Continued participation in an asbestos fiber-counting proficiency test with relocatable grid slides

Our plain-English summary of Continued participation in an asbestos fiber-counting proficiency test with relocatable grid slides, by M. Harper, J.E. Slaven, T.W. Pang (Journal of Environmental Monitoring, 2009).

The study

• Authors: M. Harper, J.E. Slaven, T.W. Pang
• Journal: Journal of Environmental Monitoring
• Published: 2009;11(2):434-8
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The effect of using relocatable reference slides of chrysotile and amosite in asbestos fiber counting proficiency testing was examined for volunteer analysts from laboratories in the USA. Results of participation in one round have been published; two more rounds are reported here. In the first round, participants were asked to draw what they saw, allowing identification of error type by comparison to the reference. In later rounds only the number of fibers per field was reported since the number of errors per field has been shown to be a reasonable estimate of proficiency. The third round included a training exercise. The total number of participants stayed reasonably constant with some reduction over time. More restricted numbers participated from round to round. Those who dropped out had lower average scores than those that remained in the program; from 2006 to 2007 this difference was significant, but for 2007 to 2008 it was not. The overall results for amosite were generally good compared to an arbitrary proficiency score of 60, and continued to improve further over time. The results for chrysotile were better in rounds 1 and 3 than round 2, so that both attention to detail (drawing the fibers in round 1) and training (round 3) may improve performance, which is consistent with the major type of error being oversight of fine fibers. However, the results are still poor, even by round 3, and no analyst achieved a score of 60 in all three rounds. Further improvement is preferred since chrysotile is the most commonly encountered type of asbestos in the USA. Depending on the adopted score for proficiency many laboratories or analysts may be labeled as poor performers and this may be a deterrent to voluntary participation in this type of exercise, especially for those in most need of assistance. Participants have tested new relocatable reference asbestos proficiency counting slides in three rounds of chrysotile and three rounds of amosite. Performance for amosite was good. Poor performance for chrysotile appears to be improved by greater attention and training.

In plain English

This study did not look at health effects. It tested how accurately laboratory analysts count asbestos fibers under a microscope. Volunteer analysts from US laboratories counted fibers on reference slides of chrysotile and amosite fitted with a relocatable grid, in three yearly rounds from 2006 to 2008. Their counts were scored against fibers agreed by reference analysts, and a score of 100 was considered optimal. Round 1 results had been published earlier, and round 3 included a training exercise. For chrysotile, the average score of all participants was 48.3, 44.6 and 53.8 in rounds 1 to 3. For amosite it was 52.0, 60.8 and 71.1. Among 27 analysts who took part in all three chrysotile rounds, the average rose from 51.7 to 55.5, a statistically significant rise. No analyst scored 60 or more in all three chrysotile rounds. Analysts who dropped out after round 1 had significantly lower average scores than those who stayed. The authors concluded that performance for amosite was good, and that poor performance for chrysotile appears to improve with greater attention and training.

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: Proficiency-testing pilot project in three rounds (2006, 2007, 2008) using relocatable-grid reference ("REF") slides. Round 1 results were published previously; rounds 2 and 3 are reported here. Score changes were compared with t-tests.
• Who was studied: Volunteer asbestos fiber-counting analysts from laboratories in the USA, with participation varying from round to round
• Exposure: Not a human exposure study. Analysts counted fibers on reference slides made from chrysotile and amosite proficiency test filters, using phase-contrast microscopy, and were scored against fibers verified by reference analysts.
• Main results:
  • Chrysotile participation: round 1 (2006) had 31 laboratories and 60 analysts, 27 of whom took part in all three rounds. Round 2 had 29 laboratories and 54 analysts; round 3 had 29 laboratories and 53 analysts.
  • Chrysotile, all participants in round 3 (2008): average score 53.8, with 41.5% proficient. In round 1 the average was 48.3 and in round 2 it was 44.6.
  • Amosite, all participants in round 3 (2008): average score 71.1, with 83.9% proficient. In round 1 the average was 52.0 and in round 2 it was 60.8.
  • Analysts who took part in all three chrysotile rounds (N equal to 27): average score rose from 51.7 to 55.5 (p equal to 0.04, significant). For amosite (N equal to 29) the average rose from 65.2 to 74.9, which was not significant (p equal to 0.33).
  • Those who dropped out after round 1 had significantly worse average scores than those who stayed, for both chrysotile and amosite. Drop-outs after round 2 also had lower average scores, but the difference was not significant.
  • Chrysotile: analysts who scored well in 2006 did significantly worse in 2007. In the table, those scoring 60 or more in round 1 (N equal to 10) fell from 70.2 to 42.6, p 0.0009.
  • Chrysotile: the average score of those who scored below 60 in 2007 and took part in 2008 rose significantly. In the table, N equal to 33 rose from 41.4 to 54.5, p 0.0009.
  • Overall chrysotile group performance improved significantly in round 3, which the authors attributed, presumably, to the training component.
  • No analyst scored 60 or above in all three chrysotile rounds.
  • In round 3, 68% of chrysotile participants met or exceeded a score of 50, compared with 72% in the last Canadian round.
  • For amosite, performance was better overall than for chrysotile.
• The authors' conclusion: The authors concluded that performance for amosite was good, and that poor performance for chrysotile appears to be improved by greater attention and training. They suggested that the REF slides be used in proficiency testing and added to required analyst training programs.
• Limitations the authors state:
  • Analysts who stayed in the study were likely above-average performers, which the authors said raises doubts about the performance of analysts who chose not to take part.
  • Low numbers of amosite analysts scoring below 60 gave less statistical power to detect differences.
  • The proficiency score of 60 was arbitrary and was used only as a divider for comparison in this study.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Amosite, Fiber Counting.

Related studies

• The quality of fiber counts using improved slides with relocatable fields — T.W. Pang, M. Harper (2008)
• A comparison of fibre counting across three European national proficiency testing schemes — A.D. Jones, M.C. Arroyo, et al. (2005)
• Producing samples for the organization of proficiency tests. Study of the homogeneity of replicas produced from two atmosphere generation systems — L. Freville, J.C. Moulut, et al. (2010)
• Proposal to adapt the WASP programme to fibre counting tests — M. Grzebyk, E. Kauffer, et al. (2006)
• A proposal for harmonising laboratory performance assessment criteria in national asbestos fibre counting schemes — M.C. Arroyo, J.M. Rojo (2001)
• The effect of a proposed change to fiber-counting rules in ASTM International Standard D7200-06 — M. Harper, E.G. Lee, et al. (2007)

Browse more research in Journal of Environmental Monitoring, or return to medical research.