Diagnostic assays for toxoplasmosis infection
- Joseph D Schwartzman, MD
Joseph D Schwartzman, MD
- Professor of Pathology
- Dartmouth Hitchcock Medical Center
Toxoplasmosis is a worldwide zoonosis caused by the intracellular protozoan parasite, Toxoplasma gondii (T. gondii). Infection in humans most commonly occurs through the ingestion of raw or undercooked meat that contains tissue cysts, through ingestion of water or food contaminated with oocysts, or congenitally through transplacental transmission from a mother who acquired infection during pregnancy.
Laboratory testing is usually necessary to establish the diagnosis of toxoplasmosis, because the clinical manifestations of infection are so protean. The diagnostic methodology is complex and requires careful consideration based on the patient’s clinical presentation.
This topic will address diagnostic techniques for toxoplasmosis in the immunocompetent and immunocompromised adult and will give guidance as to which approach should be used in various clinical scenarios. Toxoplasmosis in the pregnant female, newborn, or in the patient with ocular disease is discussed elsewhere. The epidemiology, clinical manifestations, and treatment of toxoplasmosis are found elsewhere. (See "Toxoplasmosis in HIV-infected patients" and "Toxoplasmosis in immunocompetent hosts" and "Congenital toxoplasmosis: Treatment, outcome, and prevention" and "Congenital toxoplasmosis: Clinical features and diagnosis" and "Toxoplasmosis and pregnancy" and "Approach to HIV-infected patients with central nervous system lesions".)
The clinical presentation of toxoplasmosis varies depending on the host.
Immunocompetent hosts — The vast majority of adults with primary toxoplasma infection are asymptomatic. When symptoms do occur, patients often complain of fevers, chills, and sweats in association with prominent cervical lymphadenopathy. (See "Toxoplasmosis in immunocompetent hosts".)
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- GENERAL BACKGROUND
- Immunocompetent hosts
- Immunocompromised hosts
- AVAILABLE DIAGNOSTIC MODALITIES
- Serologic assays
- - Patterns of antibody responses
- - Interpretation of antibody testing
- - False negative serologic testing
- - False positive serologic tests
- When to order additional testing
- - Avidity testing
- - Agglutination assays
- Polymerase chain reaction assays
- Tissue culture
- APPROACH TO DIAGNOSIS
- Acute infection in the immunocompetent host
- Reactivation of infection in the immunocompromised host
- Acute infection in the pregnant female or newborn
- SUMMARY AND RECOMMENDATIONS