Lithium RBC/plasma ratio in subgroups of patients with affective disorders

Area of Science:

• Pharmacology
• Psychiatry
• Clinical Chemistry

Background:

• Lithium therapy is a cornerstone treatment for bipolar disorder and other affective disorders.
• Understanding lithium distribution between red blood cells (RBCs) and plasma is crucial for optimizing therapeutic efficacy and minimizing toxicity.
• The RBC/plasma lithium ratio has been investigated as a potential biomarker for treatment response and diagnosis.

Purpose of the Study:

• To investigate the diagnostic utility of the RBC/plasma lithium ratio in patients with affective disorders.
• To determine if the lithium ratio differs between patients in remission versus those in an active phase of illness.
• To assess correlations between the lithium ratio and clinical/demographic factors.

Main Methods:

• The study included 59 patients on prophylactic lithium therapy and 20 patients in an active phase of illness, encompassing cycloid psychotics, unipolars, and bipolars.
• Lithium levels in both RBCs and plasma were measured.
• Statistical analyses, including correlation matrices, were employed to analyze the data.

Main Results:

• The lithium RBC/plasma ratio was normally distributed in both remission and illness phases.
• No significant differences in the lithium ratio were observed between patients in remission and those in an active illness phase.
• The lithium ratio did not differ between diagnostic subgroups (cycloid, unipolar, bipolar) during prophylactic therapy.
• The lithium ratio correlated with RBC lithium levels but not with age, sex, illness type, weight, lithium dosage, treatment duration, or plasma lithium levels.
• RBC lithium levels were solely determined by plasma lithium levels.

Conclusions:

• The RBC/plasma lithium ratio does not appear to hold significant diagnostic value in affective disorders.
• Lithium distribution, as indicated by the RBC/plasma ratio, is not a distinguishing factor between different phases or subtypes of affective disorders in this cohort.
• Further research may be needed to explore other biomarkers for lithium therapy management.