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Sputum Smear (KOH Test)

Definition

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.

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 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.

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

Normal Values

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.

What abnormal results mean

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

  • Blastomycosis
  • Coccidioidomycosis
  • Cryptococcus
  • Histoplasmosis

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

What the risks are

There are no risks associated with a sputum fungal smear.

References

Limper AH. Overview of pneumonia. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 97.

Review Date: 12/1/2009

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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.