Blood lead proficiency testing: overview of the federally sponsored program in the U.S.

External proficiency testing is a proven method for improving the quality of laboratory measurements, including lead in blood. Several proficiency testing programs exist to fill this need. This article describes the U.S. federally sponsored Blood Lead Proficiency Testing Program. Three specimens, composed of blood from dosed cows, are distributed to participants each month. Target values are determined by a group of 10 referee laboratories. Participant performance has shown steady improvement over time.