The Quality of Fiber Count Data

Abstract Optical fiber counts are used to determine asbestos exposure, so it is important to assess, control, and document the quality of those counts. These functions are the responsibility of the quality assurance (QA) coordinator in each laboratory. The QA coordinator must recognize that, compared to the analytical results for other substances, fiber count data are much more variable and have different statistical properties. These data, therefore, warrant special treatment. This article discusses the need to recount some samples, the procedures for determining bias and variability from these recount data, and the use of these statistics to test analytical results or assign confidence limits to them. Three kinds of bias and variability must be considered: intracounter, intra-laboratory, and interlaboratory. As data pairs (count and recount) are obtained, the first consideration is whether bias is present. If bias is detected in a set of data, that data should not be used for any purpose until the sourc...