Comparison of Quantitative PCR and Antigenemia in Cytomegalovirus Infection in Renal Transplant Recipients

Comparison of a UL111a real-time PCR and pp65 antigenemia for the detection of cytomegalovirus

Surveillance of cytomegalovirus (CMV) replication in transplant patients is crucial for the success of transplantation. To compare a CMV pp65 antigenemia (pp65Ag) and a quantitative real-time PCR targeting the CMV-UL111a (UL111aPCR), all whole blood samples taken between July 2008 and October 2009 were identified which had been analyzed prospectively by both assays in parallel. Discordant results were re-analyzed using a published CMV duplex PCR targeting regions UL55 and UL123exon4. Of 720 samples from 81 transplant patients, CMV replication was detected in 244 specimens (34%) by the UL111aPCR (median, 1,019 geq/ml), compared to 113 (16%) detected by the pp65Ag (median, 2/250,000 leukocytes). Concordant UL111aPCR/pp65Ag results were obtained in 561 (78%) samples, being positive in 99 (14%), and negative in 462 (64%). As a rule of thumb, 1 pp65Ag-positive cell per 250,000 leukocytes corresponded to 1,000 geq/ml CMV DNA of whole blood. Discordant results were found in 159 samples (22%), being UL111aPCR-positive/pp65Ag-negative in 145 (91%; median, 650 geq/ml), or UL111aPCR-negative/pp65Ag-positive in 14 (9%; median, 1/250,000 cells). Using the duplex PCR targeting the CMV UL55 and the UL123-exon4 genes, 131 of 139 (94%) discordant UL111aPCR-positives (median UL111aPCR, 639 geq/ml; median UL55PCR, 715 geq/ml; median UL123PCR, 1,103 geq/ml) were confirmed. Of 14 discordant pp65Ag-positives, duplex PCR was also negative in 8, and of low copy number in 6. Thus, CMV UL111aPCR provides more sensitive quantitation of CMV replication than pp65Ag, however, discordant results can occur at very low viral loads.

Relationship of cytomegalovirus load assessed by real-time PCR to pp65 antigenemia in organ transplant recipients

BACKGROUND

Cytomegalovirus (CMV) infection in immunocompromised patients can lead to viremia associated with morbidity and mortality. Monitoring of viral loads in blood is critical for initiating and monitoring antiviral treatment.

OBJECTIVES

Validate quantitative real-time PCR assay targeting the US17 and UL54 regions of the CMV genome for automated DNA and extraction and amplification.

STUDY DESIGN

3422 blood specimens from organ transplant recipients, including longitudinal specimens from 12 organ transplant recipients, were tested by CMV PCR and pp65 antigenemia.

RESULTS

CMV PCR for both US17 and UL54, was more sensitive and detected CMV DNA earlier and for longer than the CMV pp65 antigenemia test. Using antigenemia results as a reference standard, an optimal cutoff of 500 normalized copies was calculated for both US17 and UL54 PCR targets based on high sensitivity, specificity, and positive and negative predictive values. CMV DNA levels tracked well with clinical symptoms, response to treatment, and antigenemia.

CONCLUSIONS

Detection of persistent increases in CMV DNA levels above 500 normalized copies by this real-time PCR assay is indicative of symptomatic CMV disease in organ transplant recipients. Quantitative real-time PCR for CMV DNA can be used in lieu of antigenemia for monitoring CMV infection and determining when to initiate preemptive treatment.

Comparison of serology assays and polymerase chain reaction for the monitoring of active cytomegalovirus infection in renal transplant recipients

BACKGROUND

Cytomegalovirus (CMV) infection is a common complication of renal transplantation. It can be diagnosed serologically, mainly based on seroconversion or by the detection of viral antigen via CMV-DNA amplification (polymerase chain reaction [PCR]).

AIM

We sought diagnosis of an active CMV infection in renal transplant patients comparing serologic assays of CMV-IgM antibodies with CMV-DNA amplification.

METHODS

We retrospectively studied renal transplant recipients 26 (including 15 women) hospitalized with clinical suspicion of CMV disease. The diagnosis of CMV infection was suspected on the basis of nonspecific symptoms, including fever, leukopenia, hyperbilirubinemia, and alanine aminotransferase elevation, alone or in combination. At the time of admission, all patients were screened for CMV-IgM antibody (immunoassays AxSYM/IMx) and CMV-DNA (qualitative PCR).

RESULTS

The confirmation of CMV infection by the two methods (immunoassay and PCR) was obtained in only three patients (11.5%), its unambiguous exclusion--in four cases (15.4%). Nineteen patients (73.1%) were positive for CMV-IgM and negative for CMV-DNA.

CONCLUSION

Detection of CMV-IgM antibodies by various immunoassays is not sensitive enough for diagnosis and cannot be used for monitoring during the active period in renal transplant recipients. This observation supported the prolonged presence of IgM antibodies after recent CMV infection in this patient group.