The ability to establish a standardized laboratory protocol in the performance of the quantitative cytomegalovirus antigenemia (CMV-Ag) assay permits this assay’s application as an indicator and prognosticator of CMV disease (1, 3, 4, 6). A limitation to the overall efficacy of the CMV-Ag assay, however, is the laboratorian’s inability to control the decrease in antigen or viral (CMV) load during periods of specimen transport. As stated by Drs. Bush and Sluchak-Carlsen (2), a need exists to develop a transport stabilization system to prevent such antigen loss.
The Streck Laboratories RBC lysis solution and stabilizing reagent used by Drs. Bush and Sluchak-Carlsen appear promising as blood additives to retard antigen loss during (blood) specimen transport to the laboratory (2). However, whether the authors’ test samples permitted an accurate evaluation of the RBC lysis and stabilizing reagents needs further clarification.
Drs. Bush and Sluchak-Carlsen reported the use of “preselected,” “culture-positive” blood specimens. Accordingly, one’s interpretation of the stabilizing reagents’ efficacy needs to be addressed at the very least from specimen baseline (i.e., at the time of collection) CMV load determinations. It would not be unreasonable to suggest that the testing of low-level antigenemia blood (e.g., one to five pp65-reactive cells), in concert with the authors’ reported overall antigen level loss of 15% after storage, might adversely affect the parameter of test (CMV-Ag assay) specificity.
The use of combination drug therapy among AIDS patients has markedly reduced the number of individuals developing CMV disease. Among our CMV-positive AIDS patients, low-level antigenemia is often the rule rather than the exception (viz., <5 pp65-positive cells [7]). Identification of low-level antigenemia remains important, as it provides the physician with the first evidence of a CMV infection (5).
Application of the Streck stabilizing reagents during blood transport is indeed intriguing. However, more testing with low-level pp65-positive AIDS patients is needed prior to the routine incorporation of these reagents into the clinical setting.
Ed. Note: The authors of the published article did not respond.
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