Quantitative analysis of cytomegalovirus (CMV) viremia using the pp65 antigenemia assay and the COBAS AMPLICOR CMV MONITOR PCR test after blood and marrow allogeneic transplantation

Factors associated with cytomegalovirus infection in children undergoing allogeneic hematopoietic stem-cell transplantation

While preemptive therapy with ganciclovir (GCV) for cytomegalovirus (CMV) infection is used following allogeneic hematopoietic stem-cell transplantation (HSCT), risk factors for CMV infection in children undergoing HSCT are poorly understood.We studied CMV reactivation following allogeneic HSCT by retrospectively analyzing pediatric patients who received allogeneic HSCT and preemptive GCV therapy between 1998 and 2016. The level of viremia requiring preemptive GCV therapy was >1 CMV antigen-positive cells per 5 × 10 leukocytes during the antigenemia assay era and >1000 copies/mL in the polymerase chain reaction era. Among 290 at-risk patients, 54 (18.6%) patients had primary CMV infection or CMV reactivation occurring at a median of 76 days (range, 7-234) following HSCT. CMV reactivation occurred in 28.2% (44/156) of CMV-seropositive transplant recipients at a median of 26 days posttransplant.Univariate and multivariate analyses revealed statistically significant relationships between CMV infection and grade III-IV acute graft-vs-host disease, seronegative donor/seropositive recipient combination, and unrelated/mismatched donors. The remaining demographic factors were not predictive of CMV infection.The seronegative donor/seropositive recipient combination for HSCT was associated with an incomplete response to antiviral therapy. Human leukocyte antigen identical donors were the best choice for patients undergoing allogeneic HSCT to reduce the incidence of CMV disease and mortality.

Use of Valacyclovir for the treatment of cytomegalovirus antigenemia after hematopoietic stem cell transplantation

BACKGROUND

Valacyclovir has been used for prophylaxis against cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT). We investigated the efficacy and safety of high-dose Valacyclovir as pre-emptive therapy in patients with CMV antigenemia after HSCT.

METHODS

In a retrospective single center study of 61 patients, we compared the rates of viral clearance, recurrent antigenemia and adverse events in patients with pp65 CMV antigenemia who received high dose Valacyclovir (n = 15), Valganciclovir (n = 16), and Foscarnet (n = 30).

RESULTS

Overall, 60/61 (98 %) of cases achieved CMV antigenemia clearance by day 28, and no patient developed CMV disease. After adjusting for age, sex, diagnosis, CMV serological status, donor type, CMV antigen level, graft-versus-host disease (GVHD) therapy, and conditioning regimen, there were no significant differences in the rates of viral clearance at day 14 in patients who received Valganciclovir (0.18, 95 % confidence interval (CI) 0.01 to 2.15, p = 0.17) and Foscarnet (OR 0.22, 95 % CI 0.03 to 2.40, p = 0.22), compared with Valacyclovir (assigned OR = 1.00). Recurrent antigenemia by day 180 after clearance of the initial CMV episode occurred in 34/61 (56 %) of patients. Using the multivariate model adjusting for the same covariates, there were also no significant differences in secondary episodes of CMV between treatment groups. With regards to adverse effect monitoring, Foscarnet led to significantly increased creatinine levels (P = 0.009), while Valganciclovir led to significant decrease in neutrophil counts (P = 0.012).

CONCLUSION

High dose Valacyclovir is a potential alternative to Valganciclovir and Foscarnet in the stable post-HSCT patient who has cytopenia and is not keen for inpatient treatment of CMV antigenemia.

Rapid detection of cytomegalovirus infection in transplant patients

Human cytomegalovirus (CMV) is a well-known cause of morbidity and mortality in transplantation patients. Monitoring of CMV reactivation from latency is critical for these patients. The key to efficient and effective management of CMV infection is a test capable of rapidly monitoring and quantifying the presence of CMV in the blood. This is essential for the identification of subjects at high risk of developing CMV disease, for example, patients receiving steroid or immunosuppressive compounds for accelerated graft-versus-host disease, transplant rejection and also for the application and monitoring of pre-emptive antiviral therapeutic strategies. The assays presently available and frequently used in this setting include conventional and shell vial culture, the CMV antigenemia assay, PCR for CMV DNA, hybrid capture assay for CMV DNA and detection of CMV RNA by nucleic acid sequence-based amplification. The low sensitivity and low reproducibility of conventional cell culture and shell vial assays limit their role in the management of CMV infection to one of disease diagnosis. Diagnostic assays, such as the pp65 antigenemia and other molecular assays, have improved the ability to diagnose CMV disease quickly and accurately. These methods fulfill the requirements for a good diagnostic assay: they have high sensitivity, most can quantify viral load and they are rapid and reproducible. Their characteristics allow these assays to be used to predict the development of CMV disease and monitor response to therapy.

Failure of pre-emptive treatment of cytomegalovirus infections and antiviral resistance in stem cell transplant recipients

BACKGROUND

Treatment of cytomegalovirus (CMV) infections after stem cell transplantation (SCT) does not always lead to a rapid viral response. The causes of treatment failure may be either viral resistance or immunological failure to control viral replication. This study investigated the response to pre-emptive treatment in CMV infections in order to define risk factors for treatment failure, including the role of antiviral resistance.

METHODS

Adult recipients of allogeneic T-cell depleted SCT were studied retrospectively (n=92). CMV infections were treated with (val)ganciclovir according to a CMV DNA-load-based pre-emptive strategy. Treatment failure was defined as a CMV DNA load of 1,000 copies/ml or more after at least 2 weeks of treatment. Resistance was analysed by nucleotide sequence analysis of the UL97 and UL54 genes in the first CMV DNA-positive sample and in samples during treatment failure.

RESULTS

Treatment failure occurred in 26 of the 47 pre-emptively treated patients (55%) and in 39 of 86 (45%) treatment episodes. The risk of treatment failure was increased during first treatment episodes (P=0.01) and during the use of immunosuppressive medication (P=0.02). Antiviral resistance was found in only 1 patient (4%) with treatment failure.

CONCLUSIONS

A slow response to pre-emptive antiviral treatment occurred frequently in CMV infections in SCT recipients. Antiviral resistance was observed but played a minor role in treatment failure.

