A serological testing algorithm for the diagnosis of primary CMV infection in pregnant women

Maternal and congenital human cytomegalovirus infection: laboratory testing for detection and diagnosis

Human cytomegalovirus (CMV) is the leading cause of congenital infection worldwide and the most common cause of non-genetic sensorineural hearing loss. As there is no vaccine or other specific intervention to prevent congenital CMV infection, there is a need to identify maternal and congenital infections with sensitive and specific testing as early as possible. There is no widely accepted practice for screening during pregnancy or in all newborns for identification of possible cases of congenital CMV. Currently, screening during pregnancy is limited to those identified as at risk followed by fetal and/or neonatal testing when congenital infection is suspected. This review focuses primarily on the current status of laboratory testing for diagnosis of maternal and congenital CMV infections. Primary maternal infection is best diagnosed using serologic testing, including CMV IgM, IgG, and avidity testing, while fetal infection should be assessed by nucleic acid amplification testing (NAAT) of amniotic fluid. Urine and saliva NAATs are the mainstay for diagnosis of congenital CMV in the first 3 weeks of life. Testing of dried blood spots can be useful for diagnosis of congenital CMV outside of the newborn period. The gaps in knowledge such as the prognostic value of viral loads in various sample types are addressed.

Comparison of two serological screening strategies for cytomegalovirus primary infection in the first trimester of pregnancy

INTRODUCTION

CMV serology screening in the first trimester pregnancy is based on IgG and IgM testing followed by IgG avidity in cases with positive IgM. However, the sensitivity of this strategy to diagnose maternal primary infection has been questioned. The objective of the study was to compare this strategy 1 with a strategy 2 consisting of running avidity test on all samples with positive IgG (ignoring IgM results) using fully automated current generation CMV IgG, IgM and IgG avidity assays.

POPULATION AND METHODS

1516 consecutive pregnant women between 12 and 14 weeks were screened in one maternity. Strategy 1 was done prospectively with LIAISON® CMV IgG II and LIAISON® CMV IgM II, followed by LIAISON® CMV IgG Avidity II and VIDAS® CMV IgG avidity II testing in cases with positive or equivocal IgM. Strategy 2 was done retrospectively on the same population and consisted of running avidity with the LIAISON® CMV IgG Avidity II in all samples with positive IgG.

RESULTS

The sensitivity to diagnose a confirmed or a possible maternal primary infection in the first trimester was 91.6 % and 83 % for strategy 1 and 2 respectively (p > 0.99). Strategy 1 missed one possible primary infection and strategy 2 missed 2 confirmed primary infection. Inconclusive results happened in 0 and 0.7 % of samples with strategy 1 and 2 respectively.

CONCLUSION

This study suggests that strategy 1 has better sensitivity and practicability than strategy 2. However, to achieve a good performance with strategy 1, using highly sensitive IgM assay is mandatory.

Congenital cytomegalovirus infection: the state of the art and future perspectives

Congenital cytomegalovirus (cCMV) infection is the most common congenital infection, with an estimated incidence of approximately one in 200 infants in high-income settings. Approximately one in four children may experience life-long consequences, including sensorineural hearing loss and neurodisability. Knowledge regarding prevention, diagnosis, and treatment increased in the recent years, but some challenges remain. In this review, we tried to summarize the current knowledge on both the obstetrical and pediatric areas, while also highlighting controversial aspects and future perspectives. There is a need to enhance awareness among the general population and pregnant women through specific information programs. Further research is needed to better define the classification of individuals at birth and to have a deeper understanding of the long-term outcomes for so defined children. Finally, the availability of valaciclovir medication throughout pregnancy, where appropriate, has prompted the assessment of a universal serological antenatal screening. It is recommended to establish a dedicated unit for better evaluation and management of both mothers and children.

Universal First-Trimester Cytomegalovirus Screening and Valaciclovir Prophylaxis in Pregnant Persons: A Cost-Effectiveness Analysis

BACKGROUND

Recent studies suggest a possible benefit of valaciclovir prophylaxis to prevent vertical transmission after a positive serologic screen for primary maternal cytomegalovirus infection during pregnancy, although its cost-effectiveness remains uncertain.

OBJECTIVE

We sought to determine the circumstances under which universal first-trimester maternal serologic screening for maternal cytomegalovirus infection, with valaciclovir prophylaxis to prevent congenital cytomegalovirus, is cost-effective.

STUDY DESIGN

We performed a decision analysis from the perspective of the pregnant person to assess whether universal maternal screening in the first trimester, with subsequent valaciclovir prophylaxis (8g/day from time of positive serologic screen for primary maternal cytomegalovirus infection through 21 weeks' gestation) for those who are acutely infected, is cost-effective compared to usual care (i.e., no routine serologic screening, but amniocentesis if mid-trimester sonographic findings suggest cytomegalovirus). For baseline estimates, we assumed a 35% risk of congenital cytomegalovirus after primary maternal infection and a 71% risk reduction with valaciclovir. We varied valaciclovir's efficacy to identify whether and at what threshold universal screening would be estimated to be cost-effective, compared to usual care. Monte Carlo analyses were performed. A willingness-to-pay threshold of $100,000/quality-adjusted life year was used to define cost-effectiveness.

