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Drug and chemical metabolites in clinical toxicology investigations: the importance of ethylene glycol, methanol and cannabinoid metabolite analyses.

Metabolic pathways in humans have been elucidated for most therapeutic drugs, drugs of abuse, and various chemical/solvents. In most drug overdose cases and chemical exposures, laboratory analysis is directed toward identification and quantitation of the unchanged drug or chemical in a biologic fluid such as serum or whole blood. Specifically, most clinical laboratories routinely screen and quantitate unchanged methanol and/or ethylene glycol in suspected poisonings without toxic metabolite analysis. Martin-Amat established in 1978 that methanol associated toxicity to the optic nerve in human poisonings was due to the toxic metabolite formic acid found in methanol poisonings and not due to the direct action by unchanged methanol. Jacobsen reported in 1981 that ethylene glycol central nervous system and renal toxicity were primarily due to one acidic metabolite (glycolic acid) and not due to unchanged ethylene glycol. The first objective of this review is to describe clinical experience with formic acid and glycolic acid analysis in methanol and ethylene glycol human poisonings. Drug metabolite analysis also provides useful information in the assessment and monitoring of drug use in psychiatry and substance abusing populations. Drug analysis in substance abuse monitoring is focused on urine analysis of one or more major metabolites, and less frequently on the unchanged drug(s). Serial monitoring of the major urinary cannabinoid metabolite (delta(9)-THC-COOH) to creatinine ratios in paired urine specimens (collected at least 24 h apart) could differentiate new marijuana or hashish use from residual cannabinoid metabolite excretion in urine after drug use according to Huestis. The second objective is to demonstrate that creatinine corrected urine specimens positive for cannabinoids may help differentiate new marijuana use from the excretion of residual delta(9) -THC-COOH in chronic users of marijuana or hashish. Analysis of toxic chemical metabolites are helpful in the assessment and treatment of chemical poisoning whereas serial monitoring of urinary cannabinoid metabolites are predictive of illicit drug use in the substance abusing population.

Cannabinoids↗

The uristatin dipstick is useful in distinguishing upper respiratory from urinary tract infections.

BACKGROUND: We determined the diagnostic value of the trypsin inhibitor, uristatin, that is commonly found in urine and plasma in patients with infections or inflammations of any kind. METHODS: We collected urine specimens from patients with infections of the urinary or upper respiratory tract and from healthy controls. We also collected blood from patients with a likely upper respiratory tract infection and healthy controls. A bacterial count of >10(5) organisms/ml in urine was considered to represent infection rather than contamination. RESULTS: The uristatin dipstick test in urine showed acceptable negative predictive values (NPV of up to 93%) for patients without infection or inflammation. Here, the dipsticks could eliminate some urine cultures. For those with infection or inflammation, the positive predictive values (PPV) of the dipsticks were lower (up to 57%). Including the leukocyte esterase and nitrite values increased the PPV of the dipsticks for those with disease. CONCLUSIONS: The uristatin strip was more accurate than the leukocyte and nitrite dipsticks for predicting upper respiratory infections (URI) and C-reactive protein for those with infection or inflammation. The uristatin dipstick was able to detect both the bikunin and uristatin inhibitors.

Adolescent↗

Results of dipstick tests, visual inspection, microscopic examination of urine sediment, and microbiological cultures of urine compared for simplifying urinalysis.

Using microscopic sediment examination, reagent dipsticks, visual appearance, and microbiological culture, we studied 196 urine specimens collected under sterile conditions. We conclude that the sensitivities and specificities noted in the comparison of dipstick urinalysis with urine microscopy justify eliminating many microscopic examinations if a procedural flowchart is used. All 33 (16.8%) of the uncontaminated urine specimens showing substantial potential pathogen content on culture had either a turbid appearance or positive results for one or more dipstick tests. A positive dipstick test result for nitrite most consistently indicated that the urine should be cultured.

Bacteriuria↗

The use of creatinine output as a check on the completeness of 24-hour urine collections.

