International Proficiency Testing Scheme Research Articles

A multi-class multi-residue method for the analysis of polyether ionophores, tetracyclines and sulfonamides in multi-matrices of animal and aquaculture fish tissues by ultra-high performance liquid chromatography tandem mass spectrometry

ABSTRACTAn ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) based multiclass multi-residue method for the simultaneous analysis of 5 polyether ionophores, 4 tetracycline and 10 sulfonamides in animal and aquaculture fish tissues was developed and validated. Sample extraction and clean-up were based on a modified QuEChERS method. The method was validated using an in-house validation based on performance characteristics modified from Commission Decision 2002/657/EC. Both matrix effect and uncertainties associated with sample preparation and instrumental analysis were minimised by the use of matrix-matched calibrations. Recoveries of analytes were generally satisfactory and typically fell between 80% and 113%. The repeatability and intermediate reproducibility measured as relative standard deviations were in most cases less than 15% (n = 63). The decision limit (CCα) and detection capability (CCβ) ranged from 110.7 to 125.8 and 121.5 to 151.7 µg kg−1 for tetracyclines, 113.4 to 118.3 and 116.8 to 126.5 µg kg−1 for sulfonamides and 50.8 to 52.4 and 51.5 to 55.6 µg kg−1 for polyether ionophores, respectively. The method displayed its fitness for purpose through satisfactory results obtained in international proficiency testing schemes. The method was applied to animal and aquaculture fish tissues obtained from different sources in South Africa. Polyether ionophores were predominantly detected in samples in the range 4.26–290.10 µg/kg. Oxytetracycline was found in one porcine liver sample; however, none of the targeted analytes were present above the detection limit in the aquaculture samples.

How well do our measurements measure up? An overview of South Africa’s first proficiency testing scheme for organochlorine pesticides in water

Access to safe drinking water is a basic human right in South Africa. Therefore, the accurate measurement of water quality is critical in ensuring the safety of water prior to its intended use. Proficiency testing schemes (PTSs) are a recognised form of assessing the technical competence of laboratories performing these analyses. There are over 200 water testing laboratories in South Africa, with only 51 being accredited for testing some or all parameters (physical, chemical and microbiological content) prescribed in SANS 241. Only a limited number of laboratories test for organic contaminants, as this requires advanced, costly analytical instrumentation, such as GC-FID/ECD/MS and LC-UV/MS, as well as skilled staff. These laboratories are either looking at selected organic contaminants listed in the World Health Organisation (WHO) drinking water guidelines or performing the minimum requirements, as stipulated in SANS 241, for phenols, atrazine, trihalomethanes and total dissolved organic content. Whereas several local PTS providers are addressing the competent assessment of microbiological, physical and inorganic chemical testing of water, a clear need for a South African PTS provider for organic contaminant analysis in water was identified by NMISA (National Metrology Institute of South Africa) in 2012. The key drivers for the coordination of a local PTS stem mainly from the limited stability of analytes in the samples for analysis and the high cost and logistics of international PTS participation. During 2012 and 2013, NMISA conducted a PTS trial round, a workshop and 2 additional PTS rounds for organochlorine pesticides in water, for South African laboratories, and also several international participants from other countries in Africa. This paper will highlight some of the challenges faced by laboratories when analysing organochlorine pesticides at the ng/l concentration level. Issues surrounding the comparability of measurement results, traceability, method validation and measurement uncertainty are also discussed.

Lights and shadows of the actual European guidelines on bioanalytical method validation: the case of raltegravir.

