Retrospective evaluation and prediction of clearance and toxicity of high dose methotrexate in childhood acute lymphoblastic leukemia patients

To find the predictors of High Dose Methotrexate toxicities in childhood Acute Lymphoblastic Leukemia Patients. This study included 198 Childhood Acute Lymphoblastic Leukemia patients (303 infusions) who were treated with High Dose Methotrexate. Methotrexate levels at different time point were measured by modified enzyme multiplied immunoassay technique assay. The correlation between Methotrexate levels and toxicity was evaluated by Receiver Operating Characteristic curve. When the Methotrexate level at 42 h was lower than 0.76 µmol/L, the sensitivity for predicting thorough clearance at 66 h was 90.78%. When the Methotrexate level at 42 h was higher than1.5 µmol/L, the sensitivity for predicting delayed clearance was 82.17%. When the Methotrexate level at 66 h was higher than 0.5 µmol/L, the sensitivity for predicting Methotrexate toxicity was 89.09%. When the Methotrexate level at 66 h was lower than 0.1 µmol/L, the sensitivity for predicting Methotrexate nontoxicity was 92.73%. The Methotrexate level at 42 h could be predictor for delayed clearance. The Methotrexate level at 66 h could be predictor for toxicity.

Development of application protocols of the Emit® II Plus 6-Acetylmorphine Assay on the ADVIA® 1800 and 2400 Chemistry Systems.

New application protocols for the Emit(®) II Plus 6-Acetylmorphine Assay for human urine screening have been developed on the ADVIA(®) 1800 and 2400 Chemistry Systems. Precision was evaluated at the cutoff and ±25% controls. Recovery and linearity were studied by spiking 6-acetylmorphine (6-AM) into human urine pools. Method comparison was evaluated using urine specimens and the results were compared to those obtained from the predicate Analyzer (V-Twin(®)). Cross-reactivity with structurally related drugs was assessed at high cross-reactant concentrations. Potential interferences were assessed in the presence of 7.5 and 12.5 ng/mL of 6-AM. The qualitative repeatability coefficients of variation (CV's) ranged from 0.40 to 0.90% and the within-lab CV's ranged from 1.3 to 3.5%. In analyte units (ng/mL), the repeatability CV's ranged from 1.9 to 4.3% and the within-lab CV's ranged from 3.7 to 6.1%. The limit of detection of the assay was found to be 2.5 ng/mL on both instruments. Recovery was within 20% of expected value. Linearity was 2.5-20 ng/mL. Method comparison showed 100% agreement with the predicate analyzer. The assay had minimal cross-reactivity to structurally related opioids including with morphine, morphine-3-glucuronide, morphine-6-glucuronide. No interference was observed with endogenous interferences.

Improved sensitivity for methotrexate analysis using enzyme multiplied immunoassay technique on the Siemens Viva-E instrument.

BACKGROUND: The available assay kit for methotrexate (MTX) using the Syva enzyme multiplied immunoassay technique (EMIT) reagents on the Siemens Viva-E instrument allows for the detection of MTX in serum or plasma to concentrations as low as 0.3 µmole/L. Current clinical decision points for MTX therapeutic drug monitoring and leucorvorin rescue exist at concentrations below that limit. OBJECTIVE: The goal of this study was to lower the limit of MTX quantitation to 0.05 µmole/L using the EMIT assay technology. METHODS: EMIT MTX assay parameters were modified on the Viva-E instrument to increase the sample volume, alter the calibration method, and employ an alternate calibrator set created to achieve lower detection. Intraassay and interassay precision was assessed for MTX controls. RESULTS: We observed a CV of 9.4% for intraassay precision with a bias of <0.01% and a CV of 15.7% for interassay precision with a bias of 22.5% for the 0.05 µmole/L control. Precision data for all other controls were <4%. The modified EMIT MTX assay and the unmodified approved assay were compared with a high sensitivity fluorescence polarization immunoassay method. Linear regression of correlation data revealed that both the modified and the commercial EMIT assays produced positive bias compared with the high sensitivity fluorescence polarization immunoassay method (y-int = 0.03 and 0.08, respectively). However, the modified EMIT assay had the best correlation in the low range (0.03-2 µmole/L). Additionally, endogenous and chemical interference testing demonstrated that the modified assay was not affected to a clinically significant extent. CONCLUSIONS: The described modifications have enhanced the sensitivity of the Syva EMIT assay for MTX measurements down to 0.05 µmole/L with acceptable precision that can be used in clinical practice for monitoring MTX therapy.

