Vitamin B12 deficiency may be determined in an individual through the indirect assay of measuring the amount of the metabolite methylmalonate. This assay is performed using either the blood or urine samples of a patient. The test is more sensitive that the direct determination of vitamin B12 levels in the serum of the patient (Karademir et al. , 2007). However, there are some problems that physicians should be aware of, regarding the use of methylmalonate readings from the urine.
It is possible that the infant’s mom did not show any signs of vitamin B12 deficiency yet her urine sample contained methylmalonate because this metabolite is also associated with other medical disorders. This confounding factor thus makes screening for vitamin B12 deficiency a little more complicated. Methylmalonate is also an indicator for dysfunctional renal functions and thus caution should be taken with regards to its application in screening for vitamin B12 deficiency.
Since the infant’s mother is a vegetarian, it is less likely that this individual will develop a condition that is related to the lack of vitamin B12 intake in her daily diet. In this situation that the infant’s mother did not show any symptoms of vitamin B12 deficiency, it is not most probable that she indeed is not experiencing any problems with this cofactor. The direct measurement of vitamin B12 levels in the serum of a patient is considered as the standard diagnostic test for determining vitamin B12 deficiency. However, the serum test often leads to poor results due to other sources of generating false positive results.
In addition, this test is not highly effective in determining vitamin B12 deficiency, wherein a normal result may still be collected from a patient with vitamin B12 disorder. It is thus important that both tissue samples and a physical examination be performed in order to fully determine whether a patient has developed a vitamin B12 deficiency.
Reference
Karademir, F. , Suleymanoglu, S. , Ersen, A. , Aydinoz, S. , Gultepe, M. , Meral, C. , Ozkaya, H. and Gocmen, I. (2007). Vitamin B12, folate, homocysteine and urinary methylmalonic acid levels in infants. Journal of International Medical Research, 35,384-388.