Molecular detection of herpesviruses

In routine molecular diagnostics, detection of herpesviruses has made a major impact. Infection with herpesviruses is indicated by demonstrating the presence of the virus in selected specimens. Rapid and reliable detection of herpesvirus DNA helps to decrease the lethality as well as the sequelae of herpesvirus infection in patients at risk. This chapter discusses specimen types and both laboratory-developed and commercially available assays useful for molecular detection of herpesviruses. To meet the need for reliable laboratory results, it is advisable to employ maximum automated and standardized kits based on reagents and standards of reproducible high quality. In the routine diagnostic laboratory, introduction of IVD/CE and/or FDA-labeled tests is preferred.

Interlaboratory comparison of cytomegalovirus viral load assays

To assess interlaboratory variability in qualitative and quantitative cytomegalovirus (CMV) viral load (VL) testing, we distributed a panel of samples to 33 laboratories in the USA, Canada and Europe who performed testing using commercial reagents (n = 17) or laboratory-developed assays (n = 18). The panel included two negatives, seven samples constructed from purified CMV nucleocapsids in plasma (2.0-6.0 log(10) copies/mL) and three clinical plasma samples. Interlaboratory variation was observed in both actual (range, 2.0-4.0 log(10) copies/mL) and self-reported lower limits of detection (range, 1.0-4.0 log(10) copies/mL). Variation observed in reported results for individual samples ranged from 2.0 log(10) (minimum) to 4.3 log(10) (maximum)(.) Variation was greatest at low VLs. Assuming +/- 0.5 log(10) relative to the expected result represents an acceptable result, 57.6% of results fell within this range. Use of commercially available reagents and procedures was associated with less variability compared with laboratory-developed assays. Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). The significant interlaboratory variability in CMV VL observed may be impacting patient care and limiting interinstitutional comparisons. The creation of an international reference standard for CMV VL assay calibration would be an important step in quality improvement of this laboratory tool.

Quantification of DNA in plasma by an automated real-time PCR assay (cytomegalovirus PCR kit) for surveillance of active cytomegalovirus infection and guidance of preemptive therapy for allogeneic hematopoietic stem cell transplant recipients

The performance of a plasma real-time PCR (cytomegalovirus [CMV] PCR kit; Abbott Diagnostics) was compared with that of the antigenemia assay for the surveillance of active CMV infection in 42 allogeneic hematopoietic stem cell transplantation (Allo-SCT) recipients. A total of 1,156 samples were analyzed by the two assays. Concordance between the two assays was 82.2%. Plasma DNA levels correlated with the number of pp65-positive cells, particularly prior to the initiation of preemptive therapy. Fifty-seven episodes of active CMV infection were detected in 37 patients: 18 were defined solely by the PCR assay and four were defined on the basis of the antigenemia assay. Either a cutoff of 288 CMV DNA copies/ml or a 2.42-log(10) increase of DNAemia levels between two consecutive PCR positive samples was an optimal value to discriminate between patients requiring preemptive therapy and those not requiring therapy on the basis of the antigenemia results. The real-time PCR assay allowed an earlier diagnosis of active CMV infection and was a more reliable marker of successful clearance of CMV from the blood. Analysis of the kinetics of DNAemia levels at a median of 7 days posttreatment allowed the prediction of the response to CMV therapy. Two patients developed CMV colitis. The PCR assay tested positive both before the onset of symptoms and during the disease period. The plasma real-time PCR from Abbott is more suitable than the antigenemia assay for monitoring active CMV infection in Allo-SCT recipients and may be used for guiding preemptive therapy in this clinical setting.

Prediction of cytomegalovirus (CMV) plasma load from evaluation of CMV whole-blood load in samples from renal transplant recipients

In a prospective cohort of 82 renal transplant recipients, we evaluated the capacity of the cytomegalovirus (CMV) load in whole blood (WB) to predict the plasma CMV load, aiming to identify active CMV infections by using WB samples only and to deduce a WB threshold. Using quantitative real-time PCR, a total of 1,474 WB samples were assayed, of which 279 were positive for CMV, and 140 out of the 276 paired plasma samples tested positive. Thirty (36.6%) patients presented with at least one positive plasma PCR result, and 21 infection episodes (19 patients) required curative treatment (median follow-up time, 12 months). When the plasma CMV load was >500 copies/ml (n = 70), more than 94% (95% confidence interval, 86.0%, 98.4%) of WB samples had >500 copies/ml. Two prediction models were built: log(10) plasma viral load (VL) was calculated as -0.3777 + 0.9342 x log(10) WB VL and as -0.3777 + 0.8563 x log(10) WB VL for patients with and without treatment, respectively. In the validation sample (578 routine samples), 77.2% of the observed and expected plasma viral loads were concordant (95% confidence intervals, 73.5 and 80.5%). According to the model, the plasma viral load was >500 copies/ml when the WB load was >3,170 or >4,000 copies/ml in patients with or without treatment, respectively. WB seems to be an appropriate candidate for routine CMV monitoring of transplant recipients by using a single assay.

High Incidence of Invasive Aspergillosis Associated with Intestinal Graft-versus-Host Disease following Nonmyeloablative Transplantation

Invasive aspergillosis (IA) remains a major complication following allogeneic hematopoietic stem cell transplant (HSCT). In contrast to conventional HSCT, few investigators have examined risk factors of IA associated with nonmyeloablative (NMA) regimens characterized by outpatient administration, immunosuppression rather than cytoreduction, and short duration of neutropenia posttransplant. We report our results on a cohort of 125 patients treated homogenously who received a 6/6 matched sibling NMA HSCT designed to be performed on an outpatient basis. Conditioning regimen included fludarabine (30 mg/m(2) x 5 days) and cyclophosphamide (300 mg/m(2) x 5 days) followed by reinfusion of a minimum of 4 x 10(6) CD34(+) cells/kg. Acute graft-versus-host disease (aGVHD) prophylaxis consisted of tacrolimus and mycophenolate mofetil (MMF). Overall, 13 patients developed IA (5 proved, 6 probable, 2 possible) 44-791 days (median 229) after NMA HSCT, with a risk of 7% at 1, 11% at 2, and 15% at 3 years. Patients who suffered from IA had poorer overall survival (crude hazard ratio 2.3; 95% confidence interval [CI] 1.0-5.4; P = .045). Intestinal aGVHD or chronic GVHD (cGVHD) was significantly associated with IA at 1 (27% versus 3%, P = .003), 2 (27% versus 8%, P = .01), and 3 years (37% versus 10%, P = .005). The use of daclizumab was also significantly associated with IA at 3 years (47% versus 12%, P = .02). Age, sex, diagnosis, previous autologous transplant, duration of neutropenia, occurrence of cytomegalovirus viremia, duration of steroids or MMF intake, aGVHD, cGVHD, and cumulative number of days spent in hospital were not associated with IA. After multivariate analysis, intestinal GVHD remained the only statistically significant risk factor for IA at 1 (P = .003), 2 (P = .01), and 3 years (P = .005). We conclude that in NMA HSCT, the risk of IA increases over time and is significantly associated with intestinal GVHD. Because there is currently no surrogate in vitro markers of immunocompetence following NMA HSCT, this clinical finding is of particular importance to identify a population at higher risk who should be targeted for antimold prophylaxis.

