Situation: apparent drug overdose with negative toxicology test
Differential diagnosis:
(1) wrong diagnosis
(2) wrong specimen
(3) wrong test
The diagnosis of a drug overdose may be incorrect. It is important to review the medical record for evidence of an alternative diagnosis (metabolic disorder, toxic exposure, infection).
The specimen test may not be the optimum one for drug detection.
(1) Drugs may not be detectable in blood or urine 1-3 days after drug intake. A sample collected at autopsy may be negative if the patient survives several days.
(2) Testing of admission blood and urine samples is more likely to reflect a recent drug exposure.
(3) Hair testing should be considered if the patient survives more than 10 days after the exposure.
(4) Drugs given to the patient during the hospitalization need to be recognized.
Most common drug screening tests only detect common drugs of abuse.
(1) More complex testing is required to detect synthetic or designer drugs.
(2) Scene investigation, review of personal effects and interviews of family and friends may help to narrow the search.
