At a Glance
Factor X deficiency is the most severe among the so-called rare bleeding disorders (i.e. deficiencies of factors II, V, VII, X, XI, and XIII). Factor X deficiency may cause a variety of symptoms, such as umbilical stump bleeding, hemarthroses, hematomas, gastrointestinal hemorrhage, hematuria and central nervous system (CNS) bleeding, depending on how low the plasma level of factor X is. The most common symptom is epistaxis, regardless of the severity of the deficiency. Women with factor X deficiency also commonly have menorrhagia. Patients with factor X activity of less than 1% (severely affected) are usually diagnosed at birth with bleeding from the umbilical stump or CNS hemorrhage. Since the factor X gene is on chromosome 13, factor X deficiency should be suspected in both men and women.
What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?
The prothrombin time (PT) and the diluted Russel Viper Venom Time (dRVVT) should be prolonged in all patients with factor X deficiency. Depending on the reagent used to perform the partial thromboplastin time (PTT) and the activity level of factor X in the plasma, the PTT is also expected to be prolonged, although mild deficiencies of factor X may not affect the PTT. With abnormal results of these screening clotting tests, a factor X activity assay or functional level should be ordered to confirm the clinical suspicion. (Table 1)
Table 1
| PT | PTT |
|---|---|
| Prolonged | Prolonged |
Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?
Since factor X is synthesized in the liver in the presence of vitamin K, acute or chronic liver disease, such as cirrhosis, or vitamin K deficiency, may decrease the factor X level to varying degrees. Vitamin K deficiency may be due to poor diet, antibiotics, poor absorption or antagonism by warfarin. Thus, patients anticoagulated with warfarin are expected to have factor X level below the reference range. In liver disease and in all of these other conditions, including warfarin intake, however, the patient will have deficiencies of other factors, as well as factor X.
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What Lab Results Are Absolutely Confirmatory?
For clinical purposes, factor X activity level in the plasma is sufficient. To classify the type of deficiency, factor X antigen level may be measured as well. In type I deficiency, both functional (activity) and antigenic levels are proportionately decreased. In type 2 deficiency, there is a discrepancy between the activity of factor X and the circulating antigen concentration, suggesting a dysfunctional molecule.
What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?
Levels of other vitamin K-dependent factors, such as factors VII and IX, are helpful to exclude an acquired condition, such as liver disease or malabsorption.
Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?
Warfarin is the main drug that causes deficiencies of all vitamin-K dependent factors, II, VII, IX, and X. Drugs that cause vitamin K deficiency, such as antibiotics, also cause deficiencies of the same factors over time.
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