241 - Performance Characteristics of Capillary Lead Levels in a Large Pediatric Primary Care Network

Poster Number: 241
Publication Number: 241.1307

Background: Lead exposure increases risk for adverse neurodevelopment. The convenience of capillary testing increases access to lead screening. However, elevated capillary blood lead (CBL) results must be confirmed with venous blood lead (VBL) levels, so falsely elevated results have implications for timely, appropriate care.

Objective: Assess frequency of falsely high CBL tests in a pediatric primary care network

Design/Methods: We examined CBL tests at 25 offices from January 1 to December 31, 2022. For CBL levels ≥7 µg/dL where a confirmatory VBL level was obtained, we compared those results. We identified abnormal CBLs where the VBL was normal ( < 3.5 µg/dL), as well as CBLs where the VBL resulted in a change of CDC management category. We assessed CBLs ≥45 µg/dL, which must be evaluated emergently. Using chi-square analysis, we compared payor, preferred language, race/ethnicity, and office, between samples where confirmation resulted in a change of management category versus those that did not.

Results: Of 16,152 CBL tests, 845 (5.2%) were ≥3.5µg/dL; 179 were ≥7µg/dL and had a confirmatory VBL. Among CBLs ≥7 µg/dL, median time to VBL was 9 days (IQR 4 – 28) and median change from CBL to VBL was 5.3 µg/dL (IQR 2 – 11). In our network, CBLs ≥7 µg/dL often miscategorized children as having elevated blood lead: 42% (76/179) had VBLs < 3.5 µg/dL. 68% (122/179) of CBLs ≥7 µg/dL had VBLs leading to change of CDC management category (Table 1.) The proportion of CBLs with a VBL in a different management category varied across offices from 22% to 100% (p=0.11). There was no association between preferred language or Medicaid insurance and CBL to VBL change in management category, but reporting Hispanic or non-Hispanic White race and ethnicity was associated with an increased proportion of VBLs changing management category (Table 2). In addition, CBLs identified < 1% (6/845) of elevated lead levels as having a blood lead >45µg /dL, but only 1 of 6 had a VBL >45 µg/dL; the other 5 had VBLs < 15 µg/dL (Table 3).

Conclusion(s): Consistent with prior work, falsely elevated CBLs occurred frequently and initial levels ≥45 µg/dL rarely represented a true emergency. Availability of CBL screening may improve adherence to lead testing recommendations; the socioeconomic cost of false categorization of some children as having very high BLLs needs elucidation. Variation in falsely elevated capillary blood lead levels between offices suggests an opportunity to improve reliability of CBL tests in our network.