Evaluation of the GeneXpert MTB/RIF in patients with presumptive tuberculous meningitis

Background

Meningitis caused by Mycobacterium tuberculosis is a major cause of morbidity and mortality worldwide. We evaluated the performance of cerebrospinal fluid (CSF) testing with the GeneXpert MTB/RIF assay versus traditional approaches for diagnosing tuberculosis meningitis (TBM).

Methods

Patients were adults (n = 37) presenting with suspected TBM to the Hospital Nacional Dos de Mayo, Lima, Peru, during 12 months until 1st January 2015. Each participant had a single CSF specimen that was divided into aliquots that were concurrently tested for M. tuberculosis using GeneXpert, Ziehl-Neelsen smear and culture on solid and liquid media. Drug susceptibility testing used Mycobacteria Growth Indicator Tube (MGIT 960) and the proportions method.

Results

81% (30/37) of patients received a final clinical diagnosis of TBM, of whom 63% (19/30, 95% confidence intervals, CI: 44–80%) were HIV-positive. 22% (8/37, 95%CI: 9.8–38%), of patients had definite TBM. Because definite TBM was defined by positivity in any laboratory test, all laboratory tests had 100% specificity. Considering the 30 patients who had a clinical diagnosis of TBM: diagnostic sensitivity was 23% (7/30, 95%CI: 9.9–42%) for GeneXpert and was the same for all culture results combined; considerably greater than 7% (2/30, 95%CI: 0.82–22%) for microscopy; whereas all laboratory tests had poor negative predictive values (20–23%). Considering only the 8 patients with definite TBM: diagnostic sensitivity was 88% (7/8, 95%CI: 47–100%) for GeneXpert; 75% (6/8, 95%CI: 35–97%) for MGIT culture or LJ culture; 50% (4/8, 95%CI 16–84) for Ogawa culture and 25% (2/8, 95%CI: 3.2–65%) for microscopy. GeneXpert and microscopy provided same-day results, whereas culture took 20–56 days. GeneXpert provided same-day rifampicin-susceptibility results, whereas culture-based testing took 32–71 days. 38% (3/8, 95%CI: 8.5–76%) of patients with definite TBM with data had evidence of drug-resistant TB, but 73% (22/30) of all clinically diagnosed TBM (definite, probable, and possible TBM) had no drug-susceptibility results available.

Conclusions

Compared with traditional culture-based methods of CSF testing, GeneXpert had similar yield and faster results for both the detection of M. tuberculosis and drug-susceptibility testing. Including use of the GeneXpert has the capacity to improve the diagnosis of TBM cases.

An Investigation into the Automated Measurement of Urinary Oestrogens in Pregnancy

Changes in the relative sensitivity of reaction of oestrone, oestradiol, oestriol, and their monoglucuronides due to changes in reaction temperature and the acid and quinol concentrations of Kober's reagent have been investigated by means of an automated system. Similar investigations have been carried out with a number of standardized pregnancy urines. All measurements have been made with reference to an oestriol-16α(β-D-glucuronide) standard. These changes have been examined with trichloracetic acid and p-nitrophenol in Ittrich's reagent. The importance of the final acid concentration has also been examined. As a result of these investigations a modified scheme is suggested which gives maximal sensitivity to oestriol conjugates and minimal sensitivity to oestradiol conjugates, and may be calibrated by using an oestriol conjugate as a primary standard. The effect of varying the concentration of trichloracetic acid and p-nitrophenol in Ittrich's reagent has been examined under these modified conditions. More than 200 urines have been assayed by this method and the results compared with those obtained by the present automated procedure. The effect of dilution on many of these specimens has also been examined.

Evaluation of the albumin cobalt binding (ACB®) assay for measurement of ischaemia-modified albumin (IMA®) on the Beckman Coulter LX-20

Background: In the presence of ischaemia, albumin undergoes changes resulting in the formation of ischaemia-modified albumin (IMA). Increased serum concentrations of IMA have been found in patients with myocardial ischaemia. The purpose of this study was threefold: to evaluate the albumin cobalt binding (ACB) assay for measurement of IMA on the Beckman Coulter LX-20; to establish a reference range for IMA; and to investigate the relationship between IMA and total albumin concentrations.

Methods: The ACB assay was evaluated under the following headings: imprecision, accuracy and reliability. A reference range was established on a population of 81 healthy subjects.

Results: The within-batch coefficient of variation (CV) at IMA concentrations of 88, 99 and 120 KU/L were 1.4, 2.0 and 2.5%, respectively. The between-batch CVs at 74, 84 and 123 KU/L were 3.4, 3.3 and 3.0%, respectively. Comparison with the Cobas Mira Plus showed a mean negative bias of 7 KU/L. The 97.5th percentile established on our reference population was 110 KU/L. A significant inverse relationship was found between total serum albumin and IMA concentrations ( r = -0.66, P < 0.0001). Correcting the IMA concentrations for total albumin in our reference population, using a formula devised in this study, yielded a range similar to that of uncorrected IMA.

Conclusions: The ACB assay was found to have acceptable precision and performed very satisfactorily on the Beckman Coulter LX-20. A correction to measured IMA concentrations, to take into account total albumin concentrations, may need to be applied for the proper interpretation of IMA results.

The Performance of the ‘Centrifichem’ Parallel Fast Analyser Using Packaged Reagents

The CentrifiChem system was used with packaged reagent kits for the following determinations: albumin, alanine and aspartate aminotransferases, creatinine, glucose, and α-hydroxybutyrate and lactate dehydrogenases. The linearity obtainable for each assay was investigated, and particular attention was paid to finding the most suitable instrument settings.

Haemoglobin A1c: Evaluation of three point of care analysers for use in a paediatric diabetes clinic

Background: The measurement of haemoglobin A1c(HbA1c) by high-performance liquid chromatography (HPLC) is generally deemed unsuitable for point of care testing (POCT) due to its complexity and extended turnaround times (TAT). The aim of this project was to evaluate two new HPLC instruments, the Bio-Rad D10 and the Primus PDQ, as POCT instruments compared with Bayer's DCA2000 HbA1c immunoassay analyser in our paediatric diabetes clinic.

Methods: A total of 228 samples were analysed, of which 160 analyses were performed in our paediatric diabetes clinic. HbA1c results were compared by the Passing-Bablok agreement test, the Bland-Altman difference analysis, within- and between-run imprecision, and TAT.

