Assessment of interlaboratory performance on the measurement of blood lead levels in Taiwanese adults.

The purpose of this proficiency study was to assess the accuracy and consistency of blood lead level (BLLs) measurements in a study of Taiwanese adults. Three methods, including a certified blood accuracy test, an interlaboratory precision test and an intertime repeated measurement test, were applied to the six participating laboratories. Accuracy tests showed that most of the blood lead measurements were within the acceptable criteria proposed by United States Center for Disease Control and Prevention (U.S. CDC). However, an average of 11% underestimation was found at BLLs below 15 micrograms/dl. Coefficients of variation (CVs) were high in the first 3 months. After technical improvements, the CVs were reduced to acceptable limits of around 15% at low target lead values and 7% at high lead values. Interlaboratory variations of measurements in blood from ten normal healthy donors showed that the standard deviations were less than 2 micrograms/dl, which is within the acceptable criteria of +/- 4 micrograms/dl, in 8 out of 10 samples. Repeated measurements of BLLs in 54 blood samples over two months showed that most of the differences were within the acceptable range with a few exceptions. The mean BLLs measured in the baseline (pre-test) and two months later (post-test) were nearly identical. This proficiency test provides comparable and reliable results of BLL estimations in this multilaboratory study. However, the accuracy and consistency at low BLLs need to be improved.