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acidified serum test (Ham test, acid hemolysin test)
Indications:
- paroxysmal nocturnal hemoglobinuria
Clinical significance:
- definitive diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) depends upon the acidified serum or Ham test
- the alternate pathway of complement is activated by acidified serum, binds to & lyses the abnormal PNH cells that are unusually sensitive to complement
Procedure:
- the patients erythrocytes are saline washed, mixed with ABO-compatible serum & 0.2 M HCl
- after 1 hour of incubation, PNH cells are lysed
- the test is run in parallel using the patient's own serum along with 5 controls systematically isolating the effect of eliminating each of the reagents used, including serum with & without heat-inactivation, 0.2 N HCl & erythrocytes (normal & patient's)
- in PNH 10-50% of cells are lysed
- if lysis also occurs with heat-inactivated serum, spherocytes or antibody-sensitized cells may be responsible
Note:
- a positive Ham's test occurs in congenital dyserythropoietic anemia-2 (CDA-2 or HEM-PAS)
- however, lysis does not occur with the patient's serum & only with about 30% of normal sera
- additionally, the sucrose hemolysis test is negative in CDA-2
Related
paroxysmal nocturnal hemoglobinuria (PNH, Marchiafava-Micheli syndrome)
General
clinical hematology test
References
- Clinical Diagnosis & Management by Laboratory Methods,
19th edition, J.B. Henry (ed), W.B. Saunders Co.,
Philadelphia, PA. 1996, pg 635
- Acid Hemolysin (Ham Test)
Laboratory Test Directory ARUP: 49010