Need for an External Proficiency Testing Program for Cytokines, Chemokines, and Plasma Markers of Immune Activation

Abstract

The appearance of new diseases, therapies, or technologies often leads to new clinical laboratory measurements. This is often accompanied by novel instrumentation and reagents. Under these circumstances and until laboratory procedures and reagents are standardized and laboratory leaders and technologists have been trained, laboratories may differ substantially in analytic results with comparable samples, with resultant confusion and possible misinterpretation of clinical status. Thus, external performance evaluation programs are usually introduced to achieve better performance and comparability in laboratory testing.A good example occurred early in the spread of human immunodeficiency virus (HIV) infection and AIDS. Measurements of CD4 T-cell levels were found to be central to evaluation of disease course and therapeutic decisions. However, no national proficiency testing procedures were in place. AIDS patients who were tested for CD4 levels at different locations often reported that laboratories differed substantially in their analytic results obtained by flow cytometry. Thus, investigatorinitiated programs such as the Multicenter AIDS Cohort Study (MACS) (7) and the AIDS Clinical Trials Group (ACTG) (15) under National Institute of Allergy and Infectious Diseases (NIAID) auspices instituted successful external proficiency testing programs that achieved satisfactory comparability of peripheral blood lymphocyte subset measurements by flow cytometry. Subsequently, the Centers for Disease Control and Prevention and the College of American Pathologists introduced flow cytometry proficiency testing programs. More recently, an international program for quality assurance and standardization of CD4, CD8, and CD3 measurements (the QASI program) has been instituted (12). The ACTG has also instituted a performance evaluation program for quantitative HIV assays (11).Immune system activation is increasingly recognized as a

Multisite Comparison of High-Sensitivity Multiplex Cytokine Assays

“…These considerations are not unique to multiplex assays, as prior studies focused on ELISAs demonstrated that the absolute concentration of cytokines measured by ELISA varied depending on which lab performed the testing, but trends in cytokine concentrations were consistent across multiple labs (5). Strategies to address assay reproducibility could focus on including an aliquot of a pedigreed control sample of human serum or plasma to be run on each assay or testing cytokines singly and randomly retesting 15 to 20% of samples, as has been suggested for radioimmunoassay and enzyme immunoassay testing (1).…”

“…These comparison studies have shown variable agreement among assays and have indicated that absolute cytokine concentrations differ across testing platforms. Such variability is not unique to multiplex assays, as proficiency testing has demonstrated that absolute concentrations of cytokines measured by a singleanalyte ELISA can vary widely from lab to lab, although a similar rank order of cytokine concentrations between samples is often preserved (5).…”

Comparative evaluation of postmortem serum concentrations of neopterin and C-reactive protein

“…The stimulation of cellular immunity associated with the activation of macrophages in the early phase causes an increase in the concentration of neopterin in urine, serum, and other body fluids. Thus, neopterin is considered an indicator of the activation of local macrophages in the early nonspecific phase of the human host defense immune system, although its role has not been fully clarified [34][35][36][37][38][39].…”

Flight Factors Influence on Human Lymphocyte Radioadaptive Response and Gamma-Interferon Production

“…However, the absolute concentrations of cytokines and other markers of immune system activation measured in different laboratories can differ by two orders of magnitude [16]. It should be noted that these differences were detected when processing both the sera and supernatants; hence, they were determined by the quality of the used kits.…”