A diagnostic blind spot: false-negative IMMY CrAg LFA and CrAg SQ in an immunocompetent patient with Cryptococcus gattii meningitis.
M Supriya, Anoop Joshi, M Pooja et al.
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Case in brief
A 43-year-old immunocompetent man presented with fever, chronic progressive headache, diplopia, and papilledema. Despite persistently negative IMMY CrAg lateral flow assays and semi-quantitative CrAg results in both cerebrospinal fluid and serum, CSF analysis revealed lymphocytic pleocytosis and budding yeast cells. Culture and sequencing confirmed Cryptococcus gattii VGI meningitis. The patient was managed effectively after diagnosis.
What made this case unusual
The case is notable for the false-negative results of the IMMY CrAg LFA and CrAg SQ tests in the presence of confirmed Cryptococcus gattii meningitis, despite high clinical suspicion.
Diagnostic / clinical pearl
Clinicians should be aware that negative cryptococcal antigen tests do not rule out cryptococcal meningitis, especially when clinical signs are suggestive.
Why it matters
This case emphasizes the necessity of using a combination of diagnostic methods, including microscopy and culture, when faced with high clinical suspicion of cryptococcal infection despite negative antigen tests.