Postmortem urine immunoassay showing false-positive phencyclidine reactivity in a case of fatal tramadol overdose.
This is a report of postmortem false-positive reactivity using an enzyme-multiplied urine phencyclidine (PCP) immunoassay (EMIT II+) due to a single-agent fatal tramadol overdose. An autopsy of a 42-year-old male who died alone at home revealed no identifiable lethal anatomic abnormalities, thus leading to toxicologic analysis. Femoral blood was obtained for drug testing by high-performance liquid chromatography (HPLC) and showed a tramadol level of 14.0 mg/L, 2 orders of magnitude greater than the therapeutic range (0.1 to 0.3 mg/L). Urine was also obtained and EMIT II+ immunoassay revealed positivity for PCP at 88 mAU/min. However, confirmatory testing by HPLC failed to identify PCP in either the urine or serum. To verify the suspicion that this was a false-positive PCP result, stock solutions of tramadol and its major metabolite (O-desmethyltramadol) at concentrations of 100 mg/L in 10% methanol/H2O were compared with a blank solution (10% methanol/H2O) for EMIT II+ PCP reactivity and demonstrated reactivities of 44 mAU/min and 27 mAU/min, respectively. While these individual results were below the cutoff reactivity for a positive EMIT II+ PCP result (ca. 85 mAU/min), they were much more reactive than the blank calibrator (set at 0 mAU/min). Therefore, we conclude that the immunoreactivity of tramadol and its metabolites in aggregate is responsible for the PCP immunoassay interference and false-positive result.
Hull
Mindy J
MJ
Clinical Chemistry and Toxicology, Department of Pathology and Laboratory Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.
Griggs
David
D
Knoepp
Stewart M
SM
Smogorzewska
Agata
A
Nixon
Andrea
A
Flood
James G
JG
D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects* / Q000097:blood / Q000652:urine; D001344:Autopsy; D062787:Drug Overdose / Q000473:pathology; D005189:False Positive Reactions; D005554:Forensic Medicine; D006801:Humans; D007118:Immunoassay; D008297:Male; D010622:Phencyclidine / Q000737:chemistry*; D011180:Postmortem Changes; D015813:Substance Abuse Detection; D014147:Tramadol / Q000009:adverse effects* / Q000097:blood / Q000652:urine; D016482:Urinalysis
D000701:Analgesics, Opioid; D014147:Tramadol; D010622:Phencyclidine