Review of micro- and nanoplastic contamination in the food chain.

Whereas the dramatic environmental impact of plastic waste rightfully receives considerable attention by scientists, policy makers and public in general, the human health impact of micro- and nanoplastics contamination of our food and beverages remains largely unknown. Indeed, most studies aim at understanding the environmental impact rather than the human health impact of a possible exposure to micro- and nanoplastics. In addition, these papers generally lack a methodological, standardised approach. Furthermore, some studies focus on the damage to and contamination level of animal species collected from the wild environment, and others investigate the rate and biology of microplastic uptake of animals fed with microplastics in laboratory. This review aims at understanding human exposure. Since there is, with few exceptions, no evidence available on the presence of micro- and nanoplastics in a normal diet, this study takes an indirect approach and analyses peer-reviewed publications since 2010 that document the presence of micro- and nanoplastics in those animals (more than 200 species) and food products that are part of the human food chain and that may thus contribute directly or indirectly to the uptake of micro- and nanoplastics via the human diet. It also addresses the question of the definitions, the methodologies and the quality criteria applied to obtain the reported results. This review suggests that, beyond a few estimations and comparisons, precise data to assess the exact exposure of humans to micro- and nanoplastics through their diet cannot be produced until standardised methods and definitions are available.

Commutability Assessment of Candidate Reference Materials for Pancreatic α-Amylase.

BACKGROUND: Measurement standardization of the catalytic concentration of α-amylase in serum is based on 3 pillars: the primary reference measurement procedure (PRMP), reference laboratories, and suitable certified reference materials (CRMs). Commutability is a prerequisite when using a CRM for calibration and trueness control of routine methods or for value transfer from the PRMP to end-user calibrators of routine methods through a calibration hierarchy. METHODS: We performed a commutability study with 30 serum pools and 5 candidate reference materials (RMs) for pancreatic α-amylase using an automated version of the PRMP and 5 different routine methods. Four candidate RMs had an artificial matrix, each with a different composition, and 1 candidate RM was based on human serum. Data were analyzed according to a linear regression analysis with prediction interval as described in the Clinical and Laboratory Standards Institute guideline EP30-A and a difference in bias analysis as described in the recommendations of the IFCC Working Group on Commutability. RESULTS: The commutability profile of the 4 candidate RMs with an artificial matrix was variable. Only 1 candidate RM, with human serum albumin in the matrix, showed a good profile like that of the candidate RM based on serum. The comparison of both commutability assessment approaches indicated some differences because of inconclusive results for the difference in bias approach, suggesting a large uncertainty on the commutability assessment. CONCLUSIONS: A CRM for pancreatic amylase in an artificial matrix can be commutable for routine methods using the same substrate as the PRMP, but the matrix composition is crucial.

Traceability of values for catalytic activity concentration of enzymes: a Certified Reference Material for aspartate transaminase.

BACKGROUND: A new reference material for the liver enzyme aspartate transaminase (AST) (L-aspartate: 2-oxoglutarate-aminotransferase, EC 2.6.1.1), also called aspartate aminotransferase (ASAT), has been developed under the code ERM-AD457/IFCC. This certified reference material (CRM) for AST has been produced from a human type recombinant AST expressed in Escherichia coli and a buffer containing bovine serum albumin, and has been lyophilised. METHODS: The homogeneity and the stability of the material have been tested and the catalytic activity concentration has been characterised by 12 laboratories using the reference procedure for AST at 37 degrees C from the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). RESULTS: The certified catalytic activity concentration and certified uncertainty of AST in the reconstituted material are (1.74+/-0.05) microkat/L or (104.6+/-2.7) U/L (with a coverage factor k=2; 95% confidence interval). CONCLUSIONS: Both the certified value and uncertainty are traceable to the International System of Units (SI). The material is aiming to control the IFCC reference procedure for AST at 37 degrees C, which will then be used to assign values to calibrants and control materials. The present paper highlights the scientific challenges and innovations which were encountered during the development of this new CRM.

Report of the IFCC Working Group for Standardization of Thyroid Function Tests; part 3: total thyroxine and total triiodothyronine.

BACKGROUND: Because total thyroid hormone testing is performed on many automated clinical chemistry instruments, the IFCC Scientific Division commissioned the Working Group for Standardization of Thyroid Function Tests to include total thyroxine (TT4) and total triiodothyronine (TT3) in its standardization efforts. METHODS: Existing SI-traceable reference measurement procedures (RMPs) were used to assign TT4 and TT3 values to 40 single-donor serum samples for subsequent use in a method comparison study with 11 TT4 and 12 TT3 immunoassays. Data from comparison of each immunoassay with the RMPs provided a basis for mathematical assay recalibration. RESULTS: Seven TT4 assays had a mean bias within 10% of the RMP, but 2 deviated by an average of -12% and another 2 by +17%. All TT3 assays showed positive biases, 4 within and 8 outside 10%, up to 32%. Mathematical recalibration effectively eliminated assay-specific biases, but sample-related effects remained, particularly for TT3. Correlation coefficients with the RMPs ranged from 0.82 to 0.97 for TT4 and from 0.32 to 0.92 for TT3. The within-run and total imprecision ranges for TT4 were 1.4% to 9.1% and 3.0% to 9.4%, respectively, and for TT3 2.1% to 7.8% and 2.8% to 12.7%, respectively. Approximately one-half of the assays matched the internal QC targets within approximately 5%; however, we observed within-run drifts/shifts. CONCLUSIONS: The study showed that of the assays we examined, only 4 TT4 but the majority of the TT3 assays needed establishment of calibration traceability to the existing RMPs. Most assays performed well, but some would benefit from improved precision, within-run stability, and between-run consistency.