The use of creatinine as a check on the completeness of 24-h urine collections is based on the assumption that excretion per kg body mass is constant. In a study of eight volunteers maintained on uniform diets the within-subject coefficient of variation (CV) in daily 24-h creatinine excretion was only 4 per cent under conditions in which the completeness of collections was assured. Cooked meat contains creatine and creatinine and an addition of 260 g/d cooked meat to the diet of four volunteers on a metabolic diet increased urine creatinine excretion by 23 per cent. A further source of variation in urine creatinine is the completeness of the collection itself. A new marker, PABA, was used to check the completeness of 24-h urine collections in eight subjects studied for 28 d whilst eating their normal diets. The within-subject CV of 9 per cent for 24-h creatinine excretion was not significantly different from that of 13 per cent for overall urinary N. In 122 complete 24-h urine specimens collected from a randomly selected population, the CV in creatinine excretion was 18 per cent. Twenty-one urine samples were incomplete, of which only 3 would have been detected on the basis of low creatinine by conventional standards. Of 39 hospital patients asked to collect 24-h urine samples, 12 provided incomplete samples, of which only 4 had low creatinine excretion. It is concluded that PABA is a more sensitive and reliable verification of the completeness of 24-h urine collections than creatinine.

4-Aminobenzoic Acid↗

Forensic drug testing for opiates. V. Urine testing for heroin, morphine, and codeine with commercial opiate immunoassays.

Urine specimens collected after heroin, morphine, and codeine administration were tested by four commercial opiate immunoassays (TDx, CAC, ABUS, and EMIT) and GC/MS. Quantitative immunoassay results (morphine equivalents) were compared with results by GC/MS for total morphine, free morphine, or total codeine. Mean detection times for the broadly cross-reacting immunoassays (TDx, ABUS, and EMIT, 300 ng/mL cutoff) ranged from 15-44 hours following heroin and morphine administration and 33-54 hours following codeine administration. Detection times obtained with CAC (25 ng/mL cutoff) tended to be somewhat shorter as a result of the high selectivity of the antibody for free morphine. High correlations over a wide concentration range were obtained for TDx, CAC, and ABUS versus GC/MS, with specimens collected after heroin and morphine administration. EMIT showed a high correlation over a narrow concentration range (0-1000 ng/mL) with heroin and morphine specimens, but responses plateaued at higher concentrations. There was substantial variability in immunoassay responses with specimens collected after codeine administration. Generally, this study demonstrated that immunoassay responses for opiate urine testing can be used as a semi-quantitative guide for GC/MS confirmation; however, the presence of codeine increased variability and diminished the accuracy of the immunoassay response.

Codeine↗

Patterns of concordance between hair assays and urinalysis for cocaine: longitudinal analysis of probationers in Pinellas County, Florida.

This chapter reports on a field trial involving the application of hair assays to a probation population. The objectives were to evaluate the general reactions of probation officers and probationers to the collection of hair samples, to compare the outcomes of the hair samples with the outcomes of urinalyses (which the probationers undergo routinely), to note and react to differences in the prevalence as indicated by the two assay types, and to assess the general monitoring potential for hair assays in a correctional setting. In general, hair assays showed an increased capability of detecting cocaine exposure when compared to urinalysis. The detection of cannabis was, however, problematic for hair. The hair assays, using urine as a comparator, appeared to result in several apparent false negatives for cannabinoids. There were no false negatives for cocaine, and an approximately fourfold increase in the detection rate when compared to urine. The collection of hair samples was not difficult and the cooperation of the probationers was quite good. Probation officers appear to prefer the use of hair specimens to urine specimen collection, and appeared enthusiastic about the potential use of hair analysis in their routine monitoring of clients.

Biological Assay↗

Urine culture from bag specimens in young children: are the risks too high?

OBJECTIVE: To compare the risks of contaminated culture results and consequent adverse clinical outcomes in urine specimens obtained by "clean-voided" bag method versus catheterization. STUDY DESIGN: Hospital-based cohort study of all children </=24 months with outpatient urine cultures (n = 7584) obtained from January 1993 to December 1995. Medical records were followed up for all children with contaminated culture results who had 1 or more additional cultures within 7 days of the original culture. Contamination rates of bag urine cultures from the emergency department and a pediatric test center were compared. RESULTS: Contamination rates were 62.8% and 9.1% (P <.001) in bag versus catheter specimens, respectively. Contamination rates of bag urine specimens collected in the emergency department and pediatric test center were 56.4% versus 69. 25%, respectively. Of the 3440 contaminated urines, 132 (1.7%) resulted in 1 or more adverse clinical outcomes. Adjusted odds ratios (and 95% CI) for these outcomes in bag versus catheter specimens were as follows: 4.9 (2.3 to 10.5) for unnecessary recall, infinite for delayed diagnosis and treatment, 4.8 (1.8 to 12.4) for unnecessary treatment, 15.6 (2.1 to 116.8) for unnecessary prolonged treatment, 4.1 (1.4 to 12.1) for unnecessary radiologic investigation, and 12.4 (1.6 to 95.5) for unnecessary hospital admission. CONCLUSIONS: The risks of the "noninvasive" bag urine culture appear to exceed its benefits.