Results: : The agreement test and difference analysis showed a correlation of r2=0.96 and a mean HbA1c difference of <0.1% between the three analysers. The PDQ and the D10 achieved the within-run target coefficient of variation (CV) of <2% at an HbA1c of 7.5%. Between-run imprecision at an HbA1c of 10.8% produced CV of 3.5%, 2.4% and 1.6% for the D10, DCA2000 and PDQ, respectively. TAT studies confirmed that the PDQ was substantially faster than the DCA2000 and D10.

Conclusions: The PDQ had the shortest TAT, afforded random access and exhibited acceptable imprecision, and hence is the preferred instrument for our POCT environment.

An Assessment of the Performance of the SMA 12/micro Autoanalyser in Clinical Use

The performance of the SMA 12/micro autoanalyser in clinical use in a children's hospital is described. Details of the precision and accuracy over a period of 134 operating days are given, and some of the factors which influence the results are discussed. The slow operating speed and analytical difficulties on the sodium, potassium, and cholesterol channels made the analyser unsuitable for routine use in this laboratory.

An Evaluation of the Greiner Selective Analyzer and its Role in the Clinical Laboratory

The Greiner Selective Analyzer (GSA II) was evaluated over a period of six months. The evaluation assessed the reliability, accuracy, and precision of the analyser for six determinations. The methods evaluated were for glucose, urea, creatinine, total protein, total bilirubin, and alkaline phosphatase. Comparison of results was also made with those obtained for the same specimens using the Technicon SMA 12/60 Analyzer. Correlation and comparison of results indicate that the Greiner Selective Analyzer performed better for three of the methods but worse for serum creatinine determination. The role of the analyser as a routine tool in the clinical laboratory was also evaluated during analyses of approximately 900 patient specimens.

Other features evaluated were analytical range of the six methods under study, the economics of operation, temperature control, and electrical and mechanical safety.

Development and Evaluation of a Blood Culture PCR Assay for Rapid Detection of Salmonella Paratyphi A in Clinical Samples

Background

Enteric fever remains an important cause of morbidity in many low-income countries and Salmonella Paratyphi A has emerged as the aetiological agent in an increasing proportion of cases. Lack of adequate diagnostics hinders early diagnosis and prompt treatment of both typhoid and paratyphoid but development of assays to identify paratyphoid has been particularly neglected. Here we describe the development of a rapid and sensitive blood culture PCR method for detection of Salmonella Paratyphi A from blood, potentially allowing for appropriate diagnosis and antimicrobial treatment to be initiated on the same day.

Methods

Venous blood samples from volunteers experimentally challenged orally with Salmonella Paratyphi A, who subsequently developed paratyphoid, were taken on the day of diagnosis; 10 ml for quantitative blood culture and automated blood culture, and 5 ml for blood culture PCR. In the latter assay, bacteria were grown in tryptone soy broth containing 2.4% ox bile and micrococcal nuclease for 5 hours (37°C) before bacterial DNA was isolated for PCR detection targeting the fliC-a gene of Salmonella Paratyphi A.

Results

An optimized broth containing 2.4% ox bile and micrococcal nuclease, as well as a PCR test was developed for a blood culture PCR assay of Salmonella Paratyphi A. The volunteers diagnosed with paratyphoid had a median bacterial burden of 1 (range 0.1–6.9) CFU/ml blood. All the blood culture PCR positive cases where a positive bacterial growth was shown by quantitative blood culture had a bacterial burden of ≥ 0.3 CFU/ ml blood. The blood culture PCR assay identified an equal number of positive cases as automated blood culture at higher bacterial loads (≥0.3 CFU/ml blood), but utilized only half the volume of specimens.

Conclusions

The blood culture PCR method for detection of Salmonella Paratyphi A can be completed within 9 hours and offers the potential for same-day diagnosis of enteric fever. Using 5 ml blood, it exhibited a lower limit of detection equal to 0.3 CFU/ml blood, and it performed at least as well as automated blood culture at higher bacterial loads (≥0.3 CFU/ml blood) of clinical specimens despite using half the volume of blood. The findings warrant its further study in endemic populations with a potential use as a novel diagnostic which fills the present gap of paratyphoid diagnostics.

Automated urine screening devices make urine sediment microscopy in diagnostic laboratories economically viable

Automated urinalysis devices are reproducible, accurate and faster than the standard manual microscopy. Economic analysis has shown that decreases in turn-around-time and labour cost savings offered by these devices make them more economic than manual microscopy.

[The count of urine corpuscles using automated analyzer Iris IQ 200 TM]

The volume of urine of high power field of analyzer Iris IQ 200 TM was identified according standard of stabilizing erythrocytes and amounted up to 0.18 mkl. The amount of urine corpuscles detected by analyzer in this volume corresponds to amount of urine corpuscles under microscopy of sediment often times concentrated urine at thickness of preparation in 0.1 mm, under microscope with objective x40 and ocular 10/18. The count of corpuscles by analyzer in 1 mkl of urine is the most objective and convenient technique for quantitative evaluation of urine corpuscles.

Long-term automated sampling of PCDD/PCDF flue gas: current status and critical issues

After entry into force of the Stockholm Convention and Aarhus Protocol and in order to implement the upcoming European legal background, the European countries are asked to apply control measures to reduce the release of persistent organic pollutants (POPs) such as dioxins and furans (PCDD/PCDF) and polychlorinated biphenyls as well as to establish POPs release inventories. In this perspective, development of measuring techniques of emissions is a focal issue in acquiring useful information. In this paper, results of various measurement campaigns at different municipal waste incineration (MWI) plants using long-term automated sampling of PCDD/PCDF are presented. The samples collected from both manual and automated campaigns were analyzed following the European Standard EN-1948:2006 by high-resolution gas chromatograph/high-resolution mass spectrometer. Performances of two different commercial systems have been investigated. Anomalous values occurred during one long-term campaign (22.16 pg I-toxic equivalent (TEQ)/Nm(3)), compared to average values (4-5 pg I-TEQ/Nm(3)) of the MWI. At this maximum value, a main occurrence of abnormal and instable operating conditions has been found. Sampling based on long-term basis was found to be more reliable to monitor PCDD/PCDF emissions than occasional short-term sampling. Nevertheless, the results of long-term campaigns demonstrate that emission levels detected in 15-30 days campaigns, when unsteady operating conditions can occur, as start-up and shut down, are not immediately comparable to the typical levels in a 6-8 h, when operating conditions are generally stable. Moreover, there are often differences observed in the congener profiles between short- and long-term campaigns.

