Cryptococcal Meningitis: Likelihood Ratios

Introduction: Cryptococcal meningitis is caused by Cryptococcus neoformans and typically causes extremely high intracerebral pressures. Note that the serum antigen test is sensitive for AIDS patients only.

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The likelihood ratios of findings for Cryptococcal Meningitis 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
[ + ] Cryptococcal Antigen in Serum	+ 0 -	5.9	0
in AIDS patients! Specificity is from the first reference, which gives a sensitivity of only 91%. Study: J Med Assoc Thai. 1999;82(1):65-71. PMID 10087741 J Clin Microbiol. 2005 Nov;43(11):5828-9. PMID: 16272534
[ + ] Cryptococcal Antigen in CSF	+ 0 -	13.3	0.1
at least 93% sensitivity and specificity (depending on the kit), versus culture as gold standard similar sensitivity numbers from different series, across host types (see second reference) Study: J Clin Microbiol. 1994;32(7):1680-4. PMID 7929757 J Clin Microbiol. 2005 Nov;43(11):5828-9. PMID: 16272534

Poorly Diagnostic Findings
Finding	Result	+LR	-LR
[ + ] Cryptococcal Antigen in Serum		Sensitivity = 87%
non-HIV immunocompromised. No data for immunocompetent hosts. Study: J Clin Microbiol. 2005 Nov;43(11):5828-9. PMID: 16272534
[ + ] India Ink stain of CSF		Sensitivity = 75%
in AIDS patients. sensitivity is 50% in non-AIDS patients Study: UpToDate, references PMID 3299095 and PMID 4811791
[ + ] Non-contrast Head CT		Sensitivity = 17%
abnormal findings include cryptococcomas and hydrocephalus. these were more common in non-AIDS and especially immunocompetent hosts. Study: Clin Infect Dis. (2000) 31 (2): 499-508. http://cid.oxfordjournals.org/content/31/2/499.long