Cell Culture Techniques↗

Urinary screening for alpha-OH triazolam by FPIA and EIA with confirmation by GC/MS.

Triazolam is a very short-acting triazolobenzodiazepine with sedative-hypnotic properties. Approximately 2% of an oral dose is excreted unchanged in the urine. The major urinary metabolite is alpha-hydroxytriazolam glucuronide (70% of the dose). The objective of this study was to characterize the reactivity of alpha-hydroxytriazolam in the urine benzodiazepine assay by fluorescence polarization immunoassay (FPIA; Abbott TDx) in comparison with enzyme immunoassay (EIA; Syva EMIT d.a.u. benzodiazepine assay). alpha-OH triazolam at 300 ng/mL gave a response equivalent to the 200-ng/mL nordiazepam Abbott calibrator. In the EMIT assay, alpha-OH triazolam gave a response equivalent to the 300-ng/mL calibrator (Syva) at 100-200 ng/mL. Both immunoassays gave positive results in 9 out of 9 urine specimens collected from individuals receiving triazolam. Confirmation was performed by analyzing for alpha-OH triazolam after enzymatic hydrolysis and formation of a TMS derivative for GC/MS. All urine specimens were positive for alpha-OH triazolam. In conclusion, both the FPIA and EIA immunoassay screening assays are acceptable for detecting the presence of alpha-OH triazolam in the urine of patients receiving therapeutic doses of triazolam.

Fluorescence Polarization↗

Simplified quantitation of urinary benzoylecgonine in cocaine addiction research and for related pharmacotherapeutic trials.

In clinical trials of potential pharmacotherapies for cocaine addiction, objective determination of subject relapse relies on qualitative urine analysis for benzoylecgonine, the major metabolite of cocaine. Unlike qualitative analysis, quantitative measurement allows differentiation between continued cocaine use and a single use, as well as identification of changes in the quantity of cocaine used at different times. The only quantitative technique that has been used is expensive and not generally feasible. This study was performed to modify an existing qualitative technique for use as a new simple and readily available quantitative method for identifying cocaine use among research subjects. Benzoylecgonine levels in 24-hour urine specimens collected from 11 cocaine-addicted subjects hospitalized in a research setting were measured semi-quantitatively by fluorescence polarization immunoassay. Accurate results required thorough mixing of urine specimens prior to analysis. At admission, eight subjects had urinary benzoylecgonine levels > or = 0.30 microgram/ml, the standard positive/negative cut-off used in qualitative analysis. The mean half-life of benzoylecgonine during initial elimination was 0.46 +/- 0.08 (SEM, n = 8) days. Benzoylecgonine (BE)/creatinine (C) levels remained > or = 0.30 microgramBE/mgC for 4.8 +/- 0.5 (n = 8) days and > or = 0.03 microgramBE/mgC for 10.5 +/- 1.5 (n = 8) days. Relapses in three subjects could be identified by quantitative analysis. This study indicates that quantitation of benzoylecgonine in daily urine specimens provides a sensitive, objective index to cocaine use.

Adolescent↗

Clastogenic activity in urine of workers occupationally exposed to pesticides.

Genotoxicity in the urine of orchardists occupationally exposed to pesticides was investigated. Urine samples were obtained during pre-spraying and spraying periods from 22 non-smoking orchardists who spray large amounts of pesticides during the fruit growing season. For comparison purposes, urine was collected from 11 non-smoking personnel at an agricultural research station located near the application site and from 21 non-smoking individuals (reference controls) in a non-agricultural area. Organic material was isolated from urine by preparative reversed-phase high-pressure liquid chromatography, and assayed for clastogenic activity using Chinese hamster ovary cells. Urine samples collected during the pre-spraying period showed no significant differences in clastogenic activity compared to that found for the reference control group. However, clastogenic activity of urine specimens collected during the spraying period was significantly elevated (p less than 0.001) for the highly-exposed orchardists, but not for the research station personnel. Clastogenicity of orchardists' urine was observed within 8 h of pesticide application.

