Interdependency of lithium ratio, plasma lithium level and clinical state in patients with affective disorders.

The interrelationship between lithium ratio, lithium plasma level and the different clinical phases of 31 patients with bipolar affective disorder has been investigated. the interdependency of these variables was followed longitudinally during different phases of the illness while under lithium therapy. Although positive correlations between lithium ratio and lithium plasma levels were evident, the lithium ratio values in the euthymic group were significantly higher than those in the manic and depressive groups, independently of the plasma lithium level. Our data suggested that RBC/plasma lithium ratio might be a sensitive state dependent index in affective bipolar illness.