Recently, the European Medicines Agency (EMA) has released new guidelines on the validation of bioanalytical methods. In this work, we compared the analytical performance of 2 high-performance liquid chromatography with tandem mass spectrometry methods designed for the quantification of the antiretroviral drug raltegravir (RAL) that fully accomplish the criteria according to the new EMA guidelines. The first method was developed with the goal of separating RAL from its main metabolite, whereas in the second method, we deliberately did not discriminate the parent drug from its metabolite. After validation, both methods were used for the quantification of plasma samples from HIV-infected patients on RAL-based maintenance antiretroviral therapy. Incurred reanalysis of samples obtained from patients receiving RAL as therapy evidenced optimal performance for both methods. Similarly, the comparison of both methods performed by the Deming test showed that they correlate significantly with each other (Pearson coefficient of regression 0.97, P < 0.0001) with no significant deviation from linearity according to the Cusum test. The Bland-Altman test, however, showed a mean difference between the 2 methods of 54.1% (limits of agreements of ±1.96 SD ranged from -163.3% to +271.5%). Such differences were significantly affected by interindividual variations in the production of RAL metabolites. We conclude that the recently released EMA guidelines on bioanalytical method validation present some limitations related to the process of method development. To have confidence in the drug-concentration measurements, laboratories must demonstrate their performance through the participation in international proficiency testing schemes that must include patient samples.

Low Plasma Concentrations of Albumin Influence the Affinity Column–Mediated Immunoassay Method for the Measurement of Tacrolimus in Blood During the Early Period After Liver Transplantation

Monitoring of tacrolimus (TAC) concentrations in transplanted patients is necessary to ensure effective immunosuppression and to avoid adverse side effects. The fully automated analysis of TAC by the affinity column-mediated immunoassay (ACMIA), which does not require a precipitation step, may represent an efficient alternative to liquid chromatography-tandem mass spectrometry (LC-MS/MS), including in the clinically urgent situation. The aim of this work was to compare the analytical performances of ACMIA with those of LC-MS/MS and to evaluate the influence of hematological parameters, time posttransplant, and type of transplant on the results obtained from routine blood samples. Performance characteristics of ACMIA were evaluated using quality control materials and samples spiked with TAC from the International Proficiency Testing Scheme. One hundred and fifty-eight whole-blood samples from patients who received a liver (n = 55) or kidney (n = 14) transplant were assayed by ACMIA and LC-MS/MS, and hematologic, biochemical, and demographic data were collected. Univariate and multivariate statistical analyses were also performed to assess associations between the interassay differences with clinical and laboratory parameters. For artificially spiked samples, the average difference between results obtained by ACMIA and LC-MS/MS was 0.24 ± 0.51 ng/mL (2.91 ± 7.03%). Crosschecking of calibrators and controls by both methods was in accordance with the nominal concentrations of TAC. The lower limit of quantification of ACMIA was found to be 3.0 ng/mL. The results with the 2 methods using routine samples from the transplant recipients correlated well (Spearman's r = 0.90). However, the ACMIA method demonstrated a positive mean bias of 1.78 ng/mL in comparison with LC-MS/MS. Multivariate analysis showed that liver transplant and albumin plasma concentrations significantly and independently affected ACMIA results (P = 0.033 and P = 0.001, respectively). Samples from liver transplant recipients early postsurgery were associated with a larger method bias than those from renal transplant recipients. Results obtained by ACMIA must be interpreted cautiously, particularly at lower TAC concentrations. Patients with low plasma concentrations of albumin are likely to display higher concentrations of TAC compared with LC-MS/MS in the early postsurgery period.

Evaluation of a Novel Commercial Assay for the Determination of Cyclosporine A, Tacrolimus, Sirolimus, and Everolimus by Liquid Chromatography–Tandem Mass Spectrometric Assay

