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Introduction ⬇

PK deficiency is a genetic disorder characterized by a lowered concentration of adenosine triphosphate in the RBC and consequential membrane defect. The result is a nonspherocytic, chronic hemolytic anemia. PK deficiency is the most common and most important form of hemolytic anemia resulting from a deficiency of glycolytic enzymes in the RBC.

Normal Findings ⬆ ⬇

2.8–8.8 U/g Hb or 46.7–146.7 nkat/g Hb

To convert to U/mL of packed RBCs: U/g Hb × 0.34 = U/mL packed RBCs

Normal values vary greatly; check with your reference laboratory.

Procedure ⬆ ⬇

  1. Obtain 5 mL of whole blood in a green-topped tube (with EDTA or heparin anticoagulant). Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.

  2. Refrigerate immediately; do not freeze.

Clinical Implications ⬆ ⬇

PK is decreased in:

  1. Congenital PK deficiency: recessive, nonspherocytic hemolytic anemia. Patients tolerate anemia well because of increased 2,3-diphosphoglycerate (2,3-DPG).

  2. Acquired PK deficiency caused by (level returns to normal after treating underlying disorder):

    1. Myelodysplastic disorders

    2. Acute leukemias

    3. Anemias

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure. There should be no exercising before tests.

  2. Withhold transfusion until after blood samples are drawn (especially with osmotic fragility).

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for hemolytic anemia, hypoxia, or polycythemia.

  2. Splenectomy is indicated when anemia is severe enough to require transfusions.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

Many prescribed drugs interfere with the normal functioning of Hb in susceptible persons, especially sulfonamides, antipyretic drugs, analgesic agents, large doses of vitamin K, and nitrofurans. Any increase in PK level should be brought to the immediate attention of the healthcare provider

Interfering Factors ⬆

In congenital PK deficiency, intravascular hemolysis increases during pregnancy or following use of oral contraceptives.