The India ink preparation (test) is a rapid microscopic test used primarily to detect encapsulated yeasts, especially Cryptococcosis caused by Cryptococcus neoformans and Crytococcus gatti. This test is a simple negative staining technique (meaning it stains the background rather than the organism) used in the microbiology laboratory.

India ink contains fine carbon particles that do not penetrate the fungal capsule. The polysaccharide capsule will exclude the particles of ink, and the capsule will appear as a clear halo around the organism.

The India ink preparation is examined under the light microscope, first with 10X to scan slide for yeast cells, then with 40X for detailed examination. Oil immersion (100X) is generally unnecessary.

The test is most commonly performed on cerebrospinal fluid (CSF) from patients suspected of having Cryptococcus neoformans

The India preparation has largely been replaced in many laboratories by the Cryptococcus antigen test, which is much more sensitive and specific. Although still taught and occasionally used in resource-limited settings.