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

Abstract

Background: Cobalamin/folate deficiency in elderly subjects may lead to psychiatric symptoms, but more often it increases the severity of various organic and nonorganic mental diseases. A major clinical problem, however, is the uncertainty and controversy concerning biochemical markers of cobalamin/folate deficiency to be used in the diagnostic evaluation of suspected cobalamin/folate deficiency. Methods: We measured plasma homocysteine (tHcy), blood folate, serum methylmalonic 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 associations 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 μmol/L vs 15.3 ± 4.7 μmol/L for controls; P <0.01). Plasma tHcy correlated with severity of dementia (r = 0.36; P <0.01), the 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 population. Similarly, blood folate was significantly correlated with these measures, but the concentrations of serum cobalamin and methylmalonic acid were not. In a stepwise multiple regression analysis including the biochemical markers, tHcy was the only significant predictor of the severity of dementia (r2 = 0.11; P <0.01) and the score of symptoms (r2 = 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 Association for Clinical Chemistry.