K. Nilsson et al., PLASMA METHYLMALONIC ACID IN RELATION TO SERUM COBALAMIN AND PLASMA HOMOCYSTEINE IN A PSYCHOGERIATRIC POPULATION AND THE EFFECT OF COBALAMIN TREATMENT, International journal of geriatric psychiatry, 12(1), 1997, pp. 67-72
Cobalamin deficiency seems to be a relatively common condition in psyc
hogeriatric patients. To elucidate the diagnostic possibility of cobal
amin deficiency we have in this study analysed three markers for cobal
amin deficiency, plasma methylmalonic acid, plasma homocysteine and se
rum cobalamin, in 96 psychogeriatric patients. Patients were divided i
nto four groups according to serum cobalamins above or below 150 pmol/
l and normal (<19.9 mu mol/l) or increased plasma homocysteine. The up
per reference limit (95th percentile) for plasma methylmalonic acid in
100 healthy subjects was established to 0.42 mu mol/l. The mean value
of methylmalonic acid was increased only in the group of patients wit
h serum cobalamin below 150 pmol/l and increased plasma homocysteine c
ompared to the other groups. In this group six (46%) out of 13 patient
s exhibited increased plasma methylmalonic acid, whereas in the other
groups the frequency of increased plasma methylmalonic acid only varie
d from 10 to 13%. During cobalamin supplementation the most pronounced
decrease of plasma methylmalonic acid also occurred in the group of p
atients with low serum cobalamin levels and increased plasma homocyste
ine. Only 39% of the initial mean value for plasma methylmalonic acid
was noted after 7-10 days of cobalamin administration.