Editor’s Note:
Newborns can be infected with congenital cytomegalovirus (CMV) through vertical mother-to-child transmission, and CMV infection screening is required for some newborns with specific indications. Polymerase chain reaction (PCR) is a commonly used clinical method for qualitative or quantitative diagnosis of CMV, and it can test specimens such as urine, plasma, and dried blood spots, each with its own advantages and disadvantages. A recent study evaluating the consistency of plasma PCR and dried blood spot PCR for CMV infection diagnosis was presented at the 2023 IDWeek congress. Dr. Hong-mei Xu from the Department of Infectious Diseases at Children’s Hospital of Chongqing Medical University introduces and comments on this study.
Research Introduction
The sensitivity of dried blood spot (DBS) PCR screening for congenital cytomegalovirus (cCMV) infection is 34%-86%, but it is not clear whether DBS PCR negativity is due to the lack of CMV viremia or limitations in DBS PCR detection technology. This study aimed to determine the consistency between plasma CMV PCR and DBS CMV PCR testing in newborns with cCMV infection.
This single-center retrospective cohort study included infants (age ≤21 days) diagnosed with cCMV infection through urine CMV PCR testing due to clinical symptoms, failed newborn hearing screening, or NICU admission screening. Included infants underwent both plasma CMV PCR testing and DBS CMV PCR testing within one month after birth. The Cohen’s kappa coefficient was used to evaluate the consistency between plasma and DBS PCR tests. Clinical characteristics and viral loads were compared between the groups with consistent and inconsistent DBS and plasma PCR results using Kruskal-Wallis or Mann-Whitney U tests.
The study included a total of 70 cases of cCMV-infected infants. There were 30 females (43%), 51 Whites (73%), 13 Blacks (19%), 6 other/multiracial (8%), and 3 Hispanics (4%). 54 infants (77%) had symptoms of cCMV infection. In total, 49 infants (70%) had both DBS+ and plasma+ PCR results, 1 infant (1.4%) had DBS+/plasma-, 14 infants (20%) had DBS-/plasma+, and 6 infants (9%) had DBS-/plasma-.
The groups were similar in terms of gender, race, ethnicity, gestational age, birth weight, birth length, birth head circumference, and symptomatic infection. Overall, the sensitivity of DBS CMV PCR testing was 71%, and its consistency with plasma CMV PCR testing was fair (κ= 0.348, 95% CI: 0.115-0.581).
Among the 20 infants with DBS PCR negativity, 70% had plasma PCR positivity, and 30% had plasma PCR negativity (no CMV DNA detected in plasma). Compared to infants with DBS-/plasma+ results, infants with DBS+/plasma+ results had significantly higher plasma viral loads (2245 vs. 321 IU/ml, P < 0.0001).
Dr. Hong-mei Xu Expert Commentary:
Cytomegalovirus (CMV) infection is widely prevalent in the population, and newborns are susceptible to congenital infection through vertical mother-to-child transmission or postnatal transmission via breastfeeding, transfusion, and other routes. In recent times, the rate of CMV infection in infants with hepatitis may have been overestimated, while the infection rate in non-hepatic infants may have been overlooked. The incidence of congenital CMV infection in newborns varies by region, with an approximate range of 0.15%-2.50%. Although the specific screening time is not mentioned, this single-center sample is not small (70 cases). Congenital CMV infection in newborns requires attention and the adoption of appropriate screening strategies and accurate screening methods.
Laboratory diagnostic methods for newborn CMV infection include virus isolation, serological tests, histopathological examination, pp65 antigen testing, virus DNA qualitative and quantitative polymerase chain reaction (PCR), among others. Among these methods, PCR testing has been widely used for qualitative or quantitative diagnosis of CMV in newborns. The commonly used specimens for PCR testing in clinical practice are plasma and urine. Urine PCR has high sensitivity (100%) and specificity (99%), but it cannot determine the presence of viremia. A negative plasma PCR result does not rule out CMV infection. In addition, both urine and plasma specimens are subject to storage conditions (e.g., short urine shelf life, plasma requiring anticoagulation and freeze-drying, etc.).
Dried blood spots have high stability (can be stored at room temperature for 3 months), require a small sample, and do not require additional needlestick injury. Therefore, dried blood spot qualitative CMV PCR has the advantage of convenience, speed, and ease of promotion in screening for congenital CMV infection in newborns. However, its diagnostic performance still needs further confirmation. This single-center study shows that the sensitivity of dried blood spot PCR testing for cCMV is 71%, and its consistency with plasma PCR is only at a fair level (κ= 0.348). Among those with negative dried blood spot PCR testing, 70% still had positive plasma PCR or positive CMV viremia, raising questions about whether such a rate of false negatives is clinically acceptable and needs to be considered when formulating screening strategies. Additionally, there are limitations in this study as the researchers used urine PCR results as the CMV diagnostic criteria, but urine PCR cannot distinguish whether it is an active infection (viremia). If screening is treatment-oriented, then plasma PCR remains the better choice.
There is no standard for screening for congenital CMV infection in newborns. When formulating screening strategies, factors such as the selection of the population (e.g., high-risk newborns with clinical symptoms, hearing impairment, maternal CMV infection, etc.), methods of screening diagnosis (each with its own advantages and disadvantages, as mentioned in this article), risk-benefit, and cost-effectiveness need to be considered. The study results above demonstrate the diagnostic performance of dried blood spot PCR testing and provide insights for the development of future CMV screening strategies.
References:
[1] Juhyeong Kim, et al. CMV PCR Agreement between Blood and Dried Blood Spots in Infants with Congenital Cytomegalovirus Infection. IDWeek 2023; abstract 1099.
[2] Chinese Society of Pediatricians, Chinese Society of Pediatricians, Infectious Diseases Committee, Editorial Board of Chinese Journal of Pediatrics. Expert Consensus on the Management of Congenital Cytomegalovirus Infection in Newborns [J]. Chinese Journal of Pediatrics, 2021, 36(6): 1-7. DOI: 10.3760/cma.j.issn.2096-2932.2021.06.001.
Dr. Hongmei Xu
Director of the Department of Infectious Diseases, Children’s Hospital, Chongqing Medical University
TAG: IDWeek 2023, CMV infection, commentary
