Elevated serum levels of unsaturated folate binding protein: clinical correlates in a general hospital population.

We measured the capactiy of unsaturated folate binding protein to bind 3H-pteroylglutamic acid (UFBC) in serums from 489 general hospital patients. Of the patients 20% had mild-to-moderate elevations in UFBC (250 to 500 pg/ml), but only 6% had marked elevations (greater than 650 pg/ml), which correlated with metastatic cancer, active granulomatous disease, and especially with liver disease. The poor correlation of serum UFBC with folate status of the patient suggests that in many instances the elevated serum UFBC is neither the consequence nor the cause of folate deficiency. Although the role of folate binding protein remains unknown, it may be primarily an intracellular protein that is released into the serum as an index of activity of liver cells, granulocytes, and perhaps certain cancer cells.