Abstract: A method of diagnosing cobalamin deficiency in warm-blooded animals is described. In one embodiment, this method comprises the measurement of methylmalonic acid levels in cerebral spinal fluid to determine if such levels exceed normal range. A finding of elevated levels indicates a cobalamin deficiency. In another embodiment, the method comprises the measurement of methylmalonic acid levels in cerebral spinal fluid and serum. A finding that the ratio of methylmalonic acid in cerebral spinal fluid to that in serum is above normal is indicative of a cobalamin deficiency. Additionally, a method for assessing the effectiveness of cobalamin therapy is described. The effectiveness of therapy is assessed by determining whether cerebral spinal fluid levels of methylmalonic acid have returned to normal, or by determining whether the ratio of methylmalonic acid in cerebral spinal fluid to that in serum has returned to normal range.

Abstract: A method for screening and distinguishing between cobalamin deficiency and folic acid deficiency by relating elevated levels of cystathionine to cobalamin or folic acid deficiency and relating elevated levels of 2-methylcitric acid to cobalamin deficiency but not folic acid deficiency. The methods can be used alone or in combination with other methods for detecting and distinguishing between cobalamin deficiency and folic acid deficiency.

Abstract: Method for determining levels of sulfhydryl amino acids, particularly total homocysteine levels in samples of body tissue from warm-blooded animals, methods of detecting cobalamin and folic acid deficiency using an assay for total homocysteine levels, and methods for distinguishing cobalamin from folic acid deficiency using an assay for total homocysteine levels in conjunction with an assay for methylmalonic acid.