Erythrocyte Studies

Erythrocyte (red blood cell) defects commonly cause hemolytic anemia and are conveniently separated into hemoglobin abnormalities, membrane derangements and enzyme deficiencies.

Phosphofructokinase (PFK deficiency)
PFK deficiency has been described in English Springer spaniels, American cocker spaniels and mixed breed dogs, We have established a DNA test that identifies affected as well as carrier animals (please see Phosphofructokinase deficiency). Pyruvate Kinase (PK) deficiency has been described in a variety of breeds of dogs and cats. A DNA based test is available for Basenji, West Highland White Terriers, and Cairn terriers, as well as Abyssinian, Somali, and domestic shorthair cats (please see Pyruvate Kinase deficiency).

For many other anemic animals with a suspected hereditary erythrocyte defect, special laboratory tests may be available:

Osmotic Fragility (OF) test
Hemoglobin-Oxygen Affinity
2,3-diphosphoglycerate
Variety of erythrocyte enzymes
Methemoglobin reductase
Hemoglobin assays

Osmotic Fragility
The osmotic fragility (OF) test measures the stability of erythrocytes by testing the cells' ability to withstand hemolysis in decreasing concentrations of saline solution. The OF test measures the amount hemolysis that occurs in decreasing concentrations of saline solution and compares the results with a normal control. In human medicine, increased as well as decreased osmotic fragility of erythrocytes have been described in different types of anemia. This test might add some useful information in the differentiation among some forms of anemia in the dog and cat.

The OF test is a rough index of red cell surface-to-volume ratio. When erythrocytes are placed in a hypotonic solution, water osmotically enters the cells and causes them to swell. The cell reaches a point where the membrane starts to leak, and, finally, the cell bursts and releases hemoglobin. Damage to the red cell membrane also allows hemoglobin to escape from the cells but does not cause osmotic swelling. Red cells injured by the action of complement and antibody can hemolyse in this manner. With the OF test, the amount of hemoglobin in the supernatant is measured colorimetrically. The exact relationship between the in vitro measurement of red cell fragility and the cell's ability to survive in vivo is unknown. A positive correlation exists between abnormal OF test results and decreased survival time for red cells.

In human medicine, OF is described in hereditary erythrocyte defects and in autoimmune hemolytic disease. Increased resistance to hemolysis is characteristic of thalassemia, is seen in iron deficiency, and is noted in other conditions which causes an increase in the surface-to-volume ratio of the red cell (for example, in some forms of liver disease). Reticulocytes are also more resistant to hemolysis because of their greater surface area. The mean OF expresses the concentration of NaCl in which 50 percent hemolysis occurs. Several extrinsic factors (for example, pH and temperature of the saline solution) influence the OF and every laboratory has to establish it own normal values. Marked increases in OF were seen in a dog and a cat with autoimmune hemolytic anemia as well as in a cat with hemobartonellosis. Increased OF has been found in dogs infected with Babesia canis or hookworms. Inherited membrane defects, which cause an elevated OF, have been studied in the dog. In dogs with inherited erythrocyte enzyme defects as well as chronic renal failure, the OF was normal. Recently, we have identified young adult Abyssinian and Somali cats with chronic intermittent anemia of unknown cause. They share similar clinical signs and blood test abnormalities. Their red blood cells are osmotically fragile. Another recent finding showed a puppy with severe iron deficiency anemia and decreased OF. However, much remains to be learned about the changes that occur in different disease states in dogs and cats.

Only on prearranged date. Please contact the lab at (215) 898-3375 or Dr. Urs Giger (215) 898-8830. A control blood sample is required.