Reproducibility of low galactomannan enzyme immunoassay index values tested in multiple laboratories.

Published

Journal Article

The Platelia galactomannan enzyme immunoassay is a commercially available nonculture method for diagnosing invasive aspergillosis. Recently, steps have been taken to improve sensitivity; specifically, a low (0.5 to 0.7) galactomannan index (GMI) value to determine positivity has been validated by multiple groups. We evaluated the intra-assay and interassay reproducibility at low index levels using three different kit lots on three different days in three different microbiology laboratories. Clinical and spiked sera were blinded and sent with galactomannan enzyme immunoassay (EIA) kits to the participating laboratories. We also prospectively collected data on all galactomannan EIAs performed between 1 September 2003 and 21 July 2004 at the University of Washington Medical Center microbiology laboratory to assess reproducibility of clinical samples analyzed in "real time." From the multilaboratory study, a total of 836 results were available for evaluation. Reproducibility was excellent between laboratories and on different days. Significant variability was seen between runs/lots, which may in part be associated with different threshold control values in different kits. Among the 1,410 clinical samples that were prospectively analyzed, 168 (90%) were confirmed to be positive on repeat testing (GMI, > or =0.5). Among the 19 (10.2%) initially positive samples not confirmed on repeat testing, the majority had a GMI at the threshold of the assay (between 0.5 and 0.7). Our findings suggest that the Platelia galactomannan immunoassay has good reproducibility. However, changes in GMI levels when different kit lots are used, and single samples with low-positive (GMI of 0.5 to 0.7) indices, should be interpreted with caution.

Full Text

Duke Authors

Cited Authors

  • Upton, A; Gugel, A; Leisenring, W; Limaye, A; Alexander, B; Hayden, R; Marr, KA

Published Date

  • September 2005

Published In

Volume / Issue

  • 43 / 9

Start / End Page

  • 4796 - 4800

PubMed ID

  • 16145143

Pubmed Central ID

  • 16145143

International Standard Serial Number (ISSN)

  • 0095-1137

Digital Object Identifier (DOI)

  • 10.1128/JCM.43.9.4796-4800.2005

Language

  • eng

Conference Location

  • United States