largest proportional changes occurred in three unconfirmed categories between 5-<20 mcg/dL, as the new indicators better captured potential EBLLs. A smaller group of children (12 children, <0.1% of children tested) reclassified more than one category using the new indicators.
CONCLUSIONS:
Based on our findings, we recommended that the Lead Team approve the proposed indicators as they better described the changing picture of childhood lead exposure. Despite the small magnitude of change, the new indicators more accurately reflected the new reference level and are more protective of children’s health. The Lead Team submitted the new indicators for approval in January 2016 and the National Tracking Network will soon display new nationally-consistent indicators utilizing the lower reference level.