Which CSF analysis findings are characteristic of cryptococcal meningitis in patients with HIV infection?

Updated: Aug 24, 2017
  • Author: Gulshan Uppal, MD; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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In one study of patients with AIDS, 26% of patients with cryptococcal meningitis had normal CSF findings; 40% had high protein levels, low glucose levels, and pleocytosis; and 55% had fewer than 10 lymphocytes/mL.

The CSF may have a clear or turbid appearance in cryptococcal meningitis. Variable mononuclear pleocytosis is observed, and the white blood cell (WBC) count may be over 20 x 109/L. A high CSF opening pressure is present in about two thirds of patients and is a poor prognostic sign.

CSF cultures are the criterion standard in diagnosing cryptococcal meningitis, but weeks and several specimens may be needed to obtain a positive result. Results of the India ink test are supportive of the diagnosis if positive, but they do not exclude the diagnosis if they are negative

Cryptococcal antigen is present several weeks before overt signs of meningitis develop; therefore, its detection provides an opportunity to catch infection early, and, hence, screening persons with HIV for cryptococcal infection when they access health care can identify asymptomatic infected patients, allowing for prompt treatment and prevention of death. [3] This can be used as a point-of-care assay and serve as a cost-effective screening.

Test results for serum and CSF cryptococcal antigen may be positive in cryptococcal meningitis. The initial diagnostic sensitivity of cryptococcal CSF antigen is 94.1%, followed by the serum antigen of 93.6%; however, this tool is unreliable in assessing point of discontinuation of antifungal therapy, at least among patients who are HIV positive.

The definitive diagnosis of cryptococcal meningoencephalitis is made by culture of the organism from the cerebrospinal fluid (CSF). A positive cryptococcal polysaccharide antigen in the CSF or serum strongly suggests the presence of infection well before the cultures become positive. 

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