REFERENCE INTERVALS FOR BLOOD LEAD AND EVALUATION OF ZINC PROTOPORPHYRIN AS A SCREENING-TEST FOR LEAD TOXICITY

We evaluated, retrospectively, 2921 blood samples for the distribution of blood lead values in children below age 16, and in adult female an d male subjects. An upper reference value for children and females at 0.48 mumol/L, and for males at 0.72 mumol/L is used. Over 70% of the a dult males and >80% of the children and adult females were within thes e reference limits, and considered to be at low risk for lead toxicity . The diagnostic utility of zinc protoporphyrin (ZPP) to screen for a positive blood lead result was evaluated using receiver operating char acteristic (ROC) curves and likelihood ratios (LR). These studies conf irmed that ZPP was insensitive for the detection of elevated blood lea d at the critical thresholds of 0.48-1.21 mumol/L in children and adul t females with subclinical lead poisoning. ZPP was more diagnostically useful for screening the higher lead-exposed adult male occupational worker.