Tricyclic Antidepressant Toxicity: Sensitivity and Specificity

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 sensitivity and specificity of findings for Tricyclic Antidepressant Toxicity are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Specific Findings
Finding	Result	Sensitivity	Specificity
[ + ] ECG R/S Ratio	+ 0 -	47%	97%
R/S ratio > 0.7 for ventricular arrhythmias Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027

Poorly Diagnostic Findings
Finding	Result	Sensitivity	Specificity
[ + ] Terminal QRS Axis	+ 0 -	33%	71%
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
[ + ] TCA Level	+ 0 -	78%	57%
for ventricular arrhythmia. For seizures, Sens 75% Spec 72% Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027
[ + ] Prolonged QTc	+ 0 -	78%	56%
QTc > 430ms. for ventricular arrhythmias Study: J Toxicol Clin Toxicol. 2004;42(6):877-88. PMID: 15533027
[ + ] Wide QRS	+ 0 -	79%	46%
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