Analytic Validation of a Quantitative Real-time PCR Assay to Measure CMV Viral Load in Whole Blood

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in immunocompromised patients. We compared the CMV pp65 antigenemia test with a less labor intensive quantitative polymerase chain reaction (PCR) assay in 109 whole blood samples predominantly from transplant patients and patients with AIDS. DNA was amplified on an Applied Biosystems 7900 instrument using a TaqMan probe targeting the CMV polymerase gene and the APOB human control gene. The DNA assay was linear over a 6-log range from 8 to 800,000 CMV genomes per reaction; coefficient of variation was 20%. CMV DNA was undetectable in 20 blood samples from healthy donors whereas it was detected in 55 of 109 patient samples. Results were concordant in a nonlinear fashion with those of the antigenemia test in 90/109 (83%). Evaluation of the discrepancies suggested that either PCR or antigenemia assays could be falsely negative when virus levels were quite low. A point mutation interfered with probe binding in 1 sample. A second real-time PCR targeting the immediate early gene was even more likely to be false negative. In summary, CMV viral load measurement targeting the polymerase gene is nearly equivalent to the antigenemia assay for detecting and monitoring active CMV infection in whole blood samples.

Analysis of cytomegalovirus (CMV) viremia using the pp65 antigenemia assay, the amplicor CMV test, and a semi-quantitative polymerase chain reaction test after allogeneic marrow transplantation

A pp65 antigenemia assay for polymorphonuclear leukocytes (PMNLs) (CINAkit Rapid Antigenemia), and a qualitative polymerase chain reaction (PCR) test for plasma 'PCR-P qual' (Amplicor cytomegalovirus [CMV] test) were performed for 126 samples (blood and plasma) obtained from 18 bone marrow transplant patients, over a 9-month surveillance period. Among those samples, 92 were assayed with a semi-quantitative PCR test for PMNLs 'PCR-L quant.' The number of samples with a positive CMV test for antigenemia and PCR-P qual assays was 20.63% and 12.7%, respectively, whereas the PCR-L quant assay was positive in 48 of the 92 samples assayed (52.17%). The rates of concordance of the results of PCR-P qual and antigenemia, PCR-P qual and PCR-L quant, antigenemia and PCR-L quant were 92%, 65.2% and 66.8%, respectively. The analysis of the results for the 92 specimens tested by all 3 methods showed a rate of concordance of 63% among all methods. Good agreement (kappa=0.72) was found only between pp65 Ag and PCR-P qual assays. Clinical disease correlates with an antigenemia high viral load. Three patients had CMV disease despite preemptive therapy, and all of them had graft-versus-host-disease (GVHD). PMNLs-based assays are more efficient in monitoring CMV reactivation, but for high-risk patients with GVHD, more sensitive assays (real-time PCR) must be done.

CMV monitoring using blood cells and plasma: a comparison of apples with oranges?

Quantitative cytomegalovirus (CMV) monitoring is still far from being standardized between transplant centers. In the present study, we compared assays for quantitative CMV monitoring using blood cells and plasma. Four hundred and thirty-five consecutive samples from 29 patients with active CMV infection after allogeneic T-cell-depleted hemopoietic stem cell transplantation were tested in parallel using pp65 antigenemia and quantitative CMV polymerase chain reaction (PCR) in blood cells and plasma (COBAS AMPLICOR CMV MONITOR). Although only 142 (53.1%) of 253 positive samples were concordantly identified by all three assays, the number of positive samples detected by each assay was not different and the quantitative values were correlated, provided that nucleic acid (NA) in plasma was isolated by COBAS AmpliPrep and not by the manual protocol. Six (18%) of 34 episodes with active CMV infection were not detected using CMV PCR in plasma; whereas in times of white blood cell aplasia or blast crisis of leukemia, samples with active CMV infection in plasma could not be detected using blood cells. We conclude that CMV monitoring in whole blood could be favorable compared with assays using plasma or blood cells alone. Automated NA isolation could become an attractive tool for a more sensitive and better standardized molecular diagnostics.

Detection and monitoring of cytomegalovirus infection in renal transplant patients by quantitative real-time PCR

OBJECTIVES

To establish a sensitive and specific real-time PCR for quantitation of cytomegalovirus (CMV) DNA in clinical specimens.

SUBJECTS AND METHODS

In a prospective study, CMV DNA was quantified in blood samples of 255 kidney recipients with and without CMV-related symptoms between the years 2000 and 2005 in Kuwait. In a selected group of patients, the effect of anti-CMV chemotherapy was monitored by quantitative real-time PCR (qRT-PCR).

RESULTS

The established qRT-PCR assay had a sensitivity to detect 30 CMV DNA copies. CMV DNA was detected in 54/255 (24%) patients; of these, 17 (31.5%) were asymptomatic, and 37 patients (68.5%) had symptomatic CMV infection. Sequential blood specimens were collected from all CMV-positive patients and tested by CMV pp65 antigenemia and qRT-PCR assays. There was a moderate positive correlation between the two assays (Pearson's correlation = 0.52). The median CMV viral load measured by qRT-PCR was higher in symptomatic (6.5 x 10(4) copies/ml) than in asymptomatic (185copies/ml) patients (p = 0.001). The estimated cut-off value of CMV DNA for CMV symptoms/disease was > or =800 copies/ml of blood. Testing of sequential samples from patients treated with symptomatic CMV infection showed that the viral load was significantly reduced after 3 weeks of anti-CMV chemotherapy (p = 0.001).

CONCLUSION

The reported qRT-PCR is a sensitive method for quantitation of CMV DNA in the blood of kidney recipients and can be useful in monitoring the efficacy of anti-CMV therapy.

