Correlation of paired plasma and saliva paracetamol levels following deliberate self-poisoning with paracetamol (The Salivary Paracetamol In Toxicology (SPIT) study)

Aim. To determine the correlation between plasma and saliva paracetamol levels following paracetamol deliberate self-poisoning. Methods. Paired plasma and saliva paracetamol levels were measured. Saliva analysis was performed contemporaneously using a colorimetric method. Results. 21 patients (76% female) mean age 28.3 +/- 12.9 years (range 15-55) were enrolled. Mean reported paracetamol ingestion was 10.3 g (range 2-20 g). Specimens were collected at a mean of 6.2 +/- 3.1 hours post-ingestion (range 4-13 hours) and mean plasma and saliva paracetamol levels were 48 mg/L and 62 mg/L respectively (mean difference 14; 95% CI 5-22; p < 0.004); Pearson's correlation r = 0.95 (p < 0.0001). No patient needing treatment would have been missed using saliva levels only. Conclusion. There is concordance between the indications for treatment of paracetamol deliberate self-poisoning based on plasma and saliva paracetamol levels. Saliva paracetamol levels are typically higher than plasma levels. Further studies involving larger numbers of patients, comparing plasma and saliva paracetamol levels in patients with potentially toxic plasma paracetamol concentrations, would be useful in determining the potential clinical value of this method.