Development of a population-specific risk assessment to predict elevated blood lead levels in Santa Clara County, California

To determine: (1) the prevalence of a blood lead level (PbB) of 10 micrograms/dL or greater and 20 micrograms/dL or greater among children aged 6 to 72 months attending the Santa Clara County (SCC), California, public clinics, (2) risk factors for elevated PbB in this population, and (3) whether an SCC public clinic population-specific risk-assessment tool and a five-question lead poisoning questionnaire developed by the Centers for Disease Control and Prevention are useful for prospectively identifying children at higher risk for elevated PbB. We tested for PbB 3630 children aged 6 to 72 months attending SCC public outpatient clinics between August 8, 1991, and September 1, 1992. We then conducted two matched case-control studies. Five local risk-factor questions were combined with the CDC's five-question lead poisoning questionnaire, and from May 1, 1993, to June 30, 1993, we conducted risk assessments on 247 children tested for PbB. Two hundred twenty-two of 3630 children (6.1%) had a PbB of 10 micrograms/dL or greater. Thirty-nine (1.1%) had a PbB at least 20 micrograms/dL. Seventy-nine percent of the children screened and 91.0% of the children with PbB at least 10 micrograms/dL were Hispanic. Twenty percent of Mexican-born Hispanic children had a PbB of 10 micrograms/dL or greater, versus 7% of U.S.-born Hispanic children. Several factors were associated with elevated PbB among Hispanic children. For identifying children with a PbB of at least 10 micrograms/dL, the sensitivity and predictive value negative for the CDC's "high risk" definition were 30% and 93%, respectively, whereas for the SCC population-specific high-risk definition, the sensitivity was 90% and the predictive value negative was 98%. Hispanic children attending SCC public clinics have risk factors for elevated PbB that were not included in the CDC's lead poisoning questionnaire. Methods for prioritizing the frequency of lead screening may be improved by combining the CDC's questions with a population-specific risk assessment.