Toxoplasmosis laboratory findings: Difference between revisions

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*Retinochoroidal lesions can be highly suggestive or, at times, diagnostic of congenital Toxoplasmosis
*Retinochoroidal lesions can be highly suggestive or, at times, diagnostic of congenital Toxoplasmosis
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===Interpretation of Serological Tests===
{{familytree/start}}
{{familytree | | | | | | | A01 | | | | | | | | | | | | | | | | |A01=IgG/IgM(ideally performed in the first trimester}}
{{familytree | | | | | | | |!| | | | | | | | | | | | | | | | | | | | | | }}
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{{familytree | |!| | | |!| | | |!| | | |!| | | | | | | | | | | | | | | | }}
{{familytree | B01 | | B02 | | B03 | | B04 | | | | | | | | | | |B01='''Negative IgG and IgM'''|B02='''Positive IgG''' <br>'''Negative IgM'''|B03='''Positive IgM'''<br>'''Negative IgG'''|B04='''Positive IgG and IgM'''}}
{{familytree | |!| | | |!| | | |!| | | |!| | | | | | | | | | | | | | | | }}
{{familytree | |!| | | |!| | | |!| | | |!| | | | | | | | | | | | | | | | }}
{{familytree | C01 | | C02 | | C03 | | C04 | | | | | | | | | | | C01= ❑ No serologic evidence of Toxoplasma infection<br>❑ Risk of congenital Toxoplasmosis only if the woman aquires infection during the pregnancy<br>❑ Counsel about the preventive measures for T.gondii| C02= '''<18 weeks of gestation''' Infection aquired in the past and prior to the pregnancy<br>❑ Risk of infection is zero unless the patient is immunocompromised<br>  '''≥18 weeks of gestation'''<br>❑ It is difficult to establish the timing of infection|C03=Repeat IgG and IgM in 1 to 3weeks|C04=Serum should be sent to reference laboratory for confirmatory testing<br>❑ If the confirmatory test is positive initiate treatment and if negative follow up for 12 months}}
{{familytree | |!| | | |!| | | |!| | | | | | | | | | | | | | | | | | | | }}
{{familytree | |!| | | |!| | |,|^|-|-|-|-|-|-|-|-|-|-|.| | | | | | | | | }}
{{familytree | |!| | | |!| | |!| | | | | | | | | | | |!| | | | | | | | | }}
{{familytree | D01 | | D02 | |D03| | | | | | | | | | D04 | | | | | | |D01= Follow up testing is indicated during gestation to detect seroconversion|D02= '''≤ 18 weeks of gestation'''<br> ❑  No further action indicated <br> '''>18 weeks of gestation'''<br>❑ Compare to previous serological tests and send samples to a reference laboratory to confirm the timing of infection| D03= ❑ '''Negative IgG''' and '''Positive IgM''' <br>❑ Does not have clinical relevance<ref name="pmid8968902">{{cite journal| author=Liesenfeld O, Press C, Montoya JG, Gill R, Isaac-Renton JL, Hedman K et al.| title=False-positive results in immunoglobulin M (IgM) toxoplasma antibody tests and importance of confirmatory testing: the Platelia Toxo IgM test. | journal=J Clin Microbiol | year= 1997 | volume= 35 | issue= 1 | pages= 174-8 | pmid=8968902 | doi= | pmc=229533 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8968902  }} </ref>|D04= ❑ '''Positive IgG and IgM'''<br> ❑ Seroconverted and fetus is at risk<br> ❑ Initiate treatment and consider PCR}}
{{familytree/end}}
<small>Table adopted from Management of Toxoplasma gondii Infection during Pregnancy<ref name="MontoyaRemington2008">{{cite journal|last1=Montoya|first1=Jose G.|last2=Remington|first2=Jack S.|title=Clinical Practice: Management ofToxoplasma gondiiInfection during Pregnancy|journal=Clinical Infectious Diseases|volume=47|issue=4|year=2008|pages=554–566|issn=1058-4838|doi=10.1086/590149}}</ref> </small>


