The reliable measurement of metal in biological media in human body is one of critical indicators for the proper evaluation of its toxic effect on human health. Recently in Korea the necessity of quality assurance of measurement in occupational health and occupational hygiene fields brought out regulatory quality control program. Lead is often used as a standard metal for the program in both fields of occupational health and hygiene. During last 20 years lead poisoning was prevalent in Korea and still is one of main heavy metal poisoning and the capability of the measurement of blood lead is one of prerequisites for institute of specialized occupational health in Korea. Furthermore blood lead is most important indicator to evaluate lead burden of human exposure to lead and the reliable and accurate analysis is most needed whenever possible. To evaluate the extent of the interlaboratory differences of blood lead measurement in several well-known institute specialized in occupational health in Korea, authors prepared 68 blood samples from two storage battery industries and all samples were divided into samples with 2 ㎖. One set of 68 samples were analyzed by authors´s laboratory(Soonchunhyang University Institute of Industrial Medicine: SIIM) and 40 samples of other set were analyzed by C University Institute of Industrial Medicine(CIIM) and the rest 28 samples of other set were analyzed by Japanese institute(K Occupational Health Center: KOHC). Authors also prepared test bovine samples which were obtained from Japanese Federation of Occupational Health Organization (JFOHO) for quality control. Authors selected 2 other well-known occupational health laboratories and one laboratory specialized for instrumental analysis. A total of 6 laboratories joined the interlaboratory comparison of blood lead measurement and the results obtained were as follows:
1. There was no significant difference in average blood lead between SIIM and CIIM in different group of blood lead concentration, and the relative standard deviation of two laboratories was less than 3.0%. On the other hand, there was also no significant difference of average blood lead between SIIM and KOHC with relative standard deviation of 6.84% as maximum.
2. Taking less than 15% difference of mean or less than 6 ㎍/㎗ difference in below 40 ㎍/㎗ in whole blood as a criteria of agreement of measurement between two laboratories, agreement rates were 87.5%(35/40) and 78.6%(22/28) between SIIM and CIIM, SIIM and KOHC respectively.
3. The correlation of blood lead between SIIM and CIIM was 0.975 (p=0.0001) and the regression equation was SLIM = 2.19 + 0.9243 CIIM, whereas the correlation between SIIM and KOHC was 0.965(p=0.0001) with the equation of SIIM = 1.91 + 0.9794 KOHC.
4. Taking the reference value as a dependent variable and each of 6 laboratories´s measurement value as a independent variable, the determination coefficient(R²) of simple regression equations of blood lead measurement for bovine test samples were very high(R²$gt;0.99), and the regression coefficient(β) was between 0.972 and 1.15 which indicated fairly good agreement of measurement results.
|