RBC-choline: a biological marker of the outcome of lithium prophylaxis?

We explored whether the elevation of RBC-choline and choline ratio (RBC-choline/plasma-choline) by lithium is a specific effect of lithium, whether these choline parameters are characteristics of the individual patient, and whether they are related to prophylactic lithium response. In lithium-treated patients RBC-choline and choline ratio were highly elevated compared with untreated controls. In contrast, both values were slightly decreased in patients on antidepressants, and essentially unchanged in patients on neuroleptics. Repeated measurements showed that choline parameters were fairly stable in the individual patient. The interindividual variance was significantly greater than the intraindividual variance. In 58 affective disorder patients with established lithium response, high choline ratios were found to be associated with a poor outcome of stabilizing therapy with lithium. This finding was replicated in a new sample of 15 bipolar patients. If confirmed, it could be an important clue as to the mode of action of lithium.