Comparison of a new quantitative cytomegalovirus DNA assay with other detection methods

Clinical utility of viral load in management of cytomegalovirus infection after solid organ transplantation

The negative impact of cytomegalovirus (CMV) infection on transplant outcomes warrants efforts toward improving its prevention, diagnosis, and treatment. During the last 2 decades, significant breakthroughs in diagnostic virology have facilitated remarkable improvements in CMV disease management. During this period, CMV nucleic acid amplification testing (NAT) evolved to become one of the most commonly performed tests in clinical virology laboratories. NAT provides a means for rapid and sensitive diagnosis of CMV infection in transplant recipients. Viral quantification also introduced several principles of CMV disease management. Specifically, viral load has been utilized (i) for prognostication of CMV disease, (ii) to guide preemptive therapy, (iii) to assess the efficacy of antiviral treatment, (iv) to guide the duration of treatment, and (v) to indicate the risk of clinical relapse or antiviral drug resistance. However, there remain important limitations that require further optimization, including the interassay variability in viral load reporting, which has limited the generation of standardized viral load thresholds for various clinical indications. The recent introduction of an international reference standard should advance the major goal of uniform viral load reporting and interpretation. However, it has also become apparent that other aspects of NAT should be standardized, including sample selection, nucleic acid extraction, amplification, detection, and calibration, among others. This review article synthesizes the vast amount of information on CMV NAT and provides a timely review of the clinical utility of viral load testing in the management of CMV in solid organ transplant recipients. Current limitations are highlighted, and avenues for further research are suggested to optimize the clinical application of NAT in the management of CMV after transplantation.

Comparison of cytomegalovirus pp-65 antigenemia assay and plasma DNA correlation with the clinical outcome in transplant recipients

The relationship between quantitative antigenemia and plasma DNAemia was studied for monitoring cytomegalovirus (CMV) viremia in CMV infection (CMVI) or disease (CMVD), in 20 transplant recipients (13 CMD, seven CMVI). A total of 142 samples of blood were assayed for CMV-DNA and pp-65 antigenemia (CMV-Ag). A quantitative correlation between both markers was found (P < 0.0001). First CMV antigenemia as well as first plasma DNA viral load was similar in CMVI and CMVD (29 vs. 24 CMV-Ag+ cells/10(5) PMN; and 7445 vs. 12407 CMV-DNA copies/ml). The maximum antigenemia was higher in CMVD than in CMVI (146 +/- 87 vs. 61 +/- 54 +cells/10(5) PMN, P < 0.05), but the highest CMV plasma viral load was similar in both groups (62592 +/- 33000 vs. 42055 +/- 38600 copies/ml). In nine patients, maximum antigenemia coincided with highest plasma DNA viral load, but in 10 highest DNAemia occurred 6 days later. On the contrary, antigenemia declined faster than CMV-DNAnemia, after treatment.

Cytomegalovirus infection after liver transplantation: viral load as a guide to treating clinical infection

BACKGROUND

Quantitative commercial assays for early and accurate detection of active cytomegalovirus (CMV) infection after liver transplantation are widely available. However, meaningful interpretation of viral load measurements is hampered by the lack of definitive cutoff points that correlate with clinically significant disease.

METHODS

One hundred fifty liver allograft recipients were prospectively monitored for the presence of CMV DNA for the first 12 weeks after orthotopic liver transplantation using the Murex hybrid capture system. The first CMV DNA value after liver transplantation, a weekly rise in CMV DNA (gradient value), and the CMV DNA value on clinical detection of active infection (critical value) were analyzed as risk factors for CMV infection.

RESULTS

Forty-four (29.3%) of 150 patients had detectable CMV DNA within 12 weeks of transplantation, and 20 (13.3%) experienced symptomatic CMV infection. Multiple regression analysis demonstrated that baseline CMV DNA level above 10 pg/mL, positive weekly increase in CMV DNA level, and critical CMV DNA level above 13 pg/mL were independent risk factors for clinically significant infection. Using Cox's multiple regression model, the hazard ratio was 13.9 for baseline CMV DNA above 10 (P =0.0001; 95% confidence interval, 3.5-54) and 13 for a weekly increase in the gradient (P =0.0003; 95% confidence interval, 3.5-50). Critical CMV DNA level above 13 correlated with active infection (100% sensitivity, 98% specificity, 90% positive predictive value, 100% negative predictive value).

CONCLUSION

Baseline and gradient CMV DNA viral load levels correlate with active CMV infection in liver allograft recipients. These data indicate that CMV viral load detection by hybridization methodology is useful in predicting active CMV infection and could be used in a preemptive strategy in liver allograft recipients.