The aim of this study was the evaluation of the first commercially available in-vitro diagnostic (IVD)- mass spectrometric immunosuppressant assay from Chromsystems (MassTox Immunosuppressants ONEMINUTE Test) and the comparison to a routinely used online solid phase extraction liquid chromatography-tandem mass spectrometric assay method for the measurement of cyclosporine A, everolimus, sirolimus, and tacrolimus in patient whole blood samples. An API 4000 [tandem mass spectrometer (AB SCIEX)] combined with a CTC Pal autosampler (CTC Analytics AG) and a Shimadzu ultra-fast liquid chromatography (UFLC) system were applied for the direct liquid chromatography-tandem mass spectrometric assay analysis using electrospray ionization in positive ion mode. Isotope-labeled internal standards were used for the commercial assay. Within- and between-day variation, accuracy, and limits of quantification were determined. Samples from external international proficiency testing schemes were measured to assess the accuracy of the commercial assay. About 100 patient samples were reanalyzed with the commercial test kit, and the results were compared with our in-house results. The limit of quantification for the commercial assay was 0.5 ng/mL for everolimus, sirolimus, and tacrolimus and 5 ng/mL for cyclosporine A. The coefficient of variation for all immunosuppressants was lower than 7% (within day) and 12% (between days) for all 5 concentration levels. Accuracy ranged between 82% and 111% for quality control samples and between 89% and 112% for samples from the external quality assurance program. Both methods showed a very good agreement (r > 0.91) in patient samples over the whole concentration range for all immunosuppressants. The commercial immunosuppressant assay from Chromsystems represents a standardized IVD-certified alternative to our in-house developed assay.

High-throughput LC-MS/MS method for monitoring sirolimus and everolimus in the routine clinical laboratory

Immunosuppressant therapeutic drug monitoring (TDM) is an important requirement in post-transplant patient care. In recent years, high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) has become a valid alternative to antibody-based immunoassays in TDM due to its high specificity and sensitivity. Furthermore, this technology allows for the simultaneous measurement of several immunosuppressive drugs. The aim of the present study was to establish a straightforward, robust, and high-throughput LC-MS/MS method for the simultaneous determination of sirolimus and everolimus in whole blood in order to replace immunoassays in our routine practice. Five-level blood calibrators were employed for assay development, while three materials at different concentrations were used for internal quality control. The proposed method uses protein precipitation for sample preparation. Analyses were performed using a triple quadrupole LC-MS/MS, with a C18 held at 60°C. Using an appropriate gradient elution profile and SPE on-line, elution times for all compounds analysed were 2.6 min with a total run-time of 3.5 min. Calibration curves were linear throughout the selected ranges. The intra- and inter-assay CVs (<7%), the limit of quantification (0.2 μg/L) and accuracy were highly satisfactory. On testing the results using the international proficiency testing scheme (UK-NEQAS), the performance of the proposed method was found to be highly reliable. The findings made by us indicate that the proposed method is of value, since it is speedy, straightforward, accurate, and applicable to different LC-MS/MS instruments for the routine TDM of organ transplant recipients.

An Evaluation of the Inter-Method Discrepancies in Ferromanganese Nodule Proficiency Test GeoPT 23A

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Multisite Analytical Evaluation of the Abbott ARCHITECT Cyclosporine Assay

The objective of this study was to evaluate the analytical performance of the Abbott ARCHITECT Cyclosporine (CsA) immunoassay in 7 clinical laboratories in comparison to liquid chromatography/tandem mass spectrometry (LC/MS/MS), Abbott TDx, Cobas Integra 800, and the Dade Dimension Xpand immunoassay. The ARCHITECT assay uses a whole blood specimen, a pretreatment step with organic reagents to precipitate proteins and extract the drug, followed by a 2-step automated immunoassay with magnetic microparticles coated with anti-CsA antibody and an acridinium-CsA tracer. Imprecision testing at the 7 evaluation sites gave a range of total % coefficient of variations of 7.5%-12.2% at 87.5 ng/mL, 6.6%-14.3% at 411 ng/mL, and 5.2%-10.7% at 916 ng/mL. The lower limit of quantification ranged from 12 to 20 ng/mL. Purified CsA metabolites AM1, AM1c, AM4N, AM9, and AM19 were tested in whole blood by the ARCHITECT assay and showed minimal cross-reactivity at all 7 sites. In particular, AM1 and AM9 cross-reactivity in the ARCHITECT assay, ranged from -2.5% to 0.2% and -0.8% to 2.2%, respectively, and was significantly lower than for the TDx assay, in which the values were 3.2% and 16.1%, respectively. Comparable testing of metabolites in the Dade Dimension Xpand assay at 2 evaluation sites showed cross-reactivity to AM4N (6.4% and 6.8%) and AM9 (2.6% and 3.6%) and testing on the Roche Integra 800 showed cross-reactivity to AM1c (2.4%), AM9 (10.7%), and AM19 (2.8%). Cyclosporine International Proficiency Testing Scheme samples, consisting of both pooled specimens from patients receiving CsA therapy as well as whole-blood specimens supplemented with CsA, were tested by the ARCHITECT assay at 6 sites and showed an average bias of -24 to -58 ng/mL versus LC/MSMS CsA and -2 to -37 ng/mL versus AxSYM CsA. Studies were performed with the ARCHITECT CsA assay on patient specimens with the following results: ARCHITECT CsA assay versus LC/MSMS, average bias of 31 ng/mL; ARCHITECT versus the Dade Dimension assay (4 sites), average biases of -7 to -228 ng/mL; ARCHITECT versus AxSYM and TDx, average biases of -4 and -53 ng/mL, respectively. Spearman correlation coefficients were >or=0.89. The ARCHITECT CsA assay has significantly reduced CsA metabolite interference relative to other immunoassays and is a convenient and sensitive semiautomated method to measure CsA in whole blood.

