ABSTRACT
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: ⢠Paracetamol is commonly used in deliberate self poisoning (DSP) and this requires blood sampling to refine risk assessment. If saliva concentrations agreed with plasma concentrations, then this could support the development of non-invasive testing. Our pilot work supports this hypothesis, but was largely confined to nontoxic concentrations. WHAT THIS STUDY ADDS: ⢠We found agreement between the indications for treatment of paracetamol DSP based on plasma and saliva paracetamol concentrations. Saliva may hold promise as a non-invasive method to risk stratify paracetamol poisoning. AIMS: Paracetamol is commonly used in deliberate self poisoning (DSP) and requires blood sampling to refine risk assessment. We aimed to test the agreement between plasma and saliva paracetamol concentrations in the toxic range in DSP. METHODS: Contemporaneous paired plasma and saliva paracetamol concentrations were measured. Saliva was collected using a Sarstedt Salivette® device and the concentration was measured using a colorimetric method. RESULTS: Fifty-six patients (44, 78% female) median age 26 years (IQR 20-41) were enrolled. The median reported paracetamol ingestion was 10 g (IQR 6-14). Specimens were collected at a median of 4 h (IQR 4-5.3) post ingestion. The median plasma and saliva paracetamol concentrations were 29 mg l(-1) (IQR 8-110) and 38 mg l(-1) (IQR 10-105) respectively [mean difference 8 mg l(-1) , 95% confidence interval (CI) 2, 14]. Lin's concordance correlation was 0.97 (95% CI 0.96, 0.98). There were 15 patients who were treated with N-acetylcysteine. Their median reported paracetamol ingestion was 14 g (IQR 10-23) and samples were collected at a median of 4 h post ingestion. The median plasma and saliva paracetamol concentrations were 167 mg l(-1) (IQR 110-200) and 170 mg l(-1) (IQR 103-210) respectively (mean difference 15 mg l(-1) , 95% CI -4, 35). Lin's concordance correlation was 0.94 (95% CI 0.88, 0.99). No patient needing treatment would have been missed using saliva concentrations only. CONCLUSIONS: The agreement between the indications for treatment of paracetamol DSP based on plasma and saliva paracetamol concentrations extends into the toxic range, but with slightly lower agreement. Saliva may hold promise as a non-invasive method to risk stratify paracetamol poisoning.