Agriculture↗

Monitoring urinary excretion of cannabinoids by fluorescence-polarization immunoassay: a cannabinoid-to-creatinine ratio study.

Drug testing in substance abuse treatment programs is focused on urine analysis of parent drugs and major metabolites. Huestis reported that serial monitoring of the major urinary cannabinoid metabolite (delta9-THC-COOH)-to-creatinine ratios in paired urine specimens (collected at least 24 hours apart) could differentiate new marijuana or hashish use from residual cannabinoid metabolite excretion in urine after previous drug use. Subjects with a history of chronic marijuana use were screened for cannabinoids in urine over several months by an enzyme immunoassay (EMIT) with a cut-off value of 50 ng/mL. Presumptive positive specimens were confirmed by gas chromatography-mass spectrometry (GC-MS) for delta9-THC-COOH with a cut-off value of 15 ng/mL. The objective of this study was to determine whether a semiquantitative cannabinoids immunoassay (corrected for creatinine concentration) could differentiate new marijuana use from residual cannabinoid excretion in chronic users of marijuana or hashish compared with GC-MS. The criterion for new marijuana use was a cannabinoid-to-creatinine ratio > or =0.5 (dividing the immunoassay quantitative result to creatinine ratio of specimen 2 by the specimen 1 ratio, specimen 3 by the specimen 2 ratio, etc.). Urine specimens were analyzed by fluorescence-polarization immunoassay (FPIA) on an Abbott TDxFLx analyzer after analysis by GC-MS. In 90 urine specimens (group A) with delta9-THC-COOH values determined by GC-MS, the mean delta9-THC-COOH concentration was 44.4 ng/mL (range, 16-100), and the mean FPIA total cannabinoids value was 91.7 ng/mL (range, 21-204 ng/mL) with a correlation coefficient of 0.993 (group A). In 111 specimens (group B), the mean delta9-THC-COOH concentration was 361 ng/mL (range, 101-960 ng/mL). The mean FPIA value was 657 ng/mL (range, 211-1,270 ng/mL), and the correlation coefficient of the B series was 0.975. Percent cross-reactivity for delta9-THC-COOH standards prepared in drug-free urine by FPIA was 82% at 25 ng/mL, 45% at 50 ng/mL, and 50% at 100 ng/mL. Overall, there was 89% agreement (132 of 148 specimens) between FPIA and GC-MS. In 16 of 148 specimens, however, the FPIA and GC-MS paired urine data did not agree. The sensitivity of the FPIA assay was 95.3%, and the specificity was 44.4%. The authors conclude that FPIA cannabinoid analysis should be further evaluated as an alternative to GC-MS quantitation to help distinguish new marijuana use from residual marijuana metabolite excretion in clinical drug treatment programs.

Calibration↗

Urinary screening for midazolam and its major metabolites with the Abbott ADx and TDx analyzers and the EMIT d.a.u. benzodiazepine assay with confirmation by GC/MS.

Midazolam is a short-acting 1,4-imidazole benzodiazepine with sedative-hypnotic, anxiolytic, and amnestic properties. It is administered orally for sleeping disorders and intravenously for sedation during surgery. This drug has a short half-life (1.5-3.5 h), with less than 1% of a midazolam dose being excreted unchanged. The major urinary metabolite is alpha-hydroxy midazolam glucuronide. The objective of this study was to characterize the reactivity of midazolam and its two major metabolites in the EMIT d.a.u. benzodiazepine assay and in the Abbott TDx and ADx urine benzodiazepine assays. Midazolam and alpha-OH midazolam gave an equivalent response to the EMIT low calibrator at 200 ng/mL. On both Abbott analyzers, midazolam and alpha-OH midazolam gave an equivalent net polarization at 500 ng/mL to the Abbott low control. All three screening assays were positive in all of 21 random urine specimens collected from midazolam-treated patients. Confirmation testing was performed by analyzing for alpha-OH midazolam after enzymatic hydrolysis and formation of a TMS derivative for GC/MS. All urine specimens were confirmed positive for alpha-OH midazolam. In conclusion, all three immunoassay screening assays are acceptable for detecting the presence of midazolam metabolites in urine.

