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Estimation of red cell folate activity
  1. G. H. Spray
  1. Nuffield Department of Clinical Medicine, Radcliffe Infirmary, Oxford


    The conditions described by Hoffbrand, Newcombe, and Mollin (1966) for the estimation of red cell folate activity have been confirmed using a different method (Spray, 1964) of micro-biological assay with Lactobacillus casei.

    In 81 control subjects the levels of folate activity in the red cells were between 80 and 470 mμg/ml (mean 192), and in plasma between 2·1 and 13 mμg/ml (mean 4·9). In 16 patients with megaloblastic anaemia due to folic acid deficiency, the red cell folate level was between 3 and 74 mμg/ml (mean 32). In 15 of these patients the plasma level was between 0·1 and 1·0 mμg/ml; in the other patient it was 3·3 mμg/ml. Subnormal red cell levels were found in only eight out of 29 other patients whose plasma folate level was below 2·0 mμg/ml. In 26 patients with untreated pernicious anaemia, the red cell folate activity was between 44 and 280 mμg/ml (mean 129) and the plasma level was between 1·6 and 19 mμg/ml (mean 7·5).

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