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KMID : 0371019970300040741
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Journal of Preventive Medicine and Public Health
1997 Volume.30 No. 4 p.741 ~ p.751
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The change of validity of blood zinc protoporphyrin test by different cut-off level in lead workers
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Kim Yong-Bae
Ahn Hyun-Cheol
Hwangbo Young
Lee Gap-Soo
Lee Sung-Soo
Ahn Kyu-Dong
Lee Byung-Kook
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Abstract
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Measurement of blood lead (PbB) and blood zinc protopo~rphyrin (ZPP) are most common biological indices to identify the individual at risk (´or excess or the health sequences by lead exposure. Because PbB is known most important and reliable index of lead exposure, PbB is often regarded as a gold standard to detect lead exposure. But in Korea PbB is a secondary test item of detailed health check-up with positive fin-ding of screening test in most occasion. Our lead standard requires all lead workers to take annual heath-check twice a year for investigation of thjeir health effect due to lead exposure. Blood ZPP is one of most important index to detect high lead absorption in lead workers as a screening test. Measurement of blood ZPP is known well to correlate with PbB in steady state of exposure in most lead workers and is often used as a primary screening test to detect high lead absorption of lead workers with the ad-vantage of simplicity, easiness, portability and low cost. The ca,rrent cut-off criteria of blood ZPP for further detailed health check-up is 100 ~g/de which is supposed to match the level of 40 yg/d8 of PbB according to our standard.
Authors tried to investigate the validity of current criteria of cut-off level (100 ,ug Me) of blood ZPP and possible another better cut-off level of it, to detect the lead workers whose PbB level over 40 ygl d .
The subjects in our study were 212 male workers in three small scale storage battery industries. Blood ZPP, PbB and hemoglobin (Hb) were selected as the indices of lead exposure.
The results were as follows.
1. The mean of blood ZPP, PbB and Hb in lead workers were´`79.546.7 uglde, 38.715.1 ,ug/d2, and 14.81.2 g/dP, respectively. There were significant differences in blood ZPP, PbB and Hb by industry (P0.01).
2. The percents of lead workers whose blood ZPP were above ;100 ug/dP in the group of work duration below 1, 1-4, 5-9 and above 10 years were´ 8.6%, 17.2%, 47. 6%, and 50.0%, respectively. The percents of lead workers whose PB were above 40 ug/dP in those were 31.4%, 40.4%, 71.4%, and 86.4%, respectively. l~,
3. The percents of lead workers whose PbB were- below 40 ,ug/dP, 40-59 ug/dP and above 60 ug/dP were 54.7%, 34.9% and 10.4%, respectively. Those of lead workers whose blood ZPP were below 100 ,ug/dg, 100-149 pg/dP and above 150 ug/dP were 79. 2%, 13.7% and 7.1%, respectively.
4. Simple linear regression of PbB on blood ZPP was statistically significant W0.01) and as PbB was 40 ug/dP, blood ZPP was 82.1 ug/dP.
5. While the highest sensitivity and specificity of blood ZPP test to{ detect lead workers with PbB over 40 ug/dP were observed in the cut-off level of SO ug/dP and 100 ,ug/dP of blood ZPP, respectively, the highest validity (sensitivity~+specificity) of blood ZPP to detect lead workers with PbB over 40 ug/dP was observed in the cut-off level of around 70. ug/dP of blood ZPP. But even with optimal cut-ofd´ level of around 70 ,ug/dP of blood ZPP, still 25.0% of false negative and 20.7% false positive lead workers were found.
As the result of this study, it was suggested that reconsideration of current blood ZPP cut-off of our lead standard from 100 ug/dP to somewhat lower level such as around 70 ug/d2 and the inclusion-of -.PbB measurement as a primary screening test for lead workers was highly recommended for the effective prevention of dead workers.
Key words : blood lead, ZPP, cut off-level, lead workers
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KEYWORD
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blood lead, ZPP, cut off-level, lead workers
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