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Ham test


Definition:

The Ham test is a blood test done to diagnose paroxysmal nocturnal hemoglobinuria (PNH). The test checks whether red blood cells become more fragile when they are placed in mild acid.

Alternative Names:

Acid hemolysin test

How the Test is Performed:

A blood sample is needed.

How to Prepare for the Test:

There is no special preparation needed for this test.

How the Test will Feel:

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed:

A positive test can confirm the diagnosis of PNH.

The Ham test can also be used to diagnose another rare disorder called congenital dyserythropoietic anemia.

The Ham test is increasingly being replaced by a test called flow cytometry.

Normal Risks:

A negative test is normal.

What Abnormal Results Mean:

Abnormal results may be due to:

  • Paroxysmal nocturnal hemoglobinuria
  • Congenital dyserythropoietic anemia
Risks:

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)
References:

Brodsky RA. Paroxysmal nocturnal hemoglobinuria. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al., eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, Pa: Elsevier Saunders; 2012:chap 29.

Elghetany M, Banki K. Erythrocytic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 32.


Review Date: 2/24/2014
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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