Tricyclic Antidepressant Toxicity: Likelihood Ratios

Introduction: Overdose of tricyclic antidepressants can lead to a number of serious side effects, including cardiac arrhythmias (ventricular and blocks), seizures, and anticholinergic delirium.

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The likelihood ratios of findings for Tricyclic Antidepressant Toxicity are listed below. See the left navigation bar to change the display.

Good Positive and Negative Likelihood Ratios

ECG R/S Ratio

15.7

0.5

R/S ratio > 0.7 for ventricular arrhythmias

Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027

Good Negative Likelihood Ratio

Finding	+LR	-LR	Comments, Study
TCA Level	1.8	0.4	for ventricular arrhythmia. For seizures, Sens 75% Spec 72% Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027
Prolonged QTc	1.8	0.4	QTc > 430ms. for ventricular arrhythmias Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027
Wide QRS	1.5	0.5	QRS > 0.1 s for ventricular arrhythmias. For seizures, Sens 69% and Spec 69%. Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027

Poorly Diagnostic Findings

Terminal QRS Axis

1.1

0.9

Right axis deviation of 120-270 degrees in the terminal 40ms frontal plane QRS vector

for ventricular arrhythmias

Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027