Test Catalog

Test Id : TOXB

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Toxoplasma gondii, Molecular Detection, PCR, Blood

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Overview

Test Catalog

Useful For
Suggests clinical disorders or settings where the test may be helpful

Supporting the diagnosis of active toxoplasmosis, particularly in immunocompromised individuals

Method Name
A short description of the method used to perform the test

Polymerase Chain Reaction (PCR)/DNA Probe Hybridization

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Toxoplasma gondii PCR, B

Aliases
Lists additional common names for a test, as an aid in searching

Toxoplasma gondii (T. gondii)

Specimen Type
Describes the specimen type validated for testing

Whole Blood EDTA

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Container/Tube: Lavender top (EDTA)

Specimen Volume: 1 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.

Forms

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

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.3 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Whole Blood EDTA Refrigerated (preferred) 7 days
Frozen 7 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Supporting the diagnosis of active toxoplasmosis, particularly in immunocompromised individuals

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Toxoplasma gondii is an obligate intracellular protozoan parasite that can infect a variety of intermediate hosts, including humans. Infected definitive hosts (cats) shed oocysts in feces that rapidly mature in the soil and become infectious.(1,2) 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 years and 49 years have antibodies to T gondii.(3)

 

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.(4)

 

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.(3) 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. Most 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.

 

Detection of T gondii DNA by polymerase chain reaction (PCR) has proven to be a rapid and reliable alternative or supportive method for the diagnosis of toxoplasmosis. When performed on blood, it may detect circulating parasite DNA and thus confirm or support the results of serologic testing. PCR testing on peripheral blood has been used successfully to detect cases of ocular toxoplasmosis (3) as well as invasive disease in allogeneic stem cell recipients.(4,5) However, blood may not be a sensitive specimen for detecting organ specific disease (eg, ocular or cerebral toxoplasmosis). In this case, other specimens (eg, ocular fluid, CSF, fresh tissue) should be considered (order PTOX / Toxoplasma gondii, Molecular Detection, PCR, Varies).

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Interpretation
Provides information to assist in interpretation of the test results

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.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This assay is designed for use in patients with a clinical history and symptoms consistent with toxoplasmosis. This test should not be used to screen healthy patients.

 

Blood may not be a sensitive specimen for detecting organ specific disease (eg, ocular or cerebral toxoplasmosis). In this case, other specimens (eg, ocular fluid, spinal fluid, fresh tissue) should be considered.

 

Results should be interpreted with consideration of clinical and laboratory findings. A negative result does not indicate absence of disease. Reliable results depend on adequate specimen collection and the absence of inhibiting substances.

Supportive Data

Accuracy/Diagnostic Sensitivity and Specificity:

Accuracy was determined using a combination of spiking and clinical specimens for each source accepted for testing. Accuracy ranges from 97% to 100%.

 

Analytical Sensitivity/Limit of Detection:

The limit of detection for this assay is less than 5000 copies/mL

 

Analytical Specificity:

No PCR signal was obtained from extracts of 20 bacterial, parasitic, and viral isolates from similar organisms and from organisms commonly found in the specimen types tested.

 

Precision:

Intra-assay precision and interassay precision are 100%.

 

Reference Range:

The reference range is "Negative" for this assay.

 

Reportable Range:

This is a qualitative assay and results are reported as "Negative" or "Positive."

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Robert-Gangneux F, Darde M. Epidemiology of and diagnostic strategies for toxoplasmosis. Clin Microbiol Rev. 2012 Apr ;25(2):264-296

2. McAuley JB, Singh K: Toxoplasma, In: Carroll KC, Pfaller MA, eds. Manual of Clinical Microbiology, 12th ed. ASM Press; 2019: chap141.

3. 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 Jul;70(3):362-366

4. 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 Jan 1;40(1):67-78

5. 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 Description
Describes how the test is performed and provides a method-specific reference

DNA from clinical specimens is extracted using the Roche MagNA Pure system. Toxoplasma gondii DNA is then detected by using real-time polymerase chain reaction (PCR) to amplify the target sequence . The LightCycler amplifies and monitors fluorescent development of target nucleic acid after each cycle. The continuous monitoring is derived from the fluorescence resonance energy transfer (FRET) principle: a hybridization probe with a donor fluorophore on the 3' end is excited by an external light source and emits light that is absorbed by a second hybridization probe with an acceptor fluorophore at the 5' end. The acceptor fluorophore emits light of a different wavelength that can be measured with a signal that is proportional to the amount of specific PCR product. Melting temperature analysis is used following amplification for sensitive and specific detection of amplified target DNA.(Cockerill FR, Uhl FR: Applications and challenges of real-time PCR for the clinical microbiology laboratory. In: Reischl U, Wittwer C, Cockerill F, eds. Rapid Cycle Real-Time PCR, 2002; Nolte FS. Target amplification techniques. In Carroll KC, Pfaller MA, Landry ML, et al, eds. Manual of Clinical Microbiology. 12th ed. ASM Press; 2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Saturday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 4 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 week

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

87798

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
TOXB Toxoplasma gondii PCR, B 16279-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
62977 Toxoplasma gondii PCR, B 16279-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | PHP Pdf | CMS Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports