SCREENING CHILDREN EXPOSED TO LEAD - AN ASSESSMENT OF THE CAPILLARY BLOOD LEAD FINGERSTICK TEST

We describe results of a 3-year study in which 499 paired venous and c apillary blood specimens, collected by fingerstick on the same day, we re analyzed for lead (BPb) and erythrocyte protoporphyrin (EP). False- positive rates (FPRs) and the proportion of false positives were calcu lated at four BPb thresholds. At the 100 mu g/L threshold, the FPR for all data was 13%, but the proportion of false positives was only 5%. The log ratios of capillary-to-venous BPb data indicate that, with the exception of eight outliers, two subpopulations exist that follow a l og-normal distribution. These two sub-populations, the ''core'' (n = 3 03) and ''shifted'' (n = 188) groups, on average generated a positive bias at 100 mu g/L BPb of 8.6% and 30.3%, respectively. The log ratios of capillary-to-venous EP data followed a normal distribution, indica ting that capillary EP is not statistically different from venous EP.