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HelpTest Code PFKC Phosphofructokinase Enzyme Activity, Blood
Specimen Required
Only available as part of a profile. For more information see:
-HAEV1 / Hemolytic Anemia Evaluation, Blood
-EEEV1 / Red Blood Cell (RBC) Enzyme Evaluation, Blood
Useful For
Evaluation of individuals with Coombs-negative nonspherocytic hemolytic anemia
Evaluation of individuals with exercise intolerance or myopathy
Genetic studies in families with phosphofructokinase deficiency
Method Name
Only available as part of a profile. For more information see:
-HAEV1 / Hemolytic Anemia Evaluation, Blood
-EEEV1 / Red Blood Cell (RBC) Enzyme Evaluation, Blood
Kinetic Spectrophotometry (KS)
Reporting Name
Phosphofructokinase, BSpecimen Type
Whole Blood ACD-BSpecimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood ACD-B | Refrigerated | 11 days |
Reject Due To
| Gross hemolysis | Reject |
Clinical Information
Phosphofructokinase (PFK) is the third enzyme in glycolysis. It converts fructose 6-phosphate to fructose 1,6-diphosphate. PFK deficiency, also called glycogen storage disease, type VII or Tarui disease (OMIM 232800), is a rare hereditary autosomal recessive disorder that is typically noticed in childhood. Different clinical subtypes, classical, late-onset, infantile, and hemolytic, have been described. Manifestations can vary and include exercise intolerance, exertional myopathy, nausea, stiffness, and myoglobinuria. Although not classically described, a second-wind effect is noticed by some patients.(1) A subset of individuals has compensated (high normal hemoglobin values) or mild hemolytic anemia, episodic jaundice, hyperuricemia, or gout-like symptoms. No distinctive morphologic abnormalities are seen on the peripheral blood smear. Red blood cell PFK activity is typically partially decreased (30%-50% mean normal) and muscle biopsy PFK activity is markedly decreased.
Reference Values
Only available as part of a profile. For more information see:
-HAEV1 / Hemolytic Anemia Evaluation, Blood
-EEEV1 / Red Blood Cell (RBC) Enzyme Evaluation, Blood
≥12 months of age: 5.8-10.9 U/g Hb
Reference values have not been established for patients who are younger than 12 months.
Interpretation
Clinically significant disorders due to phosphofructokinase (PFK) deficiency are associated with red blood cell activity levels less than 50% of mean normal. Unaffected heterozygous individuals have been reported with levels of 63% of normal. Therefore, genetic correlation will often be important in ambiguous cases.
Cautions
Recent transfusion may mask the patient's intrinsic erythrocyte (RBC) enzyme activity and cause unreliable results.
Some enzyme deficiency disorders can be masked by reticulocytosis and comparison of activities of other RBC enzyme activities in this panel can be useful.
Some enzyme deficiency disorders can be slightly decreased in normal neonates or conversely masked in the neonatal period. Repeat testing after 1 year of age can be useful if features of myopathy are present.
Method Description
Phosphofructokinase (PFK) catalyzes the phosphorylation of fructose 6-phosphate by adenosine triphosphate (ATP) to fructose 1,6-diphosphate (FDP). FDP is then converted to dihydroxyacetone phosphate (DHAP) through subsequent aldolase and triosephosphate isomerase (TPI) catalyzed reactions. The rate of formation of DHAP is measured by linking its reduction to alpha-glycerophosphate by alpha-glycerophosphate dehydrogenase which results in the oxidation of 1,4-dihydronicotinamide adenine dinucleotide (NADH) to NAD(+). The decrease in absorbance at 340 nm is measured spectrophotometrically as the NADH is oxidized on an automated chemistry analyzer.(Beutler E: Red cell metabolism. A Manual of Biochemical Methods. 3rd ed. Grune and Stratton; 1984:68-71; 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 |
|---|---|---|
| PFKC | Phosphofructokinase, B | 72664-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| PFKCL | Phosphofructokinase, B | 72664-6 |
Day(s) Performed
Weekly