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CMV Avidity test - Serum

Pregnancy
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Report in 120Hrs

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nofastingrequire

No Fasting Required

Details

Differentiates primary vs past CMV infection.

₹1,406₹2,009

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CMV Avidity Test - Serum: Comprehensive Medical Information Guide

  • Why is it done?
    • Test Purpose: The CMV avidity test measures the binding strength (avidity) of IgG antibodies to cytomegalovirus (CMV). This helps differentiate between primary CMV infection and past/chronic CMV infection or reactivation. Avidity refers to the overall strength of antibody binding, which increases as the immune response matures over weeks to months.
    • Primary Indications for Testing: Evaluation of CMV IgG-positive patients to determine if infection is recent or chronic; Assessment in pregnant women to evaluate for primary CMV infection risk to the fetus; Investigation of immunocompromised patients with CMV symptoms; Confirmation of CMV status in solid organ or bone marrow transplant candidates; Evaluation of congenital CMV concerns in newborns with suggestive symptoms.
    • Typical Timing and Circumstances: Performed when CMV IgG is detected and IgM is negative or indeterminate; Most useful when performed within 3-6 months of suspected primary CMV infection; Particularly important in pregnancy for prenatal counseling; Useful in immunocompromised populations experiencing CMV reactivation or primary infection.
  • Normal Range
    • Reference Values: Low Avidity: <0.40 (or <40%) indicates recent primary infection, typically within 3-4 months of infection onset Equivocal/Intermediate Avidity: 0.40-0.60 (or 40-60%) suggests possible early infection or early seroconversion phase; may require repeat testing after 1-2 weeks High Avidity: >0.60 (or >60%) indicates remote/past infection or chronic infection, typical of immune responses >4 months old or reactivation.
    • Units of Measurement: Avidity index expressed as a decimal ratio (0.00-1.00) or as a percentage (0-100%); Methods may vary slightly between laboratories; Always compare results within the context of the specific laboratory's reference range.
    • Interpretation Framework: Negative CMV IgG: No previous CMV exposure; susceptible to primary infection Positive CMV IgG + Low Avidity: Suggestive of primary CMV infection within recent months (high risk period for vertical transmission in pregnancy) Positive CMV IgG + High Avidity: Indicates past infection with immune response established; lower risk of congenital transmission if pregnant Results must be interpreted alongside CMV IgM status, clinical presentation, and patient immunological status.
  • Interpretation
    • Low Avidity Results (<0.40): Indicates recent primary CMV infection, typically within 3-4 months of infection onset; Associated with presence of CMV IgM antibodies; Suggests developing immune response with antibodies still undergoing affinity maturation; In pregnant women, indicates risk period for intrauterine transmission; Requires close clinical monitoring and consideration of antiviral therapy in immunocompromised patients.
    • Equivocal/Intermediate Avidity (0.40-0.60): Represents borderline zone between primary and past infection; May indicate infection in early phase of seroconversion (1-4 months); Requires repeat testing after 1-2 weeks to establish trend; If avidity increases on repeat testing, supports past infection diagnosis; If avidity remains stable or decreases, suggests recent primary infection; Clinical correlation essential for proper interpretation.
    • High Avidity Results (>0.60): Indicates remote past infection with well-established immune response; Typical of infection occurring >4 months prior to testing; May represent reactivation of latent infection in immunocompromised patients; Associated with immune memory and typically negative CMV IgM; In pregnant women, suggests lower risk of congenital CMV transmission; Does not exclude active CMV disease in immunocompromised hosts.
    • Factors Affecting Results: Timing of testing relative to infection onset is critical; Some immunocompromised patients may have delayed or abnormal avidity development; Rare cases of low avidity despite remote infection reported in severely immunosuppressed individuals; Laboratory methodology variations between testing platforms; CMV IgM status influences interpretation; Pregnancy status affects clinical significance; Transplant status and immunosuppressive medications impact results.
    • Clinical Significance and Patterns: Low avidity + positive IgM = most sensitive for recent primary infection Low avidity + negative IgM = possible early primary infection still being evaluated High avidity + negative IgM = past infection with established immunity High avidity + positive IgM = rare; may indicate reactivation or unusual immune response Test is particularly valuable in pregnancy for assessing fetal risk Informs antiviral therapy decisions in immunocompromised patients Helps guide counseling and management strategies based on infection timing.
  • Associated Organs
    • Primary Organ Systems Involved: Immune system (primary target for viral replication) Central nervous system (CNS), particularly in immunocompromised patients Gastrointestinal tract (esophagus, colon) Respiratory tract (lungs) Retinas (CMV retinitis in severe immunosuppression) Reproductive system (placental transmission in congenital infections) Blood and lymphoid tissues (viral replication sites).