RESULTS

Under base-case estimates, first-trimester universal screening and valaciclovir prophylaxis for seropositive pregnant persons with acute cytomegalovirus infection is not cost-effective, with a cost of $137,854 per maternal QALY, but results in 14 fewer cytomegalovirus-affected children per 100,000 pregnancies compared to usual care. In one-way sensitivity analysis, universal screening and treatment is estimated to be the cost-effective strategy if the incidence of primary maternal cytomegalovirus infection exceeds 2.6%, baseline risk of vertical transmission of cytomegalovirus without prophylaxis is greater than 36.8%, and the risk reduction of vertical transmission of cytomegalovirus with valaciclovir prophylaxis exceeds 75.9%. In Monte Carlo analyses, first-trimester universal serologic screening with valaciclovir prophylaxis is estimated to be the cost-effective strategy in 46.8% of runs.

CONCLUSION

Universal first-trimester serologic screening with valaciclovir prophylaxis is not the cost-effective strategy for antenatal management of cytomegalovirus under the base-case estimates. Although universal screening is cost-effective in certain circumstances when the efficacy of valaciclovir exceeds the base case, that result is not robust to variation of estimates across their reasonable ranges. These data can inform future studies to evaluate screening and treatment to prevent congenital CMV.

Advocating for cytomegalovirus maternal serologic screening in the first trimester of pregnancy: if you do not know where you are going, you will wind up somewhere else

Congenital cytomegalovirus infection is an important health problem for the individual and the community. Although it could derive from both primary and nonprimary maternal infection, the prospective risk of congenital infection in seronegative pregnant women is 4 times than that of immune women. Maternal serology is the only reliable screening tool in pregnancy that would identify up to 50% of all congenital cytomegalovirus infections, by yielding positive immunoglobulin M and immunoglobulin G and low immunoglobulin G avidity in approximately 0.5% of the population at 11 to 14 weeks. The exceptionally high risk for young parous seronegative women planning a second pregnancy makes a compelling case for offering serologic screening as soon as pregnancy is planned or diagnosed and by the end of the first trimester. The 11- to 14-week consultation has become an unmissable one worldwide and would represent the most practical compromise if only 1 sample can be taken. Valaciclovir that can be safely used in the early fetal period decreases vertical transmission by 70% and should be implemented as early as possible after maternal infection. Facilities for diagnosis and treatment are available in high- and middle-income countries through laboratory and fetal medicine networks. Amniocentesis with amplification of the viral DNA by polymerase chain reaction in the amniotic fluid is a reliable diagnostic test but chorionic villi sampled by chorionic villus sampling could achieve the same performance 2 months earlier. Fetal imaging of a known infected fetus yields a negative predictive value on symptoms at birth and congenital handicap of between 95% and 99%, and prenatal treatment of infected fetuses decreases the occurrence of symptoms at birth and at 2 years of age.

Positive predictive values of CMV-IgM and importance of CMV-IgG avidity testing in detecting primary infection in three different clinical settings. A French retrospective cohort study

BACKGROUND

Diagnosis of Cytomegalovirus (CMV) primary infection during pregnancy or in immunocompetent patients relies on serology with detection of specific CMV-IgG and IgM. In case of positive CMV-IgM in pregnant women, CMV-IgG avidity is now widely recommended, but in general population it is not currently performed.

OBJECTIVE

In this study, we aimed to determine CMV-IgM positive predictive values (PPV) in different clinical settings.

MATERIAL AND METHODS

We conducted a retrospective study on positive CMV-IgM in our virology laboratory from 2013 to 2019, in three clinical groups: screening in non-symptomatic pregnant women (group 1), pregnant women with ultrasound (US) abnormalities (group 2) and patients (general population) with clinical signs suggestive of CMV primary infection (group 3). CMV-IgG avidity had been performed in all cases allowing to evaluate PPV of positive CMV-IgM to diagnose CMV primary-infection in each group.

RESULTS

Between 2013 and 2019, 6859 serum samples were found positive for CMV-IgM and had been tested for CMV-IgG avidity, with 6560 sera for group 1, 30 for group 2 and 269 for group 3. Overall, low avidity confirming primary infection was observed respectively in 16.4 % for group 1, 36.7 % for group 2, and 35.3 % for group 3. CMV-IgM PPV was significantly lower in group 1 compared to groups 2 (p = 0.01) and 3 (p < 0.001).

DISCUSSION

Our observations highlight the major importance of including CMV-IgG avidity in the diagnostic algorithm, whatever the clinical situation (for immunocompetent patients), to confirm or exclude a recent CMV primary infection in case of positive CMV-IgM.