===Microscopy===
===Microscopy===

Revision as of 00:07, 1 June 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Overview

Toxoplasma infection is diagnosed by the presence of parasite in the fluids such as blood, body fluids, or tissue by DNA amplification, microscopy or by isolation of the organism. The most commonly used diagnostic test is the PCR of the amniotic fluid and a positive test is diagnostic of congenital toxoplasmosis.[1]

Laboratory Findings

Toxoplasma infection is diagnosed by the presence of parasite in the fluids such as blood, body fluids, or tissue by DNA amplification, microscopy or by isolation of the organism. The most commonly used diagnostic test is the PCR of the amniotic fluid and a positive test is diagnostic of congenital toxoplasmosis.[1]

Principles and various methods used for the diagnosis of toxoplasmosis:

Principle Detection Method Findings supporting the diagnosis of Toxoplasmosis
Toxoplasma specific humoral responses[2] IgG, IgM, IgA Dye test, ELISA, ELISA-like assays, immunofluorescence, agglutination
  • Positive IgM after 5 days of life and in the absence of blood transfusions
  • Positive IgA after 10 days of life
  • Persistence of Toxoplasma IgG beyond 1 year of age
IgG, IgM, and IgA to specific Toxoplasma antigen

Western blot

  • Presence of specific bands only seen in the newborn or bands with higher intensity than maternal ones for IgG and/or IgM and/or IgA in a reference laboratory
Toxoplasma nucleic acid amplification DNA PCR
Immunohistochemistry of Toxoplasma specific antigens in tissue Antigens Immunoperoxidase
  • Positive result in any tissue(e.g., brain or other fetal tissue)
Visualization by microscopy Visual identification of tachyzoites and/or cysts Stains such as hematoxylin/eosin, Giemsa
  • Positive identification in a reference laboratory
Isolation of Toxoplasma Whole live parasite Inoculation in peritoneal cavity of mice
  • Detection of live cysts from any body fluid or tissue that has been inoculated in mice in a reference laboratory
Brain imaging

Ultrasound, CT, brain MRI

  • Findings can be suggestive but are not diagnostic of congenital Toxoplasmosis since other etiologies may result in similar findings
Retinal exam Inflammation in choroidal and retinal layers Ophthalmologic exam
  • Retinochoroidal lesions can be highly suggestive or, at times, diagnostic of congenital Toxoplasmosis

Microscopy

A: Toxoplasma gondii tachyzoites, stained with Giemsa, from a smear of peritoneal fluid obtained from a mouse inoculated with T. gondii. Tachyzoites are typically crescent shaped with a prominent, centrally placed nucleus.

Toxoplasma gondii tachyzoites, stained with Giemsa
Toxoplasma gondii tachyzoites, stained with Giemsa


B: Toxoplasma gondii cyst in brain tissue stained with hematoxylin and eosin (100×). C: Zoom of Image B, T. gondii cyst.

Toxoplasma gondii cyst, hematoxylin and eosin stain
Toxoplasma gondii cyst, hematoxylin and eosin stain


References

  1. 1.0 1.1 Foulon W, Pinon JM, Stray-Pedersen B, Pollak A, Lappalainen M, Decoster A; et al. (1999). "Prenatal diagnosis of congenital toxoplasmosis: a multicenter evaluation of different diagnostic parameters". Am J Obstet Gynecol. 181 (4): 843–7. PMID 10521739.
  2. Tanimura K, Nishikawa A, Tairaku S, Shinozaki N, Deguchi M, Morizane M; et al. (2015). "The IgG avidity value for the prediction of Toxoplasma gondii infection in the amniotic fluid". J Infect Chemother. 21 (9): 668–71. doi:10.1016/j.jiac.2015.05.013. PMID 26141811.


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