Pediatric Factor XIII Deficiency Workup

Updated: Mar 15, 2019
  • Author: Helge Dirk Hartung, MD; Chief Editor: Cameron K Tebbi, MD  more...
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Workup

Laboratory Studies

Screening tests

Results from standard hemostatic screening tests such as activated partial thromboplastin time (aPTT) and international normalized ratio (INR) assessments are normal in factor XIII (FXIII) deficiency.

Assessment of clot stability is the most common screening test for factor XIII deficiency, even though sensitivity and specificity are low.

The patient's plasma is incubated with thrombin with or without calcium for a sufficient period to allow formation of a stable clot; the formed clot is suspended in 5 mol/L urea, 2% acetic acid, or 1% monochloroacetic acid. Thrombin (without calcium) and acetic acid may provide the most sensitive combination.

In the presence of factor XIII, the clot is stable for more than 24 hours; in its absence, the clot dissolves in minutes to hours.

The qualitative test findings are positive in the absence of factor XIII; however, factor XIII levels as low as 1-3% may be sufficient to crosslink the fibrin, stabilizing the clot. Therefore, in patients with milder deficiencies or in patients who have recently received a transfusion, results of the clot stability assay may be normal.

A quantitative assay is required to confirm the diagnosis of factor XIII deficiency.

Functional assays

The two methods used to measure the enzymatic activity of factor XIII include measurement of synthetic amine incorporation into a fibrin clot, and measurement of ammonium ion release during the transglutaminase reaction. [6] Both assays are available as commercial kits.

Immunologic assays

Factor XIIIa and factor XIIIb antigen levels can be quantified by means of enzyme-linked immunosorbent assay (ELISA).

Patients with subunit A mutations have less than 2% of the reference range levels of A antigen.

The rare individuals with B subunit mutations have low B antigen levels, and, because of the shorter half-life of the A subunit in the absence of the B subunit, the A subunit antigen levels are also reduced.

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Imaging Studies

Appropriate imaging studies are required in the evaluation of suspected bleeding.

For instance, CT scanning or MRI of the brain is indicated in patients with a suspected CNS hemorrhage.

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