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Test ID: PTOX Toxoplasma gondii, Molecular Detection, PCR, Varies

Reporting Name

Toxoplasma gondii PCR

Useful For

Supporting the diagnosis of acute cerebral, ocular, disseminated, or congenital toxoplasmosis

Clinical Information

Toxoplasma gondii is an obligate intracellular protozoan parasite that is capable of infecting a variety of intermediate hosts including humans. Infected definitive hosts (cats) shed oocysts in feces that rapidly mature in the soil and become infectious.(1) Toxoplasmosis is acquired by humans through ingestion of food or water contaminated with cat feces or through eating undercooked meat containing viable oocysts. Vertical transmission of the parasite through the placenta can also occur, leading to congenital toxoplasmosis. Following primary infection, T gondii can remain latent for the life of the host; the risk for reactivation is highest among immunosuppressed individuals.

 

Seroprevalence studies performed in the United States indicate that approximately 9% to 11% of individuals between the ages of 6 and 49 have antibodies to T gondii.(2)

 

Infection of immunocompetent adults is typically asymptomatic. In symptomatic cases, patients most commonly present with lymphadenopathy and other nonspecific constitutional symptoms, making definitive diagnosis difficult to determine.

 

Severe-to-fatal infections can occur among patients with AIDS or individuals who are otherwise immunosuppressed. These infections are thought to be caused by reactivation of latent infections and commonly involved the central nervous system.(3)

 

Transplacental transmission of the parasites resulting in congenital toxoplasmosis can occur during the acute phase of acquired maternal infection. The risk of fetal infection is a function of the time at which acute maternal infection occurs during gestation.(4) The incidence of congenital toxoplasmosis increases as pregnancy progresses; conversely, the severity of congenital toxoplasmosis is greatest when maternal infection is acquired early during pregnancy. A majority of infants infected in utero are asymptomatic at birth, particularly if maternal infection occurs during the third trimester, with sequelae appearing later in life. Congenital toxoplasmosis results in severe generalized or neurologic disease in about 20% to 30% of the infants infected in utero; approximately 10% exhibit ocular involvement only and the remainder are asymptomatic at birth. Subclinical infection may result in premature delivery and subsequent neurologic, intellectual, and audiologic defects.

 

Serology is the traditional method for diagnosing toxoplasmosis and ascertaining the previous exposure history of the host. However, serology may be unreliable or challenging to interpret in immunocompromised patients and in suspected intrauterine infection. Detection of T gondii DNA by PCR has proven to be a rapid and reliable alternative or supportive method for the diagnosis of toxoplasmosis.

Interpretation

A positive result indicates presence of DNA from Toxoplasma gondii.

 

Negative results indicate absence of detectable DNA but do not exclude the presence of organism or active or recent disease.

Testing Algorithm

See Meningitis/Encephalitis Panel Algorithm in Special Instructions.

Analytic Time

Same day/1 day

Day(s) and Time(s) Performed

Monday through Saturday; Varies

Clinical Reference

1. Robert-Gangneux F, Darde M: Epidemiology of and Diagnostic Strategies for Toxoplasmosis. Clin Microbiol Rev 2012;25(2):264

2. Mattos CCB, Meira CS, Ferreira AIC, et al: Contribution of laboratory methods in diagnosing clinically suspected ocular toxoplasmosis in Brazilian patients. Diagn Microbiol Infec Dis 2011;70:362-366

3. Martino R, Bretagne S, Einsele H, et al: Early detection of Toxoplasma infection by molecular monitoring of Toxoplasma gondii in peripheral blood samples after allogeneic stem cell transplantation. Clin Infect Dis 2005;40:67-78

4. Fricker-Hidalgo H, Bulabois C, Brenier-Pinchart M, et al: Diagnosis of toxoplasmosis after allogeneic stem cell transplantation: results of DNA detection and serological techniques. Clin Infect Dis 2009;48:e9-e15

Method Name

Polymerase Chain Reaction (PCR)/DNA Probe Hybridization

Specimen Type

Varies


Necessary Information


Specimen source is required.



Specimen Required


Submit only 1 of the following specimens:

 

Specimen Type: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 0.5 mL

Collection Instructions: Do not centrifuge.

 

Specimen Type: Spinal fluid

Supplies: Aliquot Tube, 5 mL (T465)

Container/Tube:

Preferred: 12 x 75-mm screw cap vial (T465)

Acceptable: Sterile vial

Specimen Volume: 0.5 mL

Collection Instructions: Do not centrifuge.

 

Specimen Type: Fresh tissue

Supplies: M4-RT (T605)

Container/Tube:

Preferred: Multimicrobe Medium (M4-RT) (T605)

Acceptable: Sterile container with 1 to 2 mL of sterile saline

Specimen Volume: Entire collection

Collection Instructions: Submit only fresh tissue in a sterile container containing 1 mL to 2 mL of sterile saline or multimicrobe medium (M4-RT, M4, or M5)

 

Specimen Type: Ocular fluid

Supplies: Aliquot Tube, 5 mL (T465)

Collection Container: 12 x 75-mm screw cap vial (T465)

Specimen Volume: 0.3 mL

Collection Instructions: Do not centrifuge.


Specimen Minimum Volume

Amniotic Fluid, Ocular Fluid, Spinal Fluid: 0.3 mL
Tissue: 2 × 2mm biopsy

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Refrigerated (preferred) 7 days
  Frozen  7 days

Reference Values

Negative

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

87798

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PTOX Toxoplasma gondii PCR 42626-2

 

Result ID Test Result Name Result LOINC Value
SRC74 Specimen Source 31208-2
81795 Toxoplasma gondii PCR 42626-2

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-CNS-Infections, mml-Pediatric