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KMID : 0606019990050010033
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Soonchunhyang Journal of Industrial Medicine
1999 Volume.5 No. 1 p.33 ~ p.47
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Validity of Blood Zinc Protoporphyrin as the Screening Test for Different Blood Lead Levels for Occupational Lead Exposure
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Han Ku-Seok
Ahn Hyun-Cheol
Kim Yong-Bae
Lee Gap-Soo
Kim Hwa-Sung
Hwang Kyu-Yoon
Jang Bong-Ki
Lee Sung-Soo
Ahn Kyu-Dong
Lee Byung-Kook
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Abstract
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In order to evaluate the validity of current screening criteria of lead exposure and to provide effective information for the better health management of lead workers, author investigated the interrelationship between blood lead and blood zinc protoporphyrin(ZPP) and evaluate the validity of blood zinc protoporphyrin as the screening test and blood lead as gold standard of diagnostic test.
The total of 2245 lead workers (male workers: 1982, female workers : 263) from 12 lead using industries were studied.
Blood lead, ZPP, hemoglobin and hematocrit were selected as lead exposure variables. Personal information on sex, age and work duration were also checked.
Blood lead was measured with flameless atomic absorption spectrometry (model: Hitachi 8100) using standard addition method. Blood ZPP was measured with portable hematoflurometer (model: Aviv 206).
The results obtained were as follows:
1. The mean blood lead of all lead workers were 0.7±14.3㎍/㎗(Male: 31.0±14.4㎍/㎗, Female: 28.2±12.9㎍/㎗), whereas the mean blood ZPP of those were 68.1±47.5㎍/㎗(Male: 63.9±43.7㎍/㎗, Female: 100.1±61.0㎍/㎗). The mean value of hemoglobin and hematocrit of all lead workers were 14.5±1.5g/㎗(Male: 14.7±1.3g/㎗, Female: 12.3±1.2g/㎗) and 45.4±3.6(Male: 46.2±2.8, Female: 39.5±3.1) respectively.
2. Validity of test using blood zinc protoporphyrin as screening test for blood lead levels of 30㎍/㎗ as gold standard of diagnostic test revealed that the highest validity value for male and female lead workers were 50 and 90 ㎍/㎗ of ZPP respectively, showing 50 and 60 ㎍/㎗ of ZPP for all lead workers.
While those test for blood lead levels of 40㎍/㎗ as gold standard of diagnostic test revealed that the highest validity value for male and female lead workers were 60 and 90 ㎍/㎗ of ZPP respectively, showing 60 ㎍/㎗ of ZPP for all lead workers, those test for blood lead levels of 50 and 60㎍/㎗ as gold standard of diagnostic test revealed that the highest validity value for male and female lead workers were 60 or 70 and 100 ㎍/㎗ ZPP respectively, showing 60and 70 or 80 ㎍/㎗ of ZPP for all lead workers.
3. Predictive value of test using blood zinc protoporphyrin as the screening test for different blood lead levels of 30, 40, 50 and 60㎍/㎗ as gold standard of diagnostic test revealed that positive predictive value of screening test were decreased by the increase of blood lead level regardless of csreening criteria value ZPP and negative predictive value of screening test were increased accordingly regardless of screening criteria value of ZPP. On the other hand, within same blood lead level as a gold standard positive predictive values were inceased by the increase of screening criteria value of ZPP, whereas the negative predictive value were decreased accordingly by the the increase of screening criteria value of ZPP.
4. The correlation analysis of all lead workers among study variables revealed that CPbB and natural log transformation ZPP(LZPP) were better correlated with other variables and found to be better estimate than PbB and ZPP themselves. The age was correlated with all other variables, but the work duration was not. The correlation analysis of male and female workers among study variables revealed the same results with all lead workers.
5. The slope of simple linear regression of CPbB (independent variable) with ZPP in female workers(3.223)was steeper than in male workers(2.144). That of lead workers with work duration of less than 1 year was steeper than that of lead workers whose work duration was more than 1 year. But there was no slope difference between two groups divided by their work duration of 2 years less and more. The slope of simple linear regression of CPbB lead (independent variable)with ZPP in lead workers whose blood lead were higher than 30㎍/㎗and 40㎍/㎗ were steeper than those whose blood lead were less than 30㎍/㎗ and 40㎍/㎗.
6. The slope of simple linear regression of CPbB (independent variable) with ZPP in lead industries with low mean blood lead were less steeper than those with high mean blood lead.
7. The slope of simple linear regression of CPbB (independent variable) with LZPP in female workers(0.0308was steeper than in male workers(0.0253). That of lead workers with work duration of less than 1 year was steeper than that of lead workers whose work duration was more than 1 year. But where was no slope difference between two groups divided by their work duration of 2 years less and more. While the slope of simple linear regression of CPbB lead (independent variable) with LZPP in lead workers whose blood lead were hogher than 30㎍/㎗ was not steeper than those whose blood lead were less than 30㎍/㎗, there was no slope difference between two groups whose blood lead were less than 40㎍/㎗ and more than 40㎍/㎗.
8. The slope of simple linear regression of CPbB (independent variable) with LZPP in lead industries with low mean blood lead were less steeper than those with high mean blood lead, but the difference was not significant then that of CPbB and ZPP.
With above results, it is recommended that the screening criteria value of ZPP should be down to 60-70㎍/㎗ from 100㎍/㎗ for male lead workers and screening criteria of ZPP for female lead workers was all right with current value of 100㎍/㎗. So it is recommended to make different screening criteria of ZPP for male and female workers like the hemoglobin and hematocrit screening criteria.
It is also preferable to use CPbB and LZPP rather than uncorrected PbB and ZPP in the evaluation of lead exposure for lead workers.
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KEYWORD
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Zinc protoporphyrin (ZPP), Screening test, Blood lead, Lead workers
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