Test Catalog

Test ID: CH8    
Chromogenic Factor VIII Activity Assay, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Monitoring coagulation factor replacement therapy of selected extended half-life coagulation factor replacements


Aiding in the diagnosis of hemophilia A using a 2-stage assay, especially when the 1-stage assay was normal

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

This assay is indicated in situations where there is a clinical suspicion of hemophilia A diagnosis, but the 1-stage Factor VIII assay is normal. However, recent guidelines also recommend this assay be performed in addition to the 1-stage assay in the initial workup of hemophilia A.


Testing for autoantibodies to FVIII in the presence of a low FVIII activity may be clinically indicated. For adding on FVIII inhibitor, contact Mayo Clinic Laboratories within 7 days to assess if adequate plasma sample is available.


Coagulation testing is highly complex, often requiring the performance of multiple assays and correlation with clinical information. For that reason, we recommend requesting a coagulation consultation.


See Hemophilia Testing Algorithm in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Factor VIII (FVIII) is synthesized in the endothelial cells of the liver, and perhaps in other tissues. It is a coagulation cofactor that circulates bound to von Willebrand factor and is part of the intrinsic coagulation pathway. The biological half-life is 9 to 18 hours (average is 12 hours).


Congenital FVIII deficiency results in hemophilia A, which has an incidence of 1 in 10,000 live male births, and is inherited in a recessive X-linked manner. Patients with severe deficiency (<1%) experience spontaneous bleeding episodes (eg, hemarthrosis, deep-tissue bleeding, etc), whereas patients with moderate or mild deficiency (>1%) typically experience posttrauma or surgical bleeding.


FVIII activity assays (FVIII:C) are performed to diagnose hemophilia A and to monitor FVIII replacement therapy. FVIII:C assays are typically 1-stage clotting assays. However, there is a subset of mild hemophilia A patients who have shown discrepantly low results when measured with the 2-stage (chromogenic) assay, indicating that testing patients with a mild bleeding history with both a 1- and 2-stage assay would aid in diagnosis. In addition, there are new treatment options using long-acting glycoPEGylated products. Pharmacokinetic studies are showing that ideal monitoring of patients should be performed by the 2-stage chromogenic assay.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.



Chromogenic Factor VIII activity generally correlates with the one-stage FVIII activity. In full term/premature neonates, infants, children, and adolescents the one-stage FVIII activity* is similar to adults. However, no similar data for chromogenic FVIII activity are available.(Appel JTH 2012;10:2254)


*See Pediatric Hemostasis References section in Coagulation Guidelines for Specimen Handling and Processing in Special Instructions.

Interpretation Provides information to assist in interpretation of the test results

Factor VIII deficiency may be seen in congenital hemophilia A, acquired (autoimmune) hemophilia A, or von Willebrand disease (congenital and acquired). Laboratory artifacts that may result in artificially reduced factor VIII include samples collected in EDTA, instead of citrate, or heparin contamination of the plasma sample.


Elevated factor VIII may be seen in acute or chronic inflammatory states, or excess factor VIII replacement therapy.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Excess heparin and dilution contamination due to improper specimen collection through an intravenous access device may result in artifactually decreased results.


The 1-stage and chromogenic factor VIII (FVIII) assay results should correlate in the normal population, but may be discordant in the hemophilia population and when measuring FVIII replacement.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Rodgers SE, Duncan EM, Sobieraj-Teague M, Lloyd JV: Evaluation of three automated chromogenic FVIII kits for the diagnosis of mild discrepant haemophilia A. Int J Lab Hematol 2009;31(2):180-188

2. Kitchen S, Beckman H, Katterle Y, et al: BAY 81-8973, a full-length recombinant factor VIII: results from an International comparative laboratory field study. Haemophilia 2016 May;22(3):e192-199 doi: 10.1111/hae.12925

3. Peyvandi F, Oldenburg J, Friedman KD: A critical appraisal of one-stage and chromogenic assays of factor VIII activity. J Thromb Haemost 2016 Feb;14(2):248-261

4. Dodt J, Hubbard AR, Wicks SJ, et al: Potency determination of factor VIII and factor IX for new product labelling and postinfusion testing: challenges for caregivers and regulators. Haemophilia 2015 Jul;21(4):543-549

Special Instructions Library of PDFs including pertinent information and forms related to the test