Prospective randomized trial to assess the value of preemptive oral therapy for CMV infection following liver transplantation

BACKGROUND

With the development of sensitive tests to detect cytomegalovirus (CMV) viremia, preemptive approaches become a reasonable alternative to general CMV prophylaxis. We performed a randomized trial comparing pp65-antigenemia guided preemptive therapy using oral ganciclovir with symptom-triggered intravenous ganciclovir treatment.

METHODS

Eighty-eight of 372 liver transplant recipients developed antigenemia early after orthotopic liver transplantation. Twenty-eight symptomatic patients with antigenemia were excluded from randomization and treated with intravenous ganciclovir. Sixty pp65-antigen-positive asymptomatic patients were randomized to receive either oral ganciclovir 3x1 g/day for 14 days (group 1) or no preemptive treatment (group 2). Patients that developed CMV disease were treated with intravenous ganciclovir 2x5 mg/kg body weight for 14 days. The high-risk (Donor+/Recipient-) patients were equally distributed in the two study groups.

RESULTS

Three of 30 (10%) patients on oral ganciclovir developed mild to moderate CMV disease compared with 6/30 (20%) patients in the control group. In the Donor+/Recipient- patients, the incidence of CMV disease was 1/6 and 3/7. All disease episodes resolved after intravenous treatment. The 1- and 3-year patient and organ survival was the same in the study groups and in the patients with or without CMV infection. No deaths related to CMV occurred.

CONCLUSIONS

The positive predictive value of pp65-antigenemia for the development of CMV disease was very low, and, in 28/88 patients (32%), antigenemia did not precede symptoms. Therefore, pp65-antigenemia is of limited value in deciding on the timing and need for ganciclovir therapy after liver transplantation.

Quantification of cytomegalovirus (CMV) viral load by the hybrid capture assay allows for early detection of CMV disease in lung transplant recipients

BACKGROUND

We prospectively compared the hybrid capture system (HCS) assay with conventional cell culture and shell vial assay for the detection of cytomegalovirus (CMV) infection and disease in the lung transplant population.

METHODS

Between January 1999 and February 2000, 34 lung transplant patients at Loyola University Medical Center, who were considered to be at risk for CMV disease, underwent surveillance testing for CMV cell culture, shell vial assay and HCS assay according to a pre-determined schedule. In addition, bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy were performed at regular intervals and for clinical indications. All BAL samples were sent for CMV cultures and biopsy specimens were analyzed for histopathologic evidence of CMV by immunoperoxidase staining using antibody to early immediate nuclear antigen.

RESULTS

Ten patients developed CMV disease/syndrome during the course of the study. The sensitivity, specificity, positive predictive value and negative predictive value were >90% for the HCS assay. The sensitivity of the HCS assay (90%) was statistically significantly higher than the sensitivity of either the SV assay (40%) or the cell culture (50%). In addition, the HCS assay was able to detect CMV 50 +/- 67 days prior to clinical evidence of CMV disease and an average of 36 days prior to the other detection techniques.

CONCLUSION

The HCS assay is a sensitive diagnostic technique able to reliably detect CMV disease earlier than other diagnostic methods in the lung transplant population. Future studies may be able to evaluate whether pre-emptive anti-viral therapy targeted to specific viral loads using the HCS assay will be beneficial in preventing morbidity associated with CMV disease.

Evaluation of the Murex CMV DNA Hybrid Capture assay (version 2.0) for early diagnosis of cytomegalovirus infection in recipients of an allogeneic stem cell transplant

Early diagnosis of CMV infection based on sensitive diagnostic assays has helped to reduce CMV-related mortality after allogeneic stem cell transplantation (SCT). In this study, the commercialized Murex CMV DNA Hybrid Capture assay (version 2.0) (HCS) was prospectively compared to an in-house CMV-DNA PCR assay from whole blood in patients after allogeneic stem cell transplantation. Overall, a high concordance between HCS and PCR was documented (kappa = 0.686; n = 385). The HCS assay was found to be as sensitive as the PCR indicating active CMV infection at a median of 35 and 34 days after transplantation, respectively. None of the HCS-negative patients developed CMV-related symptoms (negative predictive value 100%). Declining CMV DNA load in the blood was found to be an indicator for effective antiviral therapy, whereas persistence of a high viral load was associated with fatal CMV disease. In conclusion, the Hybrid Capture CMV DNA assay (v 2.0) allows early diagnosis of CMV infection after allogeneic SCT and assessment of the efficacy of antiviral therapy.

CMV infection of liver transplant recipients: comparison of antigenemia and molecular biology assays

BACKGROUND

CMV is a major clinical problem in transplant recipients. Thus, it is important to use sensitive and specific diagnostic techniques to rapidly and accurately detect CMV infection and identify patients at risk of developing CMV disease. In the present study, CMV infection after liver transplantation was monitored retrospectively by two molecular biology assays - a quantitative PCR assay and a qualitative NASBA assay. The results were compared with those obtained by prospective pp65 antigenemia determinations.

