A proposal for harmonising laboratory performance assessment criteria in national asbestos fibre counting schemes

Our plain-English summary of A proposal for harmonising laboratory performance assessment criteria in national asbestos fibre counting schemes, by M.C. Arroyo, J.M. Rojo (The Annals of Occupational Hygiene, 2001).

The study

• Authors: M.C. Arroyo, J.M. Rojo
• Journal: The Annals of Occupational Hygiene
• Published: 2001;45(6):447-55
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Four European national asbestos fibre counting proficiency testing schemes have been studied in order to compare their criteria for the assessment of laboratory performance. Performance assessment is based on each laboratory's results after counting a certain number of samples. Two methods are currently being applied. To be classified 'satisfactory' laboratories must obtain at least 75% of normalised counts lying within defined performance limits (in three schemes), or the median and coefficient of variation of normalised counts must be within performance limits (in the fourth scheme). Differences in the numbers of test samples mean that the schemes are operating with different selectivity in assessing their laboratories' performances. Differences in the percentage of laboratory results falling within performance limits indicate that the schemes do not operate the same confidence probability in correctly assessing individual counts. It means that some schemes may be more lenient than others. This paper discusses two proposals to move towards harmonisation of the asbestos fibre counting proficiency testing schemes: (i) standardisation of the number of samples used for laboratory assessment and (ii) changes to the criteria to establish the limits of satisfactory performance.

In plain English

This paper compared how four European national proficiency testing schemes for asbestos fibre counting (Belgian, French, UK RICE and Spanish PICC-FA) judged performance. Three schemes assessed laboratories, while the French scheme assessed individual counters. It studied quality-control rules, not anyone's health or exposure. Assessment used 32 samples in the UK and Spain, 21 in France, and 20 to 24 in Belgium. Between 81% and 87% of laboratories in the Spanish and Belgian schemes, and of individual counters in the French scheme, were rated satisfactory. All laboratories in the RICE scheme were rated satisfactory in this dataset. The authors proposed that all schemes use 32 samples and set limits enclosing the central 85% of results. When tried on the data, this narrowed the satisfactory band in every scheme and brought the schemes closer together. The authors concluded that some schemes appear more lenient than others. They assumed an earlier finding held here: imposing one scheme's full assessment criteria on another's data left laboratory assessments unchanged. They excluded counts with reference values below 64 fibres per square millimetre.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: comparative analysis of the laboratory performance assessment criteria and data of four national proficiency testing schemes, with a proposal for harmonisation
• Who was studied: four European national asbestos fibre counting proficiency testing schemes (Belgian, French, UK RICE, Spanish PICC-FA) and their participants, using data from their last laboratory performance assessments (1996–1997); three schemes assess laboratories, the French scheme assesses individual counters
• Exposure: not an exposure study; test samples were fibre-bearing membrane filters (fiber types not named) from asbestos removal operations, the asbestos industry and laboratory-generated dust from asbestos-containing materials
• Main results:
  • Number of samples used for laboratory assessment: 32 in UK RICE and Spanish PICC-FA, 21 in the French scheme, 20 to 24 in the Belgian scheme
  • 81–87% rated satisfactory in PICC-FA, the Belgian and the French schemes (laboratories in the first two, individual counters in the French scheme)
  • All laboratories in the RICE scheme were rated satisfactory in this dataset
  • The authors interpreted the differences in laboratory classification as suggesting some schemes are more lenient than others
  • The authors simulated new limits covering the central 85% of each scheme's normalised counts (7.5th to 92.5th percentile)
  • Proposed upper outer limits: 1.26 (PICC-FA), 1.46 (Belgian), 1.45 (RICE), 1.50 (French), compared with present upper limits of 1.35, 1.67 and 2.00 for the first three
  • Proposed lower outer limits: 0.74 (PICC-FA), 0.57 (Belgian), 0.56 (RICE), 0.48 (French), compared with present lower limits of 0.65, 0.60 and 0.5 for the first three
  • Under the proposed criterion the band of satisfactory performance tightened in all schemes
  • Under the proposed criterion the schemes agreed more closely on the positions of the performance limits
  • The authors proposed that the two schemes using fewer samples increase to 32
• The authors' conclusion: The authors proposed that all schemes use 32 samples for laboratory assessment and set performance limits to include the same percentage (85%) of the population of results, so that schemes run with the same probability of a 'satisfactory' assessment
• Limitations the authors state:
  • An earlier comparison between AFRICA and PICC-FA imposed each scheme's full assessment criteria on the other's data, meaning both its reference-count calculation and its performance limits together. Laboratory performance assessment was not affected, although classification of individual counts differed. The authors assumed, without testing it here, that this also applies to the four schemes studied.
  • Counts with reference values below 64 fibres/mm2 (low-density samples) were discarded to simplify the analysis
  • The authors attributed the remaining differences to the nature of each scheme's test samples, which they said still needs careful study

Related studies

• A comparison of fibre counting across three European national proficiency testing schemes — A.D. Jones, M.C. Arroyo, et al. (2005)
• Statistical uncertainties in asbestos-laboratory classification through the RICE scheme — T.L. Ogden (1984)
• Proposal to adapt the WASP programme to fibre counting tests — M. Grzebyk, E. Kauffer, et al. (2006)
• Within-laboratory quality control of asbestos counting — T.L. Ogden, T. Shenton-Taylor, et al. (1986)
• Evaluation of airborne asbestos exposure from routine handling of asbestos-containing wire gauze pads in the research laboratory — E. Garcia, D. Newfang, et al. (2018)
• A PC-based quality control (QC) program for an industrial hygiene laboratory — D.K. Verma, K. Ferguson, et al. (2006)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.