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No. 12 (PC 12)
Reference value for serum folic acid level in Japanese adults
Naoko Yamaguchi, Tomohiro Takeda, Chizuko Kuramoto, Takao Uchiike, Masaharu Yamazaki,
and Yasuyuki Okamoto
Central Clinical Laboratories, Nara Medical University, Japan
Since folic acid deficiency in early pregnancy may cause neural tube closure defect in embryos,
Japanese Ministry of Health, Labour and Welfare recommends a daily intake of 0.4 mg folic acid for
women who can become pregnant. It has been believed that the food folate is generally sufficient in
Japanese adults, however, it has been suggested that recent changes in domestic eating habits might
have reduced the intake. Thus, we measured folic acid in sera of Japanese healthy adults using a
chemiluminescent enzyme immunoassay (CLEIA), and here report the reference value obtained as a
result.
Materials and Methods
Three hundreds and fifty-nine healthy volunteers in our hospital were enrolled in the study. Serum
folic acid, vitamin B12 and ferritin were measured on an Access2 analyzer (Beckman-Coulter Inc.).
Results
The reference value between the 2.5th and 97.5th percentiles in the frequency distribution of serum
folate levels was determined as 2.41-11.93 ng/mL. Median values for serum folate levels were: 4.16
ng/mL in males, 4.75 ng/mL in females, and 4.57 ng/mL in all subjects. Serum folate levels tended to be
higher in females and lower in younger subjects.
Discussion
Our reference value for serum folate levels is similar to that reported previously in the UK using the
same analyzer. The finding that serum folate levels are higher in female subjects is also consistent with
the previous reports. The reason why serum folate levels were lower in our younger subjects is
unknown, but might be explained by differences in eating habits between generations. We are preparing
to report a further study on serum folate levels in pregnant women and anemic patients.
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