A new filter paper method to measure capillary blood lead level in children.

Objective: To develop and evaluate a new filter paper method to determine capillary blood lead levels accurately in children.
Design: Paired comparison of lead levels determined in capillary whole blood dried on filter paper with lead levels in venous whole blood samples determined by a reference method.
Setting: Children's Hospital of Michigan clinics, Detroit.
Patients: One hundred children aged 9 months to 6 years.
Interventions: Lead concentrations determined in capillary whole blood samples dried on filter paper were compared with concentrations measured in paired venous whole blood samples by a reference method.
Main Outcome Measures: Comparability of the two lead assay methods was assessed with the concordance coefficient. The sensitivity, specificity, and positive predictivity of the capillary filter paper method relative to the reference method were determined at three intervention decision concentrations of blood lead defined by the Centers for Disease Control and Prevention.
Results: There was high agreement between the two assay methods, with a concordance coefficient of O.96. The capillary filter paper assay had a sensitivity of 90% and specificity of 90% for differentiating blood lead levels of 0.48 mumol/L (10 micrograms/dL) or more. Blood lead levels of 0.72 mumol/L (15 micrograms/dL) or more and 0.96 mumol/L (20 micrograms/dL) or more were identified with 98% and 94% sensitivity and 98% and 99% specificity, respectively. Positive predictivity was 93%, 98%, and 97%, respectively, at the three blood lead concentration decision points.
Conclusion: The capillary filter paper method for blood lead analysis described herein provides a convenient, sensitive, accurate, and inexpensive method to examine children for elevated blood lead levels.