Article2010

An approach to integrated data assessment in a proficiency test on the enumeration of Escherichia coli

Wolfram Bremser · Friedrich‐Karl Lücke · C. Urmetzer · U. Leist

11 citations0/0 files storedJournal of Applied Microbiology

No readable copy stored yet — this record is metadata only.

No open-access location is known for this record yet.

Literature note Cite in a project Citation map

Scientific Measurement and Uncertainty Evaluation Clinical Laboratory Practices and Quality Control Food Safety and Hygiene

Abstract

AIMS: To develop appropriate statistical approaches to plan and evaluate proficiency tests for the enumeration of Escherichia coli, addressing, in particular, a possible but frequently unavoidable lack of test sample homogeneity. METHODS AND RESULTS: Each of 50 laboratories analysed two samples of a stabilized suspension of E. coli in duplicate, using various media, inoculation methods, and incubation times and conditions. In parallel, the E. coli suspension was tested by the organiser for homogeneity and stability. Escherichia coli counts followed a log-normal distribution. After eliminating, by Youden analysis, two data sets that were considered outliers and eight data sets for underperformance of the laboratories (substantial lack of repeatability), the standard deviation of the mean was about 0·06 log(10) units. There was no evidence of bimodality of the data. Lack of homogeneity of distribution of bacteria had a strong effect on measurement uncertainty, in addition to laboratory bias and method repeatability. The homogeneity decreases during storage of the individual test vials; this effect could be modelled by the known kinetics of inactivation of micro-organisms. The results were confirmed by Monte Carlo simulations. CONCLUSIONS: By a tailored analysis of proficiency testing data, it is possible to distinguish the effect of lack of homogeneity, laboratory bias and method repeatability, on the measurement uncertainty. SIGNIFICANCE AND IMPACT OF THE STUDY: A statistic tool is provided to solve problems related to lack of stability of microbiological test material and to separate the effects of sample inhomogeneity from the performance of the individual laboratory.

Paper brief

Loading…

Cite this work

Citation unavailable for this work.

BibTeX RIS CSL-JSON

No public copy is stored for this record, so only the metadata is cited.

Citations in this library

Citation map →

Stored only when both papers are in the corpus — 11 citations exist upstream.

References

1958On Growth Measurement 2005General requirements for the competence of testing and calibration laboratories 2005Statistical methods for use in proficiency testing by interlaboratory comparisons 2006A critical review of measurement uncertainty in the enumeration of food micro-organisms 2005Lessons from the organization of a proficiency testing program in food microbiology by interlaboratory comparison: Analytical methods in use, impact of methods on bacterial counts and measurement uncertainty of bacterial counts 2007Assessment of measurement uncertainty for quantitative methods of analysis: Comparative assessment of the precision (uncertainty) of bacterial colony counts 2007Development of reference materials for microbiological analysis 2006Estimation of measurement uncertainty in food microbiology: The ISO approach

Explore the map →

Papers that cite the same references — the relational fallback while embeddings are still backfilling.

Imported from OpenAlex (CC0) — nothing here is generated.