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A sputum fungal smear is a laboratory test that looks for fungus in a sputum sample. Sputum is the material that comes up from air passages when you cough very deeply.

A sputum sample is needed. You will be asked to cough deeply and spit any material that comes up from your lung into a special container.

The sample is sent to a lab. A small amount is lightly smeared onto a microscope slide and mixed with potassium hydroxide (KOH). The slide is examined under the microscope and checked for fungus parts.

There is no special preparation.

There is no discomfort.

Your doctor may order this test if you have abnormal sputum production or signs of a lung infection.

A normal test should show no fungus on the microscope slide.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Abnormal results may be a sign of a fungal infection. Such infections include:

• Blastomycosis
• Coccidioidomycosis
• Histoplasmosis

White blood cells called eosinophils may also be present. An abnormal result may also be due to acute pulmonary eosinophilia (Loeffler syndrome).

There are no risks associated with a sputum fungal smear.

KOH test; Fungal smear - sputum

Updated by: D. Scott Smith, M.D., MSc, DTM&H, Chief of Infectious Disease & Geographic Medicine, Kaiser Redwood City, CA & Adjunct Assistant Professor, Stanford University. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.