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.

Clinical and laboratory observations on serum folate-binding protein.

We studied the effect of serum folate-binding protein (FBP) on folate radioassays and the relationship of the serum level of unsaturated FBP to the serum folate level in various clinical states. Our modification of a heat-extracted radioassay was compared to a whole serum radioassay. Our results confirmed the existence of elevated serum levels of unsaturated FBP in some normal subjects, in some women taking oral contraceptives, and in most patients with uremia.

Oral contraceptives, serum folate, and hematologic status.

Previous reports have suggested deleterious effects on folate balance in users of contraceptives. A study of folate in 526 women attending a family-planning clinic demonstrated, both with the Lactobacillus casei assay and with a new radioassay, that the mean serum folate level for women taking oral contraceptives was not significantly lower than that for women in a control group. There was no correlation between serum folate level and length of time oral contraceptives were taken.