[Evaluation of Viva-E drug testing system].

BACKGROUND: The importance and usefulness of therapeutic drug monitoring (TDM) have been emphasized, and analysis of drugs has been increased in clinical laboratories. We evaluated the analytical performance and clinical usefulness of a recently introduced enzyme multiplied immunoassay instrument, Viva-E Drug Testing System (Dade Behring Inc., USA). METHODS: Using patients' samples and quality control material, we evaluated the analytical performance of Viva-E for a total of 11 drugs (cyclosporine, tacrolimus, mycophenolic acid, valproic acid, digoxin, theophylline, carbamazepine, phenytoin, phenobarbital, vancomycin, and gentamicin) with respect to linearity, precision, and correlations with other methods according to CLSI guidelines. Cobas Integra 800 (Roche Diagnostics, Switzerland) and API 4000 LC-MS/MS System (Applied Biosystems, USA) were used to make a comparison. In addition, we analyzed analysis time. RESULTS: Viva-E showed a good linearity (r2 >or= 0.97) for all items. Within-run CVs were within 5% and total CVs were within 10% for all drugs except for tacrolimus and digoxin at low concentrations. The system correlated well with the other methods (r=0.9283-0.9778). The time required for reporting the first sample was 11 min and the analysis time was 1.1 min. CONCLUSIONS: Since Viva-E showed a good analytical performance required for TDM in its linearity, precision, and accuracy with its wide drug menus including cyclosporine, tacrolimus, and mycophenolic acid, stat and random accessing functions, and the consolidation to a single workstation, it could be very useful in the clinical laboratory for various needs.

Evaluation of Viva-E Drug Testing System / 대한진단검사의학회지

BACKGROUND: The importance and usefulness of therapeutic drug monitoring (TDM) have been emphasized, and analysis of drugs has been increased in clinical laboratories. We evaluated the analytical performance and clinical usefulness of a recently introduced enzyme multiplied immunoassay instrument, Viva-E Drug Testing System (Dade Behring Inc., USA). METHODS: Using patients' samples and quality control material, we evaluated the analytical performance of Viva-E for a total of 11 drugs (cyclosporine, tacrolimus, mycophenolic acid, valproic acid, digoxin, theophylline, carbamazepine, phenytoin, phenobarbital, vancomycin, and gentamicin) with respect to linearity, precision, and correlations with other methods according to CLSI guidelines. Cobas Integra 800 (Roche Diagnostics, Switzerland) and API 4000 LC-MS/MS System (Applied Biosystems, USA) were used to make a comparison. In addition, we analyzed analysis time. RESULTS: Viva-E showed a good linearity (r2 > or = 0.97) for all items. Within-run CVs were within 5% and total CVs were within 10% for all drugs except for tacrolimus and digoxin at low concentrations. The system correlated well with the other methods (r=0.9283-0.9778). The time required for reporting the first sample was 11 min and the analysis time was 1.1 min. CONCLUSIONS: Since Viva-E showed a good analytical performance required for TDM in its linearity, precision, and accuracy with its wide drug menus including cyclosporine, tacrolimus, and mycophenolic acid, stat and random accessing functions, and the consolidation to a single workstation, it could be very useful in the clinical laboratory for various needs.

Determination of beta2-microglobulin in biological samples using an immunoenzymometric assay (chemiluminescence detection) or an immunoturbidimetric assay: comparison with a radioimmunoassay.

