Paracetamol-associated interference in an HPLC-ECD assay for urinary free metadrenalines and catecholamines.
BACKGROUND
Some high-performance liquid chromatography techniques with electrochemical detection for urinary catecholamines and their metabolites can be subject to interference from drugs and their metabolites. Prime amongst these interferences are those due to paracetamol ingestion.


METHODS
The prevalence of paracetamol contamination was determined by measuring the drug in all patient specimens submitted for catecholamine analysis over a 2-month period. These findings were then related to the proportion of unreportable results at each range of specimen paracetamol concentration. The apparent results from a small representative sample of the paracetamol-positive specimens are illustrated.


RESULTS
Approximately one-third of urine specimens were found to contain paracetamol. Low-level contamination can produce apparent patterns of results which may easily be confused with those found in predominantly adrenaline-, or metadrenaline-secreting phaeochromocytomas.


CONCLUSIONS
Despite the fact that significantly less than 5% of an oral dose of paracetamol is excreted as the free drug, its analysis provides a good surrogate marker for the likelihood of spurious results. It is useful to know prior to urinary free metadrenaline or catecholamine analysis which urine specimens are likely to contain potentially interfering paracetamol metabolites.
Biochemistry Department, Crosshouse Hospital, Kilmarnock KA2 0BE, UK. fraser.davidson@aaaht.scot.nhs.uk
Fraser D
FD
Davidson
D000082:Acetaminophen / Q000652:urine*; D002395:Catecholamines / Q000652:urine*; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry; D004837:Epinephrine / Q000652:urine; D006801:Humans; D008297:Male; D008676:Metanephrine / Q000652:urine; D008875:Middle Aged; D009638:Norepinephrine / Q000652:urine; D009647:Normetanephrine / Q000652:urine
D002395:Catecholamines; D009647:Normetanephrine; D000082:Acetaminophen; D008676:Metanephrine; D009638:Norepinephrine; D004837:Epinephrine