Sputum Smear (KOH Test)


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 deeply.

Alternative Names

KOH test; Fungal smear - sputum; Fungal wet prep; Wet prep - fungal

How the Test is Performed

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

The sample is sent to a lab and examined under a microscope.

How to Prepare for the Test

There is no special preparation.

How the Test will Feel

There is no discomfort.

Why the Test is Performed

Your health care provider may order this test if you have symptoms or signs of a lung infection, especially if you have a weakened immune system due to certain medicines or diseases such as cancer or HIV/AIDS.

Normal Results

A normal (negative) result means no fungus was seen in the test sample.

Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

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

  • Aspergillosis
  • Blastomycosis
  • Coccidioidomycosis
  • Cryptococcosis
  • Histoplasmosis


There are no risks associated with a sputum fungal smear.


Chernecky CC, Berger BJ. Sputum, fungus - culture. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:1038-9.

Horan-Saullo JL, Alexander BD. Opportunistic mycoses. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 38.

Review Date: 12/10/2015

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright ©2017 A.D.A.M., Inc., as modified by University of California San Francisco. Any duplication or distribution of the information contained herein is strictly prohibited.

Information developed by A.D.A.M., Inc. regarding tests and test results may not directly correspond with information provided by UCSF Medical Center. Please discuss with your doctor any questions or concerns you may have.