A prospective study comparing quantitative Cytomegalovirus (CMV) polymerase chain reaction in plasma and pp65 antigenemia assay in monitoring patients after allogeneic stem cell transplantation

Background

Low levels of Cytomegalovirus (CMV) viral load are frequently detected following allogeneic stem cell transplantation (SCT) and CMV disease may still develop in some allogeneic SCT patients who have negative pp65-antigenemia (pp65-Ag) or undetectable DNA. Pp65Ag is a sensitive method to diagnose CMV infection. Quantitative CMV-DNA PCR assay in plasma has been proposed to monitor CMV infection in SCT patients. We evaluated the clinical utility of pp65Ag and PCR assay in plasma of SCT recipients.

Methods

In a prospective longitudinal study, 38 consecutive patients at risk of CMV infection (donor and/or recipient CMV seropositive) were weekly monitored for CMV infection by both quantitative CMV-PCR in plasma (COBAS AMPLICOR CMV MONITOR) and pp65 Ag, during the first 100 days after SCT.

Results

A total of 534 blood samples were simultaneously analysed for pp65Ag and PCR. Overall, 28/38 patients (74%) had active CMV infection within 100 days from SCT. In 16 patients, CMV was first detected by pp65 Ag alone; in 5 patients by both methods and in 6 by PCR assay alone; one patient had CMV biopsy-proven intestinal disease without pp65Ag and PCR assays positivity before CMV disease. Overall, three patients developed intestinal CMV disease (7.9%): one had negative both pp65Ag and PCR assays before CMV disease, one had disease and concomitant positivity of both methods, while in the remaining patient, only pp65Ag was positive before CMV disease.

Conclusion

Plasma PCR(COBAS AMPLICOR CMV MONITOR) and pp65Ag assays were effective in detecting CMV infection, however, discordance between both methods were frequently observed. Plasma PCR and pp65Ag assays may be complementary for diagnosis and management of CMV infection.

Evaluation of the COBAS Amplicor HCMV Monitor for early detection and monitoring of human cytomegalovirus infection after allogeneic stem cell transplantation

Early diagnosis of human cytomegalovirus (HCMV) infection and the introduction of preemptive antiviral therapy have reduced HCMV-related mortality after allogeneic stem cell transplantation. A critical goal remains stratifying risk profiles and minimizing potential harm owing to antiviral overtreatment. We compared the commercially available standardized COBAS Amplicor CMV Monitor (CACM) to an in-house PCR assay, for the monitoring of HCMV infection. Seventy-two patients were surveyed by an in-house PCR of whole blood, quantitative viral load assessment by CACM and virus culture assays in a prospective and a retrospective study. A high concordance between CACM and PCR was documented. The viral load at onset correlated with the peak viral load (Spearman rank correlation R=0.634, P=0.0004). In patients developing HCMV disease, both viral loads were in trend higher (P=0.823, respectively P=0.053), and the viremic episodes longer (P=0.015), as compared to asymptomatically HCMV-infected patients. The serological pre-transplant status was the major risk factor for the development of HCMV disease, showing highest risk for seropositive patients receiving a seronegative graft, whereas donor type (related or unrelated) and graft type (bone marrow or peripheral blood mobilized stem cells) did not have an influence. HCMV infection proved to be a risk factor for the development of non-viral opportunistic infections (P=0.002).

Comparison of two commercially available pp65 antigenemia tests and COBAS Amplicor CMV Monitor for early detection and quantification of episodes of human CMV-viremia in transplant recipients

The performance of two commercially available CMV pp65 antigenemia (AG) assays (CINA kit, Argene Biosoft, CK, and CMV Brite kit, IQ Products, CBK), and a quantitative PCR test (COBAS Amplicor CMV Monitor Test, Roche Diagnostics, CACM) was evaluated with 667 blood samples from 215 transplant recipients. The diagnostic value of the three tests was defined by their ability to detect episodes of systemic CMV activity. A test score was defined, assigning 7 virtual units (VU) for any episode detected first, 5 VU for any episode detected second, and three VU for any episode detected last. Within the evaluated collective, the following overall scores could be determined for the three assays: 45 VU for the CK, 39 for CACM and 31 for the CBK assay. We conclude from our results that (1) the CK is superior to the CBK assay in detecting episodes of CMV antigenemia, and (2) quantitative serum CMV PCR with CACM is not generally superior to pp65 antigenemia testing.

Comparative evaluation of three serological methods for detection of human herpesvirus 8-specific antibodies in Canadian allogeneic stem cell transplant recipients

Human herpesvirus 8 (HHV-8) has been associated with all types of Kaposi's sarcoma (KS), including posttransplantation KS. However, little is known regarding HHV-8 infections in hematopoietic stem cell transplant (SCT) recipients. In this study, we used a variety of serological assays, including in-house-developed enzyme immunoassays (EIAs) utilizing synthetic peptides corresponding to lytic viral antigens (ORFs 65 and K8.1) and a commercial EIA kit based on a whole virus lysate (Advanced Biotechnologies Inc.), as well as latent- and lytyc-antigen-based immunofluorescence assays (IFAs) to determine the seroprevalence of HHV-8 in 42 allogeneic SCT recipients from Canada. Using the two peptide-based EIA methods as for screening, HHV-8-specific antibodies were detected in five (12%) patients between days 21 and 91, although only one (2%) subject was positive for HHV-8-specific antibodies before transplantation. All positive results from these five patients were confirmed by at least one of the IFAs, with an additional patient showing seropositivity before transplantation. However, the commercial EIA was negative at all time points (days -7, 21, and 91) in those five patients. The episodes of seroconversion or reactivation were not associated with sustained viremia, since HHV-8 DNA was not detected by real-time PCR in the corresponding leukocytes and plasma of the seropositive patients. No clinical or laboratory abnormalities were clearly associated with HHV-8 seropositivity. This study confirms the utility of simple peptide-based EIA methods to assess the presence of HHV-8-specific antibodies in immunocompromised patients and emphasizes the need of conducting prospective studies to determine the source of HHV-8 infection in SCT recipients.

Quantitation of cytomegalovirus DNA in cerebrospinal fluid and serum specimens from AIDS patients using a novel highly sensitive nested competitive PCR and the cobas amplicor CMV monitor

A novel nested quantitative-competitive polymerase chain reaction (nQC-PCR) assay was developed to quantify as few as ten copies per tube of human cytomegalovirus DNA with an overall dynamic range of 10-10(5) copies per tube. This nQC-PCR assay is based on co-amplification of a mimic DNA and it was evaluated with 26 cerebrospinal fluid (CSF) specimens and 44 serum specimens from 70 CMV-infected AIDS patients, 35 of them were diagnosed of CMV retinitis. An excellent correlation was found between nQC-PCR assay and the commercially available Cobas Amplicor CMV Monitor trade mark (CACM) assay (R = 0.9999; P < 0.001; n = 42). Moreover, 13 serum samples with CMV viral loads undetectable with the CACM were successfully quantified by nQC-PCR. CMV viral load was significantly higher in patients with CMV retinitis (P = 0.003). The nQC-PCR assay described below is a very sensitive test for accurate quantitative detection of CMV DNA in different clinical specimens that avoids the need for high-cost instrumentation.