Monitoring beta2-microglobulin (beta2M) in biological fluids has gained considerable interest in pathologies such as haematologic malignancies, renal diseases, and chronic inflammatory diseases. Due to limitations of the RIA in the routine laboratory, we measure beta2M with non-isotopic methods. 189 patients suffering from myeloma (n=66), end stage renal failure (n=54) or inflammation (n=69) were included in this study. beta2M was determined in serum, urine and dialysate using an immunoenzymometric assay with chemiluminescence detection [Immulite Diagnostic Products Corporation (DPC), La Garenne Colombes, France] and an immunoturbidimetric assay (Olympus, Rungis, France). The data were compared with a radioimmunoassay (Immunotech, Marseille, France) taken as a reference. Using serum samples, the immunoenzymometric assay with chemiluminescence detection and the immunoturbidimetric assay have reliable analytical performances. Values obtained with serum samples are highly correlated with the radioimmunoassay (DPC/RIA r2=0.84; Olympus/RIA r2=0.94) whatever the type of pathology; however an over-estimation which could be related to cross reactivity with beta2M fragments was observed with the RIA method as suggested by crossover calibration and recovery studies. Values obtained with urinary samples (n=96) are closely related to those obtained with the RIA (DPC/RIA r2 = 0.98; Olympus/RIA: r2=0.99). Despite the low levels observed in dialysate (n=57) good correlations were observed between Olympus vs DPC (r2=0.85). By contrast, the two non-isotope methods are poorly related with the RIA method (DPC vs RIA r2=0.47 and Olympus vs RIA r2=0.54). In conclusion, the immunoenzymometric assay with chemiluminescence detection or the immunoturbidimetric assay could be used in the routine laboratory in order to determine beta2M in plasma, urine and dialysate.

The EMIT 2000 tacrolimus assay: an application protocol for the Beckman Synchron LX20 PRO analyzer.

OBJECTIVE: To develop and evaluate the performance of an application protocol for the EMIT 2000 tacrolimus (Tac) assay on the Beckman Synchron LX20 PRO Analyzer. DESIGN AND METHODS: Precision, accuracy, linearity, and lower limit of quantitation were investigated. Specimens from 212 kidney, liver, heart/heart-lung, and islet cell transplant patients were analyzed and results were compared to those from the Abbott MEIA II assay. A separate population of 232 specimens was coanalyzed by the enzyme-multiplied immunoassay technique (EMIT) assay and liquid chromatography tandem mass spectrometry (LC-MS/MS). RESULTS: Total imprecision was 13.7% and 6.0% at concentrations of 3.4 and 19.1 microg/L, respectively. Recoveries from assayed reference materials ranged from 103% to 109%. A quantitation range of 3.2-30.0 microg/L was validated. The EMIT assay on the LX20 PRO analyzer showed an average negative bias of 1% compared to the MEIA assay and an average positive bias of 17% compared to LC-MS/MS. CONCLUSION: This application for the EMIT 2000 Tac assay on the Beckman Synchron LX20 PRO analyzer enhances the versatility of the immunoassay for routine therapeutic drug monitoring (TDM) of this immunosuppressant in the clinical setting.

Evaluation of the Dade Behring Syva EMIT 2000 tacrolimus assay on the Bayer Advia 1650.

BACKGROUND: The Dade Behring Syva(R) EMIT (enzyme multiplied immunoassay technique) method for the measurement of tacrolimus in whole blood was evaluated against the Abbott IMx(R) microparticle enzyme immunoassay (MEIA) method. EMIT measures tacrolimus colorimetrically, whereas MEIA measures the analyte using fluorimetry. Both methods incorporate a protein precipitation step prior to measurement. METHOD: Whole blood specimens were treated by two types of precipitation technique followed by analysis for tacrolimus by either MEIA or EMIT on the Bayer Advia 1650. Linearity and precision were assessed and correlation analysis performed to evaluate the EMIT assay on the Bayer Advia 1650. RESULTS: The EMIT tacrolimus assay was linear over the concentration range 0.0-22.0 micro g/L; the limit of detection was 1.2 micro g/L. Correlation between the Syva EMIT and IMx tacrolimus assays was excellent (r = 0.959) and no significant bias existed between the two methods (mean difference, delta = 0.221 micro g/L). Calibration data for the EMIT assay was stable for a period of 24-48 h on the Advia between runs. CONCLUSION: The Syva EMIT assay for the measurement of tacrolimus in whole blood is suited for daily routine use on the Bayer Advia 1650.

Evaluation of a new pretreatment reagent for use with the EMIT 2000 cyclosporine assay.

OBJECTIVES: Evaluate the performance of the new pretreatment (NPT) reagent for use with the EMIT cyclosporine A (CsA) assay. DESIGN AND METHODS: Samples from transplant patients receiving CsA were tested using a COBAS MIRA S. RESULTS: A downward shift in target values for commercial controls was observed using the NPT reagent. There was excellent correlation for patient results when comparing the NPT reagent with methanol pretreatment. CONCLUSION: The NPT reagent is an acceptable substitute for methanol in the EMIT(R) extraction procedure for CsA.

