Preliminary Report on the Results of the Second Phase of a Round-Robin Endotoxin Assay Study Using Cotton Dust

Abstract

In an on-going endotoxin assay study, a two-part interlaboratory endotoxin assay study has been completed. The purpose of the study was to compare the variation in assay results between different laboratories, and, if the variation was high, to see if a common protocol would reduce the variation. In both parts of the study, membrane filters laden with the same approximate amount and type of cotton dust were sent for analysis to laboratories that "routinely" perform endotoxin analyses. First, each of these laboratories performed the analysis using the methodology common to its laboratory. In the second part of the study, membrane filters with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The preliminary results from the first phase of the study have been collected and showed that intra-laboratory variations were small, but large and significant interlaboratory variation was observed. The results were reported elsewhere. The preliminary results from the second part of the study consisting of the data currently collected are presented here. Again, intra-laboratory variations were small, but, also again, large and significant inter-laboratory variation was observed. However, in this part of the study, the range between the highest and lowest average results was narrower than in the first part of the study. Influence of the assay kit type was examined. The variation within assay kit type was small but significant differences in results were observed between assay kit types. The findings suggest that endotoxin concentration in samples can be ranked within laboratories, but not necessarily between laboratories. However, some of the variation between laboratories has been reduced by a common extraction protocol which suggests the possibility of further standardization that may lead to better comparability between laboratories.

Endotoxins in Indoor Air and Settled Dust in Primary Schools in a Subtropical Climate

“…Similarly, a ij and τ a ij were defined for the airborne measurements. The metaregression model was then given as (4) where the meta-analysis estimate, θ ij , contained an estimate of the background level of floor dust endotoxin, β 0 , and the rate at which dust endotoxin occurred with respect to airborne endotoxin, β 1 . A 95% credible interval for β 1 , which contained zero, indicated that at a level of 95% there was no relationship between the indoor air concentration and floor dust load.…”

Characterization of the Microbial Community in Indoor Environments: a Chemical-Analytical Approach

“…Direct microscopy is at best semiquantitative. Although the Limulus amebocyte lysate test is extremely sensitive to endotoxin and can detect glucans, it measures bioactivity rather than absolute amounts and its reproducibility and specificity have been questioned (5). Nucleic acid-based methods including PCR are very specific, and by using broad-range (universal) probes and primers sets based on 16S rDNA (20) and 18S rRNA (31), most bacteria and fungi present in a sample can be identified.…”

Comparison of Endotoxin Assays Using Agricultural Dusts

“…(32,40,41) Researchers have investigated differences in collection filter material, extraction media, and extraction time. (29,32,39) Gordon et al suggested that aerosol binding to filters can be affected by chemical and physical differences in the filters, thus causing variation in endotoxin extraction. (34) Using an endpoint chromogenic method, Gordon et al found significantly higher recoveries of endotoxin from glass fiber and cellulose acetate filters compared with polycarbonate, polyvinyl chloride, polysulfone, and polytetrafluoroethylene filters.…”

“…(28)(29)(30) Variability in endotoxin evaluation methods reported to date include sample environment (dust type); collection of sample (pumps, flow rates, filter types); sample handling and storage (use of desiccant, storage temperature); analysis of sample (extraction media, extraction time, rocking, sonication, temperature, assay type, control standards); and reporting of results (units). (32)(33)(34)(35)(36)(37)(38)(39)(40) The composition of organic dust from different environments is variable, and thus could alter the outcome of analysis through differences in type of endotoxin, and inhibition or enhancement. (32,40,41) Researchers have investigated differences in collection filter material, extraction media, and extraction time.…”

“…(38,39) Twelve laboratories participated in the first phase and 13 in the second phase. Cotton dust was collected on PVC filters in a model cardroom.…”