Toxoplasma gondii, Molecular Detection, PCR
Supporting the diagnosis of acute cerebral, ocular, disseminated, or congenital toxoplasmosis
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Toxoplasma gondii is an intracellular protozoan parasite that chronically infects 10% or more of the adult population in the United States. Transmission may occur by ingestion of undercooked meat containing cysts, by direct contact with the feces of an infected cat excreting infectious oocysts, and vertically through the placenta. Accurate diagnosis is crucial because of the different therapeutic options.
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 Toxoplasma gondii DNA by PCR has proven to be a rapid and reliable alternative or supportive method for the diagnosis of toxoplasmosis.
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. Depending on the population, varying percentages of patients may be found to be positive.
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.
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 (LoD):
The limit of detection for this assay is <5,000 copies/mL in CSF, tissue, ocular fluid, and amniotic fluid.
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.
Intra-assay precision and interassay precision are 100%.
The reference range is "Negative" for this assay.
This is a qualitative assay and results are reported as "Negative" or "Positive."
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Robert-Gangneux F, Darde M: Epidemiology of and Diagnostic Strategies for Toxoplasmosis. Clin Microbiol Rev 2012;25(2):264