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Test ID HK1 Hexokinase Enzyme Activity, Blood

Specimen Required


Preferred: Yellow top (ACD solution B)

Acceptable: Lavender top (EDTA)

Specimen Volume: 6 mL

Collection Instructions: Send specimen in original tube. Do not transfer blood to other containers.

Useful For

The evaluation of individuals with Coombs-negative chronic hemolysis

Method Name

Kinetic Spectrophotometry (KS)

Reporting Name

Hexokinase, B

Specimen Type

Whole Blood ACD-B

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD-B Refrigerated 20 days

Clinical Information

Hexokinase (HK) is the first enzymatic step in glycolysis, converting glucose to glucose 6-phosphate. Hexokinase deficiency (OMIM 235700) is a rare cause of chronic nonspherocytic hemolytic anemia, and its inheritance is autosomal recessive. Clinically significant HK deficiency manifests in early onset anemia with variable severity ranging from mild to severe. Some patients show neurologic impairment of which the mechanism is unclear.

Reference Values

≥ 12 months: 0.7-1.7 U/g Hb

Reference values have not been established for patients who are <12 months of age.


Clinical correlation or genetic confirmation may be required to establish hexokinase (HK) deficiency as a cause of hemolytic anemia as the assayed activity level in confirmed cases can vary from markedly decreased to borderline normal levels due to a compensated increase in enzyme by reticulocytes. Comparison of HK activity levels to other RBC enzyme activity can be very useful. Heterozygotes have moderately decreased to low normal HK levels and are expected to be clinically unaffected. 


Increased HK activity may be seen when reticulocytes are increased and is not supportive of a diagnosis of HK deficiency.

Clinical Reference

1. Koralkova P, Mojzikova R, van Oirschot B, et al: Molecular characterization of six new cases of red blood cell hexokinase deficiency yields four novel mutations in HK1. Blood Cells Mol Dis. 2016 Jul;59:71-76

2. Koralkova P, van Solinge WW, van Wijk R: Rare hereditary red blood cell enzymopathies associated with hemolytic anemia-pathophysiology, clinical aspects and laboratory diagnosis. Int J Lab Hematol. 2014;36:388-397

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
HK1 Hexokinase, B 49216-5


Result ID Test Result Name Result LOINC Value
HKCL Hexokinase, B 49216-5

Day(s) Performed

Tuesday, Thursday

Report Available

1 to 6 days