Autoanalysis↗

Use of mailed urine specimens in diagnosing urothelial carcinoma by cytology and DNA image analysis.

OBJECTIVE: To evaluate the usefulness of urine specimens collected via a mailer system and analyzed by cytology and DNA ploidy for the detection of urothelial carcinoma (UC). STUDY DESIGN: We retrospectively reviewed the diagnoses of 91 mailed urine specimens received from 72 patients, 67% of whom had a history of UC. The specimens were fixed in an equal volume of 50% ethanol solution before being mailed. The cytologic findings were interpreted in conjunction with DNA ploidy image analysis. We compared these initial diagnoses with those of follow-up examinations, including biopsies, cystoscopic findings and urinary cytology/DNA ploidy analyses. In addition, to examine the quality of the mailed samples, 3 cytopathologists performed a blinded assessment of cytologic slides of 20 mailed and 17 fresh urinary samples for bacterial overgrowth, urothelial degeneration, and presence of proteinaceous material and crystals. RESULTS: Follow-up was available for 68 of the 91 mailed specimens. The sensitivity for detecting UC using mailed urine specimens that were analyzed by both cytology and DNA ploidy was 61%, while specificity was 92%. The levels of bacterial overgrowth and urothelial degeneration in the mailed specimens were not significantly greater than in the fresh specimens (p>0.05). The levels of proteinaceous material and crystals were significantly higher in the mailed specimens (p<0.05). CONCLUSION: The results of combined cytology and DNA ploidy image analysis by using mailed urine samples were comparable to those of fresh urine specimens for the detection of UC reported in previous publications. The increase in crystals and proteinaceous material did not impede diagnostic interpretation. The mailing system is a reliable and convenient method of monitoring and triaging patients with UC or related symptoms.

Adult↗

Allopurinol kinetics in humans as a means to assess liver function: design of a loading test.

A six-compartment model of allopurinol and oxipurinol kinetics, after intravenous allopurinol injection in the human, is studied further to improve the blood and urine specimen collection schedule for clinical use. The effects of various error sources are also investigated by simple techniques like real data set truncation and adding normally distributed random errors to data obtained from simulation of allopurinol and oxipurinol plasma curves with preset parameters. All parameters estimation is performed with the NONLIN parameter estimation program. Main interest was focused on estimation of the fractional rate constant of transport from the central "extracellular" compartment to the metabolically active compartment. This parameter is regarded as a lumped measure of liver perfusion and liver cell membrane transport. The blood sampling schedule can be reduced to six specimens collected over 60 min, without affecting the accuracy and precision of estimated clinical parameters. The maximum allowable coefficient of variation for preanalytical errors and the analytical within-run and between-run errors are around 5, 4, and 5%, respectively. Analytical between-run bias up to 20% does not affect the estimate of the principal parameter, when both allopurinol and oxipurinol are biased in the same direction. Collection and analysis of urine samples was shown to be unnecessary.

Allopurinol↗

The microbiology of bacteriuria in men: a 5-year study at a Veterans' Affairs hospital.

Bacteriuria and urinary tract infection occur relatively frequently in older men, but data regarding the causative microorganisms are limited. We retrospectively identified all positive cultures of urine specimens (n = 4943) obtained over a 5-year period at our institution. We determined the frequency of causative microorganisms and grouped these by Gram type, setting of patient care, and method of urine specimen collection. We also assessed the performance characteristics of the Gram-stained smear of uncentrifuged urine. Among our patients, Gram-positive cocci (GPC) were isolated as often as Gram-negative rods (GNR). Escherichia coli was the single or predominant isolate in only 14% of cases, and Enterococcus was the single most commonly identified genus (22.5%). The Gram stain was accurate in predicting the culture results (positive likelihood ratio, 7.0 for GPC and 8.1 for GNR). We conclude that the microorganisms causing bacteriuria in older male veterans are substantially different from those found in women, and the Gram-stained smear provides useful information on the causative organisms.

Aged↗