Ordering Recommendation

Most useful if severe FXIII deficiency is suspected (<1% of normal activity). Use to distinguish between FXIII deficiency and a FXIII inhibitor. Abnormal results should be confirmed with quantitative testing; refer to Factor XIII Activity (2006182).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Lt. blue (sodium citrate). Refer to Specimen Handling at aruplab.com for hemostasis/thrombosis specimen handling guidelines.

Specimen Preparation

Transfer 2 mL platelet-poor plasma to an ARUP standard transport tube. (Min: 1 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Serum. EDTA plasma, clotted or hemolyzed specimens.


Ambient: 4 hours; Refrigerated: Unacceptable; Frozen: 2 weeks


Qualitative Solubility Assay




2-3 days

Reference Interval

Test Number
Reference Interval
  Factor XIII, Qualitative No Lysis within 24 hours

Interpretive Data

Compliance Category



This is a qualitative screening test; clot lysis only occurs in specimens with severe factor XIII deficiency (less than 1 percent of normal activity). Severe deficiency may be inherited or acquired (typically due to a factor XIII antibody). If clot lysis occurs in the initial testing, then Factor XIII 1:1 Mix will be added where the test is repeated using a 1:1 mix of patient plasma and pooled normal plasma to distinguish between FXIII deficiency and a FXIII inhibitor. Additional charges apply.

False-positive results (lysis) can be caused by heparin (therapy with unfractionated or low molecular weight heparin or contamination from a line), decreased or abnormal fibrinogen, increased fibrinolysis (inherited or acquired fibrinolytic disorders), fibrinolytic drugs, or other factors that affect clot structure or stability.

Hotline History


CPT Codes

85291; if reflexed, add 85291


Component Test Code* Component Chart Name LOINC
2002915 Factor XIII, Qualitative 3241-7
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • Clot Solubility
  • F13
  • Factor 13
  • Factor XIII
  • Fibrin Stabilizing Factor
Factor 13, Qualitative, With Reflex to Factor 13 1:1 Mix