Comparison of EMIT II, CEDIA, and DPC RIA assays for the detection of lysergic acid diethylamide in forensic urine samples.

In an effort to determine a practical, efficient, and economical alternative for the use of a radioimmunoassay (RIA) for the detection of lysergic acid diethylamide (LSD) in human urine, the performance of two photometric immunoassays (Dade Behring EMIT II and Microgenics CEDIA) and the Diagnostics Products Corp. (DPC) RIA were compared. Precision, accuracy, and linearity of the 3 assays were determined by testing 60 replicates (10 for RIA) at 5 different concentrations below and above the 500-pg/mL LSD cut-off. The CEDIA and RIA exhibited better accuracy and precision than the EMIT II immunoassay. In contrast, the EMIT II and CEDIA demonstrated superior linearity r2 = 0.9809 and 0.9540, respectively, as compared with the RIA (r2 = 0.9062). The specificity of the three assays was assessed using compounds that have structural and chemical properties similar to LSD, common over-the-counter products, prescription drugs and some of their metabolites, and other drugs of abuse. Of the 144 compounds studied, the EMIT II cross-reacted with twice as many compounds as did the CEDIA and RIA. Specificity was also assessed in 221 forensic human urine specimens that previously screened positive for LSD by the EMIT II assay. Of these, only 11 tested positive by CEDIA, and 3 were positive by RIA. This indicated a comparable specificity performance between CEDIA and RIA. This also was consistent with a previously reported high false-positive rate of EMIT II (low specificity). Each of the immunoassays correctly identified LSD in 23 out of 24 human urine specimens that had previously been found to contain LSD by gas chromatography-mass spectrometry at a cut-off concentration of 200 pg/mL. The CEDIA exhibited superior precision, accuracy, and decreased cross-reactivity to compounds other than LSD as compared with the EMIT II assay and does not necessitate the handling of radioactive materials.

[Evaluation of Emit netilmicin and amikacin assays on Dimension RXL HM (Dade Behring) open channels]. / Adaptation des trousses Emit nétilmicine et amikacine sur canaux ouverts du Dimension RXL HM (Dade Behring).

The aim of this study was to evaluate and to validate an enzyme immunoassay in homogeneous phase for netilmicin and amikacin, adapted on the Dimension RXL HM (Dade Behring) machine. The results were compared with those obtained with automated polarization of fluorescence immunoassay using TDx FLx (Abbott). The protocol of the study and the analytical criteria were inspired by the protocol Valtec version 2002 recommended by the French Society of Clinical Biology (SFBC). The validation of this technique as adapted to the Dimension RXL HM has allowed its use for routine dosage adjustment of amikacin and netilmicin. The practicability is however the weak point of the adaptation of these techniques, even limiting as for their implementation.

Aplicação da técnica de imunoensaio enzimático de multiplicação (EMIT) para dosagem de ciclosporina na amostra de sangue absorvido em papel-filtro / Application of the enzymeðmultiplied imunoassay technique (EMIT) to measure ciclosporin in the blood sample absorbed in filter paper

Objetivo: Investigar a aplicabilidade da técnica de imunoensaio enzimático de multiplicação (enzymeðmultiplied immunoassay technique ð EMIT) para dosagem de ciclosporina A (CsA) nas amostras de sangue absorvido em papelðfiltro (STAP). Material e método: Realizaramðse determinações de CsA utilizandoðse técnica de EMIT em 110 amostras; 24 eram de pacientes transplantados cardíacos e 86, dos pacientes transplantados renais. Todos faziam uso da CsA por via oral. Exatamente 12 horas após a tomada da CsA, coletouðse o sangue e prepararamðse as amostras de STAP. As amostras de STAP foram estocadas à temperatura ambiente por períodos de 15 e 30 dias, e as amostras de sangue toral foram estocados a ñ 4ºC, por um tempo inferior a 48 horas, para o teste. Resultados: O coeficiente de correlação entre a técnica que utiliza como amostra sangue total e a amostra de STAP realizada 15 dias após a preparação foi de 0,963, e de 30 dias doi de 0,972 (p < 0,0001). Correlação entre as amostras de STAP de 15 e 30 dias foi de 0,968 (p < 0,0001). A análise de variância nãoðparamétrica de Friedman para os três grupos comparados revelou que ela não foi estatisticamente significante (p < 0,005). Conclusões: A técnica de STAP pode ser utilizada rotineiramente por ser estável, reprodutível e prática. Considerandoðse a dimensão continental de muitos países, este método pode ser bastante útil para a otimização da terapia

Homogenous enzyme immunoassay for cyclosporine in whole blood using the EMIT 2000 cyclosporine specific assay with the COBAS MIRA-plus analyzer.