Quantitative real-time PCR with automated sample preparation for diagnosis and monitoring of cytomegalovirus infection in bone marrow transplant patients

BACKGROUND

In bone marrow and stem cell transplant patients, the widespread use of preemptive cytomegalovirus (CMV) antiviral therapy necessitates faster, more precise, and more sensitive quantitative laboratory methods for serial viral load monitoring.

METHODS

We developed a novel CMV viral load assay using real-time PCR of plasma DNA prepared by an automated robotic workstation. Fluorescent hybridization probes directed at the glycoprotein B (gB) gene (or EcoRI D region) of CMV were used to detect and quantify PCR products. The beta-globin gene was amplified in parallel to control for the efficiency of the extraction and PCR steps.

RESULTS

The assay was linear (R = 0.999) from a lower detection limit of 125 copies/mL to 5 x 10(9) copies/mL with a PCR efficiency of 1.975 (gB) or 2.02 (EcoRI D). The viral loads determined by PCRs directed at these two different viral targets were no different (n = 53; R = 0.928). The interassay CV was 3.5%, and the intraassay CV was 1-4%. Compared with a commercially available quantitative competitive PCR assay (Roche MONITOR; R = 0.59), the mean CMV viral load by real-time PCR was 3.1 times higher (mean ratio; P = 0.002). The diagnostic sensitivity and specificity of the real-time assay were 96% and 100%, respectively (n = 147), compared with 74% and 98% for a qualitative PCR assay (Roche AMPLICOR). On a subset of samples, the diagnostic sensitivity of viral culture was no greater than 50% (n = 44). Of 1115 clinical referral samples from 252 patients, 10% of the samples and 18% of the patients had low-level CMV viremia (median, 500 copies/mL). In this predominantly (85%) bone marrow transplant testing cohort, serial CMV viral load results were the predominant clinical trigger for the initiation, monitoring, and cessation of preemptive antiviral therapy.

CONCLUSIONS

The combination of automated DNA preparation and semiautomated real-time fluorescent PCR detection allows for a sensitive, precise, and accurate high-throughput assay of CMV viral load that can be used as the laboratory trigger for preemptive antiviral therapy.

Comparison of DNA amplification, mRNA amplification, and DNA hybridization techniques for detection of cytomegalovirus in bone marrow transplant recipients

A total of 676 specimens from 63 recipients of bone marrow allografts were tested for cytomegalovirus (CMV) by the following assays: CMV pp67 NucliSens (NS), AMPLICOR CMV MONITOR (RA), and the Digene CMV DNA test (DG). In a consensus analysis, the sensitivities and specificities were 60 and 99% (NS), 96 and 98% (RA), and 90 and 76% (DG), respectively; for detection of symptomatic CMV infection, they were 60 and 97% (NS), 65 and 97% (RA), and 95 and 77% (DG), respectively. In multivariate analysis, the major risk factor for symptomatic CMV infection was an increase in the viral load in the DG assay; in univariate analyses, maximum viral loads in both DG and RA assays and a rising viral load in the RA assay were also significant. The earliest detection of CMV replication was provided by the RA assay (mean, 39 days posttransplantation), followed by the DG assay (mean, 48 days) and the NS assay (mean, 58 days).

Prevention of cytomegalovirus disease in recipients of allogeneic stem cell transplants

The main risk factors for cytomegalovirus (CMV) disease in recipients of allogeneic stem cell transplants (SCT) are recipient CMV seropositivity and acute graft-versus-host disease. Currently, two antiviral strategies, prophylactic or preemptive antiviral treatment, are used for prevention of CMV disease. Preemptive treatment is most favorable when short-term (14-day) treatment is applied. Several methods are available for monitoring of CMV reactivation. PCR-based CMV DNA detection assays are the most sensitive methods; however, the clinical benefit of this high sensitivity is unclear. Even more, there is lack of clarity whether PCR tests can better be performed with plasma, whole blood, or peripheral blood leukocyte samples. Recovery of a CMV-specific CD8(+) cytotoxic-T-lymphocyte (CTL) response is necessary for preventing CMV reactivation and disease. Reconstitution of absolute CMV-specific CTL counts to values above 10 x 10(6) to 20 x 10(6) CTLs/liter is associated with protection from CMV disease. In the near future, preemptive therapy might be withheld in patients with CMV reactivation who are shown to have adequate CMV-specific cytotoxic T-cell levels. Antiviral therapy with (val)acyclovir has been studied only as prophylactic treatment for prevention of CMV infection. High-dose oral valacyclovir is more effective than acyclovir when used in addition to preemptive treatment of CMV reactivation with ganciclovir or foscarnet. Three antiviral drugs have been tested for preemptive therapy of CMV reactivation and/or treatment of CMV disease. Although intravenous ganciclovir is considered the drug of choice, foscarnet has similar efficacy and less toxicity, especially hematologic toxicity. Cidofovir has not been tested extensively, but so far the results are disappointing. Oral valganciclovir for preemptive treatment of SCT recipients is currently being studied. In addition to antiviral therapy, adoptive immunotherapy with CMV-specific cytotoxic T cells as prophylactic or preemptive therapy is a very elegant strategy; however, generation of these cells is expensive and time-consuming, and therefore the therapy is not available at every transplantation center. Magnetic selection of CMV-specific CD8(+) T cells from peripheral blood by using HLA class I-peptide tetramers may be very promising, making this strategy more accessible.

