Ordering Recommendation

Most useful if severe FXIII deficiency is suspected (<1% of normal activity). Distinguish between FXIII deficiency and a FXIII inhibitor. Abnormal results should be confirmed with quantitative testing.


Qualitative Solubility Assay




2-3 days

New York DOH Approval Status

This test is New York DOH 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

Reference Interval

Test Number
Reference Interval
  Factor XIII, 1:1 Mix Not Applicable
  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
2002818 Factor XIII, 1:1 Mix 3241-7
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
  • Factor 13
  • Fibrin Stabilizing Factor
Factor XIII, Qualitative, with Reflex to Factor XIII 1:1 Mix