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Do routine paracetamol levels need to be taken in all patients presenting with overdose ?

Three Part Question

In [alert cooperative adults who present following overdose] do [paracetamol levels] detect [unsuspected paracetamol overdoses requiring treatment]?

Clinical Scenario

A 22 year old woman attends the accident and emergency department immediately following a deliberate injestion of 8 ibuprofen tablets. You have no reason to doubt her story of impulsive overdose taken with suicidal intent. You wonder whether her management should include 4 hour paracetamol levels.

Search Strategy

Medline 1950 to April Week 3 2009 via OVID interphase:
({[ or exp overdose or deliberate self or exp self-injurious behaviour] AND [ or or exp acetaminophen] limit to "diagnosis(sensitivity)"} OR {[ or exp overdose or deliberate self or exp self-injurious behaviour] AND [ or or exp acetaminophen] limit to "clinical prediction guides (sensitivity)"}) limit to adult and human and English language.

Search Outcome

A total of 185 papers was found, three were relevant to the question and a further five were found from paper references.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Graham et al,
Consious overdose patients attending ED with a clear time of ingestion (not staggered)Prospective Observational study of 134 patients63/134 History +ve40/63 (63%) detected, 15/63 (23.8%) treatedSmall sample
71/134 History -ve0/71 detected
Harington et al,
All adult suspected overdose patients attending the ED attending between Feb and May 2000307 consecutive patients152/307 History +ve8 no levels, 99/152 (65%) detected, 4/152 (2.6%) needed antidote6/13 GCS <15, 10/13 significant alcohol injestion other 3 frequent ovedose or multiple drugs in overdose
155/307 History -ve13 no levels, 13/155 (8.4%) detected, 0/155 (0%) needed antidote
Dargan et al,
All adult patients attending the ED over a 12 month period who had paracetamol levels measuredRetrospective audit of 411 patients (115 after collapse and 296 after OD)122/411 history +ve non staggered <24 hrs94/122 (77%) detected, 16/122 (13%) treatedSmall Numbers
136/411 history -ve0/136 (0%) detected
115/411 Collapse low GCS4/115 (3.5%) detected, 4/115 (3.5%) treated
Sporer et al,
All adult patients with altered mental state or overdose who had levels taken.Retrospective chart audit of all patients with blood levels over 20 months 1992-3. 1820 patients177/1820 history +ve120/177 (68%) detected2 patients had taken "everything" 3 with low GCS and suspected overdose
1643/1820 history -ve55/1643 (3.3%) detected, 5/1643 (0.3%) levels >20mcg/ml(>50mcg/ml), 0/1643 (0%) treated
Ashbourne et al,
Adults presenting with suspected or confirmed intentional overdose486 prospectively identified patients February to July 1986 (101 other eligible patients missed)114/486 history +ve43/114 (38%) detected1 treated patient didn't speak English and the paracetamol history had not been obtained initiallly. No clear reason for other 6 but treatment not required. Small study
372/486 history -ve7/372 (1.9%) detected, 1/372 (0.27%) required treatment
Lucanie et al,
All non-paracetamol overdoses reported to a regional poison control centre over 6 months.Retrospective study of 320/471 patients (151 missing levels)History -ve23/320 (7.2%) detected >10mcg/ml, 12/320 (3.8) treatedNo information on the patients treated.
Chan et al,
Hong Kong
Chinese patients presenting with overdose to the general medical wards between January 1992 and June 1993.Retrospective study of 294 overdose patients86/294 History +ve8/86 (9.3%) treatedSmall study
208/294 History -ve4/208 (1.9%) detected, 0/208 (0%) treated
Skelton et al,
200 Patients selected at random from ED, with a provisional diagnosis of deliberate self-harmProspective cohortNumber of patients testing positive for paracetamol48/200 (24%)No breakdown of results giving overall number of history +ve and –ve patients

No breakdown of results for number of history –ve patients with paracetamol levels >100 mg/l
Number of patients testing positive for paracetamol with -ve history7/48 (14.6%)
Overall % with >100 mg/l plasma concentration13/48 (27%)


Most papers in this BET show no patients with an uncomplicated negative history who required antidote. In the paper from the regional poison centre in New York it was difficult to extract individual details of cases. I suspect that their patient population does not represent the alert cooperative patient in the three-part question.

Editor Comment

ED, emergency department; GCS, Glasgow coma scale.

Clinical Bottom Line

Paracetamol levels in history-negative patients have a low yield. However, the test is cheap and readily available and treating significant overdoses is lifesaving.


  1. Graham, CA; Irons, AJ; Munro PT. Paracetamol and salicylate testing: routinely required for all overdose patients? European Journal of Emergency Medicine Feb 2006; 13(1):26-28.
  2. Harington, K; Hartley, J; Clancy, M. Measuring plasma paracetamol concentrations in all patients with drug overdoses; development of a clinical decision rule and clinicians willingness to use it. Emerg Med J Sept 2002;19:408-411.
  3. Dargan PI; Ladhani S; Jones AL. Measuring plasma paracetamol concentrations in all patients with drug overdose or altered consiousness: does it change outcome? Emerg Med J 2001;18:178-182.
  4. Sporer KA; Khayam-Bashi H. Acetaminophen and Salicylate serum levels in patients with suicidal ingestion or altered mental status. American Journal of Emergency Medicine Sept 1996; 14(5), 443-446.
  5. Ashbourne J; Olsen K; Khayam-Bashi H. Value of rapid screening for acetaminophen in all patients with intentional drug overdose. Annals of emergency medicine October 1989;18, 1035-8.
  6. Lucanie R; Chianf WK; Reilly R. Utility of acetaminophen screening in unsuspected suicidal ingestions. Veterinary and Human Toxicology 2002 June;44(3):171-3.
  7. Chan TY; Chan AY; Ho CS; Critchley JA. The clinical value of screening for paracetamol in patients with acute poisoning. Human Experimental Toxicology 1995 Feb; 14(2):187-9.
  8. Skelton H, Dann LM, Ong RT, et al. Drug screening of patients who deliberately harm themselves admitted to the emergency department. Therapeut Drug Monit 1998;20:98–103.