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Test Code PFK1 Phosphofructokinase Enzyme Activity, Blood


Specimen Required


Collection Container/Tube:

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

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

Kinetic Spectrophotometry

Reporting Name

Phosphofructokinase, 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 11 days

Reject Due To

Gross hemolysis Reject
Fully clotted 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, including 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 have 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

≥12 months of age: 5.8-10.9 U/g Hb

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

Interpretation

Clinically significant disorders due to phosphofructokinase deficiency are associated with red blood cell activity levels less than 50% of mean normal. Unaffected heterozygotes 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 (F6P) by adenosine triphosphate (ATP) to fructose-1,6-diphosphate (F1,6-diP). F1,6-diP 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 reduced nicotinamide 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

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PFK1 Phosphofructokinase, B 72664-6

 

Result ID Test Result Name Result LOINC Value
PFKCL Phosphofructokinase, B 72664-6

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.

Day(s) Performed

Tuesday, Thursday

Report Available

1 to 6 days