Can we check serum lithium levels less often without compromising patient safety?

Area of Science:

• Pharmacology
• Psychiatry
• Clinical Chemistry

Background:

• Lithium is a primary long-term treatment for bipolar disorder relapse prevention.
• Maintaining therapeutic serum lithium levels is crucial for efficacy and safety.

Purpose of the Study:

• To identify factors influencing stable serum lithium levels.
• To evaluate the possibility of extending monitoring intervals for lithium therapy.

Main Methods:

• Analysis of 46,555 lithium test requests from 3371 individuals over seven years.
• Categorization of lithium results (<0.4, 0.40-0.79, 0.80-0.99, ≥1.0 mmol/L).
• Assessment of result stability and category changes based on age, therapy duration, and testing history.

Main Results:

• 84.5% of tests remained within the 0.40-0.99 mmol/L therapeutic range.
• Three-month testing yielded 90% of results within range, versus 85% at six-month intervals.
• Lithium levels of 0.80-0.99 mmol/L showed a higher risk (10%) of exceeding the upper limit compared to 0.4-0.79 mmol/L (2%).

Conclusions:

• Patients with 12 months of lithium levels in the 0.40-0.79 mmol/L range can safely transition to six-month testing intervals.
• Individuals with lithium levels of 0.80-0.99 mmol/L should maintain three-month monitoring.
• Proposed changes could decrease lithium test frequency by 15%, reducing annual costs by approximately $0.4 million.