Table. 1.

Characteristics of cytomegalovirus assays in solid organ transplantation

Assay Technique Advantage Limitation
For virus detection
CMV QNAT • Detects and quantifies CMV DNA
• Reporting unit: IU/mL
• Various commercial assays are available
• Rapid and sensitive tool for diagnosis of CMV infection
• Surveillance for preemptive treatment
• Monitoring the response of antiviral therapy
• Implementation of the WHO internal standard for calibration
• Lack of universal viral load threshold
• Lack of standardization despite WHO internal standard material due to various aspects of assay (limit of detection, quantification range, sample type, amplicon size, gene target)
Antigenemia • Immunofluorescence-based assay
• Detect CMV pp65 antigen expressed in leukocytes using monoclonal antibody
• Reporting unit: number of pp65 positive cells per number of leukocytes
• Monitoring CMV infection
• Monitoring the response of antiviral therapy
• Lack of assay standardization
• Need for enough leukocytes in sample (limited in neutropenia)
• Lack of automation
• Interpretation is subjective
• Labor-intensive
For CMV-specific cell-mediated immunity
Serology • Usually detects CMV IgG antibodies • The risk of CMV infection is determined depending on the CMV serology in donor and transplant candidate • IgM is not recommended due to false positivity
• The use of serology is limited for diagnosis of CMV infection after transplantation
QuantiFERON-CMV • ELISA-based
• Measures IFN-γ
• Collecting whole blood into tubes containing the CMV peptide pool
• Commercial assay
• Standardized high-throughput assay
• Can be performed routinely in laboratories
• HLA class I restricted
• Only measures CD8+ T cells (not CD4+ T cells)
• Indeterminate results in immunosuppressed patients
ELISpot • Measures IFN-γ
• Stimulates PBMCs with CMV-overlapping peptides
• Reporting unit: spot forming units/PBMCs
• Commercial assays are available: T-SPOT.CMV, T-Track CMV
• Highly sensitive
• Not limited by HLA
• Measures both CD4+ T cells and CD8+ T cells
• Requires PBMC isolation procedure
• Lack of proper cut-offs for positivity
• Requires ELISpot reader
• Unable to differentiate between CD4+ T cells and CD8+ T cell response
• Lack of standardization as many laboratories use in-house methods
Intracellular staining and flow cytometry • Detects intra-cytoplasmic cytokines produced by stimulation of whole blood or PBMCs with CMV peptides using a fluorochrome antibody • Simultaneous detection of multiple cytokines and cell surface markers
• Can differentiate T-cell phenotypes
• Can differentiate between CD4+ T cells and CD8+ T cell response
• Requires flow cytometer
• Lack of standardization
• Expensive
• Labor-intensive
• Limited to research use only

CMV, cytomegalovirus; QNAT, quantitative nucleic acid amplification test; WHO, World Health Organization; IgG, immunoglobulin G; IgM, immunoglobulin M; ELISA, enzyme-linked immunosorbent assay; IFN-γ, interferon-gamma; HLA, human leukocyte antigen; ELISpot, enzyme-linked immunosorbent spot; PBMC, peripheral blood mononuclear cell.

Korean J Transplant 2022;36:15~28 https://doi.org/10.4285/kjt.22.0001
© Korean Journal of Transplantation