We describe the evaluation of the EMIT 2000 cyclosporine specific assay kit, an enzyme-multiplied immunoassay for cyclosporine in whole blood, with a COBAS MIRA-plus analyzer. The enzyme used for the assay was glucose-6-phosphate dehydrogenase (EC 1.1.1.49 G6PDH) from Leuconostoc mesenteroides; the monoclonal antibody is fairly specific for cyclosporine, and is not reactive with most metabolites. The assay principle is based on competitive immunoassay with G6PDH-labeled cyclosporine and cyclosporine in sample to the anticyclosporine mouse monoclonal antibody binding site. The within-assay coefficient of variation (CV) of this method was 2.7-4.2% (n = 10) at the levels of 56.2-339.7 microg/L. Day-to-day CVs ranged from 4.2-8.1% at the levels of 47.2-350.2 microg/L. The within-day CVs ranged from 2.0-6.4% at the levels of 43.3-330.5 microg/L. The functional detection limit was 24.9 microg/L. Samples treated with pretreatment reagent were stable at least 5 hr. Calibration was stable at least 10 days. The analytical recovery was 81-109%. The correlation between values obtained with the EMIT 2000 cyclosporine specific assay kit (y) and fluorescence polarization immunoassay (FPIA) (TDxFLx) (x) was: y = 0.880x - 13.053 microg/L (r = 0.984, Sy/x = 15.968, n = 71) with a mean difference of 31.42 +/- 19.89 microg/L ((TDxFLx - EMIT 2000) +/- SD); for the FPIA (AxSYM) (x): y = 0.989 - 4.144 microg/L (r = 0.981, Sy/x = 17.478, n = 71) with a mean difference of 5.56 +/- 17.38 microg/L ((AxSYM - EMIT 2000) +/- SD); and for the radioimmunoassay (RIA, CYCLO-Trac SP) (x): y = 0.893 - 6.764 microg/L (r = 0.993, Sy/x = 10.582, n = 71) with a mean difference of 22.18 +/- 14.98 microg/L ((RIA - EMIT 2000) +/- SD) using the Bland-Altman technique.

Evaluation of DRI enzyme immunoassays for drugs-of-abuse screening on the Cobas Mira.

OBJECTIVE: To establish optimal performance parameters (ratios of sample and reagents, reaction time, and distinction of absorbance values between calibrators) on the Roche Cobas Mira analyzer for the evaluation of Diagnostic Reagents Inc enzyme immunoassay reagents for urine screening of amphetamines, cannabinoids, cocaine metabolite, opiates, and phencyclidine. SETTING: Laboratory in a physician's office. PRACTICE DESCRIPTION: Two laboratorians analyze a daily average of 25 urine samples for employment screening purposes. PRODUCT COMPARISON: DRI reagents were compared to Syva EMIT reagents. RESULTS: Within-run and between-run precision at the cutoff concentration for DRI reagents ranged from 1.1% to 1.6% CV and 2.2% to 5.7% CV respectively. Results (positive or negative) using DRI or Syva EMIT reagents were identical for cannabinoids, cocaine metabolite, opiates and PCP. Direct comparison for amphetamines was not possible because of different cutoff concentrations of the 2 reagents systems. CONCLUSION: DRI reagents are acceptable alternatives to EMIT reagents for the analysis of amphetamines, cannabinoids, cocaine metabolite, opiates and phencyclidine in urine on the Cobas Mira analyzer. Utilization of DRI reagents for more than 12 months demonstrated the reliability of the reagents and allowed cost comparison. ABBREVIATIONS: DRI = Diagnostic Reagents Inc; EMIT = enzyme multiplied immunoassay technique; d.a.u. = drugs of abuse; PCP = phencyclidine; GC/MS = gas chromatography/mass spectrometry.

Modification and evaluation of Abuscreen OnLine assays for drug metabolites in urine performed on a COBAS FARA II in comparison with EMIT d.a.u. Cannabinoid 20.