Report of the IFCC Working Group for Standardization of Thyroid Function Tests; part 2: free thyroxine and free triiodothyronine.

BACKGROUND: Free thyroxine (FT4) and free triiodothyronine (FT3) measurements are useful in the diagnosis and treatment of a variety of thyroid disorders. The IFCC Scientific Division established a Working Group to resolve issues of method performance to meet clinical requirements. METHODS: We compared results for measurement of a panel of single donor sera using clinical laboratory procedures based on equilibrium dialysis-isotope dilution-mass spectrometry (ED-ID-MS) (2 for FT4, 1 for FT3) and immunoassays from 9 manufacturers (15 for FT4, 13 for FT3) to a candidate international conventional reference measurement procedure (cRMP) also based on ED-ID-MS. RESULTS: For FT4 (FT3), the mean bias of 2 (4) assays was within 10% of the cRMP, whereas for 15 (9) assays, negative biases up to -42% (-30%) were seen; 1 FT3 assay was positively biased by +22%. Recalibration to the cRMP eliminated assay-specific biases; however, sample-related effects remained, as judged from difference plots with biologic total error limits. Correlation coefficients to the cRMPs ranged for FT4 (FT3) from 0.92 to 0.78 (0.88 to 0.30). Within-run and total imprecision ranged for FT4 (FT3) from 1.0% to 11.1% (1.8% to 9.4%) and 1.5% to 14.1% (2.4% to 10.0%), respectively. Approximately half of the manufacturers matched the internal QC targets within approximately 5%; however, within-run instability was observed. CONCLUSIONS: The study showed that most assays had bias largely correctable by establishing calibration traceability to a cRMP and that the majority performed well. Some assays, however, would benefit from improved precision, within-run stability, and between-run consistency.

Report of the IFCC Working Group for Standardization of Thyroid Function Tests; part 1: thyroid-stimulating hormone.

BACKGROUND: Laboratory testing of serum thyroid-stimulating hormone (TSH) is an essential tool for the diagnosis and management of various thyroid disorders whose collective prevalence lies between 4% and 8%. However, between-assay discrepancies in TSH results limit the application of clinical practice guidelines. METHODS: We performed a method comparison study with 40 sera to assess the result comparability and performance attributes of 16 immunoassays. RESULTS: Thirteen of 16 assays gave mean results within 10% of the overall mean. The difference between the most extreme means was 39%. Assay-specific biases could be eliminated by recalibration to the overall mean. After recalibration of singlicate results, all assays showed results within the biological total error goal (22.8%), except for 1 result in each of 4 assays. For a sample with a TSH concentration of 0.016 mIU/L, 6 assays either did not report results or demonstrated CVs >20%. Within-run and total imprecision ranged from 1.5% to 5.5% and 2.5% to 7.7%, respectively. Most assays were able to match the internal QC targets within 5%. Within-run drifts and shifts were observed. CONCLUSIONS: Harmonization of TSH measurements would be particularly beneficial for 3 of the 16 examined assays. These data demonstrate that harmonization may be accomplished by establishing calibration traceability to the overall mean values for a panel of patient samples. However, the full impact of the approach must be further explored with a wider range of samples. Although a majority of assays showed excellent quality of performance, some would benefit from improved within-run stability.

Proposal of a candidate international conventional reference measurement procedure for free thyroxine in serum.

In the present paper the IFCC WG-STFT recommends and provides the rationale to establish metrological traceability of serum free thyroxine (FT4) measurements to a candidate international conventional reference measurement procedure. It is proposed that this procedure be based on equilibrium dialysis combined with determination of thyroxine in the dialysate with a trueness-based reference measurement procedure. The measurand is thus operationally defined as "thyroxine in the dialysate from equilibrium dialysis of serum prepared under defined conditions". With regard to the trueness-based reference measurement procedure, the WG-STFT recommends use of an isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC/tandem MS) procedure for total thyroxine that has been optimized towards measurement at picomolar concentration levels and that is listed in the database of the Joint Committee for Traceability in Laboratory Medicine (JCTLM). For calibration, the purified thyroxine material IRMM-468 (resulting from a project funded by the European Commission and recently submitted to the JCTLM) is proposed. The WG-STFT stresses that according to this recommendation it is a prerequisite to strictly adhere to the defined equilibrium dialysis procedure, whereas it is permissible to introduce variants in the ID-LC/tandem MS procedure.

Multiresidue determination of (fluoro)quinolone antibiotics in swine kidney using liquid chromatography-tandem mass spectrometry.

New antibiotics were recently developed, among which are the (fluoro)quinolones. This paper presents an analytical method which allows the determination of 11 (fluoro)quinolones in swine kidneys: norfloxacin, ofloxacin, cinoxacin, oxolinic acid, nalidixic acid, flumequine, enrofloxacin, enoxacin, ciprofloxacin, danofloxacin and marbofloxacin. The procedure involves a rapid and efficient pre-treatment by solid-phase extraction (recoveries 83-98%), followed by the sensitive and selective determination of all compounds in a single run using LC-ESI-MS-MS. Multiple reaction monitoring (MRM) was used for selective detection of each (fluoro)quinolone. Quinine was selected as internal standard. The accuracy of the method, expressed as recovery, was between 89 and 109%; the repeatability had a maximum RSD lower than 15%. The limits of detection (LOD) were much lower than the respective Maximum Residue Limits (MRL)/4.