Principle: India ink provides a dark background, while the polysaccharide capsule of Cryptococcus excludes the ink, appearing as a clear halo around the yeast cell.

Sample Type: Cerebrospinal fluid (CSF) is most commonly used; other fluids may also be tested.

Clinical Uses:

Rapid diagnosis of cryptococcal meningitis, especially in immunocompromised patients (e.g., HIV/AIDS).

Screening tool in resource‑limited settings where advanced tests (like antigen detection or PCR) may not be available.

Advantages: Quick, inexpensive, and requires minimal equipment.

Limitations:

Sensitivity is relatively low (~50–80%).

Negative results do not rule out infection; confirmatory tests (Cryptococcal Antigen, Culture, PCR) are recommended.

Analyte: Presence of encapsulated yeast cells (Cryptococcus neoformans) in CSF.

Normal Result: No encapsulated yeast cells seen.

Abnormal Findings:

Positive India Ink Prep: Clear halo around yeast cells, indicating Cryptococcus infection.

Negative India Ink Prep: No capsule seen; does not exclude infection.

Clinical Use:

Provides a rapid, point‑of‑care diagnostic tool for cryptococcal meningitis.

Helps guide urgent antifungal therapy decisions.

Supports screening in HIV/AIDS patients with suspected meningitis.