A new screening method for proteinuria using Erythrosin B and an automated analyzer--rapid, sensitive and inexpensive determination

BACKGROUND

In spite of the urgent necessity for a screening test of urinary protein for the early diagnosis of kidney diseases, a rapid, accurate and cost-effective method for their detection has yet to be developed.

METHODS

A solution containing a buffer agent (pH 2.3) and surfactants and a solution of Erythrosin B are added to a urine sample. After letting the mixture stand for 5 min at 37°C, the dye-bound protein is measured by a spectrophotometer at 546 nm using a Hitachi 7170S automated analyzer.

RESULTS

The calibration curve was linear with human serum albumin concentration in the range of 2.4-200 mg/l. The detection limit, 2.4 mg/l was superior to conventional dye-binding methods by one order of magnitude and comparable to the turbidimetric immunoassay (TIA). Spot urine samples from 70 patients who showed (-) or (±) in the dip-stick screening test for proteinuria and 79 healthy volunteers were analyzed. There was an excellent correlation (r=0.978, n=149) between the results given by the proposed method and those by the TIA.

CONCLUSIONS

This method provides a viable alternative to the conventional immunoassay-based methods for urinary protein measurement, and will be useful in the diagnosis of early stage kidney disease.

Nonspecific biochemical changes under different health statuses and a quantitative model based on biological markers to evaluate systemic function in humans

BACKGROUND

To investigate the markers of systemic function by using laboratory parameters as life parameters.

METHODS

Lymphocyte count, albumin, and creatinine levels were measured using automatic analyzers in young, healthy individuals (20-39 years) and senior individuals (80-95 years) as well as in terminally ill patients. We developed a mathematic model and scoring system (indexes of systemic function, ISF) based on the above mentioned biological markers.

RESULTS

ISF scores were significantly lower in the senior group (P < 0.05) than those in the young, healthy group. A significant decrease was observed in the ISF of the terminally ill group and that of the senior group (P < 0.05).

CONCLUSIONS

Our results suggest that the ISF scoring system of systemic function can be used to objectively evaluate the systemic function in individuals with different health statuses.

New generation IQ-200 automated urine microscopy analyzer compared with KOVA cell chamber

OBJECTIVE

The examination of the urine remains to be one of the most commonly performed tests in laboratory practice. Currently, laboratories also need to accredit their urine diagnostics by comparing their measurement methods to acceptable references. In this study we compared particle counts obtained by new generation automated technique, image capture analysis (IQ-200) with those of a standardized chamber counts.

DESIGN AND METHODS

The same 258 urine samples from different departments of a hospital assayed by IQ-200 were analyzed in parallel with the KOVA cell chamber system. Clinically significant discrepancy results (positive vs. negative) for red blood cell (RBC) and white blood cell (WBC) were also compared with those obtained by dipstick testing.

RESULTS

There was a good agreement between the automated system and sediment microscopy for RBCs, WBCs, and squamous epithelial cells (SCs) (r=0.90; r=0.80; r=0.72, respectively: P<0.001). The IQ-200 was more sensitive for determining RBCs, WBCs, and SCs than other formed elements.

CONCLUSIONS

IQ-200 can perform accurate quantification of microscopic element in urine. However, automated techniques are not completely free of error. Therefore, by adopting an appropriate algorithm and combining the results with stript analysis and other laboratory tests allows further reduction of clinically important errors.

A1C variability predicts incident cardiovascular events, microalbuminuria, and overt diabetic nephropathy in patients with type 1 diabetes

OBJECTIVE

Recent data from the Diabetes Control and Complications Trial (DCCT) indicated that A1C variability is associated with the risk of diabetes microvascular complications. However, these results might have been influenced by the interventional study design. Therefore, we investigated the longitudinal associations between A1C variability and diabetes complications in patients with type 1 diabetes in the observational Finnish Diabetic Nephropathy (FinnDiane) Study.

RESEARCH DESIGN AND METHODS

A total of 2,107 patients in the FinnDiane Study had complete data on renal status and serial measurements of A1C from baseline to follow-up (median 5.7 years), and 1,845 patients had similar data on cardiovascular disease (CVD) events. Intrapersonal SD of serially measured A1C was considered a measure of variability.

RESULTS

During follow-up, 10.2% progressed to a higher albuminuria level or to end-stage renal disease, whereas 8.6% had a CVD event. The SD of serial A1C was 1.01 versus 0.75 (P < 0.001) for renal status and 0.87 versus 0.79 (P = 0.023) for CVD in progressors versus nonprogressors, respectively. In a Cox regression model, SD of serial A1C was independently associated with progression of renal disease (hazard ratio 1.92 [95% CI 1.49-2.47]) and of a CVD event (1.98 [1.39-2.82]) even when adjusting for mean A1C and traditional risk factors. Interestingly for CVD, mean serial A1C itself was not predictive even though SD of A1C was.

CONCLUSIONS

In patients with type 1 diabetes, A1C variability was not only predictive of incident microalbuminuria and progression of renal disease but also of incident CVD events.

[Assessment of the performance of an automated analysis system in detecting C3 and C4]

OBJECTIVE

To evaluate the performance of BNII auto-analyzer system in detecting C3 and C4.

METHODS

CLSI protocols (EP15-A, EP6-A, EP9-A2) and other relevant literatures were use to or evaluate the precision, accuracy, linearity of C3 and C4 detection by the auto-analyzer system, and the results were compared with the recognized standards.

RESULTS

The relative bias of C3 and C4 was less than one third of the CLIA'88 standard and the precision met the clinical requirement. The results tested by DADE BNII system were not compatible with those by Roche Modular System. C3 showed good linearity in the tests (R2>0.975, P<0.05) with a linearity range of 0.18-5.1 g/L. The linearity of C4 was not available because of lack of high-level samples.

CONCLUSION

The performances of DADE BNII System basically meet the recognized standards in clinical detection of C3 and C4, but the method comparison needs further validation.

