Urine Adulteration in Drug Testing

Abstract Drug abusers may attempt to conceal their drug intake by interfering with the clinical specimens sent to the laboratory for toxicology screening. This report describes a 27-year-old drug abuser who repeatedly submitted urine samples with abnormally low creatinine concentrations in order to invalidate drug screening. Adulteration by addition of ammonia-containing cleanser was suspected and eventually admitted by the patient. This case illustrates common features of urine adulteration. Various strategies for the prevention and detection of adulteration are also discussed. Key words: High pressure liquid chromatography, Immunoassay, Substance abuse testing, Substance-related disorders, Urine chemistry Introduction Drug abuse is a secretive drug-seeking behaviour and relapse from rehabilitation is common. Successful abstinence determines employment opportunities, financial security, and other lifestyle factors, whereas failure may invite familial or social pressure. Denial is therefore a common feature and psychiatrists are not always provided with accurate information about drug use. When clinical symptoms or signs of drug abuse are absent during rehabilitation, biochemical testing of urine or serum is an important aspect of the follow-up procedure. To avoid unwanted consequences, patients may try to interfere with the normal analytical procedure by manipulating the specimen submitted to the laboratory. Case Report A 27-year-old man, who had no relevant family history, presented at a psychiatric clinic with substance-induced psychotic disorder with hallucination, which was mainly auditory. He consumed half a bottle of cough mixture prepared by a local pharmacy every day, and his consumption was limited by financial constraint. He was prescribed benzhexol, zuclopenthixol, risperidone, and propranolol. Urine drug testing was arranged and the clinician advised the patient that his disability allowance would be discontinued if the abused drug was found in his urine. Clear, straw-yellow urine was submitted by the patient on repeated occasions during the course of treatment. Urine drug screening by high-pressure liquid chromatography coupled with ultraviolet spectral scanning (REMEDi HS analyser; Bio-Rad Laboratories, Hercules, USA), was negative. However, a very low creatinine concentration of 0.05 mmol/L was found (normal range, 7.1 to 17.7 mmol/ day). (1) Urine adulteration was suspected and additional tests were therefore performed with the following results: magnesium 0.09 mmol/L (normal excretion, 3.0-5.0 mmol/ day), osmolality 517 mmol/kg [H.sub.2]O (normal range, 250-900 mmol/kg [H.sub.2]O), urine pH of 9 (normal range, 4.5-8), urea concentration 134.3 mmol/L (normal range, 430-710 mmol/day). The patient was required to provide another urine specimen when supervised by a male nurse. Analysis revealed a similar biochemical profile (creatinine, 0.16 mmol/L; pH 10). It was suspected that an alkaline adulterant had been added to the specimen. On further inquiry, the nurse revealed that the urine collection procedure was not directly supervised. Another sample collection was scheduled 2 months later, using a special urine collection bottle with a temperature chart and seal. The creatinine concentration was within the normal range and ephedrine/pseudoephedrine, codeine, risperidone metabolites, and promethazine were detected in the urine. The patient admitted that he was still abusing cough medicine and upon repeated questioning eventually revealed that he had added soap solution to his urine specimens. His request for a disability allowance was refused and he subsequently defaulted follow-up. He then attended another hospital and submitted a similarly diluted urine specimen (creatinine, 1.7 mmol/L; pH 9). Amphetamine was detectable (473 ng/mL) but at a level below the conventional cut-off concentration (1000 ng/mL). Discussion Urine adulteration is the manipulation of urine specimens intended for drug testing to provide false-negative, or less commonly, false-positive results. …