A 34-year-old man with advanced HIV presents with headache and low-grade fever. CSF examination shows lymphocytic pleocytosis with 80 mg/dL glucose. India ink preparation of the CSF is negative. Which additional test should be performed to exclude cryptococcal meningitis?

• A CSF culture on Löwenstein-Jensen medium
• B Latex agglutination for cryptococcal polysaccharide capsular antigen in CSF ✓
• C Gram stain of CSF sediment
• D Counter-immunoelectrophoresis for bacterial polysaccharides

Explanation

Cryptococcal antigen latex agglutination detects capsular polysaccharide antigen in CSF or serum with sensitivity exceeding 90 percent and outperforms India ink microscopy, which can miss low fungal burdens. In AIDS patients with subacute meningitis and this CSF profile, a negative India ink does not exclude Cryptococcus neoformans. Löwenstein-Jensen medium grows mycobacteria, and counter-immunoelectrophoresis targets bacterial capsular antigens, neither relevant here.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.