DeBaun M R, Sox H C
Department of Pediatrics, St. Louis Children's Hospital, Washington University Medical School, Missouri.
Pediatrics. 1991 Jul;88(1):121-31.
Erythrocyte protoporphyrin (EP) was introduced in the 1970s as an inexpensive screening test for lead poisoning. As greater knowledge of lead poisoning has accumulated, the recommended EP level at which further evaluation for lead poisoning should be initiated has been lowered from greater than or equal to 50 micrograms/dL to greater than or equal to 35 micrograms/dL. The purpose of this study was to evaluate the utility of this EP threshold. A receiver operator characteristic curve was constructed to assess the relationship between the true-positive rate and false-positive rate of EP at various decision thresholds. The receiver operator characteristic curve was constructed with data from the second National Health and Nutrition Examination Survey from 1976 to 1980, which included 2673 children 6 years of age or younger who had both blood lead and EP level determinations. Decision analysis was then used to determine the optimal EP decision threshold for detecting a blood lead level greater than or equal to 25 micrograms/dL. The receiver operator characteristic curve demonstrated that EP is a poor predictor of a blood lead level greater than or equal to 25 micrograms/dL. At the currently recommended EP decision threshold of 35 micrograms/dL, the true-positive rates and false-positive rates of EP are 0.23 and 0.04, respectively. As a result of the inadequate performance of EP screening for lead poisoning, when the prevalence of lead poisoning is greater than 8%, there is no EP decision threshold that optimizes the relationship between the cost of screening normal children and the benefit of detecting lead-poisoned children. Erythrocyte protoporphyrin measurement is not sufficiently sensitive to be recommended uniformly as a screening test for lead poisoning.
红细胞原卟啉（EP）在20世纪70年代被引入作为铅中毒的一种廉价筛查试验。随着对铅中毒的认识不断积累，建议启动铅中毒进一步评估的EP水平已从大于或等于50微克/分升降至大于或等于35微克/分升。本研究的目的是评估该EP阈值的效用。构建了一个受试者工作特征曲线，以评估在各种决策阈值下EP的真阳性率和假阳性率之间的关系。受试者工作特征曲线是根据1976年至1980年第二次全国健康和营养检查调查的数据构建的，该调查包括2673名6岁及以下同时进行了血铅和EP水平测定的儿童。然后使用决策分析来确定检测血铅水平大于或等于25微克/分升的最佳EP决策阈值。受试者工作特征曲线表明，EP对血铅水平大于或等于25微克/分升的预测能力较差。在目前推荐的35微克/分升的EP决策阈值下，EP的真阳性率和假阳性率分别为0.23和0.04。由于EP筛查铅中毒的表现不佳，当铅中毒患病率大于8%时，不存在能优化筛查正常儿童成本与检测铅中毒儿童益处之间关系的EP决策阈值。红细胞原卟啉测量不够敏感，不足以统一推荐作为铅中毒的筛查试验。
