Toxoplasmosis: diagnosis
Last reviewed: 23.04.2024
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Clinical diagnosis of toxoplasmosis
Diagnosis of toxoplasmosis is based on epidemiological risk factors for infection and clinical and laboratory diagnosis data.
[Specific and nonspecific laboratory diagnostics of toxoplasmosis
Parasitological diagnosis of toxoplasmosis (the investigation of biopsies of lymph nodes and other organs) has not found wide application because of its complexity and laboriousness. To detect toxoplasm, microscopy, a direct version of the fluorescence assay (MFA) method and a bioassay method in white mice with T. Gondii isolation are used. A method of immunoblotting was developed to detect proteins of the pathogen with antibodies IgM, IgG, IgA and polymerase chain reaction. Diagnosis of intrauterine toxoplasmosis is based on the methods of cordocentesis and amniocentesis. However, these techniques have limited application in practical medicine, since they are expensive, requiring special equipment and certain training of personnel.
In the vast majority of cases, the diagnosis of toxoplasmosis is the use of serological tests. Serological diagnosis of toxoplasmosis is based on the detection of Ig classes G, M, A, E. They can be determined indirect method of fluorescent antibodies (NMPA), solid-phase enzyme immunoassay (TIFM), etc. Among the modern methods of serodiagnosis of toxoplasmosis are also tests of differential agglutination, latexagglutination and potassium TIFM for the detection of IgM to toxoplasm. Such tests for the determination of antibodies, such as precipitation reactions (RP), complement fixation (RCC) and indirect haemagglutination (RIGA), are currently rarely used due to low sensitivity and specificity. The presence of toxoplasmosis can be established with the help of a skin test with toxoplasmin. However, this test in recent years is also practically not used, because there are more sensitive modern diagnostic methods that exclude the introduction of the drug into the body of the subject. In the diagnosis of intrauterine toxoplasmosis, along with NMPA and TIFM, a reaction with the Sabin-Feldman (RK) dye is used. The test is based on the inability of toxoplasma to stain with methylene blue in the presence of antibodies to T. Gondii. This reaction is rather complicated, laborious and requires live toxoplasm, which is not possible in all laboratories.
Repeated serological diagnosis of toxoplasmosis reveals specific antibodies of IgM and IgG classes to toxoplasmic antigens: ELISA, RNGA and RIF (but they are not sufficiently informative in AIDS patients): conduct an intracutaneous test with toxoplasmin (native or recombinant). When analyzing and interpreting the results of serological diagnosis, one should take into account the "immunological" incubation - the appearance of antibodies on parasite antigens only through a certain latent period - and evaluate the results of the studies in dynamics. Skin test indicates infection with toxoplasm, but does not give information about the nature of the course of the disease. Pregnant women with positive serological reactions spend ultrasound of the fetus in dynamics.
Instrumental diagnostics of toxoplasmosis
When diagnosing cerebral toxoplasmosis (especially in patients with AIDS), CT and brain MRI are performed: in the serum and spinal fluid, IgG titers (less often IgM) are detected, the DNA of the pathogen is detected by PCR and the pathogen is isolated from them.
Differential diagnosis of toxoplasmosis
Toxoplasmosis is differentiated from many infectious and non-infectious diseases: lymphogranulomatosis, lymphatic leukemia and other pathologies of the blood system, tuberculosis, listeriosis, iersiniosis, infectious mononucleosis. Diseases of the nervous system and organs of vision. In children, taking into account age, differential diagnosis of toxoplasmosis is carried out with CMV, herpes infections and various ARI, rubella, viral hepatitis. With repeated miscarriages, the birth of children with developmental anomalies in seropositive women, it is necessary to exclude obstetric and gynecological pathologies.