Version July 2025
| Laboratory method | Sample used for testing | Reported sensitivity (%)* | Reported specificity (%)* | Comments |
| Viral culture | Urine or saliva obtained within first 3 weeks of life | 100 | 100 | Traditional reference standard. |
| Detects CMV based on cytopathic changes in cell culture with fibroblast cell lines. | ||||
| Usually positive within 1 to 3 days of incubation but may take up to 28 days before a negative result is declared. | ||||
| Disadvantages include: relatively long time required to detect the virus, labor- and resource-intensive, and requires tissue culture facilities. | ||||
| Rapid culture (also called shell vial assay or shell vial culture)¶ | Urine or saliva obtained within first 3 weeks of life | 92.3 to 100 | 100 | Enhanced culture method using centrifugation and staining for early antigen production. |
| Allows for identification of the virus within 24 hours. | ||||
| Advantage over standard viral culture is that it is rapid, simple to perform, and less expensive. | ||||
| False-positive results may occur due to retained CMV antigen on the shell vial monolayer, producing a low-positive result. | ||||
| A confirmatory test (either viral culture or PCR) should be performed to establish the diagnosis of congenital CMV. | ||||
| PCR¶ | Urine or saliva obtained within first 3 weeks of life | 97.4 to 100 | 99.9 | Detects CMV DNA in the urine or saliva. |
| Advantages over standard and shell vial culture techniques include: rapid turnaround, does not require live virus for detection of CMV and thus is not affected by storage and transport conditions, and lower cost. | ||||
| Available in many hospital-based and reference laboratories. | ||||
| Occasional false-positive results occur; we suggest confirming positive tests with repeat PCR on urine or saliva or both. | ||||
| Newborns with congenital CMV infection shed large quantities of CMV from both urine and saliva for prolonged periods; therefore, these tests should be positive repeatedly. | ||||
| PCR | Dried blood spot | 34 to 77 | 99.9 | Detects CMV DNA in the dried blood spot obtained for newborn screening. |
| Allows retrospecturive diagnosis of congenital CMV infection. | ||||
| Not all infected infants are viremic at birth, accounting for low sensitivity of this test compared with PCR in urine or saliva samples. | ||||
| Available in research or public health laboratories (CDC). | ||||
| Quantitative PCR (CMV DNAemia) | Whole blood or plasma | N/A | N/A | Measures amount of CMV DNA in the blood. |
| Used for monitoring infants during therapy; not used for establishing the diagnosis of congenital CMV. | ||||
| Preferred over CMV antigenemia for quantitative measurement of viremia. | ||||
| CMV antigenemia | Blood | N/A | N/A | Detects CMV proteins (pp65) in peripheral blood leukocytes. |
| Not recommended in the diagnostic evaluation of infants with congenital CMV. | ||||
| Serology | Blood | N/A | N/A | Not recommended for routine diagnosis of congenital CMV. |
| Presence of CMV IgG antibody in the newborn reflects passive transfer of maternal antibody; however, its absence makes CMV infection very unlikely. | ||||
| CMV IgM antibody in the newborn is insensitive and may be falsely negative in 20 to 50% of infected newborns. |
CDC: Centers for Disease Control and Prevention; CMV: cytomegalovirus; DBS: dried blood spot; IgG: immunoglobulin G; IgM: immunoglobulin M; N/A: not available; PCR: polymerase chain reaction.
* Compared with viral culture in most studies.
¶ Shell vial assay or PCR tests have largely replaced viral culture as the methods of choice for diagnosis of congenital CMV infection because of more rapidly available results and lower cost. The choice of test used may depend on the availability.