From the Guidelines
Cytomegalovirus (CMV) infection can be diagnosed through several laboratory methods, with PCR (polymerase chain reaction) being the most sensitive method, detecting viral DNA in blood, urine, or other body fluids. The diagnosis of CMV infection depends on the clinical context, patient population, and available resources.
Diagnostic Approaches
- Serologic testing measures CMV-specific antibodies (IgM and IgG) to determine current or past infection, with IgM antibodies indicating recent or active infection, and IgG antibodies suggesting past exposure 1.
- Antigenemia assays detect CMV proteins in white blood cells and are useful for monitoring infection in immunocompromised patients.
- Viral culture from blood, urine, or tissue samples can isolate the virus but takes longer than other methods.
- Tissue biopsy may be necessary in cases of organ-specific disease, where histopathological examination can reveal characteristic viral inclusions.
- For congenital CMV, testing should be performed within the first three weeks of life using urine or saliva samples.
Preferred Diagnostic Test
The choice of diagnostic test depends on the clinical context, patient population, and available resources, with PCR being preferred in most situations due to its rapid results and high sensitivity 2.
Clinical Context
In immunocompetent individuals suspected of having acute CMV infection, testing for CMV-specific antibodies is recommended as the first line laboratory diagnostic test 1. In recipients of organ or peripheral blood stem cell transplants, CMV viral load by NAAT or antigenemia is used as a marker for preemptive therapy, to diagnose CMV-associated signs and symptoms, and to monitor response to antiviral therapy 1. In patients with severe colitis, CMV has been reported in colonic tissue in 21–34% and in 33–36% of steroid-refractory colitis, and diagnosis can be made using PCR, antigenaemia assays, or histopathology combined with immunohistochemistry 2.
From the Research
Diagnosing CMV Infection
To diagnose CMV infection, several methods can be employed, including:
- Detection of CMV-DNA in various samples such as blood, urine, and cerebrospinal fluid (CSF) using real-time fluorescence quantitative polymerase chain reaction (PCR) 3
- Measurement of CMV-IgM and CMV-IgG antibodies in blood, although their clinical value is limited 3
- Viral load monitoring to assess the severity of infection and response to treatment 4, 5
Sample Types for CMV Detection
Different sample types can be used for CMV detection, including:
- Blood: CMV-DNA can be detected in blood samples, and the positive rate is similar to that of urine samples 3
- Urine: Urine samples can also be used for CMV-DNA detection, with a positive rate of 25.27% 3
- Cerebrospinal fluid (CSF): CSF samples can be used for CMV-DNA detection, although the positive rate is lower (5.70%) compared to blood and urine samples 3
Risk Factors for CMV Infection
Certain risk factors can increase the likelihood of CMV infection, including:
- Low CD4+ T lymphocyte count: Patients with low CD4+ T lymphocyte counts are more susceptible to CMV infection 3
- High HIV-1 viral load: Patients with high HIV-1 viral loads are also at increased risk of CMV infection 3
- Donor positive/recipient negative CMV serostatus: This serostatus combination can increase the risk of CMV infection and disease 4
- Anti-rejection therapy or polyclonal anti-thymocyte globulin: These treatments can also increase the risk of CMV infection and disease 4