Quantitative evaluation and selection of reference genes in a rat model of extended liver resection

Partial hepatectomy (PHx) is a frequently used experimental model for the study of liver regeneration. Real-time quantitative PCR (qPCR) has become the one of the methods of choice for expression profiling of selected genes in order to elucidate the regulation of liver function and regeneration. The expression of five commonly used housekeeping genes (HKGs; Alb, UBC, Hprt, Ywhaz, and GAPDH) were evaluated by qPCR in 70% and 90% rat PHx model at 1, 2, and 7 d after PHx. We set up a closely controlled qPCR procedure validating each critical step and the gene expression stability was statistically evaluated by linear regression and analysis of variance. Our results showed the HKG best suited for the evaluation of gene expression in the extended 90% PHx model is Hprt. The amplification of an HKG can be omitted when the same amount of cDNA from all samples is introduced into the amplification reaction. Determination of cDNA concentration employing the bioanalyzer proved to be an easy and reproducible approach. Using this technique the potential regulation of the transcription level of the HKG in response to the experimental condition tested or the stability of a housekeeping gene becomes irrelevant.

[Modeling and implementation method for the automatic biochemistry analyzer control system]

In this paper the system structure The automatic biochemistry analyzer is a necessary instrument for clinical diagnostics. First of is analyzed. The system problems description and the fundamental principles for dispatch are brought forward. Then this text puts emphasis on the modeling for the automatic biochemistry analyzer control system. The objects model and the communications model are put forward. Finally, the implementation method is designed. It indicates that the system based on the model has good performance.

Changes in total CO2 measurement according to reagent cassette rotation in chemistry autoanalyzers

The quality control (QC) failure rate in the serum total carbon dioxide (TCO(2)) test increases at a higher rate than in other tests over time after calibration. The causes of the increased QC failure rate in the TCO(2) test were examined. Using a TBA200RF analyzer (Toshiba Medical Systems), the TCO(2) of the QC material was measured at 2-hr intervals and was found to decrease by up to 16.5% at 10 hr after calibration. In contrast, using the P-module and D-module analyzers (Roche Diagnostics), the TCO(2) of the QC material did not change significantly during 10 hr after calibration. When the TCO(2) level of the QC material was measured hourly over 5 hr with the TBA200FR analyzer while the reagent bottle was rotated at 0, 80, 120, 160, or 200 rpm, the rate of decline of TCO(2), increased over time after calibration and with increasing reagent cassette rotation. Therefore, in a clinical laboratory using an automated analyzer with a rotating reagent cassette, it is necessary to set a limit to the calibration time interval in order to satisfy the QC goal.

New staining method for use in electrophoretic determination of alpha-amylase isoenzymes in serum

We have developed and evaluated a new staining method for use in electrophoretic analysis of alpha-amylase (AMY, EC3. 2. 1. 1) isoenzymes in serum. Our method based on the colorimetric determination of formazane dye formed by enzyme-coupled reactions and maltopentaose was used as a substrate. We have confirmed that this method was sensitive and stable. Liquid reagents are used, so the automatic analysis of AMY isoenzymes using a fully-automated electrophoresis system will become possible.

[Application of comparison method in internal quality control of hematology analyzer by using fresh blood]

OBJECTIVE

To investigate the comparison method on internal control of hematology analyzer by using fresh blood.

METHODS

The hematology analyzer with well function was selected as the reference analyzer, fresh blood samples from healthy subjects were measured by reference analyzer and the values were used to calibrate compared hematology analyzers. The acceptable limits of relative deviation of WBC,RBC, HGB,HCT, PLT were established by comparative experiments during three months. The results of fresh blood samples from patients with low/medium/high levels measured by compared analyzer were compared with those from reference analyzer, the relative deviation of WBC, RBC, HGB, HCT, PLT was calculated respectively. The internal quality control charts in laboratory information system were established, with date as x-axis, relative deviation as y-axis. The acceptable relative deviation limits were set to be +/-2 s, and to be used for laboratory quality control.

RESULT

The relative deviation of WBC, RBC, HGB, HCT, PLT with high, medium, low levels were(0.75+/-2.964)%, (1.19+/-2.488)%,(1.43+/-2.439)%; (-0.39+/-1.327)%, (-0.26+/-1.297)%, (-0.35+/-1.095)%û(-0.43+/-1.393)%, (-0.17+/-1.139)%, (0.24+/-1.166)%û(-.43+/-1.362)%, (-0.36+/-1.381)%, (-0.57+/-1.299)%û(-0.93+/-4.330)%,(0.04+/-4.118)%, (-0.41+/-4.149)%, respectively in 2006. As the second instrument, the compared analyzer was involved in College of American Pathologists Proficiency Testing with satisfactory results, the bias of WBC,RBC, HGB, HCT, PLT were within (-0.5 approximately 5.1)%, (-1.0 approximately 1.6)%, (-1.7 approximately 1.4)%, (-1.5 approximately 1.3)%, (-4.5 approximately 7.4)%, respectively.

CONCLUSION

The quality control on compared hematology analyzer can be effectively, conveniently and economically performed using this method.

Low serum testosterone assayed by liquid chromatography-tandem mass spectrometry. Comparison with five immunoassay techniques

BACKGROUND

Low levels of serum testosterone, as typically found in women and children, cannot be measured reliably by immunoassays. Our aim was to develop a sensitive assay to quantitate low serum testosterone concentrations using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results were compared to those obtained with various immunoassay techniques.

METHODS

Serum testosterone levels in 70 women and children were measured using LC-MS/MS and compared with two automated, non-isotopic immunoassays, and three manual, isotopic immunoassays. Serum extraction was required only for LC-MS/MS and one of the isotopic methods.

RESULTS

Deming regression analysis was used for comparison: the correlation coefficients were between 0.772 and 0.870, and the slopes between 0.972 and 1.365. Using Bland and Altman analysis, all the 5 immunoassays showed a positive mean difference compared with LC-MS/MS: all overestimated the testosterone levels in women and children.

CONCLUSION

None of the immunoassays tested proved sufficiently reliable when low testosterone concentrations (< or =3.47 nmol/L) were measured. In contrast to conventional isotopic and non-isotopic immunoassay techniques, LC-MS/MS allows the precise determination of low testosterone levels. It has adequate sensitivity and is not subject to interference from other steroids that were tested.

Is flow cytometry really adapted to the determination of sperm concentration?