Cytomegalovirus infection during pregnancy: state of the science

Cytomegalovirus is the most common congenital infection, affecting 0.5-2% of all live births and the main nongenetic cause of congenital sensorineural hearing loss and neurological damage. Congenital cytomegalovirus can follow maternal primary infection or nonprimary infection. Sensorineurological morbidity is confined to the first trimester with up to 40-50% of infected neonates developing sequelae after first-trimester primary infection. Serological testing before 14 weeks is critical to identify primary infection within 3 months around conception but is not informative in women already immune before pregnancy. In Europe and the United States, primary infection in the first trimester are mainly seen in young parous women with a previous child younger than 3 years. Congenital cytomegalovirus should be evoked on prenatal ultrasound when the fetus is small for gestation and shows echogenic bowel, effusions, or any cerebral anomaly. Although the sensitivity of routine ultrasound in predicting neonatal symptoms is around 25%, serial targeted ultrasound and magnetic resonance imaging of known infected fetuses show greater than 95% sensitivity for brain anomalies. Fetal diagnosis is done by amniocentesis from 17 weeks. Prevention consists of both parents avoiding contact with body fluids from infected individuals, especially toddlers, from before conception until 14 weeks. Candidate vaccines failed to provide more than 75% protection for >2 years in preventing cytomegalovirus infection. Medical therapies such as cytomegalovirus hyperimmune globulins aim to reduce the risk of vertical transmission but 2 randomized controlled trials have not found any benefit. Valaciclovir given from the diagnosis of primary infection up to amniocentesis decreased vertical transmission rates from 29.8% to 11.1% in the treatment group in a randomized controlled trial of 90 pregnant women. In a phase II open-label trial, oral valaciclovir (8 g/d) given to pregnant women with a mildly symptomatic fetus was associated with a higher chance of delivering an asymptomatic neonate (82%), compared with an untreated historical cohort (43%). Valganciclovir given to symptomatic neonates is likely to improve hearing and neurological symptoms, the extent of which and the duration of treatment are still debated. In conclusion, congenital cytomegalovirus infection is a public health challenge. In view of recent knowledge on diagnosis and pre- and postnatal management, health care providers should reevaluate screening programs in early pregnancy and at birth.

Cytomegalovirus seroprevalence, recurrence, and antibody levels: Associations with cadmium and lead exposures in the general United States population

BACKGROUND

The ubiquitous metals cadmium and lead are immunotoxic, but little is known about their relations to cytomegalovirus (CMV), a widespread herpesvirus. Although CMV infections are mostly asymptomatic, congenital infections are a leading cause of birth defects. In otherwise healthy individuals, there is also some evidence linking subclinical reactivations to accelerated age-related declines in immune function and chronic disease.

METHODS

Our objective was to evaluate associations of blood cadmium and lead biomarkers with CMV infection in a representative sample of the United States population. In seropositive individuals, we also examined associations with CMV-specific immunoglobulin G (IgG) antibody levels and suspected CMV recurrences. Using cross-sectional data from the 1999-2004 National Health and Nutrition Examination Surveys, we fit multivariable survey-weighted regression models accounting for potential confounding by sociodemographic and lifestyle factors and stratifying by age group to allow for heterogeneity. CMV recurrences were defined according to (1) the presence of either CMV-specific immunoglobulin M in sera or CMV viral DNA in urine, and (2) high CMV-specific IgG avidity.

RESULTS

We observed null associations for blood cadmium. Increasing blood lead quartiles were related to CMV seropositivity and higher CMV IgG levels (both P trend < 0.01), but not CMV recurrence, only among individuals who were 20-29 years of age.

CONCLUSION

Blood cadmium levels do not appear to be related to immunological markers of CMV infections. The possibility that lead exposures increase the risk of CMV infection and impair immune control of the virus in young adults was suggested. Prospective studies are needed to confirm.

HIV, Cytomegalovirus, and Malaria Infections during Pregnancy Lead to Inflammation and Shifts in Memory B Cell Subsets in Kenyan Neonates

Infections during pregnancy can expose the fetus to microbial Ags, leading to inflammation that affects B cell development. Prenatal fetal immune priming may have an important role in infant acquisition of pathogen-specific immunity. We examined plasma proinflammatory biomarkers, the proportions of various B cell subsets, and fetal priming to tetanus vaccination in cord blood from human United States and Kenyan neonates. United States neonates had no identified prenatal infectious exposures, whereas Kenyan neonates examined had congenital CMV or mothers with prenatal HIV or Plasmodium falciparum or no identified infectious exposures. Kenyan neonates had higher levels of IP-10, TNF-α, CRP, sCD14, and BAFF than United States neonates. Among the Kenyan groups, neonates with prenatal infections/infectious exposures had higher levels of cord blood IFN-γ, IL-7, sTNFR1, and sTNFR2 compared with neonates with no infectious exposures. Kenyan neonates had greater proportions of activated memory B cells (MBC) compared with United States neonates. Among the Kenyan groups, HIV-exposed neonates had greater proportions of atypical MBC compared with the other groups. Although HIV-exposed neonates had altered MBC subset distributions, detection of tetanus-specific MBC from cord blood, indicative of fetal priming with tetanus vaccine given to pregnant women, was comparable in HIV-exposed and non-HIV-exposed neonates. These results indicate that the presence of infections during pregnancy induces fetal immune activation with inflammation and increased activated MBC frequencies in neonates. The immunologic significance and long-term health consequences of these differences warrant further investigation.

Cytomegalovirus infection in pregnancy

Cytomegalovirus (CMV) is a DNA herpesvirus that is common worldwide. The two known main sources of primary CMV infection during pregnancy are through sexual activity and contact with young children. Primary infection occurs in approximately 1 to 4% of pregnancies, and is mostly asymptomatic in immunocompetent adults. However, primary infection may manifest as a mild mononucleosis or flu-like syndrome with persistent fever and fatigue. CMV can be transmitted from mother-to-child in utero, intrapartum, or during breastfeeding. Intrauterine transmission can lead to congenital CMV infection, a leading cause of permanent hearing and vision loss and neurological disability among children. Congenital CMV transmission rates are as high as 50% in women who acquire primary CMV infection during pregnancy, and less than 2% in women with nonprimary infection. There is no licensed CMV vaccine. Good hygiene practices and avoiding intimate contact with young children (e.g., kissing on the mouth and sharing utensils) have been suggested as an approach to prevent maternal primary CMV infection during pregnancy, but remains an unproven method of reducing the risk of congenital CMV infection. Approximately 1 in 10 infants who acquire CMV in utero will have clinical signs at birth, and an additional 10 to 15% will go on to develop late-onset sequelae. Antiviral treatment prenatally and postnatally has not proven effective at preventing congenital or postnatal CMV infection, and is not recommended for routine clinical care. However, antiviral treatment when initiated in the first month of life for symptomatic congenital CMV infection is recommended for improved neurodevelopmental and audiologic outcomes. Birth Defects Research 109:336-346, 2017. © 2017 Wiley Periodicals, Inc.

