Toxoplasmosis is typically diagnosed using serological analysis. Multiple immunological assays can be used, including enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody (IFA) technique, and immunosorbent agglutination assay (ISAGA). The Sabin-Feldman dye test, however, is the gold standard immunological assay. In the Sabin-Feldman dye test, the patient’s serum is treated with both live T. gondii organisms and methylene blue dye. If the patient has been previously exposed to T. gondii, antibodies will be present in the serum that will lyse the live T. gondii, leaving them clear (positive result). If no antibodies are present, the T. gondii membrane will absorb the dye and appear blue under the microscope (negative
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Acute infection is characterized by high levels of IgM antibodies, whereas patients with latent infection demonstrate high IgG seropositivity. High IgM levels indicate that the patient was infected approximately one to four weeks prior to testing, while high IgG levels show that the patient has been infected for at least three to five months. Low levels of IgM antibodies may be present in the serum for years, however, and false positives for acute infection are possible.
DNA assays are also used to diagnose toxoplasmosis. Polymerase chain reaction (PCR) is able to detect T. gondii in both amniotic and cerebrospinal fluids and is commonly used to diagnose congenital toxoplasmosis. PCR is used to diagnose cerebral toxoplasmosis less frequently due to the invasiveness of the lumbar puncture procedure.
Toxoplasmosis may also be indirectly diagnosed during routine image procedures. For example, toxoplasmic lesions or encephalitis may be observed on CT or MRI scans. If such evidence of infection is detected in immunocompromised patients, empiric treatment for acute toxoplasmosis is initiated, and the patient is monitored for signs of improvement. If the lesions and/or encephalitis resolve, toxoplasmosis is inferred to be the cause. While it is sometimes difficult to determine the source of lesions from imaging alone, new technologies are able differentiate between cancerous and toxoplasmic
Acute infection is characterized by high levels of IgM antibodies, whereas patients with latent infection demonstrate high IgG seropositivity. High IgM levels indicate that the patient was infected approximately one to four weeks prior to testing, while high IgG levels show that the patient has been infected for at least three to five months. Low levels of IgM antibodies may be present in the serum for years, however, and false positives for acute infection are possible.
DNA assays are also used to diagnose toxoplasmosis. Polymerase chain reaction (PCR) is able to detect T. gondii in both amniotic and cerebrospinal fluids and is commonly used to diagnose congenital toxoplasmosis. PCR is used to diagnose cerebral toxoplasmosis less frequently due to the invasiveness of the lumbar puncture procedure.
Toxoplasmosis may also be indirectly diagnosed during routine image procedures. For example, toxoplasmic lesions or encephalitis may be observed on CT or MRI scans. If such evidence of infection is detected in immunocompromised patients, empiric treatment for acute toxoplasmosis is initiated, and the patient is monitored for signs of improvement. If the lesions and/or encephalitis resolve, toxoplasmosis is inferred to be the cause. While it is sometimes difficult to determine the source of lesions from imaging alone, new technologies are able differentiate between cancerous and toxoplasmic