It has been reported that flow cytometry can be used as a reference procedure to determine sperm concentrations in quality control schemes in andrology laboratories, but there are no convincing quality control data. To understand comprehensively whether flow cytometry can be used to determine sperm concentration, sperm concentrations of 85 human semen samples were detected using three different methods, namely flow cytometry, computer-assisted semen analysis (CASA) and manual counting with a cell-VU chamber. The bead concentrations of both low [(18+/-2.5)x10(6)/mL] and high [(35+/-5)x10(6)/mL] pre-calibrated standard latex bead solutions were also determined with flow cytometry. The results showed that bead concentrations of both low and high pre-calibrated standard latex bead solutions counted five times with flow cytometry were (21.37+/-0.85)x10(6)/mL and (45.95+/-1.76)x10(6)/mL, respectively. Coefficient variances (CVs) and relative errors (REs) were 4%, 15.51% and 3.84%, 31.3% for low and high latex bead solutions, respectively. The overall correlation between values measured with flow cytometry and values measured with the cell-VU chamber and the CASA system was significant. However, flow cytometry overestimated the sperm concentration by 109% compared to the results with the cell-VU chamber. Moreover, for the azoospermic samples analysed, the sperm concentration was estimated at 0.12 (range from 0.04 to 0.24)x10(6)/mL. In conclusion, the data demonstrated that flow cytometry can result in an overestimation of both bead counting and sperm concentration, suggesting that flow cytometry is an inappropriate method for sperm counting, especially in the case of azoospermia.

Comparison of measurements of canine plasma glucose, creatinine, urea, total proteins, alanine aminotransferase, and alkaline phosphatase obtained with the APOLOWAKO and Vitros 250 analyzers

The APOLOWAKO is an entirely automatic benchtop biochemistry analyzer that uses stabilized liquid reagents. It was tested for canine blood and plasma glucose, creatinine, urea, total proteins, alanine aminotransferase, and alkaline phosphatase. The APOLOWAKO gave very similar results for whole blood and the corresponding plasma (n=32). Within-laboratory imprecision was below 2.2% and 5.8% for substrates and enzymes, respectively. Comparison of results with whole blood by APOLOWAKO and with the corresponding plasma by Vitros 250 (n=139) showed very good correlations. Passing-Bablok's regression slopes ranged from 0.83 to 1.12 and intercepts were close to zero, except for ALP where the results obtained by APOLOWAKO were approximately 1.5 times higher than by Vitros. The APOLOWAKO system can be a reliable instrument in veterinary practices where larger systems are not available but it should be further validated and reference intervals should be determined.

Selecting Automation for the Clinical Chemistry Laboratory

Context.—Laboratory automation proposes to improve the quality and efficiency of laboratory operations, and may provide a solution to the quality demands and staff shortages faced by today's clinical laboratories. Several vendors offer automation systems in the United States, with both subtle and obvious differences. Arriving at a decision to automate, and the ensuing evaluation of available products, can be time-consuming and challenging. Although considerable discussion concerning the decision to automate has been published, relatively little attention has been paid to the process of evaluating and selecting automation systems.

Objective.—To outline a process for evaluating and selecting automation systems as a reference for laboratories contemplating laboratory automation.

Design.—Our Clinical Chemistry Laboratory staff recently evaluated all major laboratory automation systems in the United States, with their respective chemistry and immunochemistry analyzers. Our experience is described and organized according to the selection process, the important considerations in clinical chemistry automation, decisions and implementation, and we give conclusions pertaining to this experience.

Results.—Including the formation of a committee, workflow analysis, submitting a request for proposal, site visits, and making a final decision, the process of selecting chemistry automation took approximately 14 months. We outline important considerations in automation design, preanalytical processing, analyzer selection, postanalytical storage, and data management.

Conclusions.—Selecting clinical chemistry laboratory automation is a complex, time-consuming process. Laboratories considering laboratory automation may benefit from the concise overview and narrative and tabular suggestions provided.

Effect of body weight, age and breeding history on canine sperm quality parameters measured by the Hamilton-Thorne analyser

During the last decade, several computer assisted sperm analysis (CASA) systems have been validated for canine sperm quality assessment. Regarding the impressive possibilities of these systems, further research is required to determine which CASA measurements are of clinical importance in canine andrology. In the present study, the sperm quality parameters obtained by the Hamilton-Thorne Semen Analyser (Ceros 12.1; HTR) were correlated with the body weight and the age of the dogs. Moreover, the sperm quality parameters of dogs with a different breeding history were compared. The sperm-rich fraction was collected from 111 dogs of 50 different breeds, which were presented at our department. Immediately after collection, the concentration, the total sperm output (TSO) and 13 different sperm motility and velocity characteristics were measured by the HTR. The percentage of live spermatozoa and the spermatozoal morphology were examined on eosin/nigrosin stained smears. Based on their breeding history, the dogs were divided in three groups: 'fertile' (n = 60), 'subfertile' (n = 17) or 'not used for breeding' (n = 34). Significant (p < 0.05) correlations were established between the body weight of the dogs and the TSO (r = 0.245) and velocity curvilinear (VCL; r = -0.220), respectively. The age was negatively correlated with the percentage of normal spermatozoa (r = -0.203; p < 0.05). The correlations with all the other evaluated sperm parameters were low and not significant. Significant differences between the 'fertile' and the 'subfertile' group were found for all of the evaluated sperm quality parameters (except for BCF, LIN, STR and MEDIUM). In conclusion, dogs tend to produce ejaculates with a lower percentage of normal spermatozoa with increasing age and dogs with higher body weights produce ejaculates with a higher TSO and a lower VCL. Significantly poorer sperm characteristics were found for dogs with lower in vivo fertility results.

Use of the Agilent 2100 bioanalyzer for rapid and reproducible molecular typing of Streptococcus pneumoniae

Restriction fragment length polymorphism (RFLP) analysis is an economic and fast technique for molecular typing but has the drawback of difficulties in accurately sizing DNA fragments and comparing banding patterns on agarose gels. We aimed to improve RFLP for typing of the important human pathogen Streptococcus pneumoniae and to compare the results with the commonly used typing techniques of pulsed-field gel electrophoresis and multilocus sequence typing. We designed primers to amplify a noncoding region adjacent to the pneumolysin gene. The PCR product was digested separately with six restriction endonucleases, and the DNA fragments were analyzed using an Agilent 2100 bioanalyzer for accurate sizing. The combined RFLP results for all enzymes allowed us to assign each of the 47 clinical isolates of S. pneumoniae tested to one of 33 RFLP types. RFLP analyzed using the bioanalyzer allowed discrimination between strains similar to that obtained by the more commonly used techniques of pulsed-field gel electrophoresis, which discriminated between 34 types, and multilocus sequence typing, which discriminated between 35 types, but more quickly and with less expense. RFLP of a noncoding region using the Agilent 2100 bioanalyzer could be a useful addition to the molecular typing techniques in current use for S. pneumoniae, especially as a first screen of a local population.