Congenital cytomegalovirus infection in pregnancy and the neonate: consensus recommendations for prevention, diagnosis, and therapy

Congenital cytomegalovirus is the most frequent, yet under-recognised, infectious cause of newborn malformation in developed countries. Despite its clinical and public health importance, questions remain regarding the best diagnostic methods for identifying maternal and neonatal infection, and regarding optimal prevention and therapeutic strategies for infected mothers and neonates. The absence of guidelines impairs global efforts to decrease the effect of congenital cytomegalovirus. Data in the literature suggest that congenital cytomegalovirus infection remains a research priority, but data are yet to be translated into clinical practice. An informal International Congenital Cytomegalovirus Recommendations Group was convened in 2015 to address these questions and to provide recommendations for prevention, diagnosis, and treatment. On the basis of consensus discussions and a review of the literature, we do not support universal screening of mothers and the routine use of cytomegalovirus immunoglobulin for prophylaxis or treatment of infected mothers. However, treatment guidelines for infected neonates were recommended. Consideration must be given to universal neonatal screening for cytomegalovirus to facilitate early detection and intervention for sensorineural hearing loss and developmental delay, where appropriate. The group agreed that education and prevention strategies for mothers were beneficial, and that recommendations will need continual updating as further data become available.

Fetal cytomegalovirus infection

Cytomegalovirus (CMV) congenital infection affects 0.7% of live births worldwide and is the leading cause of congenital neurological handicap of infectious origin. However, systematic screening for this infection has not been implemented in pregnancy or at birth in any country. This apparent paradox had been justified by persisting gaps in the knowledge of this congenital infection: uncertain epidemiological data, difficulty in the diagnosis of maternal infection, absence of validated prenatal prognostic markers, unavailability of an efficient vaccine and scarcity of data available on the treatment. However, in the last decade, new data have emerged towards better management of this congenital infection, including solid epidemiological data, good evidence for the accuracy of diagnosis of maternal CMV infection and good evidence for the feasibility of predicting the outcome of fetal infection by a combination of fetal imaging and fetal laboratory parameters. There is also some evidence that valaciclovir treatment of mothers carrying an infected fetus is feasible, safe and might be effective. This review provides an update on the evidence for diagnosis, prognosis and treatment of congenital infection in the antenatal period. These suggest a benefit to a proactive approach for prenatal congenital infections.

Antenatal risk factors for symptomatic congenital CMV disease following primary maternal CMV infection

OBJECTIVES

This study aimed to evaluate antenatal risk factors associated with symptomatic congenital cytomegalovirus (CMV) disease, following in utero vertical infection.

METHODS

This study included a retrospective cohort of 155 neonates with congenital CMV infection, following primary maternal CMV infection during pregnancy, and were divided to symptomatic (n=95) and asymptomatic (n=60) newborns.

RESULTS

Young maternal age (29.1±5.12 vs. 31.6±5.36 years, P=0.005), high risk occupation for viral exposure (20.0% vs. 11.7%, P=0.04), CMV IgG seroconversion at diagnosis (83.1% vs. 63.3%, P=0.005) and abnormal fetal MRI (11.6% vs. 0%, P=0.003) were found to be prognostic risk factors associated with symptomatic CMV disease of the newborn. Maternal febrile illness at diagnosis, IgG avidity, US findings and the timing of maternal infection were not associated with the occurrence of neonatal symptoms.

CONCLUSIONS

Knowledge of the reported risk factors may assist in counseling parents with intra uterine CMV infection.

Clinical Significance of IgG Avidity Testing and Other Considerations in the Diagnosis of Congenital Cytomegalovirus Infection: A Review Update

Prompt and accurate laboratory testing of women before or during antenatal days is necessary for detecting humoral immunological responses against cytomegalovirus (CMV) infection and assessing risk of congenital transmission. CMV is the most common viral etiology with the greatest propensity to induce neonatal pathologies. Most healthcare facilities in developing countries rely solely on anti-CMV IgM and IgG assays in diagnosing CMV infections. However, these parameters have some worrisome limitations. This study reviewed the significance of IgG avidity testing as a highly sensitive and specific tool that improves decisions regarding diagnosis of maternal and congenital CMV infections. We conducted this review from relevant published articles using an extensive literature search made through PubMed, Scopus and Google scholar on the concepts of congenital CMV (CCMV) transmission and clinical significance of IgG avidity testing in diagnosis of CCMV infections. Findings from our review revealed that IgG avidity testing in some developed societies was frequently utilized to resolve dilemmas associated with serodiagnosis of CMV infections, however, there is paucity of information in regards to its use in developing countries. The non-inclusion of IgG avidity testing during serological investigations of CMV could be a reason why congenital CMV infections and associated pathologies often go underdiagnosed in developing countries.

