Validation of a nomogram used to predict lithium concentration in overdose

Area of Science:

• Toxicology
• Nephrology
• Pharmacology

Background:

• Severe lithium toxicity often necessitates Extracorporeal Treatment (ECTR).
• The Extracorporeal Treatments in Poisoning (EXTRIP) group provides guidelines for ECTR, including a 36-hour threshold for lithium concentration.
• A lithium nomogram was developed to predict lithium concentration decline in chronic poisoning.

Purpose of the Study:

• To externally validate the Buckley lithium nomogram.
• To assess the nomogram's accuracy in predicting lithium concentrations in chronic and acute-on-chronic lithium poisoning cases.

Main Methods:

• Retrospective analysis of 51 suspected cases of chronic or acute-on-chronic lithium poisoning.
• Analysis focused on 37 cases after excluding those requiring hemodialysis.
• Validation of the lithium nomogram's predictive performance.

Main Results:

• The nomogram demonstrated 71.4% sensitivity and 53.3% specificity in chronic accumulation cases.
• Positive predictive value was 58.8%, negative predictive value was 66.7%, and accuracy was 62.1%.
• The nomogram correctly identified a majority of patients requiring ECTR based on the 36-hour criterion.

Conclusions:

• The lithium nomogram has moderate sensitivity for identifying patients with chronic lithium accumulation.
• It aids in predicting which patients may exceed 1.0 mmol/L at 36 hours without ECTR.
• Further validation in larger cohorts is warranted.