Automated extraction and quantification of human cytomegalovirus DNA in whole blood by real-time PCR assay

The measurement of human cytomegalovirus (HCMV) DNA in blood is becoming the standard method for monitoring HCMV infection in immune-suppressed and unsuppressed patients. As various blood compartments can be used, we have compared the HCMV DNA measured in whole blood (WB), peripheral blood leukocytes (PBL), and plasma by real-time PCR. We tested 286 samples: HCMV DNA was extracted automatically from WB and PBL with the MagNA Pure instrument (Roche Molecular Biochemicals) and manually from plasma samples. The HCMV DNA from WB, PBL, and plasma was measured by real-time Light Cycler PCR. Primers and probe were located in the UL 83 region. HCMV DNA was detected more frequently in WB (88.5%) than in the PBL (65.7%) (P < 0.0001) or the plasma (55.2%) (P < 0.0001). There was a good correlation between the positive results in WB and in PBL (r = 0.68; P < 0.0001), and 3.15 log(10) genome copies in 200000 PBL, equivalent to the threshold value of 50 pp65-positive polymorphonuclear cells per 200000 leukocytes, was equivalent to 3.4 log(10) genome copies in 200 microl of WB. WB was shown to be suitable for automated extraction and the quantitation of HCMV DNA by real-time Light Cycler PCR by analysis of serial samples from representative patients of various populations. This system may be very useful for monitoring of immune-suppressed and unsuppressed patients.

Monitoring cytomegalovirus infection in adult and pediatric bone marrow transplant recipients by a real-time PCR assay performed with blood plasma

The objective of this study was to evaluate the advantages of cytomegalovirus (CMV) real-time PCR in blood plasma to monitor CMV infection in a population of adult and pediatric bone marrow recipients in comparison with the pp65 antigenemia method. Fifty allogeneic bone marrow transplant recipients from our center, including 23 adults and 27 children, were enrolled. A CMV real-time PCR designed to amplify a well-conserved region of the UL123 gene was evaluated for its results with whole blood and blood plasma. The CMV real-time PCR assay and the CMV antigenemia method were performed in parallel with 558 blood samples. The results obtained by the two techniques were significantly correlated (r = 0.732; P < 0.0001). Twenty patients developed at least one episode of CMV replication, with a total of 24 episodes detected by CMV PCR; antigenemia assays were positive in 17 of these 24 episodes. The first positive PCR test preceded the first positive antigenemia by a median of 8 days. The median time interval necessary to obtain a negative CMV PCR test after implementation of preemptive treatment was 28 days. CMV PCR of plasma was positive in two children with CMV disease (one with early CMV pneumonia and one with CMV gastroenteritis), while CMV antigenemia remained negative. The use of CMV PCR with plasma to guide both implementation and discontinuation of CMV preemptive therapy might reduce the risk of occurrence of CMV disease since patients would be treated earlier, and it might also help to reduce the duration of treatment, which could attenuate the side effects of antiviral drugs.

Correlation between CMV genotypes, multiple infections with herpesviruses (HHV-6, 7) and development of CMV disease in kidney recipients in Kuwait

The possible correlation between cytomegalovirus, human herpesvirus types 6, 7 and cytomegalovirus-related clinical symptoms was studied in kidney transplant patients in Kuwait. Cytomegalovirus infection was diagnosed using the pp65 antigenemia assay. DNA of cytomegalovirus was detected by nested polymerase chain reaction (nested-PCR). PCR was also used to amplify the genes coding for structural proteins of human herpesvirus-6 (240 bp) and human herpesvirus-7 (186 bp). Glycoprotein B genotypes of cytomegalovirus were determined by restriction fragment length polymorphism. The average number of cells positive for cytomegalovirus pp65 antigen showed a steady increase with the severity of the cytomegalovirus-related symptoms. Furthermore, cytomegalovirus pp65 antigen positivity was significantly more frequent among recipients of cadaver kidney (45.5%) than among those who received live related kidneys (22.6%). Cytomegalovirus gB genotype 1 was detected more frequently (P<0.036) in recipients with live related donor kidney (38%) than in patients of cadaver kidney (13%). The genome of human herpesvirus-6 was detected at the same rate in patients with or without cytomegalovirus-related symptoms. However, the genome of human herpesvirus-7 was detected significantly more frequently (P<0.0001) in asymptomatic patients (41.7%) than in recipients with symptomatic cytomegalovirus infection (17%). We conclude that cytomegalovirus gB genotypes are not associated with the outcome of a cytomegalovirus infection in kidney transplant patients, that human herpesvirus-6 does not play a role in cytomegalovirus pathogenesis and that the role of human herpesvirus-7 in cytomegalovirus-related morbidity in kidney recipients remains unclear.

Pre-emptive oral ganciclovir can reduce the risk of cytomegalovirus disease in liver transplant recipients

A cohort of 65 liver transplant recipients was prospectively monitored with qualitative polymerase chain reaction (PCR) in plasma. The first 25 patients did not receive prophylaxis. From a consecutive group of 40 recipients, 11 high-risk patients donor CMV-seropositive/receptor CMV-seronegative (D+/R-), persistent CMV replication) received pre-emptive oral ganciclovir (1000 mg three times daily), when a marker of risk was identified, until day 90. The overall incidence of cytomegalovirus (CMV) disease at six months was 20% (five of 25 patients) in the non-prophylaxis group and 2.5% (one of 40 patients) in the group treated with pre-emptive oral ganciclovir (relative risk, 0.11; 95% confidence interval; 0.01-0.96; P = 0.04). The PCR sensitivity for detecting CMV disease was 80%, the specificity was 90%, and the positive and negative predictive values were 66% and 95%, respectively. Adverse events, graft rejection and survival were similar between groups. We conclude that pre-emptive oral ganciclovir in high-risk patients can reduce the risk of CMV disease.

Improved monitoring of cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation by an ultrasensitive plasma DNA PCR assay

Cytomegalovirus (CMV) DNA amplification assays in plasma have shown limited sensitivity compared to the detection of pp65 antigen in leukocytes. Our goal was to increase the sensitivity of a commercial CMV DNA PCR quantitative assay. After modification, the new assay was able to reproducibly detect 20 CMV DNA copies/ml of plasma. We compared this new ultrasensitive PCR assay with the standard PCR and the pp65 test for CMV detection and quantification in 22 consecutive allogeneic hematopoietic stem cell recipients. CMV infection or reactivation was detected in 84 of 319 (26%) samples by the ultrasensitive PCR assay compared to 38 of 319 (12%) samples by the pp65 assay (P < 0.01). All samples positive by the pp65 assay were positive by the ultrasensitive PCR, and CMV episodes were detected on average 4 days earlier and 7 days later than the first and the last pp65-positive test, respectively. In addition, during CMV episodes, the ultrasensitive assay identified positive samples that were inconsistently detected by the pp65 assay. The ultrasensitive assay was also much more sensitive than the standard PCR, with 26 versus 12% of CMV DNA-positive samples (P < 0.01). This assay improved the monitoring of CMV infection or reactivation in hematopoietic allogeneic stem cell recipients.