Congenital cytomegalovirus infection in pregnancy: a review of prevalence, clinical features, diagnosis and prevention

Human cytomegalovirus (CMV) is under-recognised, despite being the leading infectious cause of congenital malformation, affecting ~0.3% of Australian live births. Approximately 11% of infants born with congenital CMV infection are symptomatic, resulting in clinical manifestations, including jaundice, hepatosplenomegaly, petechiae, microcephaly, intrauterine growth restriction and death. Congenital CMV infection may cause severe long-term sequelae, including progressive sensorineural hearing loss and developmental delay in 40-58% of symptomatic neonates, and ~14% of initially asymptomatic infected neonates. Up to 50% of maternal CMV infections have nonspecific clinical manifestations, and most remain undetected unless specific serological testing is undertaken. The combination of serology tests for CMV-specific IgM, IgG and IgG avidity provide improved distinction between primary and secondary maternal infections. In pregnancies with confirmed primary maternal CMV infection, amniocentesis with CMV-PCR performed on amniotic fluid, undertaken after 21-22 weeks gestation, may determine whether maternofetal virus transmission has occurred. Ultrasound and, to a lesser extent, magnetic resonance imaging are valuable tools to assess fetal structural and growth abnormalities, although the absence of fetal abnormalities does not exclude fetal damage. Diagnosis of congenital CMV infection at birth or in the first 3 weeks of an infant's life is crucial, as this should prompt interventions for prevention of delayed-onset hearing loss and neurodevelopmental delay in affected infants. Prevention strategies should also target mothers because increased awareness and hygiene measures may reduce maternal infection. Recognition of the importance of CMV in pregnancy and in neonates is increasingly needed, particularly as therapeutic and preventive interventions expand for this serious problem.

Diagnosis and prognosis of congenital CMV infection: a case report and review of the literature

Congenital cytomegalovirus (CMV) infection is the leading non-genetic cause of sensori-neural hearing loss and neurodevelopmental sequelae. Despite these alarming facts, the general public healthcare system is often not aware of CMV and not enough is done to prevent congenital CMV infection.We describe the clinical and laboratory monitoring of a case with primary CMV infection occurring before the first trimester of gestation. Specific literature review is included in order to point out major goals achieved in the diagnosis and prognosis of congenital CMV infection and the many questions still unanswered. Serological diagnosis of primary CMV infection was performed based on serum-CMV specific-IgM antibodies, combined with low avidity anti-CMV IgG antibodies. The maternal infection was asymptomatic, as it is for most infections in immunocompetent patients. Therefore, disclosing primary infection depended on specific serological tests during the initial period of pregnancy (before weeks 12-16 of gestation). The invasive (amniocentesis) and non-invasive (ultrasonographic examination) prenatal tests, carried out at 21 weeks gestation, revealed a severe CMV infection in a fetus small for gestational age with ventriculomegaly. The presence of overt ultrasound abnormalities combined with high viral load in the amniotic fluid sampled at the appropriate times was highly suggestive of an unfavourable prognosis. The autopsy performed on the fetus confirmed severe disseminated CMV infection with histological brain damage.

Role of cytomegalovirus (CMV) IgG avidity testing in diagnosing primary CMV infection during pregnancy

The risk of intrauterine transmission of cytomegalovirus (CMV) during pregnancy is much greater for women who contract primary CMV infection after conception than for women with evidence of infection (circulating CMV antibodies) before conception. Thus, laboratory tests that aid in the identification of recent primary CMV infection are important tools for managing the care of pregnant women suspected of having been exposed to CMV. CMV IgM detection is a sensitive marker of primary CMV infection, but its specificity is poor because CMV IgM is also produced during viral reactivation and persists following primary infection in some individuals. Studies conducted over the last 20 years convincingly demonstrate that measurement of CMV IgG avidity is both a sensitive and a specific method for identifying pregnant women with recent primary CMV infection and thus at increased risk for vertical CMV transmission. IgG avidity is defined as the strength with which IgG binds to antigenic epitopes expressed by a given protein; it matures gradually during the 6 months following primary infection. Low CMV IgG avidity is an accurate indicator of primary infection within the preceding 3 to 4 months, whereas high avidity excludes primary infection within the preceding 3 months. In this minireview, we summarize published data demonstrating the clinical utility of CMV IgG avidity results for estimating time since primary infection in pregnant women, describe commercially available CMV IgG avidity assays, and discuss some of the issues and controversies surrounding CMV IgG avidity testing during pregnancy.

