Digital PCR is rapidly being adopted in the field of DNA-based food analysis. The direct, absolute quantification it offers makes it an attractive technology for routine analysis of food and feed samples for their composition, possible GMO content, and compliance with labelling requirements. However, assessing the performance of dPCR assays is not yet well established. This article introduces three straightforward parameters based on statistical principles that allow users to evaluate if their assays are robust. In addition, we present post-run evaluation criteria to check if quantification was accurate. Finally, we evaluate the usefulness of Poisson confidence intervals and present an alternative strategy to better capture the variability in the analytical chain.

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Dehydrin-like proteins have been detected in nuclei and cytoplasm of meristematic root tip cells from pea seedlings subjected to slow dehydration at 90 % relative humidity for 48 h or more. Evidence was gained from Western blotting and immunocytochemical experiments using an antibody raised against the conserved domain of dehydrin proteins. Flow cytometer analysis has shown that cycling cells of root tip meristems from dehydrated seedlings are mostly arrested in G2 phase. Other stress treatments thought to involve water depletion (osmotic stress, cold treatment) or to modulate cell response to water deficit (abscisic acid) gave less clear-cut results with all treatments lowering the proportion of cells entering the S phase, but without a definite and persistent arrest in any preferential phase of the cycle. Possible interrelationships between G2 arrest and dehydrin production are discussed.# 1997 Annals of Botany Company

Quality assurance is a prerequisite for accurate and reliable results in food and feed testing, ISO/IEC 17025 being recognized worldwide as the base standard. A flexible scope of accreditation enables testing laboratories to react quickly to customer demand and to cope with the large number of new methods, which have to be introduced in the laboratory. Precisely defined procedures for the validation of methods, together with performance and acceptance criteria, are the key points for flexible scope of accreditation. Testing for genetically modified organisms (GMO) is a challenging exercise, especially with more GMOs entering the world market. We describe here the organization and performance of validating quantitative detection methods for GMO testing in the context of the European Union legislation. Operational procedures for method validation organized by the Community Reference Laboratory for Genetically Modified Food and Feed, assisted by the European Network of GMO Laboratories, are described. A protocol for validating methods within an individual laboratory is proposed and discussed in terms of the requirements of flexible scope of accreditation. The system setup can be an example for other similar fields of analytical work.

Background: Albuminuria is the best and most readily available marker for glomerular damage and progressive renal function loss in patients with diabetic nephropathy. Recently, administration of the oral glycosaminoglycan sulodexide (a mixture of 80% fast-moving heparin and 20% dermatan sulphate) was shown to effectively decrease albumin excretion rate in diabetics with nephropathy. Aims: To evaluate whether the hypoalbuminuric effect of sulodexide is associated with improvement of the renal vascular or tubule function. Methods: Forty-five type 1 diabetic patients, affected by diabetic nephropathy with albuminuria for at least 5 years, were randomly allocated to sulodexide or untreated. Those allocated to sulodexide were given 100 mg of sulodexide daily for 120 days. Renal vascular function (DIR) and N-acetyl-β-D-glucosaminidase (NAG) excretion were estimated before and at the end of the study, the former in thesulodexide group only. DIR was measured as two Cr_cl lasting 120 min (before and during 2 µg/kg b.w. i.v. dopamine). Results: The analysis of trends during the study demonstrated a marked reduction of albuminuria in the sulodexide group (from 126.1 ± 15.41 to 93.6 ± 13.7 mg/day). DIR rose from 13.2 ± 2.1% to 15.44 ± 1.9% (relative increase: +16.9%), and NAG excretion showed a decreasing trend decreased in the sulodexide group only (from 5.1 ± 0.62 to 4.7 ± 0.40 U/g_creat). Conclusion: The findings presented in this study indicate for the first time that orally available sulodexide may favorably affect the renal vascular function in type 1 diabetic patients with nephropathy and microalbuminuria. The effect of sulodexide on NAG is strongly influenced by the baseline NAG values, with a significant NAG reduction in the patients with the highest baseline NAG values.

In this study, we developed, optimized, and in-house validated a real-time PCR method for the event-specific detection and quantification of Golden Rice 2, a genetically modified rice with provitamin A in the grain. We optimized and evaluated the performance of the taxon (targeting rice Phospholipase D α2 gene)- and event (targeting the 3' insert-to-plant DNA junction)-specific assays that compose the method as independent modules, using haploid genome equivalents as unit of measurement. We verified the specificity of the two real-time PCR assays and determined their dynamic range, limit of quantification, limit of detection, and robustness. We also confirmed that the taxon-specific DNA sequence is present in single copy in the rice genome and verified its stability of amplification across 132 rice varieties. A relative quantification experiment evidenced the correct performance of the two assays when used in combination.

Validation is the process establishing the suitability of an analytical method for a particular purpose. Various guidelines defining statistical procedures for validation of chemical, bio-chemical, pharmaceutical, and molecular methods have been developed, and ad hoc validation metrics (indices and test statistics) are available and routinely used, for in-house and interlaboratory testing and decision making. However, there is no universally accepted practice for assay validation, and often, subjectivity plays an important role in the interpretation of validation studies' results. Instead, the key to rational validation studies relies upon the formalization and harmonization of procedures for their design and interpretation of results. Fuzzy-based techniques can be helpful in such respect. Fuzzy logic allows summarizing the information obtained by classic independent validation statistics into one synthetic index of overall method performance. The possibility of having a comprehensive indicator of method performance has the advantage of permitting direct method comparison, facilitating the evaluation of many individual, possibly contradictory metrics. The objectives of this paper are to illustrate the advantages that a fuzzy-based aggregation method could bring into the validation of analytical methods and to propose its application for the evaluation of methods' performance. Validation metrics are compared for practical examples of assessment of method performance in collaborative studies. Fuzzy logic-based rules are shown to be applicable to improve insights into method quality and interpretation of results.