Monitoring of viral load by quantitative plasma PCR during active cytomegalovirus infection of individual liver transplant patients

A quantitative PCR test, the Cobas Amplicor CMV Monitor, was used for the monitoring of viral load in the peripheral blood of 27 individual liver transplant patients and correlated with cytomegalovirus (CMV) pp65 antigenemia. Altogether, 243 specimens were analyzed. During the first 3 months, 20 patients showed PCR positivity which correlated with pp65 antigenemia. Of those, 13 patients developed symptomatic CMV infection 27 to 52 days after transplantation, with a significantly higher peak viral load in PCR and in pp65 assay compared with the seven asymptomatic infections (median 10,200 versus 2,240 copies/ml, P < 0.05, and median 100 versus 30 pp65-positive cells/50,000 leukocytes, P < 0.01). Five were primary infections of D+/R- cases (donor CMV seropositive and recipient seronegative) and demonstrated, except in one case, a high peak viral load (>10,000 copies/ml; range, 10,200 to 21,600 copies, and > or =50 positive cells, range, 50 to 800 cells). The peak viral loads of the six D+/R+ patients with symptomatic infection varied widely (range, 2,290 to 126,000 copies and 50 to 300 positive cells). Two D-/R+ patients developed symptomatic infection with a lower viral load (range, 1,120 to 6,510 copies and 25 to 100 positive cells). All symptomatic infections were successfully treated with ganciclovir. The asymptomatic infections all in D+/R+ patients with low copy numbers (<5,500 copies) were monitored until CMV disappeared. One of the seven PCR-negative patients had one sample with low antigenemia, but the subsequent specimens were all negative. The time-related correlation of the two methods was also good. In summary, quantitative PCR could equally well be used as the CMV pp65 assay for the monitoring of viral load in individual transplant patients.

Multiplex, quantitative, real-time PCR assay for cytomegalovirus and human DNA

We created a multiplex, quantitative, real-time PCR assay that amplifies cytomegalovirus (CMV) and human DNA in the same reaction tube, allowing for a viral load determination that is normalized to measured human DNA. The assay targets a conserved region of the CMV DNA polymerase gene that is not affected by known drug resistance mutations. All 36 strains of CMV detected by culture or qualitative PCR in a population of lung transplant recipients were detected. The assay detected 1 to 10 copies of CMV plasmid DNA. The analytic sensitivity was not affected by the presence of DNA from 10(6) human cells but was reduced approximately 10-fold by alkaline lysates of leukocyte preparations. CMV quantitation was linear over a range of 10(1) to 10(6) copies. The intraassay and interassay coefficients of variation were 29 and 40%. Human DNA was regularly detected in patient plasma samples, and the amount was increased by storage of blood at room temperature before plasma separation and by plasma separation techniques that allowed leukocyte contamination. Applied to whole blood, the assay provides a measurement of CMV DNA in relation to cellular content without a need for cell counting procedures. Applied to plasma, the assay can reveal artifactual increases in plasma CMV levels resulting from leukocyte contamination. Further study of the utility of this assay to monitor patient populations at risk for CMV disease is warranted.

Rapid diagnosis in pediatric infectious diseases: the past, the present and the future

The focus of rapid diagnosis of infectious diseases of children in the last decade has shifted from variations of the conventional laboratory techniques of antigen detection, microscopy and culture to that of molecular diagnosis of infectious agents. Pediatricians will need to be able to interpret the use, limitations and results of molecular diagnostic techniques as they are increasingly integrated into routine clinical microbiology laboratory protocols. PCR is the best known and most successfully implemented diagnostic molecular technology to date. It can detect specific infectious agents and determine their virulence and antimicrobial genotypes with greater speed, sensitivity and specificity than conventional microbiology methods. Inherent technical limitations of PCR are present, although they are reduced in laboratories that follow suitable validation and quality control procedures. Variations of PCR together with advances in nucleic acid amplification technology have broadened its diagnostic capabilities in clinical infectious disease to now rival and even surpass traditional methods in some situations. Automation of all components of PCR is now possible. The completion of the genome sequencing projects for significant microbial pathogens, in combination with PCR and DNA chip technology, will revolutionize the diagnosis and management of infectious diseases.

Quantitation of CMV by real-time PCR in transfusable RBC units

BACKGROUND

CMV is one of the most significant pathogens infecting immunocompromised individuals. CMV is transmissible through transfusion of blood components. The goal of this study was to measure CMV levels in RBC units using a sensitive and quantitative DNA amplification assay.

STUDY DESIGN AND METHODS

An assay to measure CMV load was developed by using real-time PCR to target the major immediate early viral gene. A probe (TaqMan, Applied Biosystems) was used to confirm product specificity and to permit quantitation of CMV in blood samples on a sequence detection system (ABI Prism 7700, Applied Biosystems).

RESULTS

The assay was shown to be accurate, linear, and sensitive to as few as five copies of CMV DNA per PCR. The assay was applied to aliquots of RBC units from 203 healthy donors, 110 of whom were seropositive for CMV. CMV DNA was not detected in any of the 203 RBC samples.

CONCLUSION

The findings statistically imply that at least 98.5 percent of RBC units have a CMV load of less than 250 copies per mL. Future clinical studies on larger numbers of units are required to determine the utility of real-time PCR in evaluating the risk of CMV transmission and in confirming the efficacy of WBC reduction.

Performance characteristics of an automated PCR assay for the quantification of cytomegalovirus DNA in plasma

The COBAS Amplicor CMV Monitor test (Roche Diagnostics), an automated polymerase chain reaction (PCR) assay for the quantification of cytomegalovirus (CMV) DNA in plasma samples, was evaluated in a routine diagnostic laboratory. Using cell culture-derived CMV and CMV-negative human plasma, the linear detection range of the assay as well as its intra-and inter-assay variabilities were assessed. The study design allowed distinguishing variations in results related to amplification and detection from those caused by differences in the efficiency of DNA extraction. The assay was able to identify the majority of samples correctly as positive with CMV DNA concentrations above the limit of detection. However, the reported values were often twofold or more different from the (theoretical) input, which could be explained partly by inefficient DNA extraction. The following values were computed for the coefficients of determination R(2): inter-assay variability excluding DNA extraction, R(2)=0.982; including DNA extraction, R(2)=0.977; intra-assay variability excluding DNA extraction, R(2)=0.992; including DNA extraction, R(2)=0.992. On balance, the test has acceptable within-run and between-run reproducibility. It therefore allows the comparison of results obtained at different time-points as well as in different laboratories, e.g. in multi-centre studies.