Performance of a cytomegalovirus IgG enzyme immunoassay kit modified to measure avidity

The measurement of cytomegalovirus (CMV) IgG avidity accurately discriminates recent and past CMV infections. We sought to determine if the Wampole Laboratories CMV IgG enzyme immunoassay (EIA) could be modified to measure avidity. The evaluation panel consisted of 156 serum samples we used in 2002 to validate a laboratory-developed EIA, in which 78 serum samples exhibited low avidity, 7 exhibited intermediate avidity, and 71 exhibited high avidity. The qualitative agreement between the two avidity assays was 94% (147/156); all 9 sera with discordant results exhibited intermediate avidity in one of the assays. The avidity index (AI) values in the two assays showed excellent correlation (r = 0.96, P < 0.0001). The definition of high avidity was verified for the Wampole assay by demonstrating high avidity in 91/93 (98%) recently collected CMV IgG-positive/IgM-negative serum samples. The performance of the Wampole avidity assay in a reference laboratory setting was assessed using 470 consecutive serum samples submitted for CMV IgG avidity testing. Surprisingly, 101 serum samples were negative when screened for CMV IgG using the Wampole kit per the package insert; 98 of these 101 serum samples were tested using a CMV IgG chemiluminescent immunoassay, and only 5 were positive. Of the 369 CMV IgG-positive samples, 6% exhibited low IgG avidity, 6% exhibited intermediate avidity, and 88% exhibited high avidity; CMV IgM detection rates were inversely related to AI levels. These findings show that (i) the Wampole CMV IgG EIA can be modified to measure CMV IgG avidity, (ii) many samples are apparently submitted for avidity testing without knowledge of their CMV IgG status, and (iii) most CMV IgG-positive sera submitted for avidity testing exhibit high avidity.

Potential impact of different cytomegalovirus (CMV) IgM assays on an algorithm requiring IgM reactivity as a criterion for measuring CMV IgG avidity

The measurement of cytomegalovirus (CMV) IgG avidity is a powerful tool for identifying individuals with recent CMV infection. Because such patients are expected to be positive for CMV IgM, several investigators have suggested that CMV IgG-positive sera first be screened for CMV IgM and then only the IgM-reactive sera be tested for avidity. We investigated the impact of different CMV IgM assays on such a reflexing algorithm using a panel of 369 consecutive IgG-positive serum samples submitted for avidity testing. A bead-based immunofluorescent assay (BIFA) identified 105 IgM-positive serum samples, whereas an IgM-capture enzyme immunoassay (EIA) identified 48 IgM-positive serum samples; this marked difference led us to evaluate additional CMV IgM assays. An enzyme-linked immunofluorescent assay (ELFA) and a chemiluminescent immunoassay (CIA) were used to test all sera with discordant BIFA/EIA results, all sera with concordant positive results, and selected sera with concordant negative results. The findings indicated that the ELFA would identify 74 CMV IgM-positive samples and the CIA would identify 64. Of the 23 low-avidity serum samples, 2 were IgM negative by BIFA, 3 by ELFA and CIA, and 4 by EIA; of the 23 intermediate-avidity serum samples, 6 were IgM negative by BIFA, 10 by ELFA, and 15 by EIA and CIA. In both these avidity groups, BIFA IgM-negative sera were also negative by the other 3 assays. These findings demonstrate that an algorithm requiring CMV IgM reactivity as a criterion for CMV IgG avidity testing does not identify all low-avidity sera and thus misses some cases of acute CMV infection.

Development of a high-throughput assay to measure the neutralization capability of anti-cytomegalovirus antibodies

Infection by human cytomegalovirus (CMV) elicits a strong humoral immune response and robust anti-CMV antibody production. Diagnosis of virus infection can be carried out by using a variety of serological assays; however, quantification of serum antibodies against CMV may not present an accurate measure of a patient's ability to control a virus infection. CMV strains that express green fluorescent protein (GFP) fusion proteins can be used as screening tools for evaluating characteristics of CMV infection in vitro. In this study, we employed a CMV virus strain, AD169, that ectopically expresses a yellow fluorescent protein (YFP) fused to the immediate-early 2 (IE2) protein product (AD169IE2-YFP) to quantify a CMV infection in human cells. We created a high-throughput cell-based assay that requires minimal amounts of material and provides a platform for rapid analysis of the initial phase of virus infection, including virus attachment, fusion, and immediate-early viral gene expression. The AD169IE2-YFP cell infection system was utilized to develop a neutralization assay with a monoclonal antibody against the viral surface glycoprotein gH. The high-throughput assay was extended to measure the neutralization capacity of serum from CMV-positive subjects. These findings describe a sensitive and specific assay for the quantification of a key immunological response that plays a role in limiting CMV dissemination and transmission. Collectively, we have demonstrated that a robust high-throughput infection assay can analyze the early steps of the CMV life cycle and quantify the potency of biological reagents to attenuate a virus infection.

Improving diagnosis of primary cytomegalovirus infection in pregnant women using immunoblots

Human cytomegalovirus (CMV) is the most common infectious cause of mental disability in newborns of developed countries. Transmission of CMV from mother to baby is more frequent in maternal primary infection, although CMV reactivation causes more congenital infections overall. Current diagnostic tests for distinguishing primary and reactivation CMV have problems with interpretation and immunoblots may assist with diagnosis. Sera from 60 pregnant women were analyzed using conventional serology in parallel with a commercial immunoblot assay (using Recomblot, Mikrogen Diagnostik). Comparison of detection of CMV IgG, IgM, IgG avidity in maternal primary infection showed the immunoblot relative to conventional serology had sensitivity and specificity of 100% for IgG identification. The detection of IgM on immunoblot showed sensitivity of 75%, specificity of 62.5%, positive predictive value (PPV) of 81.8% and negative predictive value (NPV) of 52.6%. The immunoblot IgG avidity assay had sensitivity of 94.1%, with a PPV of 100% when identifying low avidity serum samples, and sensitivity of 100% with a PPV of 97.1% for high avidity serum samples. Overall agreement between conventional serology (IgM, IgG avidity) and immunoblot (IgM, IgG avidity) for detection of primary CMV infection was 65%. Although the immunoblot is effective in detecting IgG and determining IgG avidity, it showed no significant benefits in performance or utility as a first line diagnostic technique for IgM or primary CMV infection in pregnant women.