MATERIALS AND METHODS

87 consecutive samples from 10 liver transplanted patients were tested for CMV by pp65 antigenemia, and CMV monitor and NASBA pp67 mRNA assay.

RESULTS

CMV infection was detected in all patients by antigenemia and CMV monitor, whereas NASBA assay identified only 8/10 patients with viremia. Furthermore, CMV infection was never detected earlier by molecular biology assays than by antigenemia. Only 5/10 patients with CMV infection developed CMV disease. Using a cut off value of 8 cells/50,000, antigenemia was found to be the assay that better identified patients at risk of developing CMV disease. However, the kinetics of the onset of infection detected by NASBA and CMV monitor seemed to have better identified patients at risk of developing CMV disease. Furthermore, before onset of disease, CMV pp67 mRNA was found to have similar or better negative and positive predictive values for the development of CMV disease.

CONCLUSIONS

The present data, suggests that the concomitant use of antigenemia and pp67 mRNA assay gives the best identification of patients at risk of developing CMV disease.

New strategies for prevention and therapy of cytomegalovirus infection and disease in solid-organ transplant recipients

In the past three decades since the inception of human organ transplantation, cytomegalovirus (CMV) has gained increasing clinical import because it is a common pathogen in the immunocompromised transplant recipient. Patients may suffer from severe manifestations of this infection along with the threat of potential fatality. Additionally, the dynamic evolution of immunosuppressive and antiviral agents has brought forth changes in the natural history of CMV infection and disease. Transplant physicians now face the daunting task of recognizing and managing the changing spectrum of CMV infection and its consequences in the organ recipient. For the microbiology laboratory, the emphasis has been geared toward the development of more sophisticated detection assays, including methods to detect emerging antiviral resistance. The discovery of novel antiviral chemotherapy is an important theme of clinical research. Investigations have also focused on preventative measures for CMV disease in the solid-organ transplant population. In all, while much has been achieved in the overall management of CMV infection, the current understanding of CMV pathogenesis and therapy still leaves much to be learned before success can be claimed.

Use of molecular assays in diagnosis and monitoring of cytomegalovirus disease following renal transplantation

We compared two commercial molecular assays (the Murex Hybrid Capture CMV DNA assay [HCA], version 2, and the Roche Amplicor plasma PCR assay) with a standard shell vial assay in detecting and predicting cytomegalovirus (CMV) disease in a group of renal transplant patients and assessed the role of viral load measurements (using the HCA) in their management. The sensitivity of the HCA and Amplicor assay in terms of disease detection was 100%, compared to 71% for the shell vial assay. Both the HCA and the PCR assay detected all cases of disease, at medians of 11 and 12.5 days before the onset of symptoms, respectively. Significantly higher viral loads were detected in those patients with symptoms (7.9 x 10(5) copies/ml) than in patients without symptoms (7.9 x 10(4) copies/ml; P < 0.0001). There was also a trend towards higher viral loads in those patients with primary infections (7.8 x 10(5) copies/ml) than in those patients with reactivations of CMV disease or reinfections. Successful treatment with ganciclovir was associated with a >90% reduction in viral load. Both of these new assays are sensitive and easy to use. A comparison of accurate quantitation is also useful in monitoring responses to antiviral therapy.

Multicenter comparison of the digene hybrid capture CMV DNA assay (version 2.0), the pp65 antigenemia assay, and cell culture for detection of cytomegalovirus viremia

We compared the Digene Hybrid Capture CMV DNA Assay version 2.0, the pp65 antigenemia assay, traditional tube culture, and shell vial culture for the detection of cytomegalovirus (CMV) viremia in several patient populations at three centers. Of 561 blood specimens collected from 402 patients, complete clinical and laboratory data were available for 489. Using consensus definitions for true positives and true negatives, the sensitivities of the Hybrid Capture assay, antigenemia, shell vial, and tube culture were 95, 94, 43, and 46%, respectively. The specificities of the Hybrid Capture assay and antigenemia were 95 and 94%, respectively. At all three study sites, the detected level of CMV viremia was significantly higher with the Hybrid Capture assay or antigenemia than with shell vial and tube culture. In a group of 131 healthy nonimmunosuppressed volunteers, the Hybrid Capture assay demonstrated a specificity of over 99%. The Hybrid Capture assay is a standardized assay that is simple to perform and can utilize whole blood specimens that have been stored for up to 48 h. The high sensitivity and specificity of the Hybrid Capture assay along with its simplicity and flexibility make it a clinically useful assay for the detection of CMV viremia in immunocompromised or immunosuppressed patients. Further evaluation to determine its role in predicting CMV disease and for monitoring the therapeutic response to anti-CMV therapy is needed.

