Torch Test

This test helps detect exposure to pathogens involved in congenital and neonatal infections. TORCH is an acronym for toxoplasmosis, rubella, cytomegalovirus, and herpes simplex antibodies. These pathogens are commonly associated with congenital and neonatal infections that aren't clinically apparent and may cause severe central nervous system impairment. This test detects specific immunoglobulin M-associated antibodies in infant blood.

Purpose

• To aid diagnosis of acute, congenital, and intrapartum infections

Patient preparation

• Explain to the infant's parents the purpose of the test and mention that the test requires a blood sample.
• Tell them who will perform the venipuncture and when. Reassure them that although their child may experience transient discomfort, collecting the sample takes less than 3 minutes.

Procedure and posttest care

• Obtain a 3-ml sample of venous or cord blood.
• If a hematoma develops at the venipuncture site, apply warm soaks.

Precautions

• Handle the sample gently to prevent hemolysis.
• Send the sample to the laboratory immediately.
• Don't freeze the sample.

Normal Findings

Normal test result is negative for TORCH agents.

Abnormal findings

Toxoplasmosis is diagnosed by sequential examination that shows rising antibody titers, changing titers, and serologic conversion from negative to positive; a titer of 1:256 suggests recent Toxoplasma infection.

In infants less than 6 months old, rubella infection is associated with a marked and persistent rise in complement-fixing antibody titer over time. Persistence of rubella antibody in an infant after age 6 months strongly suggests congenital infection. Congenital rubella is associated with cardiac anomalies, neurosensory deafness, growth retardation, and encephalitic symptoms.

Detection of herpes antibodies in cerebrospinal fluid with signs of herpetie encephalitis and persistent herpes simplex virus type 2 antibody levels confirms herpes simplex infection in a neonate without obvious herpetic lesions.

Interfering factors

• Hemolysis due to rough handling of the sample
• Failure to send the sample to the laboratory immediately