OnLine assays for cannabinoids, barbiturates, opiates, and cocaine from Roche Diagnostics were run on the automatic analyzer COBAS FARA II. The assay programs and the cutoff definition were modified to obtain maximum sensitivity and reagent economy. The limits of detection and curve stability data of the modified assays were compared with the original, as well as with EMIT d.a.u. Cannabinoid 20 assay, and the modified assays were found to be more favorable. Modified OnLine assays appear to be a convenient and cost-effective method for drug screening in urine.

Evaluation of the Abuscreen ONLINE assay for amphetamines on the Hitachi 737: comparison with EMIT and GC/MS methods.

The performance of the ONLINE Assay for Amphetamines on the Hitachi 737 was compared to the Syva Emit d.a.u. Assay and GC/MS. Randomly screened (n = 2964) patient urine samples were assayed using ONLINE and Emit d.a.u. assays concurrently, using d-amphetamine, 1000 ng/mL and d-methamphetamine, 1000 ng/mL as the screening cutoff for ONLINE and Emit d.a.u. assays, respectively. All presumptive positives were confirmed by GC/MS. The specificity was 99% (2937/2964) for ONLINE and 97% (2873/2964) for Emit. Agreement with GC/MS was 80% (110/137) for ONLINE and 55% (110/201) for Emit.

Computer acquisition, analysis and presentation of results from a Cobas Bio analyser.

Two computer programs for Macintosh computers have been developed in the LabVIEW programming language to perform data acquisition, analyses and presentation of results originating from a Cobas Bio analysing machine. One program is very flexible in its human interface, and is intended for research use. The program allows the results to be combined in a variety of ways, and allows the user to generate graphs to highlight the results. The other program is intended for routinely follow-up of analyses of proteases. It only allows the user to follow strict instructions, and only limited flexibility is built-in.

Benzodiazepine screening using EMIT II and TDx: urine hydrolysis pretreatment required.

Urine specimens were collected from individuals prescribed oral doses of the following benzodiazepine tablets: diazepam, oxazepam, temazepam, lorazepam, alprazolam, flurazepam, and chlordiazepoxide. An aliquot was hydrolyzed using Helix pomatia beta-glucuronidase. Both the hydrolyzed and unhydrolyzed urine pairs were subjected to EMIT II and TDx immunoassay screening tests and to gas chromatographic-mass spectrometric quantitation. Hydrolysis is required to ensure adequate detection of oxazepam, temazepam, and lorazepam with either screening method. A 100-ng/mL cutoff is required when screening for lorazepam, following therapeutic doses. The EMIT II is more sensitive than the TDx as a screening test for benzodiazepines.

Adsorption losses from urine-based cannabinoid calibrators during routine use.

The major metabolite of cannabis found in urine, 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (delta 9-THC), is the compound most often used to calibrate cannabinoid immunoassays. The hydrophobic delta 9-THC molecule is known to adsorb to solid surfaces. This loss of analyte from calibrator solutions can lead to inaccuracy in the analytical system. Because the calibrators remain stable when not used, analyte loss is most probably caused by handling techniques. In an effort to develop an effective means of overcoming adsorption losses, we quantified cannabinoid loss from calibrators during the testing process. In studying handling of these solutions, we found noticeable, significant losses attributable to both the kind of pipette used for transfer and the contact surface-to-volume ratio of calibrator solution in the analyzer cup. Losses were quantified by immunoassay and by radioactive tracer. We suggest handling techniques that can minimize adsorption of delta 9-THC to surfaces. Using the appropriate pipette and maintaining a minimum surface-to-volume ratio in the analyzer cup effectively reduces analyte loss.

Variation in results of cost-effective EMIT assays on the Cobas-Bio analyser.

Following suggestions that spurious results occur with EMIT assays--so-called 'fliers'--many laboratories perform such assays in duplicate. In this study, using a Cobas-Bio centrifugal analyser and cost-effective assays developed in the authors' laboratory, complete EMIT assays were run, each with its own calibration curve, on three anti-epileptic drugs using plasma samples, and five drugs of abuse using urine samples. No serious spurious results were obtained. It is suggested that there is no inherent tendency for EMIT assays to produce 'fliers' and that when these occur they may be explained by factors common to many other types of assay.