TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: PKLRG    
Pyruvate Kinase Liver and Red Blood Cell (PKLR), Full Gene Sequencing and Large Deletion Detection, Varies

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

Aid in the diagnosis of pyruvate kinase (PK) deficiency

 

Ascertain a causative variant in the PKLR gene of patients with low or relatively low levels of erythrocytic PK enzymatic activity

 

Ascertain carrier status of family members of individuals diagnosed with PK deficiency for genetic counseling purposes

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

The glycolytic pathway is used by all tissues for energy production through the formation of ATP. It is particularly important in red blood cells, which are dependent upon this pathway for energy due to their lack of mitochondria. The PKLR gene encodes for pyruvate kinase, the rate-limiting glycolytic enzyme that catalyzes the transphosphorylation from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP) creating pyruvate and adenosine triphosphate (ATP). Pyruvate kinase (PK) deficiency is a relatively common cause of hereditary nonspherocytic hemolytic anemia,(2) with an estimated prevalence of 1:20,000 among people of European descent. The severity of hemolysis varies from fully compensated forms to life-threatening neonatal anemia requiring transfusions.(3) Over 200 different variants have been reported in the PKLR gene. Most are single nucleotide substitutions although rarer large deletions have also been identified. Pyruvate kinase deficiency is inherited in an autosomal recessive manner and genetic results should be correlated with enzyme levels performed remote from transfusion when possible. Pyruvate kinase deficiency can be difficult to interpret based on enzyme level alone and may be only mildly decreased or normal in those with the most severe symptoms or after splenectomy due to reticulocytosis.(3) Comparison to other RBC enzyme levels is usually very helpful in this regard. Heterozygous carriers of PKLR variants have intermediate enzyme levels and are not symptomatic.

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.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

All detected alterations will be evaluated according to current ACMG recommendations.(4) Variants will be classified based on known, predicted, or possible effect on gene pathogenicity and reported with interpretive comments detailing their potential or known clinical significance.

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

Blood samples may contain donor DNA if obtained from patients who received heterologous blood transfusions or allogeneic blood or marrow transplantation. Results from samples obtained under these circumstances may not accurately reflect the recipient's genotype.

 

For individuals who have received blood transfusions, the genotype usually reverts to that of the recipient within 6 weeks. For individuals who have received allogeneic blood or marrow transplantation, a pretransplant DNA specimen is recommended for testing. For patients who have been transfused within the preceding 6 weeks, the enzyme assay (PK / Pyruvate Kinase, Erythrocytes) will also be affected, so it is not an appropriate alternative test. 

 

Patients who have received an allogeneic blood or marrow transplant would be expected to convert to the PKLR status of the donor. However, if the patient’s transplant was partially successful or if there is a relapse of an underlying hematologic malignancy, a mixture of donor and recipient genotype may be seen on genetic analysis. The enzyme assay can be run after transplantation; order PK / Pyruvate Kinase, Erythrocytes.

 

Rare variants exist that could lead to false-negative or false-positive results. Other variants in the primer binding regions can affect the testing, and ultimately, the genotype assessment made.

 

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Large deletions or rearrangements that are not within the intron 2 through exon 11 region are not detected by this assay.

 

Sometimes a genetic alteration of unknown significance may be identified. In this case, testing of appropriate family members may be useful to determine pathogenicity of the alteration.

 

This test is not designed to provide specific dosing or drug selection recommendations and is to be used as an aid to clinical decision making only. Drug-label guidance should be used when dosing patients with medications regardless of the predicted phenotype. 

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

1. OMIN 609712 Pyruvate Kinase, Liver and Red Blood Cell; PKLR. Accessed November 2016. Available at OMIM.org

2. van Wijk R, Huizinga E, van Wesel A, et al: Fifteen novel mutations in PKLR associated with pyruvate (PK) deficiency: structural implications of amino acid substitutions in PK. Hum Mutat 2009;30(3):446-453

3. Zanella A, Fermo E, Bianchi P, et al: Pyruvate kinase deficiency: the genotype-phenotype association. Blood Rev 2007;21:217-231

4. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med 2015 May;17(5):405-424

5. Baronciani L, Beutler E: Molecular study of pyruvate deficient patients with hereditary nonspherocytic hemolytic anemia. J Clin Invest 1995 April;95:1702-1709

6. Bianchi P, Zanella A: Hematologically important mutations: red cell pyruvate kinase (Third update). Blood Cells Mol Dis 2000 Feb;26(3):47-53

7. Costa C, Albuisson J, Le TH, et al: Severe hemolytic anemia in a Vietnamese family, associated with novel mutations in the gene encoding for pyruvate kinase. Haematologica 2005;90:25-30

8. So CC, Tang M, Li CH, et al: First reported case of prenatal diagnosis for pyruvate kinase deficiency in a Chinese family. Hematology 2011;16(6):377-379

9. van Wijk R, van Solinge WW, Nerlov C, et al: Disruption of a novel regulatory element in the erythroid-specific promoter of the human PKLR gene causes severe pyruvate kinase deficiency. Blood 2003 Feb;101(4):1596-1062

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