Overview of the diagnosis of cytomegalovirus infection

Cytomegalovirus (CMV) is recognized as the most common congenital viral infection in humans and an important cause of morbidity and mortality in immunocompromised hosts. This recognition of the clinical importance of invasive CMV disease in the setting of immunodeficiency and in children with congenital CMV infection has led to the development of new diagnostic procedures for the rapid identification of CMV. Diagnosis of acute maternal CMV infection by the presence of immunoglobulin (Ig)M and low-avidity IgG requires confirmation of fetal infection, which is typically performed using polymerase chain reaction (PCR) assays for CMV on amniotic fluid. Viral culture of the urine and saliva obtained within the first two weeks of life continues to be the gold standard for diagnosis of congenitally-infected infants. PCR assays of dried blood spots from newborns have been shown to lack sufficient sensitivity for the identification of most neonates with congenital CMV infection for universal screening purposes. However, saliva PCR assays are currently being assessed as a useful screening method for congenital CMV infection. In the immunocompromised host, newer rapid diagnostic assays, such as phosphoprotein 65 antigenemia and CMV real-time PCR of blood or plasma have allowed for preemptive treatment, reducing morbidity and mortality. However, lack of standardized real-time PCR protocols hinders the comparison of data from different centers and the development of uniform guidelines for the management of invasive CMV infections in immunocompromised individuals.

Kinetics of CMV seroconversion in a Swiss pregnant women population

Retrospective evaluation of the kinetics of cytomegalovirus (CMV) seroconversion with CMV IgM, IgG, and IgG avidity assays, in a Swiss pregnant women population, has shown that the current published CMV serologic diagnostic algorithms were valid and fit for use. In 19% of the cases analyzed, CMV-specific IgM was detected before IgG.

Awareness of and attitudes toward congenital cytomegalovirus infection among pregnant women in Singapore

OBJECTIVE

To assess the level of awareness of congenital cytomegalovirus (CMV) infection and attitudes toward prenatal CMV serologic testing among pregnant women.

METHODS

A questionnaire was distributed to pregnant women who attended a specialist outpatient clinic at Singapore General Hospital, Singapore, between September and December 2010.

RESULTS

Among 200 respondents, 40 (20.0%) were aware of CMV. Healthcare workers were more likely to be aware of CMV (odds ratio 6.91, confidence interval 2.14-22.30; P=0.001). Most respondents found it "very" or "somewhat" easy to adhere to standard guidelines for primary prevention of CMV. Among the respondents, 62.0% (124/200) would like to be given the option of prenatal CMV screening and 72.0% (144/200) were keen to be screened. On multivariate analysis, respondents who were keen to undergo serologic screening for CMV were not more likely to consider invasive testing or termination of pregnancy should the test results demonstrate primary maternal CMV infection.

CONCLUSION

Pregnant women who were keen to undergo CMV testing demonstrated attitudes toward invasive testing and termination of pregnancy that were not significantly different from those of women who would refuse testing. Patient choice and expectations should be considered in the implementation of preventive measures against congenital CMV.

Detection and comparison of cytomegalovirus DNA levels in amniotic fluid and fetal ascites in a second-trimester fetus with massive ascites, hyperechogenic bowel, ventriculomegaly and intrauterine growth restriction

OBJECTIVE

To present a prenatal diagnosis of congenital cytomegalovirus (CMV) infection in a pregnancy with fetal ascites.

CASE REPORT

A 33-year-old, gravida 6, para 2, woman was referred to a hospital at 20 weeks of gestation for management of fetal ascites. The woman had not experienced recent rubella or herpes simplex infections. The maternal blood group was O and Rh(D)-positive. The maternal serum thalassemia and syphilis screen results were negative. Fetal ascites was first noted at 17 weeks of gestation. At 18 weeks, she underwent amniocentesis revealing a 46,XX karyotype. At 20 weeks of gestation, maternal serum CMV IgG and CMV IgM were positive. At 21 gestational weeks, prenatal ultrasound showed fetal ascites, hyperechogenic bowel, ventriculomegaly, and intrauterine growth restriction. Repeated amniocentesis showed CMV DNA levels of 9.72 x 10(5) copies/mL and 6.03 x 10(5) copies/mL in amniocytes and amniotic fluid supernatant, respectively. Paracentesis showed CMV DNA levels of 1.64 x 10(3) copies/mL and 114 copies/mL in ascitic cells and ascitic supernatant, respectively. The pregnancy was terminated. Postnatally, CMV DNA was detected in the umbilical cord, amnion, placenta, cord blood, lungs, liver and brain by quantitative real-time polymerase chain reaction.

CONCLUSION

A prenatal diagnosis of fetal ascites in association with ventriculomegaly, hyperechogenic bowel and intrauterine growth restriction should alert physicians to congenital CMV infection in addition to aneuploidy. The present case provides evidence that CMV DNA levels are higher in amniotic fluid (amniocytes and amniotic fluid supernatant) than in ascites (ascitic cells and ascitic supernatant) in cases of congenital CMV infection.

