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Clinical and Diagnostic Laboratory Immunology, January 1999, p. 89-95, Vol. 6, No. 1
CIRID at University of California,
Received 29 June 1998/Returned for modification 25 August
1998/Accepted 12 October 1998
Cytokines and soluble immune activation markers that reflect
cytokine activities in vivo are increasingly being measured in plasma,
serum, and other body fluids. They provide useful diagnostic and
prognostic information as well as insight into disease pathogenesis. Assays of neopterin,
1071-412X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Variables That Affect Assays for Plasma Cytokines
and Soluble Activation Markers
2-microglobulin, soluble interleukin-2
receptor, and soluble tumor necrosis factor receptor type II as well as of the cytokines tumor necrosis factor alpha and gamma interferon (IFN-
) were evaluated by using serum and plasma samples of human immunodeficiency virus (HIV)-positive and HIV-negative subjects. Many
factors were found to influence the outcomes of these assays. Substantial differences in apparent levels of analytes were frequently found when enzyme-linked immunosorbent assay (ELISA) kits from different manufacturers were used. In some cases, differences were
found in the standards provided by separate manufacturers. Furthermore,
the analytic results from different lots of ELISA kits supplied by
single manufacturers differed by as much as 50%. The need for
uniformity in the standards for quantitative assays was clearly
illustrated. International reference standards are available for
cytokines but not for soluble cytokine receptors or soluble activation
markers. Marker levels in serum or in plasma were similar except those
for IFN-
. Most of the analytes were stable under several storage
conditions. Thus, batch testing of frozen stored samples is feasible.
The findings indicate that for longitudinal studies, the levels of
cytokines and immune activation markers in plasma or serum should be
measured by using preverified reagents from one manufacturer. The
quality of laboratory performance can have an impact on clinical
relevance. Proficiency testing and external quality assurance programs
can help to develop the needed consensus.
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, UCLA School of Medicine, Los Angeles, CA 90095-1747. Phone: (310) 825-6568. Fax: (310) 206-1318. E-mail: jlfahey{at}ucla.edu.
Clinical and Diagnostic Laboratory Immunology, January 1999, p. 89-95, Vol. 6, No. 1
1071-412X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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