Spit It Out

Paracetamol overdose is the leading cause of acute liver failure, accounting for over 50 percent of all cases globally. Early and accurate detection is essential for administering the antidote, N-acetylcysteine (NAC), within its most effective time window (8 hours). Current diagnostic methods rely on invasive blood tests with turnaround times often exceeding one hour, which can cause delays to treatment, limiting NAC’s effectiveness.

With this in mind, researchers from the University of Liverpool and Alder Hey Children’s NHS Foundation Trust, UK, developed a method using paper arrow-mass spectrometry (PA-MS) to quantitate paracetamol concentrations in patient saliva in just 10 minutes.

In a prospective observational study involving 17 healthy adults, the team measured paracetamol concentrations in plasma, resting saliva (RS), and stimulated saliva (SS) at intervals up to four hours post-ingestion of 1g paracetamol. They were able to use a sample volume of just 2 µL to produce accurate results, applying saliva to arrow-shaped Whatman 1 chromatography paper, which was dried and dipped into a solvent mixture of ammonium formate in 9:1 ethyl acetate: formic acid (v/v). Once separated, the analyte was then isolated for direct analysis via mass spectrometry, in a process taking no longer than 10 minutes.

The results showed strong agreement between stimulated saliva PA-MS and the reference blood test. Stimulated saliva was shown to be more effective than resting saliva for paracetamol detection, with resting saliva exhibiting lower concordance and higher variability.

Encompassing sample collection, extraction, separation, and ionization onto a single paper strip, and with no prior sample preparation required, the team believe the PA-MS workflow has potential for use to measure other analytes in biofluids such as blood, sweat and urine.  According to the authors, this is also the first study to report systematic differences between paracetamol concentrations in resting and stimulated saliva, which suggests that further studies should be conducted to evaluate other collection methods for salivary analysis.

Looking forward, they intend to develop a fully automated point-of-care version of PA-MS.