    • Medical Conditions Associated with Abnormal Results: Primary CMV infection during pregnancy (low avidity) Congenital CMV infection in newborns CMV disease in HIV/AIDS patients (CD4 count <50 cells/mm³) CMV infection post-transplantation (solid organ or bone marrow) CMV pneumonitis CMV esophagitis or colitis CMV retinitis (vision-threatening) CMV encephalitis CMV associated with chronic illness.
    • Diseases Diagnosed or Monitored: Primary CMV infection (recent acquisition) Recurrent/reactivation CMV infection CMV disease in immunocompromised hosts Congenital CMV (evaluation and monitoring) CMV-related complications in transplant recipients CMV in perinatal infections CMV in solid organ transplant rejection evaluation.
    • Potential Complications of CMV Infection: In primary infection: Mononucleosis-like syndrome, severe hepatitis In pregnancy: Intrauterine growth restriction, fetal loss, microcephaly, hearing loss, developmental delays In congenital infection: Permanent neurological damage, blindness, deafness In HIV/AIDS: Retinitis leading to blindness, encephalitis, GI disease In transplant recipients: Organ rejection, graft failure, mortality Systemic complications: Multi-organ involvement, sepsis-like presentations Long-term sequelae: Chronic neurological issues, hearing impairment.
  • Follow-up Tests
    • Recommended Additional Tests: CMV IgM antibody testing (reflex from initial positive IgG) CMV IgG quantitative testing (viral load correlation) CMV PCR (viral DNA detection in plasma or urine) CMV pp65 antigenemia assay (active viral replication indicator) Blood culture for CMV (in critically ill patients) CMV nucleic acid amplification testing (NAT) in various body fluids based on clinical presentation.
    • Further Investigations Based on Clinical Scenario: In pregnant women with low avidity: Amniocentesis with CMV PCR after 18 weeks gestation for fetal infection assessment In transplant recipients: Regular CMV surveillance PCR; tissue biopsy if organ involvement suspected In immunocompromised patients: Ophthalmological examination if CD4 <50 (CMV retinitis screening); Endoscopy if GI symptoms present In suspected CNS disease: CSF analysis and CMV PCR; MRI brain imaging In pulmonary symptoms: Bronchoscopy with BAL for CMV PCR; chest imaging.
    • Repeat Testing Recommendations: If equivocal avidity (0.40-0.60): Repeat CMV avidity testing 1-2 weeks later; Compare results to establish trend In early pregnancy with low avidity: Consider repeat testing to confirm persistently low values Monitoring frequency: As clinically indicated based on patient status and symptoms Transplant recipients: Periodic surveillance as per institutional protocols; More frequent testing with clinical symptoms.
    • Complementary Tests for Complete Evaluation: Complete metabolic panel (assess organ function) Complete blood count with differential (lymphocytosis pattern) Liver function tests (hepatitis assessment) HIV testing (if status unknown; critical for CMV risk stratification) CD4 count (in HIV patients; guides CMV risk and prophylaxis decisions) Toxoplasma serology and CMV co-infection assessment Other TORCH testing in congenital infection evaluation General serology panel to exclude other infectious etiologies.
    • Specialized Testing for Specific Populations: Prenatal: Detailed obstetric ultrasound; Fetal MRI if intrauterine infection suspected Newborns with congenital infection: Audiological testing; Ophthalmological assessment; Developmental screening; Neuroimaging Transplant candidates: Pre-transplant CMV serostatus determination; Recipient/donor matching for risk stratification Post-transplant: Regular CMV PCR surveillance; Clinical assessments per transplant protocol.
  • Fasting Required?
    • Fasting Status: NO - Fasting is NOT required for CMV avidity serum testing. This is a serological test measuring antibody levels and does not require any specific nutritional or dietary restrictions.
    • Sample Collection Instructions: Serum collection via venipuncture into a standard serum separator tube (SST) No special preparation before blood draw Patient can eat and drink normally before testing No fluid restrictions necessary Best collected during regular daytime hours (no specific time requirement) Patient should inform phlebotomist of any recent vaccinations or medications.
    • Medications and Supplements: No specific medications need to be avoided before CMV avidity testing Continue all regularly scheduled medications as prescribed Antiviral medications (acyclovir, ganciclovir, valganciclovir) do not interfere with test results Immunosuppressive medications do not prevent accurate testing Vaccinations should be noted as they may affect interpretation in some cases Inform the healthcare provider of all current medications for context.
    • Patient Preparation Requirements: No special physical preparation required Wear loose, comfortable clothing with easily accessible arms for venipuncture Inform phlebotomist of any needle anxiety or previous difficult draws Notify healthcare provider of pregnancy status if applicable Note any recent infections, illnesses, or travel (for clinical context) Bring insurance card and identification Arrive on time; fasting can be ignored Can proceed with normal daily activities before and after blood draw Minimal risk of adverse effects; brief mild pressure at collection site is typical.
    • Post-Collection Care: Apply pressure to venipuncture site for 2-3 minutes to prevent hematoma Can resume normal diet and hydration immediately No activity restrictions following blood draw Results typically available within 1-3 business days (may vary by laboratory) Contact healthcare provider for result interpretation and clinical recommendations.

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