CNS Toxoplasmosis: Likelihood Ratios

Introduction: Infection of the brain parenchyma by Toxoplasma, almost exclusively seen in HIV/AIDS patients. Often presents as a ring-enhancing lesion.

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Tags: Infection Neurologic Tag this Diagnosis.

Differential Diagnoses include: Lymphoma, CNS

The likelihood ratios of findings for CNS Toxoplasmosis are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Good Positive and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] Thallium-201 SPECT	+ 0 -	10	0
However, an abstract found that thallium overdiagnoses lymphoma (5/8 patients thought to have toxoplasmosis by Thallium were found to have lymphoma by PET/CT). Differential Diagnosis: Lymphoma, CNS Study: J Nucl Med. 1996 Jul;37(7):1150-4. PMID: 8965186 J Nucl Med. 2006; 47 (Supplement 1):303P http://jnumedmtg.snmjournals.org/cgi/content/short/47/suppl_1/303P-a
[ + ] PET/CT scan	+ 0 -	inf	0.1
in patients with HIV, versus CNS lymphoma Differential Diagnosis: Lymphoma, CNS Study: Eur J Nucl Med Mol Imaging. 2013 Sep;40(9):1420-7. PMID: 23685752