Comparison of Oral Fluid and Urine for Detection of Cocaine Abuse Using Liquid Chromatography with Tandem Mass Spectrometry.

Background: Requests for urine (UR) and oral fluid (OF) drug testing at our institutions are increasing. However, few studies have assessed the accuracy of each matrix using paired specimens and LC-MS/MS. We compared OF and UR for detection of cocaine (COC) abuse in addiction medicine-psychiatry (AMP) clinics.
Methods: We measured COC and benzoylecgonine (BZE) in OF (limit of detection (LOD) 2.0 µg/L) and BZE in UR (LOD 5 µg/L) by LC-MS/MS in 258 paired samples, and compared the two matrices when higher UR cutoffs of 25, 50, and 150 µg/L were employed.
Results: UR detected more COC abuse than OF at the LOD (5 µg/L). BZE was detected in 63 UR specimens and COC and/or BZE in 40 OF specimens (29 OF+UR+, 11 OF+UR-, 34 OF-UR+). UR creatinine was lower in OF+UR- specimens. COC and BZE were detected in 88% (35/40) and 75% (30/40) of OF specimens, respectively. OF was equivalent to UR at detecting COC abuse using a 25 µg/L cutoff, and detected more COC abuse than UR using 50 and 150 µg/L cutoffs. The ratio of OF COC/BZE increased with decreasing UR BZE concentrations.
Conclusions: We demonstrate that OF detects more COC abuse in an AMP setting when UR BZE cutoffs ≥ 50 µg/L are utilized, and that UR creatinine concentrations are significantly lower in specimens positive for COC and/or BZE in OF and negative for BZE in UR. The presence of only COC in OF and low concentrations of UR BZE likely indicates remote use of COC.
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