Nucleated red blood cells in term fetuses: reference values using an automated analyzer

BACKGROUND

Nucleated red blood cells (NRBCs) are present in small numbers in the cord blood of healthy fetuses at birth. Acute and chronic stimuli, such as fetal hypoxia, cause increased circulating levels of NRBCs. Manual counting is presently the only way to quantify NRBCs, but it is time-consuming and inaccurate. Recently, automated approaches have been developed in order to quantify NRBCs.

OBJECTIVES

Our aim was to compare manual vs. automated NRBC counting and derive reference values in umbilical cord blood samples from healthy term fetuses.

METHODS

We analyzed blood samples from 131 healthy term fetuses by the automated approach and calculated reference values of NRBC counts as percentiles. To compare automated NRBC count with manual count we obtained umbilical cord blood samples from 50 further fetuses.

RESULTS

Significant positive correlation was obtained between the two methods (r(2) = 0.988, Bland-Altman plot mean difference NRBCs/100 WBC: -0.590). The median for NRBCs/100 WBC was 3.05 (range 0-11.6) and the median for absolute NRBC counts x10(9)/l was 0.39 (range 0-1.8).

CONCLUSIONS

We demonstrate that values obtained with the automated NRBC counting method are comparable to those obtained with the microscopic manual evaluation and give reference values for umbilical cord NRBCs at term that can be used in clinical practice.

In-situ monitoring of H2O2degradation by live cells using voltammetric detection in a lab-on-valve system

This paper describes a method for monitoring the degradation of hydrogen peroxide by cells immobilized on a beaded support. The detection is based on the voltammetric reduction of hydrogen peroxide on a mercury film working electrode, whilst combining the concept of sequential injection (SI) with the lab-on-valve (LOV) manifold allows the measurements to be carried out in real time and automatically, in well-defined conditions. The method is shown to be capable of simultaneously monitoring hydrogen peroxide in the 10-1000 microM range and oxygen in the 160-616 microM range. A correction algorithm has been used to ensure reliable H2O2 results in the presence of varying oxygen levels. The method has been successfully applied to monitoring the degradation of H2O2 by wild-type cells and by catalase-overexpressing mouse embryonic fibroblasts. Since the technique allows the monitoring of the initial response rate, it provides data not accessible by current methods that are end-point-based measurements.

Reduction of carry-over in column-switching HPLC/MS system with automated system washing procedure for highly sensitive direct analysis of donepezil in dog plasma

To solve the problem of carry-over--a persistent chromatographic challenge for bioanalytical assays with highly sensitive detector such as a mass spectrometry (MS)--a new on-line sample pretreatment HPLC/MS system using a column-switching technique was established. This system was designed to reduce carry-over based on a hydrophobic interaction mechanism using a washing function (multi-mobile phase flow system), as well as to remove impurities on-line in a mobile phase for the pretreatment. As a result, a washing function in this system was enabled to reduce carry-over and to remove impurities in a mobile phase by automatic operation. Therefore, concentration levels of donepezil (DH) in dog plasma as low as 10 pg/mL could be determined using this on-line sample pretreatment HPLC/MS system. In addition, method validation results of specificity, linearity, accuracy, precision, lower limit of quantitation (LLOQ), and carry-over demonstrated that this on-line sample pretreatment HPLC/MS system was robust and valid as a practical assay of drugs and metabolites in the biological samples.

Development of a semi-automated chemical stability system to analyze solution based formulations in support of discovery candidate selection

A semi-automated chemical stability system was developed, validated, and implemented to assess the chemical and physical stability (24 h) of intravenous and oral solution based formulations in support of preliminary in vivo drug discovery studies. The system utilizes a single Agilent 1100 LC and Xterra column with multiple UV wavelength monitoring. Mobile phase selection, either basic or acidic, is selected base upon on the physico-chemical properties of the test compound. The system was validated against 14 new chemical entities across multiple therapeutic areas. The results indicated that drug discovery compounds could be accurately quantified (<2% R.S.D.) in a wide range of formulation vehicles in greater than 90% of the test cases. This method can be used as a quantitative tool for triaging formulation variables and packaging configurations to quickly develop stable solutions for dosing.

Simultaneous determination of dextromethorphan, dextrorphan, and guaifenesin in human plasma using semi-automated liquid/liquid extraction and gradient liquid chromatography tandem mass spectrometry

A method for the simultaneous determination of dextromethorphan (DEX), dextrorphan (DET), and guaifenesin (GG) in human plasma was developed, validated, and applied to determine plasma concentrations of these compounds in samples from six clinical pharmacokinetic (PK) studies. Semi-automated liquid handling systems were used to perform the majority of the sample manipulation including liquid/liquid extraction (LLE) of the analytes from human plasma. Stable-isotope-labeled analogues were utilized as internal standards (ISTDs) for each analyte to facilitate accurate and precise quantification. Extracts were analyzed using gradient liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Use of semi-automated LLE with LC-MS/MS proved to be a very rugged and reliable approach for analysis of more than 6200 clinical study samples. The lower limit of quantification was validated at 0.010, 0.010, and 1.0 ng/mL of plasma for DEX, DET, and GG, respectively. Accuracy and precision of quality control (QC) samples for all three analytes met FDA Guidance criteria of +/-15% for average QC accuracy with coefficients of variation less than 15%. Data from the thorough evaluation of the method during development, validation, and application are presented to characterize selectivity, linearity, over-range sample analysis, accuracy, precision, autosampler carry-over, ruggedness, extraction efficiency, ionization suppression, and stability. Pharmacokinetic data are also provided to illustrate improvements in systemic drug and metabolite concentration-time profiles that were achieved by formulation optimization.

Automated capture and on-column detection of biotinylated DNA on a disposable solid support

This work comprises the development of a technique for the capture of single-stranded DNA on a solid support combined with in situ quantification. The capture is based on the strong and selective interaction between biotinylated DNA and streptavidin-coated agarose beads. Sequential Injection in the lab-on-valve format allows for automated manipulation of all components including the building and disposal of bead columns. Detection was accomplished using the OliGreen fluorescent dye and optimization of the assay achieved a limit of detection of 111 pg ssDNA, with a total assay time of roughly 2.5 min per sample.