Lack of emergence of cytomegalovirus UL97 mutations conferring ganciclovir (GCV) resistance following preemptive GCV therapy in allogeneic stem cell transplant recipients

Fifty allogeneic stem cell transplant recipients were enrolled in a prospective cytomegalovirus pp65 antigenemia-guided preemptive therapy trial. Among these, 10 of 34 patients who received ganciclovir exhibited sustained and/or recurrent antigenemia despite treatment. Thirteen leukocyte preparations from these 10 subjects were screened for the presence of the most frequent cytomegalovirus UL97 mutations conferring ganciclovir resistance. None of these mutations were detected after mean and median ganciclovir exposures of 31.6 and 28.0 days, respectively.

Allogeneic transplantation for multiple myeloma: further evidence for a GVHD-associated graft-versus-myeloma effect

We report a series of 37 consecutive patients with multiple myeloma (MM) who received an allograft between 1990 and 2000 at our institution. Median age was 47 years, and nearly 70% of patients were Durie-Salmon stage III. A median of five cycles of chemotherapy were given before transplant, with a median interval between diagnosis and transplant of 9.3 months. We report a nonrelapse mortality rate of 22% with a median follow-up period of 40 months, whereas complete remission (CR) rate at 12 months is estimated at 57%. Treatment failure rate and overall survival at 40 months are estimated at 52% and 32%, respectively. The number of chemotherapy cycles prior to allotransplantation achieved borderline statistical significance as a poor prognosis factor for overall survival (P = 0.05), while the presence of chronic graft-versus-host disease (cGVHD) was significantly correlated with CR achievement (P = 0.036). Our study confirms that early allografting in MM can yield toxicity rates significantly lower than those associated with historical cohorts, and supports the hypothesis that cumulative chemotoxicity has a negative influence on mortality and survival rates. More importantly, our study clearly demonstrates an association between cGVHD and CR and brings further evidence in favor of a graft-versus-myeloma effect.

Qualitative plasma PCR assay (AMPLICOR CMV test) versus pp65 antigenemia assay for monitoring cytomegalovirus viremia and guiding preemptive ganciclovir therapy in allogeneic stem cell transplantation

The performances of a commercially available qualitative plasma PCR assay (AMPLICOR CMV test; Roche Diagnostics) and the pp65 antigenemia assay (AG) were evaluated for the monitoring of cytomegalovirus (CMV) viremia in 43 allogeneic stem cell transplant recipients. In addition, the suitabilities of both assays for triggering the initiation of preemptive ganciclovir therapy were assessed. A total of 37 CMV viremic episodes were detected in 28 patients. Positivity of plasma PCR testing in one or more consecutive specimens was the only marker of CMV viremia in 18 of the 37 episodes (PCR positive and AG negative, n = 50 specimens). Five episodes were diagnosed on the basis of a single positive AG result (AG positive and PCR negative, n = 5 specimens); both assays were eventually positive (PCR positive and AG positive, n = 27 specimens) for 14 viremic episodes; for these episodes, conversion of the PCR assay result to a positive result occurred an average of 1 week before conversion of the AG result. Overall, the concordance between the two methods was 90%, and the sensitivities of the plasma PCR assay and AG for the detection of CMV viremic episodes were 86.5 and 51.3%, respectively. Two patients who tested positive by both assays simultaneously progressed to CMV end-stage organ disease, despite the initiation of preemptive ganciclovir therapy. Conversion of the AG result to a negative result upon administration of preemptive ganciclovir therapy occurred a median of 7.5 days earlier than conversion of the plasma PCR assay result. Nineteen of the 28 patients with CMV viremia received AG-guided preemptive ganciclovir therapy; had the positivity of the plasma PCR assay triggered the initiation of preemptive therapy, 9 additional patients would have been unnecessarily treated since none of them developed CMV end-stage organ disease. Although the AMPLICOR CMV assay is more sensitive than AG, the latter appears to be more suitable both for guiding the initiation of preemptive therapy and for monitoring a patient's response to antiviral therapy.

CMV monitoring after peripheral blood stem cell and bone marrow transplantation by pp65 antigen and quantitative PCR

We prospectively monitored 74 consecutive allogeneic and 50 autologous patients after bone marrow/stem cell transplantation from May 1999 to October 2000 at our institution with quantitative CMV PCR and pp65 antigen assay once weekly from conditioning therapy to days 120 and 80 after transplantation, respectively. Written informed consent was obtained from every patient. CMV prophylaxis consisted of acyclovir during transplant. Additionally all patients received only platelet products from CMV-negative donors. In the case of CMV infection preemptive therapy with gancyclovir was applied. In the case of CMV disease high-dose immunoglobulin was given as well. In the allogeneic setting 16 out of 74 (22%) patients developed a positive PCR. Seven episodes of a positive pp65 antigen assay occurred in six allograft recipients. In the autologous setting no positive assay was found during the whole observation period. Additionally, in 6/16 patients a lymphoproliferative assay was performed during CMV infection. Two patients showed a positive (15 and 5.4) and four a negative (2,1.6,1,1.8) stimulation index.

Comparison of plasma polymerase chain reaction and pp65-antigenemia assay in the quantification of cytomegalovirus in liver and kidney transplant patients

BACKGROUND

Cytomegalovirus (CMV) is a significant problem in transplantation. The antiviral treatment is based on the clinical symptoms and the rapid laboratory diagnosis. Although polymerase chain reaction (PCR) methods have already been widely used, the clinical correlation of the findings is not clear.

OBJECTIVE

The objective of this study was to investigate the usefulness of a quantitative plasma PCR test and compare it with the pp65-antigenemia test in the detection of clinically significant CMV infections in liver and kidney transplant patients.

STUDY DESIGN

The clinical material consisted of 253 consecutive blood samples was tested using a quantitative polymerase chain reaction test, Cobas Amplicor CMV Monitor (Roche) and pp65 antigenemia assay. Plasma was used for PCR and leucocytes were used for the antigenemia test.

RESULTS

CMV was detected in 89 out of 253 blood samples by one or both methods. PCR detected 78 (range 274-165000 copies/ml) and pp65 antigenemia test 79 (range 1-1500 positive cells/50000) of the positive findings. The sensitivity and specificity of PCR test was 86 and 94%, respectively. The PCR detected all clinically significant CMV infections (>10 positive cells in pp65 test) and infections which required antiviral treatment. In addition, the correlation between the two tests was almost linear.

CONCLUSIONS

The quantitative PCR appears to be a suitable alternative to diagnose and monitor CMV infections in transplant patients.