Role of impaired renal function as a cause of elevated plasma homocysteine concentration in psychogeriatric patients.

In previous studies a high frequency of elevated plasma tHcy concentrations has been observed in psychogeriatric patients (40-50%), but the main cause of these increased concentrations could not be established with certainty. Impaired renal function could partly contribute to elevated plasma tHcy concentrations in psychogeriatric patients. Therefore, in the present study, cystatin C was used as a sensitive marker for glomerular filtration. A linear regression analysis including age, blood folate, serum cobalamin, serum cystatin C and serum creatinine showed that only serum creatinine (p<0.001) and blood folate (p<0.001) independently predicted plasma tHcy concentration. However, about 44% of the patients with elevated plasma tHcy concentrations had signs of reduced glomerular filtration rate, as judged by increased serum cystatin C, whereas only about 13% of the patients with normal concentrations of plasma tHcy had signs of reduced glomerular filtration rate. This finding indicates that renal impairment may to some extent contribute to the elevated plasma tHcy concentration, even though serum cystatin C did not independently predict plasma tHcy concentration.