CMV (DNA detection by Real time PCR Amniotic Fluid)

Bacterial/ Viral

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No Fasting Required

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Detects fetal CMV infection.

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CMV (DNA detection by Real time PCR Amniotic Fluid) - Comprehensive Medical Test Guide

Why is it done?
- Test Purpose: This test detects cytomegalovirus (CMV) DNA in amniotic fluid using Real-time PCR (polymerase chain reaction), enabling direct identification of fetal CMV infection during pregnancy.
- Primary Indications: Diagnosis of congenital CMV infection following serological evidence of maternal CMV infection, particularly when ultrasound abnormalities are detected (microcephaly, ventriculomegaly, intrauterine growth restriction, polyhydramnios, or echogenic bowel).
- Clinical Circumstances: Performed after documented maternal primary CMV infection or reactivation during pregnancy (particularly first trimester), following abnormal ultrasound findings, or when evaluating unexplained fetal complications.
- Timing: Typically performed at least 4 weeks after confirmed maternal infection and ideally after 18 weeks of gestation to maximize detection sensitivity.
Normal Range
- Reference Range: Negative (No CMV DNA detected) or Undetectable - indicates absence of CMV viral DNA in amniotic fluid.
- Units of Measurement: Copies/mL (viral copies per milliliter of amniotic fluid) or a qualitative result (Detected/Not Detected).
- Result Interpretation: Negative Result = Normal (CMV DNA not detected); Positive Result = Abnormal (CMV DNA detected, confirming fetal CMV infection).
- Sensitivity and Specificity: Real-time PCR demonstrates >95% sensitivity and >99% specificity for detecting CMV DNA in amniotic fluid when fetal infection is present.
- Borderline/Inconclusive Results: May require repeat testing or additional investigation if initial results are equivocal.
Interpretation
- Negative Result (CMV DNA Not Detected): Indicates fetus is not infected with CMV; however, a negative result does not completely exclude fetal infection if testing is performed too early (before 4 weeks post-maternal infection) or very early in pregnancy.
- Positive Result (CMV DNA Detected): Confirms fetal CMV infection; indicates active viral replication in amniotic fluid and direct transmission of CMV to the fetus.
- Viral Load Significance: Higher CMV DNA concentrations may correlate with increased severity of fetal disease and adverse outcomes, though quantitative viral load does not definitively predict clinical severity in individual cases.
- Factors Affecting Results: Timing of amniocentesis (results more accurate after 4-6 weeks post-maternal infection); gestational age (generally more reliable after 18 weeks); presence of maternal-fetal hemorrhage; technical factors during sample collection and processing.
- Clinical Correlation: Results must be interpreted in conjunction with maternal serological testing, ultrasound findings, gestational age, and timing of maternal infection.
- Predictive Value for Disease Severity: A positive result confirms infection but cannot reliably predict symptomatic congenital CMV or long-term neurological outcomes; approximately 10-15% of infected fetuses remain asymptomatic at birth.
Associated Organs
- Primary Organ Systems: Central nervous system (CNS); auditory system; visual system; hematopoietic system; hepatic system; and reproductive organs.
- Congenital CMV-Related Conditions: Microcephaly (most common CNS finding); cerebral ventriculomegaly; periventricular leukomalacia; polymicrogyria; neuronal migration disorders; intrauterine growth restriction (IUGR); thrombocytopenia; hepatosplenomegaly; cholestasis; jaundice; sensorineural hearing loss (most common sequela); cortical visual impairment.
- Diseases and Complications Associated with Positive Results: Symptomatic congenital CMV; neurodevelopmental impairment; intellectual disability; autism spectrum disorder; cerebral palsy; chronic sensorineural hearing loss; chronic progressive visual impairment; motor dysfunction; seizure disorders.
- Potential Fetal Complications: Fetal demise; preterm labor; oligohydramnios or polyhydramnios; structural malformations; perinatal infection; neonatal sepsis; disseminated CMV disease; delayed-onset complications including progressive hearing loss and cognitive decline.
- Maternal Considerations: Maternal CMV infection (primary or recurrent) with transplacental transmission risk; gestational complications including preeclampsia; placental insufficiency; abnormal placental development.
Follow-up Tests
- Recommended Based on Positive Results: Detailed fetal ultrasound assessment for structural abnormalities, IUGR, amniotic fluid volume, and placental assessment; fetal echocardiography to exclude cardiac anomalies; referral to maternal-fetal medicine specialist for counseling and management planning.
- Complementary Testing: Maternal CMV IgG and IgM serology (if not already performed); CMV viral load in maternal blood (optional); amniocentesis culture for CMV isolation (less sensitive than PCR but may provide additional information); placental examination post-delivery.
- Neonatal Follow-up Testing: CMV PCR testing on urine or saliva within first 3 weeks of life; CMV IgM and IgG testing; clinical examination for signs of symptomatic CMV; audiological evaluation (within first 2-4 weeks and at 3-4 months of age); ophthalmological examination; neuroimaging (cranial ultrasound initially, then MRI if CNS involvement suspected).
- Long-term Monitoring Frequency: Regular auditory assessments every 1-2 months until 12 months; annual hearing screening thereafter; neurodevelopmental assessment at 6, 12, 18, and 24 months; ophthalmological surveillance at regular intervals; developmental screening throughout early childhood.
- Related Tests: CMV serology (maternal and neonatal); CMV antibody testing; other congenital infection screening (TORCH panel including toxoplasmosis, rubella, herpes simplex); genetic testing if additional anomalies present; chromosome analysis (karyotype or microarray) if chromosomal abnormality suspected.
- Repeat Testing Indication: If initial negative result obtained too early after maternal infection, repeat amniocentesis may be warranted 2-4 weeks later; repeat testing rarely needed for positive results unless technical issues present.
- Antiviral Therapy Consideration: Positive results may prompt discussion regarding maternal valganciclovir therapy (investigational); or intravenous immunoglobulin (IVIG); or combination therapy—discussion with specialists recommended.
Fasting Required?
- Fasting Requirement: No - Fasting is NOT required for this test.
- Patient Preparation: No special dietary restrictions; patient may eat and drink normally before procedure; normal hydration is acceptable.
- Pre-Procedure Instructions: Full bladder is beneficial (assists in visualization during ultrasound guidance); wear comfortable, loose-fitting clothing; arrange for transportation as patient should not drive immediately after procedure; schedule appointment when partner or support person available.
- Medications: Continue all regularly prescribed medications unless specifically instructed otherwise by physician; blood thinners (anticoagulants) or antiplatelet agents should be discussed with physician prior to procedure (typically not held for amniocentesis unless high risk).
- Procedural Considerations: This test requires amniocentesis (needle insertion through abdomen into amniotic sac under ultrasound guidance); procedure usually takes 10-15 minutes; local anesthetic may be offered; slight cramping or mild discomfort during procedure is expected; post-procedure mild cramping or spotting may occur.
- Post-Procedure Instructions: Rest for remainder of day; avoid strenuous activity for 24-48 hours; contact physician if excessive cramping, vaginal bleeding/fluid leakage, fever, or signs of infection develop; normal activities can usually resume after 24 hours if no complications.
- Results Turnaround: Real-time PCR results typically available within 5-7 business days; expedited testing may be available at selected laboratories (24-48 hours); results communicated by physician after review.

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