Serum osteocalcin and parathyroid hormone in healthy children assessed with two new automated assays

BACKGROUND

The recent introduction of new automated assays needs careful definition of reference values in healthy children. The aim of this study was to determine serum parathyroid hormone (PTH) and osteocalcin in a large group of healthy children according to age.

METHODS

We selected 2,288 healthy children (1,079 girls, 1,209 boys), aged 2-16 years. Serum PTH and osteocalcin were assayed with a two-site immunochemiluminometric assay adapted on an automated analyzer, the Liaison.

RESULTS

Significant differences were found between the mean serum values of PTH and osteocalcin in boys and girls in all age groups (p <0.001). Boys' and girls' PTH values ranged from 3.42-22.30 ng/l and 2.31-24.49 ng/l, respectively; serum osteocalcin ranged from 3.85-17.80 nmol/l in boys and 3.74-17.38 nmol/l in girls.

CONCLUSIONS

The results of this study contribute to the establishment of reference values in healthy children for PTH and osteocalcin assays.

Validation of high-throughput methods for measuring blood urea nitrogen and urinary albumin concentrations in mice

Chronic kidney disease is a substantial medical and economic burden. Animal models, including mice, are a crucial component of kidney disease research; however, recent studies disprove the ability of autoanalyzer methods to accurately quantify plasma creatinine levels, an established marker of kidney disease, in mice. Therefore, we validated autoanalyzer methods for measuring blood urea nitrogen (BUN) and urinary albumin concentrations, 2 common markers of kidney disease, in samples from mice. We used high-performance liquid chromatography to validate BUN concentrations measured using an autoanalyzer, and we utilized mouse albumin standards to determine the accuracy of the autoanalyzer over a wide range of albumin concentrations. We observed a significant, linear correlation between BUN concentrations measured by autoanalyzer and high-performance liquid chromatography. We also found a linear relationship between known and measured albumin concentrations, although the autoanalyzer method underestimated the known amount of albumin by 3.5- to 4-fold. We confirmed that plasma and urine constituents do not interfere with the autoanalyzer methods for measuring BUN and urinary albumin concentrations. In addition, we verified BUN and albuminuria as useful markers to detect kidney disease in aged mice and mice with 5/6-nephrectomy. We conclude that autoanalyzer methods are suitable for high-throughput analysis of BUN and albumin concentrations in mice. The autoanalyzer accurately quantifies BUN concentrations in mouse plasma samples and is useful for measuring urinary albumin concentrations when used with mouse albumin standards.

Rheumatoid factor interference in the determination of carbohydrate antigen 19-9 (CA 19-9)

BACKGROUND

Investigation of a 61-year-old Caucasian male suffering from fatigue and weight loss led to the finding of a carbohydrate antigen 19-9 (CA 19-9) concentration of 80 kU/L using an ADVIA Centaur analyser. Determination of CA 19-9 on Vidas, AxSYM and Architect i2000 systems gave normal results. His rheumatoid factor concentration was very high (900 kIU/L) and assay interference was suspected.

METHODS

Besides using several laboratory procedures to show the cause of the interference, we tried to estimate the frequency of the suspected interference. Therefore, two studies were performed. The first was carried out in a multicentre setting using four different CA 19-9 methods on 51 randomly selected samples with high rheumatoid factor concentrations and ten samples containing no or very low rheumatoid factor. In the second study we used heterophilic blocking tubes for 68 routinely analysed samples with CA 19-9 concentrations ranging between 37 and 250 kU/L using an ADVIA Centaur analyser.

RESULTS

In the multicentre study we found eight discrepant CA 19-9 results, but only one was clearly due to interference. We showed that the interference detected, just as in the index case, was caused by rheumatoid factor. The other discrepancies could not be explained, but are probably related to method-dependent differences. In the 68 routinely analysed samples, no interference could be shown using the heterophilic blocking tubes.

CONCLUSIONS

Although interferences in the CA 19-9 assay are not frequent, the ADVIA Centaur system appears to be more sensitive to rheumatoid factor interference. The lack of standardisation remains an important issue for this assay. The determination of CA 19-9 during the follow-up of patients should be performed using a single method. If, however, there is any clinical doubt about a result, CA 19-9 should be determined using another method to exclude possible interferences.

Evaluation of two fully automated novel enzyme-linked immunosorbent assays for the determination of human adiponectin in serum

BACKGROUND

In contrast to RIA, recently available ELISAs provide the potential for fully automated analysis of adiponectin. To date, studies reporting on the diagnostic characteristics of ELISAs and investigating on the relationship between ELISA- and RIA-based methods are rare.

METHODS

Thus, we established and evaluated a fully automated platform (BEP 2000; Dade-Behring, Switzerland) for determination of adiponectin levels in serum by two different ELISA methods (competitive human adiponectin ELISA; high sensitivity human adiponectin sandwich ELISA; both Biovendor, Czech Republic). Further, as a reference method, we also employed a human adiponectin RIA (Linco Research, USA). Samples from 150 patients routinely presenting to our cardiology unit were tested.

RESULTS

ELISA measurements could be accomplished in less than 3 h, measurement of RIA had a duration of 24 h. The ELISAs were evaluated for precision, analytical sensitivity and specificity, linearity on dilution and spiking recovery. In the investigated patients, type 2 diabetes, higher age and male gender were significantly associated with lower serum adiponectin concentrations. Correlations between the ELISA methods and the RIA were strong (competitive ELISA, r=0.82; sandwich ELISA, r=0.92; both p<0.001). However, Deming regression and Bland-Altman analysis indicated lack of agreement of the 3 methods preventing direct comparison of results. The equations of the regression lines are: Competitive ELISA=1.48 x RIA-0.88; High sensitivity sandwich ELISA=0.77 x RIA+1.01.

CONCLUSIONS

Fully automated measurement of adiponectin by ELISA is feasible and substantially more rapid than RIA. The investigated ELISA test systems seem to exhibit analytical characteristics allowing for clinical application. In addition, there is a strong correlation between the ELISA methods and RIA. These findings might promote a more widespread use of adiponectin measurements in clinical research.

Automated cell plating and sample treatments for fixed cells in high content assays

Robust and reliable methods for the manipulation of neural cell lines, by passaging, plating, dye labeling, imaging, fixation, and immunocytochemistry, are required to enable consistent, reproducible screens to be performed. We describe herein procedures and processes we have established to maximize the level of consistency of cell plating, fixation, and dye or antibody labeling, to ensure that assays which we are running on a routine basis remain consistent across long periods of time. These procedures involve a variety of fully or semiautomated steps, using high-quality commercially available liquid handling and dispensing technology.

