There were few reports on serum CA19-9 values of children. Except for the case–control studies with a limited number of controls, this is the first report of the distribution of serum CA19-9 values of subjects aged less than 20 years. The new finding is that the children in early years indicated high serum CA19-9 values and it decreases along with their maturation.
genotypes influence serum CA19-9 levels, the genotypes were taken into account for the present study. The allele frequencies were similar to those of the previous studies for Japanese population [10
]. In Le
genotype has no enzyme activity, which results in no synthesis of CA19-9 even among cancer patients. In Se
gene, 385T (sej
) and pseudogene (se5
) are no activity alleles, so that sej
, and se5
genotypes are concerned with over synthesis of CA19-9. This study reported Le
genotype frequencies and the geometric mean values of serum CA19-9 for each combination of these genotypes. The combination of the full enzyme activity genotype of Le
) and no enzyme activity genotype of Se
) indicated the highest mean value of serum CA19-9 among both of the generations.
In case of Caucasians, although the reported polymorphisms of Le
genes are partly different from Japanese, the alleles without enzyme activity are observed. The common haplotypes without enzyme activity are 59G
) and 59G
) in Japanese, and 59G
in Caucasians [19
]. Any of 508A
alleles of Le
gene could lead to lose the Lewis enzyme activity. Concerning Se
gene, common alleles without enzyme activity are sej
among Japanese, and 428A
of G428A polymorphism in Caucasians. Although there was no previous information about the frequencies of Le
genotypes among Japanese-Brazilians, their genetic background is basically the same and this study showed the similar frequencies to the previous Japanese population. Since there are no substantial differences in frequency of no activity alleles between Caucasians and Japanese, the consequence of this study would be applicable to any population groups.
The present study showed that serum CA19-9 levels were significantly higher in children than in their parents, and it seemed to be associated with body constitutions or maturity. The mean serum CA19-9 value of the parents of children whose CA19-9 values were higher than 37 U/ml was 12.3 U/ml and those of the rest of parents was 10.4 U/ml; the difference was not statistically significant (p
=0.19, ANOVA adjusted for age groups, sex and Le
genotypes). In this study, the youngest group indicated the highest mean value of serum CA19-9 in five-year age groups of the children. The regression analysis showed that younger age and high serum CA19-9 level were significantly associated among the children (p
<0.001). This result was inconsistent with the study in Finland about 20 years ago, which was concluded that the age of individuals did not have any influence on the concentrations of the CA19-9 marker [12
]. However, they also reported that the range of serum CA19-9 levels in healthy children were clearly wider than in adults and there were no detailed information about the mean values of each age groups.
At the beginning, we thought the feasible candidate for explaining the association between younger age and high serum CA19-9 was BMI. ANOVA demonstrated that children with high BMI (20 kg/m2
and more) indicated significantly lower values of serum CA19-9 (p
=0.007). Then we conducted the regression analysis with BMI, as well as height and weight, to test the hypothesis that the tendency could be associated with body constitutions. Any association with BMI, height and weight was significant, and the associations were still significant when they adjusted for age. Therefore, BMI seems to be one of the factors to determine the serum CA19-9 levels independently of ageing. Recently, one study reported that obese men had lower tumor marker levels, including CA19-9, than men in normal weight. They considered that hemodilution from increased plasma volume was the main reason of the observed decrease in tumor marker concentration in men with a high BMI [20
]. However, decreasing of serum CA19-9 was not the results for obese among the present study subjects, there could be other unknown factors we should focus on.