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HelpTest Code HK1 Hexokinase Enzyme Activity, Blood
Specimen Required
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Lavender top (EDTA)
Specimen Volume: 6 mL
Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.
Useful For
The evaluation of individuals with Coombs-negative chronic hemolysis
Method Name
Kinetic Spectrophotometry (KS)
Reporting Name
Hexokinase, BSpecimen Type
Whole Blood ACD-BSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood ACD-B | Refrigerated | 20 days |
Reject Due To
| Gross hemolysis | Reject |
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 younger than12 months.
Interpretation
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.
Cautions
Recent transfusion may mask the patient's intrinsic enzyme activity and cause unreliable results.
Hexokinase (HK) activity level can vary from markedly decreased to borderline normal levels in affected individuals due to a compensated increase in enzyme by reticulocytes. Comparison of HK activity levels to other red blood cell enzyme activity can be very useful.
Method Description
Hexokinase catalyzes the reaction of adenosine triphosphate (ATP) and glucose to glucose 6-phosphate (G6P) and adenosine diphosphate (ADP). In this assay the formation of G6P is measured by linking its further oxidation to 6-phosphogluconate to the reduction of nicotinamide adenine dinucleotide phosphate (NADP[+]) through the G6P dehydrogenase reaction. The increase in absorbance, which occurs as NADP(+) is reduced to NADPH, is measured spectrophotometrically at 340 nm on an automated chemistry analyzer.(Beutler E: Red Cell Metabolism: A Manual of Biochemical Methods. 3rd ed. Grune and Stratton; 1984:40-42; van Solinge WW, van Wijk: Enzymes of the red blood cell. In: Rifai N, Horvath AR, Wittwer CT: eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:chap 30)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82657
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