The plasma homocysteine concentration is better than that of serum methylmalonic acid as a marker for sociopsychological performance in a psychogeriatric population

Background: Cobalamin/folate deficiency in elderly subjects may lead to psy chiatric symptoms, but more often it increases the severity of various orga nic and nonorganic mental diseases. A major clinical problem, however, is t he uncertainty and controversy concerning biochemical markers of cobalamin/ folate deficiency to be used in the diagnostic evaluation of suspected coba lamin/folate deficiency. Methods: We measured plasma homocysteine (tHcy), blood folate, serum methyl malonic acid, and serum cobalamin in 80 psychogeriatric patients (age, 77.3 +/- 8.6 years) and 50 controls (age, 76.1 +/- 8.0 years). We assessed asso ciations of these tests with measures of cognitive and behavior performance by use of regression analyses. Results: Plasma tHcy was increased in 45% of the psychogeriatric population (mean, 20.5 +/- 9.2 mu mol/L vs 15.3 +/- 4.7 mu mol/L for controls; P <0.0 1). Plasma tHcy correlated with severity of dementia (r = 0.36; P <0.01), t he Katz ADL index (r = 0.29; P <0.05), the Berger scale (r = 0.29; P <0.05) , and the score of symptoms (r = 0.39; P <0.001) in the psychogeriatric pop ulation. Similarly, blood folate was significantly correlated with these me asures, but the concentrations of serum cobalamin and methylmalonic acid we re not. In a stepwise multiple regression analysis including the biochemica l markers, tHcy was the only significant predictor of the severity of demen tia (r(2) = 0.11; P <0.01) and the score of symptoms (r(2) = 0.16; P <0.001 ). Conclusion: Plasma tHcy is the best marker of those measured to investigate suspected tissue deficiency of cobalamin/folate. (C) 2000 American Associa tion for Clinical Chemistry.