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 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 micromol/L vs 15.3 +/- 4.7 micromol/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 (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.