The TORCH screen blood test is a panel of tests used to detect infections that can cause complications during pregnancy and harm to the developing foetus. The acronym TORCH stands for Toxoplasmosis, Other infections (such as syphilis, varicella-zoster, and parvovirus B19), Rubella, Cytomegalovirus (CMV), and Herpes simplex virus (HSV). This test is crucial for prenatal care to identify and manage infections that can lead to congenital anomalies or pregnancy complications.

Purpose of the TORCH Screen Blood Test

  1. Detecting Congenital Infections
    • Purpose: To identify infections that can be transmitted from mother to foetus.
    • Use: Helps in the early diagnosis and management of congenital infections to prevent foetal harm.
  2. Assessing Prenatal Risk
    • Purpose: To evaluate the risk of transmitting infections during pregnancy.
    • Use: Guides preventive measures and treatments to protect maternal and foetal health.
  3. Monitoring Pregnancy Complications
    • Purpose: To monitor and manage infections that could cause pregnancy complications.
    • Use: Ensures appropriate interventions are in place to mitigate risks to the mother and baby.

Infections Screened in the TORCH Panel

  1. Toxoplasmosis
    • Cause: Toxoplasma gondii, a parasitic infection.
    • Transmission: Through undercooked meat, contaminated water, soil, or cat faeces.
    • Risks: Can cause miscarriage, stillbirth, or severe birth defects like hydrocephalus, intracranial calcifications, and chorioretinitis.
  2. Other Infections
    • Syphilis: Caused by Treponema pallidum, can lead to stillbirth, neonatal death, or congenital syphilis.
    • Varicella-Zoster Virus (Chickenpox): Can cause congenital varicella syndrome, leading to limb hypoplasia, skin scarring, and neurological disorders.
    • Parvovirus B19: Causes erythema infectious (fifth disease) and can lead to foetal anaemia, hydrops fetalis, and miscarriage.
  3. Rubella (German Measles)
    • Cause: Rubella virus.
    • Transmission: Airborne droplets from respiratory secretions.
    • Risks: Can cause congenital rubella syndrome, leading to heart defects, cataracts, deafness, and developmental delays.
  4. Cytomegalovirus (CMV)
    • Cause: Cytomegalovirus.
    • Transmission: Through bodily fluids, including saliva, urine, blood, and sexual contact.
    • Risks: Can cause hearing loss, vision impairment, intellectual disability, and motor dysfunction.
  5. Herpes Simplex Virus (HSV)
    • Cause: Herpes simplex virus types 1 and 2.
    • Transmission: Direct contact with infected body fluids, often during childbirth.
    • Risks: Can lead to neonatal herpes, causing skin lesions, encephalitis, and multi-organ involvement.

How the Torch Screen Blood Test is Conducted

  • Sample Collection: Blood sample is drawn from a vein, typically in the arm.
  • Timing: The test can be done at any point during pregnancy, often during the first prenatal visit or when symptoms of infection are present.

Specific Test Results

  1. Toxoplasmosis
    • Positive IgM: Recent or active infection.
    • Positive IgG: Past infection or immunity.
  2. Other Infections (Syphilis, Varicella-Zoster, Parvovirus B19)
    • Syphilis: Positive indicates infection, often confirmed with additional tests (e.g., RPR, FTA-ABS).
    • Varicella-Zoster: Positive IgM indicates recent infection; positive IgG indicates past infection or immunity.
    • Parvovirus B19: Positive IgM indicates recent infection; positive IgG indicates past infection or immunity.
  3. Rubella
    • Positive IgM: Recent or active infection.
    • Positive IgG: Past infection or vaccination immunity.
  4. Cytomegalovirus (CMV)
    • Positive IgM: Recent or active infection.
    • Positive IgG: Past infection or immunity.
  5. Herpes Simplex Virus (HSV)
    • Positive IgM: Recent or active infection.
    • Positive IgG: Past infection or immunity.

Factors Affecting Test Results

  • Timing of Infection: Recent infections are more likely to show positive IgM antibodies.
  • Vaccination: Previous vaccination can lead to positive IgG antibodies for rubella and varicella.
  • Cross-Reactivity: Other infections or conditions might cause false-positive results.

Advantages of the TORCH Screen Blood Test

  • Early Detection: Identifies infections early, allowing for timely intervention.
  • Comprehensive Screening: Covers a range of critical infections that can affect pregnancy.
  • Preventive Care: Guides preventive measures to protect maternal and foetal health.

Limitations and Considerations

  • False Positives/Negatives: Test results can sometimes be inaccurate; additional testing may be needed for confirmation.
  • Clinical Correlation: Results should be interpreted alongside clinical symptoms and history.
  • Maternal Health: Maternal immune status and health can influence results.

Follow-Up

  • Consultation: Discuss results with a healthcare provider, such as an obstetrician or infectious disease specialist.
  • Additional Testing: Further tests may be recommended to confirm diagnoses or monitor infections.
  • Treatment Plans: Based on results, treatment plans may include medications, preventive measures, and regular monitoring to ensure maternal and foetal health.

Conclusion

The TORCH screen blood test is a vital tool for detecting and managing infections that can affect pregnancy and foetal development. By identifying these infections early, healthcare providers can implement appropriate interventions to minimise risks and ensure the best possible outcomes for both mother and baby. Accurate interpretation and follow-up with healthcare providers are essential for effective management and care.

Results – 2 days from Laboratory receiving sample