SYNOPSIS A method for the measurement of serum folic acid activity is described, which is a modification of previous methods.The from normal subjects and patients with primary vitamin B12 deficiency. Normal subjects had serum folic acid levels from 5 9 to 210 m,ug./ml. (mean 9-9 m,ug./ml. ± 0-3 m.tg./ml. S.E.). In patients with megaloblastic anaemia requiring treatment with folic acid, other than megaloblastic anaemia of pregnancy, the levels were less than 4-0 mptg./ml. Patients with uncomplicated pernicious anaemia had levels from 6-0 to 27-0 m,tg./ml. (mean 16-6 m,ug./ml. ± 11 m,ug./ml. S.E.). The mean level in this group was higher than in normal subjects, and the highest levels of all were found in patients with subacute combined degeneration of the cord with minimal anaemia (range 14-4 to 36-8 mp,g./ml.; mean 24-8 mpg./ml. ± 2-4 mpig./ml. S.E.).The L. casei activity of the labile component is lost during autoclaving or storage at -20°C. This loss can be prevented during autoclaving by using adequate amounts of ascorbic acid in the phosphate buffer used to dilute the serum for assay and by adding ascorbic acid to serum that is to be stored. Moreover, the activity lost during the storage of serum not protected by ascorbic acid could be restored, for periods up to three months, by adding ascorbic acid to this serum before assay.The folic acid activity of blood and serum has been measured in the past by a number of workers using Streptococcus faecalis (Schweigert and Pearson, 1947; Wolff, Drouet, and Karlin, 1949;Toennies and Gallant, 1949;Girdwood, 1953;Nieweg, Faber, de Vries, and Kroese, 1954;Condit and Grob, 1958;and Cox, Meynell, Cooke, and Gaddie, 1960) and/or Lactobacillus casei (Schweigert, 1948;Simpson and Schweigert, 1949;Spray, 1952;and Spray and Witts, 1952) as test organisms. These workers were unable to demonstrate a consistent difference in the levels of folic acid activity of blood or serum in normal 'University of Queensland Travelling Scholar in Medicine.

SYNOPSIS A simplified microbiological assay for determining the folate content of red cells is described. As in previously reported methods Lactobacillus casei is used as test organism but two modifications are introduced. First, haemolysis is carried out in water containing 1 g. % of ascorbic acid; secondly, haemolysates are not incubated before the assay. Using this assay, recovery of pteroylglutamic acid added in two different concentrations to five different whole blood samples was 97 0 ± 1l9 S.E. % and 106 1 ± 4i7 S.E. % respectively. The coefficient of variation of the assay was between 11-2 and 15-0%.Haemolysates were best stored deep frozen, showing no significant loss of L. casei activity for three to five months at -20°C. On the other hand, non-haemolysed blood samples were best stored at 40C. when there was no loss of activity for seven to 10 days.Experiments confirmed that plasma is necessary for the maximum release of red cell L. casei activity, and showed that only small amounts of plasma are necessary; folate-and B12-deficient plasma released slightly lower L. casei activities from red cells than did normal plasma. The red cell folate levels of 40 healthy normal subjects ranged from 160 to 640 m,ug. per ml. of packed red cells. One hundred and twenty patients with subnormal serum folate levels due to idiopathic steatorrhoea, nutritional folate deficiency and Crohn's disease, partial gastrectomy, myelosclerosis, and polycythaemia vera were studied. Red cell folate levels were subnormal (range from 7 to 143 m,ug. per ml.) in 40 patients with megaloblastic anaemia, the lowest levels occurring in the most anaemic patients. Subnormal red cell folate levels also occurred in 23 (29 %) of the 80 nonanaemic patients. There was a good correlation between red cell folate level and severity of folate deficiency assessed by polymorph nuclear lobe counts, and, in the non-anaemic patients bone marrow morphology. It is concluded that, in the absence of B12 deficiency, the red cell folate level is a precise guide to the severity of folate deficiency.Patients with serum folate levels less than 3-0 m,ug. per ml. almost always had megaloblastic anaemia or obvious morphological changes of folate deficiency. In patients with borderline serum folate levels (3 0-5 9 m,tg. per ml.) haematological changes varied widely. The degree of change correlated with the red cell folate level in these patients.The formiminoglutamic acid (Figlu) test was positive (range 20-660 mg. excreted in eight hours) in all 30 patients with megaloblastic anaemia due to folate deficiency tested and also in 17 (31 %) of 54 non-anaemic patients who were folate deficient. The amount of Figlu excreted paralleled the red cell folate level in both the anaemic and non-anaemic, folate-deficient patients tested. Figlu excretion, like the red cell folate level, appeared to be a satisfactory index of tissue folate stores.In 46 patients with pernicious anaemia, the red cell folate levels ranged from 26 to 396 mp,g. per ml., 29 (63 %) of them having subnormal ...

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A new method for the determination of urinary formiminoglutamic acid (FIGLU) using conventional electrophoresis at 200 to 500 v. on cellulose acetate strips is reported. Experience in 166 determinations on 137 patients shows the method to be a simple, practical, and apparently sensitive one for the determination of FIGLU in the urine.Results of the application of the measurement of urinary FIGLU with histidine loading as a test for folic acid deficiency are also reported.