Multi-site Analytical Evaluation of the Abbott ARCHITECT Tacrolimus Assay

The objective of this study was to evaluate the analytical performance of the Abbott ARCHITECT Tacrolimus immunoassay. Proficiency panels and specimens from a population of organ transplant recipients were analyzed in 6 clinical laboratories in Europe and the United States, and the results were compared with other methods. The ARCHITECT assay requires a whole blood specimen pretreatment step with methanol/zinc sulfate to precipitate protein and extract the drug, followed by a 30-minute immunoassay using anti-tacrolimus antibody-coated paramagnetic microparticles and an acridinium-tacrolimus tracer. The assay was free from hematocrit interference in the range 25%-55% and from interference by extremes of cholesterol, triglycerides, bilirubin, total protein, and uric acid. The total percent of coefficient of variations of the assay were 4.9%-7.6% at 3 ng/mL, 2.9%-4.6% at 8.6 ng/mL, and 3.1%-8.2% at 15.5 ng/mL. Limit of detection was < or =0.5 ng/mL and limit of quantification (LOQ) ranged from 0.69 to 1.07 ng/mL across the 6 sites (based on the upper 95% confidence interval concentrations). The 2007 European Consensus Conference on Tacrolimus Optimization recommended the use of assay methods with an LOQ around 1 ng/mL, based upon the need to measure trough tacrolimus blood concentrations precisely down to 3 ng/mL during low-dose tacrolimus regimens. Tacrolimus International Proficiency Testing Scheme samples were measured by the ARCHITECT immunoassay at 5 sites and showed an average bias of -0.28 to +0.85 ng/mL versus IMx Tacrolimus II immunoassay historical values and -0.21 to +0.68 ng/mL versus liquid chromatography/tandem mass spectrometry (LC-MSMS) Tacrolimus historical values. Method comparison studies were performed with the ARCHITECT Tacrolimus immunoassay on patient specimens with the following results: ARCHITECT Tacrolimus assay versus the Abbott IMx Tacrolimus II immunoassay (4 sites) yielded average biases between -0.94 and +0.26 ng/mL; ARCHITECT assay versus the Dade Dimension Tacrolimus immunoassay (2 sites) yielded average biases of -0.46 and +0.11 ng/mL; and ARCHITECT assay versus LC-MSMS methods at 2 sites yielded average biases of +0.51 and +1.63 ng/mL. Spearman correlation coefficients were >/=0.90 on all method comparisons. The ARCHITECT Tacrolimus assay is a semiautomated, robust, and highly sensitive immunoassay, representing an alternative approach for laboratories not equipped with LC-MSMS, and meets the 1 ng/mL recommendation of LOQ by the European Consensus Conference on Tacrolimus Optimization.

