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Diagnostic Tests – India Ink Stain (Cryptococcal Meningitis)
1. What is this?
An India ink stain is a microscopic examination of cerebrospinal fluid (CSF) used to detect Cryptococcus neoformans.
This organism has a thick mucopolysaccharide capsule that repels the ink, creating a characteristic clear halo surrounding the yeast against a dark background.
2. When is this the answer
You should choose India ink staining as the best initial diagnostic test when the clinical scenario describes:
CSF findings often show:
AIDS + subacute meningitis → India ink stain
3. What is the most accurate diagnostic test?
The most accurate tests for cryptococcal meningitis are:
These tests are more sensitive than India ink staining and are used to confirm the diagnosis.
Key comparison
1. What is this?
An India ink stain is a microscopic examination of cerebrospinal fluid (CSF) used to detect Cryptococcus neoformans.
This organism has a thick mucopolysaccharide capsule that repels the ink, creating a characteristic clear halo surrounding the yeast against a dark background.
2. When is this the answer
You should choose India ink staining as the best initial diagnostic test when the clinical scenario describes:
- A patient with advanced AIDS (typically CD4 <100 cells />micro;L)
- Fever and headache
- Possible neck stiffness
- A subacute presentation (slower onset and less severe than bacterial meningitis)
CSF findings often show:
- Mild lymphocytic pleocytosis
- CSF protein and white blood cell counts may be normal, which does not exclude cryptococcal meningiti
AIDS + subacute meningitis → India ink stain
3. What is the most accurate diagnostic test?
The most accurate tests for cryptococcal meningitis are:
- Cryptococcal antigen testing (CSF or serum)
- Fungal culture of the CSF
These tests are more sensitive than India ink staining and are used to confirm the diagnosis.
Key comparison
- Best initial test (classic boards) → India ink stain
- Most accurate test → Cryptococcal antigen or fungal culture
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