Guidelines on CMV congenital infection

Congenital cytomegalovirus (CMV) infection occurs in 0.6-0.7% of all newborns and is the most prevalent infection-related cause of congenital neurological handicap. Vertical transmission occurs in around 30% of cases, but the fetus is not always affected. Symptomatic newborns at birth have a much higher risk of suffering severe neurological sequelae. Detection of specific IgG and IgM and IgG avidity seem to be the most reliable tests to identify a primary infection but interpretation in a clinical context may be difficult. If a seroconversion is documented or a fetal infection is suspected by ultrasound markers, an amniocentesis should be performed to confirm a vertical transmission. In the absence of a confirmed fetal infection with fetal structural anomalies, a pregnancy termination should be discouraged. Fetal prognosis is mainly correlated to the presence of brain damage. Despite promising results with the use of antiviral drugs and CMV hyperimmune globulin (HIG), results have to be interpreted with caution. Pregnant women should not be systematically tested for CMV during pregnancy. Managing CMV screening should be restricted to pregnancies where a primary infection is suspected or among women at high risk. The magnitude of congenital CMV disease and the value of interventions to prevent its transmission or to decrease the sequelae need to be established before implementing public health interventions. In this paper, aspects of CMV infection in the pregnant woman and her infant are reviewed.

Screening and treating for primary cytomegalovirus infection in pregnancy: where do we stand? A decision-analytic and economic analysis

OBJECTIVE

To estimate which 1 of 3 screening strategies for primary maternal cytomegalovirus infection, with intention to treat with hyperimmune globulin, is most cost-effective.

STUDY DESIGN

A decision-analytic and cost-effectiveness model was constructed for pregnant women, comparing 3 strategies screening for primary maternal cytomegalovirus infection with intention to treat with cytomegalovirus-intravenous immune globulin: (1) serum screen all pregnant women, (2) serum screen women with risk factors for primary cytomegalovirus, (3) serum screen women with suspicious sonographic findings. Probability, use (or value), and cost estimates were derived from published literature.

RESULTS

Universal screening for primary maternal cytomegalovirus was the preferred and most cost-effective strategy. However, if treatment with cytomegalovirus-intravenous immune globulin achieved less than a 47% reduction (relative risk, 0.53) in clinical disease, universal screening would no longer be cost-effective.

CONCLUSION

Universal screening for primary maternal cytomegalovirus infection is cost-effective based on available evidence, highlighting the urgent need for additional study evaluating the efficacy of cytomegalovirus-intravenous immune globulin to prevent congenital cytomegalovirus.

New advances in the diagnosis of congenital cytomegalovirus infection

Although the diagnosis of congenital CMV infection is still complex, important goals have been achieved in recent years, among which are: the availability of more reliable IgM tests for screening pregnant women whose pre-pregnancy serological status for CMV is unknown, tests to determine the avidity index of anti-CMV IgG, allowing the diagnosis of a primary CMV infection and innovative and traditional virological tests to detect the virus in amniotic fluid. When a woman is found to be IgM-positive, further diagnostic evaluation focused on determining whether this is due to a primary infection should be carried out. Maternal primary infections that were difficult to determine until a few years ago unless documented by seroconversions can now be readily diagnosed from the presence of low/moderate avidity anti-CMV antibody which persists for approximately 18-20 weeks after primary infection. In mothers at risk of transmitting the virus prenatal diagnosis can be performed between 21 and 22 weeks of gestation, and the amniotic fluid represents the pathological material of choice to determine intrauterine virus transmission. At birth or in the first 2/3 weeks of life, it is essential to use appropriate tests for diagnosis of CMV congenital infection.

Impact of diagnostic and confirmatory tests and prenatal counseling on the rate of pregnancy termination among women with positive cytomegalovirus immunoglobulin M antibody titers

OBJECTIVE

The purpose of this study was to determine if diagnostic tests performed in a reference laboratory and the correct interpretation and communication of results by an expert physician to the patient can reduce the rate of unnecessary abortions among women with positive cytomegalovirus (CMV) immunoglobulin M antibody titers.

STUDY DESIGN

This was a retrospective study of 1857 consecutive pregnant women with positive screening for IgM anti-CMV, in the first or second trimester of pregnancy, referred to our unit for further diagnostic evaluation. Patients with available follow-up were divided into 2 groups according to the results of confirmatory serologic testing: women with a CMV serologic profile suggestive of primary infection and hence at high risk of vertical transmission (group 1) and women with a CMV serologic profile consistent with nonprimary infection or past infection (group 2). The number of expected pregnancy terminations and the prevented fraction of abortions was calculated.

RESULTS

Of 445 group 1 patients, 53 (11.9%) elected to terminate the pregnancy after being informed of the results of diagnostic tests; in contrast, only 5 (0.4%) women in group 2 underwent terminations (P < .001). At autopsy, 38 fetuses in group 1 proved infected. No information on fetal infection is available for pregnancies terminated in the first trimester (15 in group 1; 5 in group 2). We estimated that > or = 196 (11.9%) of all patients in groups 1 and 2 (n = 1650 patients) would have elected abortion on the basis of the positive result of screening for fetal CMV infection. After the results of confirmatory tests, only 58 women (53 in group 1 and 5 in group 2) elected to terminate the pregnancy. Thus, the number of abortions is presumed to have been decreased by 73% (P < .001).

CONCLUSION

The correct interpretation and communication of confirmatory test results by expert physicians to pregnant women with positive screening for IgM anti-CMV may significantly reduce the rate of unnecessary abortions.