Determination of cytomegalovirus DNA load for monitoring of cytomegalovirus disease and antiviral treatment in solid organ transplant patients, comparing limiting-dilution PCR and hybrid capture assay with cytomegalovirus isolation

OBJECTIVE: To improve the identification of patients at risk of developing cytomegalovirus (CMV) disease. MATERIALS AND METHODS: In a prospective study of 50 kidney or liver transplant patients who developed fever, 133 EDTA blood samples were analyzed, using two tests to measure CMV DNA: a 10-fold limiting dilution of an extract of 2 million leukocytes for CMV PCR, and a CMV hybrid capture assay. Both tests were compared with virus isolation, using an equivalent amount of leukocytes as a base for all three tests. RESULTS: The limiting-dilution CMV PCR and the hybrid capture assay presented relatively similar changes of sensitivity and specificity at different CMV DNA concentrations. The kinetics of the positive and negative predictive values were also comparable. A higher CMV DNA load corresponded to an increased risk of developing CMV disease. Furthermore, an increase in the endpoint dilution of a positive CMV PCR also corresponded to more severe disease. After antiviral treatment, the CMV PCR decreased by at least 100-fold (2 log10) in 10 cases and by 10-fold (1 log10) in five cases. Thus, there was a decrease in 15 of 18 (83%) patients. Similarly, with the hybrid capture assay, the amount of CMV DNA decreased about 100-fold in five patients and decreased by about 0.5 genome equivalents in five cases, i.e. in 10 of 12 (83%) patients. CONCLUSION: Both methods proved clinically useful for detecting patients at risk of developing CMV disease and for monitoring antiviral treatment in solid organ transplant patients.

Quantitation of cytomegalovirus: methodologic aspects and clinical applications

Cytomegalovirus (CMV) is an important pathogen in transplant recipients and human immunodeficiency virus (HIV)-infected individuals. Major progress has been made in developing quantitative detection methods for CMV in recent years. Due to their high sensitivity, these assays can detect CMV early, and quantitation may be useful in predicting the patient's risk for disease and in monitoring the effect of antiviral therapy. This review discusses methodological aspects of currently used quantitative assays for CMV (i.e., viral culture techniques, antigen detection assays, DNA detection assays including PCR, branched-DNA assay, and the DNA hybrid capture assay) and addresses the correlation of systemic and site-specific CMV load and CMV disease in different populations of immunosuppressed patients as well as the response to antiviral treatment. To date, direct antigen detection and molecular techniques have largely replaced traditional culture-based techniques for CMV quantitation. In general, a high systemic CMV load is correlated with CMV disease. This correlation is strong in the HIV-infected population and in solid-organ transplant recipients but less clear in allogeneic marrow transplant recipients. Measuring the viral load at specific anatomic sites may be an alternative way to assess disease activity in situations where the systemic viral load correlates poorly with disease activity. A reduction of the systemic CMV load also correlates with a response to antiviral treatment, but more research is needed to evaluate the role of viral load as a surrogate marker for drug resistance. Due to the widespread use of quantitative CMV detection techniques to direct and monitor antiviral treatment, there is a great need for an assessment of the reproducibility of test results and better standardization of the assays.

Evaluation of Murex CMV DNA hybrid capture assay for detection and quantitation of cytomegalovirus infection in patients following allogeneic stem cell transplantation

Murex hybrid capture DNA assay (HCS) is a solution hybridization antibody capture assay for detection and quantitation of cytomegalovirus (CMV) DNA in leukocytes. To determine whether CMV HCS is sensitive enough to initiate and monitor antiviral therapy after allogeneic stem cell transplantation (SCT), 51 consecutive SCT recipients were prospectively screened for the appearance of CMV infection by HCS, PCR, and culture assays from blood samples. Preemptive antiviral therapy was initiated after the second positive PCR result in all patients, as previously reported, and HCS was not considered for clinical decision making. A total of 417 samples were analyzed. Of these, 21 samples were found to be positive by PCR and HCS, 88 samples were PCR positive but HCS negative, and 308 were negative by both assays. Concordance of results between PCR and HCS and between HCS and blood culture was observed in 78.9 and 95.9% of the samples assayed, respectively. PCR was found to be more sensitive than HCS, and HCS was more sensitive than the blood culture assay (P < 0.0001). Four patients with symptomatic CMV infection were PCR positive prior to the onset of CMV-related symptoms, whereas HCS detected CMV DNA in three patients prior to and one at onset of CMV disease. The numbers of genomes per milliliter of blood were higher in patients with symptomatic CMV infection than in those with asymptomatic CMV infection (P = 0.06). None of the HCS-negative patients developed CMV disease. Thus, all patients with CMV disease were correctly identified by HCS; however, the lower sensitivity limit of the HCS assay may still be insufficient to allow diagnosis of CMV infection early enough to prevent CMV disease in patients following allogeneic SCT.