Simon TB Chan, CK Chan, ML Tse; Hong Kong Med J 2015;21:Epub 31 Jul 2015

Objectives: To evaluate the failure rate of the 150-treatment line for paracetamol overdose in Hong Kong, and the impact if the treatment threshold was lowered.
Design: Case series.
Setting: Public hospitals, Hong Kong.
Patients: All patients with acute paracetamol overdose reported to the Hong Kong Poison Information Centre from 1 January 2011 to 31 December 2013 were studied and analysed for the timed serum paracetamol concentration and their relationship to different treatment lines. Presence of significant liver injury following paracetamol overdose was documented. The potential financial burden of different treatment lines implemented locally was estimated.
Results: Of 893 patients, there were 187 (20.9%) with serum paracetamol concentration above the 150-treatment line; 112 (12.5%) had serum paracetamol concentration between the 100- and 150-treatment lines, and 594 (66.5%) had serum paracetamol level below the 100-treatment line. Of the 25 (2.8%) patients who developed significant liver injury, two were between the 100- and 150-treatment lines, and the other two were below the 100-treatment line. The failure rate of the 150-treatment line was 0.45%. Lowering the treatment threshold to the 100-treatment line might lower the failure rate of the treatment nomogram to 0.22% but approximately 37 more patients per year would need to be treated. It would incur an additional annual cost of HK$189 131, and an additional 1.83 anaphylactoid reactions per year. The number needed-to-treat to potentially reduce one significant liver injury is 112.
Conclusions: Lowering the treatment threshold of paracetamol overdose may reduce the treatment-line failure rate. Nonetheless such a decision must be balanced against the excess in treatment complications and health care resources.