Performance characteristics of seven automated CA 125 assays

Cancer antigen 125 (CA 125) is a high-molecular-mass glycoprotein that is used as a tumor marker to monitor disease progression and response to therapy and in early detection of recurrence after treatment for ovarian cancer. The Access 2 (Beckman Coulter, Brea, CA), ADVIA Centaur (Bayer Diagnostics, Tarrytown, NY), ARCHITECT i2000 (Abbott Diagnostics, Abbott Park, IL), AxSYM (Abbott Diagnostics), Elecsys 2010 (Roche Diagnostics, Indianapolis, IN), IMMULITE 2000 (Diagnostic Products, Los Angeles, CA), and VITROS ECi (Ortho Clinical Diagnostics, Raritan, NJ) assays for CA 125 were evaluated for detection limit, dilution linearity, imprecision, correlation, and reference intervals. The maximum average deviation from target recoveries for dilution linearity studies ranged from 3.7% for the ADVIA Centaur to 18.2% for the IMMULITE 2000. Imprecision studies yielded total coefficients of variation of 2.0% to 8.3% at CA 125 concentrations of 35 and 114 U/mL (35 and 114 kU/L). Method comparison studies revealed good agreement with the VITROS ECi comparison method, with slopes ranging between 0.88 to 1.19 and correlation coefficients of more than 0.95. All methods show acceptable performance characteristics and generally compare well. However, for some samples, substantial differences exist between methods, necessitating parallel testing when introducing a new method.

Determination of adiponectin in serum using a latex particle-enhanced turbidimetric immunoassay with an automated analyzer

BACKGROUND

Adiponectin is an adipose-derived hormone that plays a role in regulating metabolic processes such as fat partitioning and lipid and glucose metabolism. Quantification of adiponectin is useful for obtaining information on metabolic syndrome, but there is no rapid method to measure adiponectin for clinical use.

METHODS

We developed a rapid and sensitive latex particle-enhanced turbidimetric immunoassay (LTIA) using a latex bead-immobilized anti-adiponectin polyclonal antibody. The assay was performed on a Hitachi H7170 analyzer and evaluated for validity as a method to quantitate adiponectin, in parallel with the ELISA.

RESULTS

Dilution tests using LTIA showed linearity from 0.25 to 30 microg/ml. Within-run CV and total CV were obtained in the range of 0.8-1.9% and 1.1-2.0%, respectively. No interference was observed in the testing of specimens containing potentially interfering substances such as bilirubin, ditaurobilirubin, hemoglobin triglyceride, rheumatoid factor, type IV collagen, fibronectin, and complement factor (C1q). A strong correlation between LTIA and ELISA was confirmed (n=30, r=0.990, y=0.95x+0.39).

CONCLUSION

The LTIA assay is applicable to quantitating the serum concentration of adiponectin. This assay is more convenient and faster than ELISA and suitable for clinical routine analysis.

Measurement of glycated hemoglobin (HbA1c) with an automated POCT instrument in comparison with HPLC and automated immunochemistry method: evaluation of the influence of hemoglobin variants

Our study evaluates a fast and easy way to perform point-of-care testing (POCT) measurements of glycated hemoglobin HbA1c in comparison with an immunoassay on an automated biochemistry analyzer and cation exchange chromatography, the two methods routinely used in clinical laboratories for the measurement of HbA1c. A significant finding of our study is that although the POCT instrument insert claims that the method is not affected by the presence of HbS in the heterozygous state or in combination with beta-thalassemia, discrepant results were found in some cases with such hemoglobinopathies. In these cases, the two POCT and laboratory immunoassay methods showed clinically significant positive interferences with samples containing the HbS trait. We conclude that samples with the HbS trait should be interpreted with caution when tested using the POCT instrument.

Dioxin and polychlorinated biphenyl analysis: Automation and improvement of clean-up established by example of spices

To analyze polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/PCDFs) and polychlorinated biphenyls (PCBs) in spices by gas chromatography-mass spectrometry, a new clean-up method had to be developed owing to the high content of essential oils in the samples. A solid-phase extraction (SPE) column with activated silica endowed with sulfuric acid and sodium hydroxide was used. Under these conditions, clean-up was achieved using at least 5-7 g of pepper and even higher amounts of other spices. The automatized clean-up comprised three additional chromatographic steps after accelerated solvent extraction (ASE) followed by gel permeation: chromatography on a florisil SPE column, extract cleaning with the above-mentioned silica SPE column and chromatography with an activated charcoal column. On the basis of this automatized clean-up, a method that is more effective, rapid, simplified and economical than the available methods for PCDD/PCDF and PCB analysis is proposed. In model studies, the average recoveries for PCDDs/PCDFs ranged between 82.6% and 105.6% and for the PCBs between 71.3% and 113.3%.

Cholesterol crystals causing falsely elevated automated cell count

This is a report of 3 cases of body fluid containing numerous cholesterol crystals that caused falsely elevated cell counts on an automated cell counter. Two of the cases were pleural effusion fluid from patients with long-standing rheumatoid arthritis. Fluid in the third case was from upper extremity cystic lesions of a patient with squamous cell carcinoma of the head and neck. Microscopic examination revealed abundant cholesterol crystals in all fluid samples. In all 3 cases, initially, the automated cell counter reported very elevated WBC and RBC counts that were much higher than those from the manual count. This interference by cholesterol in the automated cell counter is discussed. In addition, possible pathophysiology of cholesterol formation in the body fluid is discussed and chylous and pseudochylous (chyliform) effusions are reviewed. Finally, the use of automated instruments in the evaluation of body fluid is reviewed.

Semiautomated determination of pesticides in water using solid phase extraction disks and gas chromatography-mass spectrometry

A method based on semiautomated solid phase extraction using octadecyl-bonded silica disks and gas chromatography-mass spectrometry, operated in selected ion monitoring mode, allows detection and quantification of approximately 100 pesticides and transformation products in drinking water. Samples (500 mL) were passed through the disk, and the retained pesticides were eluted with acetone and ethyl acetate. Typical recoveries for pesticides at 0.1 microg L(-1) in water were in the range of 72-120% with relative standard deviations less than 20%. Calibration curves were linear over the range of 0.025-0.5 microg mL(-1) (equivalent to a concentration range in drinking water of 0.05-1.0 microg L(-1)).