View Case

Back

Questions
Discussion
References

879) A 42-year-old man presents to the emergency department with a spontaneous bleeding into his knee. The patient has a history of severe hemophilia B. He is on factor IX prophylactic therapy at home. He weighs 75 kg. Laboratory results are shown in the table:

Patient Reference Range Units

Hemoglobin 12.2 13.3–16.2 g/dL

Hematocrit 36.9 38.8–46.4 %

Platelets 278 165–415 ×10⁹/L

Factor IX 20 50–150 %

The hematologist on-call asks you to calculate the appropriate loading dose of factor IX. The final factor IX level should be 100%. Which one of the following is the correct dose for this patient?

	Patient	Reference Range	Units
Hemoglobin	12.2	13.3–16.2	g/dL
Hematocrit	36.9	38.8–46.4	%
Platelets	278	165–415	×10⁹/L
Factor IX	20	50–150	%

1,500 IU. 3,000 IU. 4,500 IU. 6,000 IU. 7,500 IU.

Show Diagnosis/Topic

• Hemophilia B is a sex-linked recessive genetic disorder leading to a deficiency in factor IX.

• Patients have a prolonged activated partial thromboplastin time, normal prothrombin time, and decreased factor IX activity.

• Hemophilia B is divided clinically into three groups: mild, greater than 5% factor IX activity; moderate, 1% to 5% factor IX activity; and severe, less than 1% factor IX activity.

• Treatment involves administration of factor IX concentrates to prevent and manage bleeding episodes.

• The factor IX dose is calculated using this formula: dose required (IU) = weight (kg) × desired factor IX increase (IU/dL) × 1 IU/kg.

• Factor IX does not remain in the intravascular space. About 50% of the administered factor IX will distribute to the extravascular space.

• Factor IX should be dosed every 24 hours due to the in vivo half-life of factor IX.

Back

Clinical Pathology: General Principles, Hematology & Coagulation, Transfusion Medicine

View Notes

Add a Note