A rapid HPLC-MS/MS method for the simultaneous quantification of cyclosporine A, tacrolimus, sirolimus and everolimus in human blood samples

In the past few years, high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) has matured to a true alternative to antibody-based immunoassays in routine therapeutic drug monitoring. In transplantation medicine, mass spectrometry-based assessment of immunosuppressant drug levels is considered a gold standard diagnostic procedure. We describe a fast state-of-the-art routine online solid-phase extraction (SPE) HPLC-MS/MS analysis platform that allows monitoring of cyclosporine A, tacrolimus, sirolimus and everolimus from 50-microl aliquots of EDTA whole blood specimens within 3.4 min total analysis time. Sample purification is done by offline protein precipitation followed by two automated chromatographic separation steps. Mass spectrometry-based analyte quantification relies on selected reaction monitoring experiments. The assay underwent complete validation and performance evaluation studies and performs very well in several international proficiency testing schemes. In daily routine, it allows reporting of about 75 patient sample results per work shift with a typical total individual sample turnaround time of less than 3 h.

Comparative Study of Different Milk Samples Preservation Procedures for Bacteriologic Examination

The control of pathogenic bacteria present in foods, as well as scientific data concerning their behavior, are closely linked to analytical methods used and the way they are implemented. To assess the capacity of the laboratories to conduct correctly microbiological analyses, national and international proficiency testing schemes are organized. To set up these inter-laboratory studies (ILS), it is necessary to prepare artificially contaminated samples, which contamination level is sufficiently stable regarding their transportation conditions to the participating laboratories. In this context, we tested several procedures to maintain the concentration of Listeria monocytogenes and coagulase-positive staphylococci in milk samples: freezing temperature and addition of bacteriostatic agents at refrigeration temperatures, such as nystatin, boric acid, sodium azide, the lactoperoxidase system, or a boric acid mixture. Through this study we selected preservation procedures, which could be used to stabilize the contamination level of artificially contaminated milk samples during transportation without preventing the growth of the target bacteria during the analysis and after the initial dilution step. Boric acid mixture and boric acid were found to be effective in stabilizing the contamination level of Staphylococcus aureus in milk samples, whereas freezing, a boric acid mixture, and boric acid were suitable for milk samples containing L. monocytogenes, depending on the samples’ contamination rate.

Organic Solvents Compromise Performance of Internal Standard (Ascomycin) in Proficiency Testing of Mass Spectrometry-Based Assays for Tacrolimus

Therapeutic drug monitoring of immunosuppressive agents by liquid chromatography (LC) coupled with mass spectrometry (MS) can provide highly selective and sensitive quantification from biological fluids. Interlaboratory performance for cyclosporine, tacrolimus, and sirolimus, as assessed by LC/MS, in proficiency testing (PT) programs [e.g., College of American Pathologists (CAP) (1) and the International Proficiency Testing Scheme (IPTS) (2)] has been poor, albeit improving, although individual laboratories report excellent interassay imprecision (CV <5.5%) at drug concentrations across analytical ranges (3)(4)(5)(6). Lack of industry-wide standardization may contribute to variations in PT program performance across MS laboratories because it requires that those laboratories develop “home brew” assays, use reference materials with potentially different purities obtained from numerous sources, and prepare either whole-blood calibrator/quality-control (QC) materials in house or purchase commercial materials that may be verified only for a specific procedure. In addition, most PT samples are unlike routine specimens, being prepared from either artificial or whole-blood–like matrices (sometimes pooled patient blood) that are subjected to the rigors of batch preparation and shipping. I describe here an experience of specific and unusual performance of PT samples, which likely resulted from instabilities of the internal …

Quality control procedures for chloride and nitrate ions analysis in plant samples by ion chromatography

This paper describes useful procedures to monitor quality of chloride and nitrate ions analysis in plant samples by ion chromatography. The use of certified reference materials (CRMs) provided an efficient way to verify the accuracy of the method. Data generated by the method of analysis for chloride compared favourably with certified values. The quality system included also the systematic analysis of an internal reference sample in each batch of samples routinely analysed. The performance of the method, including extraction and measurement, over a period of 3 years was reported with control charts. The yearly variation coefficients were less than 6.5% for chloride and nitrate ions. Finally, the analytical method was evaluated through the participation of laboratory to an international proficiency testing scheme. Found results were not significantly different from published medians.