Laboratory Assessment of Coagulation Factor XIII

Laboratory diagnosis of congenital and acquired deficiencies of coagulation factor XIII (FXIII) can be challenging. Determination of FXIII function requires specific and sensitive assays which are not always available. This brief review article summarizes currently used FXIII assay methods, their principles and difficulties, and discusses the recommended diagnostic workup in case of a suspected FXIII deficiency. The article also briefly touches on experimental methods used in FXIII research.

Factor XIII deficiency diagnosis: Challenges and tools

Factor XIII deficiency (FXIIID) is a rare hereditary bleeding disorder arising from heterogeneous mutations, which can lead to life-threatening hemorrhage. The diagnosis of FXIIID is challenging due to normal standard coagulation assays requiring specific FXIII assays for diagnosis, which is especially difficult in developing countries. This report presents an overview of FXIIID diagnosis and laboratory methods and suggests an algorithm to improve diagnostic efficiency and prevent missed or delayed FXIIID diagnosis. Assays measuring FXIII activity: The currently available assays utilized to diagnose FXIIID, including an overview of their complexity, reliability, sensitivity, and specificity, as well as mutational analysis are reviewed. The use of a FXIII inhibitor assay is described. Diagnostic tools in FXIIID: Many laboratories are not equipped with quantitative FXIII activity assays, and if available, limitations in lower activity ranges are important to consider. Clot solubility tests are not standardized, have a low sensitivity, and are therefore not recommended as routine screening test; however, they are the first screening test in almost all coagulation laboratories in developing countries. To minimize the number of patients with undiagnosed FXIIID, test quality should be improved in less well-equipped laboratories. Common country-specific mutations may facilitate diagnosis through targeted genetic analysis in reference laboratories in suspected cases. However, genetic analysis may not be feasible in every country and may miss spontaneous mutations. Centralized FXIII activity measurements should also be considered. An algorithm for diagnosis of FXIIID including different approaches dependent upon laboratory capability is proposed.

Detection of Factor XIII deficiency: data from multicentre exercises amongst UK NEQAS and PRO-RBDD project laboratories

INTRODUCTION

FXIII deficiency is a rare bleeding disorders, and specific FXIII assays are recommended to detect this deficiency. We investigated the performance and accuracy of FXIII investigations in two exercises, comparing centres enrolled in the PRO-RBDD project (prospective data collection on patients with fibrinogen and Factor XIII deficiencies), and UK NEQAS BC centres.

METHODS

Samples from a FXIII deficient subject and a normal donor were sent to participating centres, to investigate for FXIII deficiency, and interpret their results. Median, coefficient of variation and range were determined.

RESULTS

Results were returned from 98 UK NEQAS BC and 28 PRO-RBDD centres. Up to 40% of UK NEQAS BC and 52% of PRO-RBDD centres reported clot solubility results - with diagnostic errors by two NEQAS BC centres (false negatives for the FXIII deficient sample) and one PRO-RBDD centre (false positive for the normal sample). Over 70% of UK NEQAS BC centres and PRO-RBDD centres performed FXIII assays. Median results were similar between the two groups, with the exception of sample 3 in survey 2 (5.5 vs. 14.0 μ/dl for UK NEQAS BC and PRO-RBDD centres respectively, P < 0.001). Diagnostic errors were made by 2 UK NEQAS BC centres.

CONCLUSION

Approximately 70% of centres now employ FXIII assays, complying with international recommendations. However, solubility tests continue to be used. Our data show this can be successful, depending on the sensitivity of the method in use. Diagnostic errors are made by centres using both solubility screens and FXIII assays, and laboratories should ensure good quality assurance procedures to improve diagnostic accuracy.

Assessment of Factor XIII

Blood coagulation factor XIII (FXIII) is essential for maintaining hemostasis. The absence of FXIII results in severe bleeding diathesis, which without prophylaxis frequently leads to fatal bleeding. As the usual hemostasis screening tests remain normal, the diagnosis of FXIII deficiency needs specific tests. Here, we describe FXIII activity determination by the ammonia release assay, which is the first-line test in the diagnostic algorithm for FXIII deficiency. The method for another activity test, the undeservedly rarely used fibrin cross-linking assay, is also presented. Further tests used for the classification of FXIII deficiencies, measurement of FXIII activity in platelets, ELISAs for the measurement of complex plasma FXIII (FXIII-A₂B₂) antigen and for FXIII-A₂ in plasma and platelets are also included. Detailed description of the methods for the detection and measurement of neutralizing auto- and alloantibodies is also provided.