What is the stepped approach to diagnostic testing of factor XIII (FXIII) deficiency?

Updated: Aug 01, 2019
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Perumal Thiagarajan, MD  more...
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A sensitive assay used to quantitate FXIII activity is based on monitoring the amount of ammonia (NH3) released by using glutamate dehydrogenase and nicotinamide adenine dinucleotide phosphate during the transamidation reaction (cross-linking) by FXIII. Note the following:

  • Reportedly, this test is sensitive over a wide range of activities, from a low of 1 U/L (0.1%) to a high of 470 U/L (47%), with an impressive coefficient of variation (CV) of less than 8%, even at very low FXIII activity levels. Note that a low CV in the low range of FXIII activity is a desirable feature of assays of this enzyme. [98]

  • Compared to the cumbersome conventional quantitative amine incorporation assays, the newer method appears to be simple, rapid, and reproducible not only in the assessment of inherited or acquired reductions of FXIII activity levels but also in the ability to measure increased FXIII activity levels resulting from certain mutations. The test fulfills the need for a simpler method to quantify FXIII activity.

  • The same group also has published results of a simple, quick (2 h), 1-step, enzyme-linked immunoassay (ELISA) to determine the presence of the plasma tetramer (A2 B2). Results demonstrated high sensitivity and low CVs within batches and in day-to-day variations. [99]

Another sensitive colorimetric assay based on incorporation of 5-(biotinamido) pentylamine into fibrin/fibrinogen was compared to a photometric method based on ammonia release and an ELISA of FXIII subunit A to quantitate FXIII activity. The test was shown to be sensitive to both reductions and increases in activity; the increases resulted from the FXIII Val34Leu mutation. [5]

In addition, a2 PI and plasminogen activator inhibitor-1 assays should be performed to exclude abnormalities in the fibrinolytic pathway, which accelerate clot lysis.

Sodium dodecylsulfate polyacrylamide gel electrophoresis under reducing conditions has been used to assess the presence of cross-linked g or a chains of fibrin, which is a reflection of FXIII activity. The studies must be performed by laboratory personnel with special expertise.

If the presence of an inhibitor is suspected in a patient with a positive urea solubility test result, the next step is to repeat the urea solubility test with mixtures containing varying proportions of patient and normal plasma to differentiate between a deficiency or an inhibitor as the cause of a positive result. Since FXIII activity is present in serum, serum also may be substituted for plasma in the test.

Semiquantitation of the susceptibility of the fibrin clot to fibrinolysis can be obtained by adding iodine-125-labeled fibrinogen, tissue plasminogen activator, thrombin, and Ca2+ to the patient's plasma, with measurement of the time to 50% clot lysis. This method is useful in evaluating inhibitors but must be performed by laboratory personnel with special expertise.

See Lorand for a recent review of further details of the sequence of necessary testing to confirm the presence of a FXIII inhibitor. [89]

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