GRHPR Testing: Full Gene Analysis vs. Familial Mutation Targeted Testing [A Test in Focus]


 
The new GRHPR Gene, Full Gene Analysis, test is now available to the Mayo Clinic practice and Mayo Medical Laboratories clients. This test should be ordered to confirm the diagnosis of primary hyperoxaluria type 2 in a patient with hyperoxaluria and/or kidney stones, or for carrier testing of individuals with a family history of primary hyperoxaluria type 2 in the absence of known mutations in the family.

The complementing Familial Mutation, Targeted Test, for GRHPR should be ordered in individuals with a family history of primary hyperoxaluria type 2 when a familial mutation is already known, including prenatal testing when familial mutations in the GRHPR gene have previously been identified.

 

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  • Primary hyperoxaluria type 2 is a hereditary disorder caused by mutations in the GRHPR gene, which encodes the hepatic enzyme glyoxylate reductase/hydroxypyruvate reductase (GRHPR).
  • Deficiency or absence of GRHPR activity results in excess urinary excretion of oxalate leading to kidney stones and sometimes renal failure; urinary excretion of L-glycerate is often elevated as well.
  • Biochemical testing is indicated in patients with possible primary hyperoxaluria; quantitation of urinary oxalate in a timed, 24-hour urine collection is strongly preferred. See HYOX / Hyperoxaluria Panel, Urine and OXU / Oxalate, Urine.
  • Molecular testing for mutations in the GRHPR gene can confirm the diagnosis of primary hyperoxaluria type 2 among affected individuals or potential carriers.
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How to Use This Test

  • The GRHPR Gene, Full Gene Analysis test should be ordered to confirm the diagnosis of primary hyperoxaluria type 2 in a patient with hyperoxaluria and/or kidney stones, or for carrier testing of individuals with a family history of primary hyperoxaluria type 2 in the absence of known mutations in the family.
  • The Familial Mutation, Targeted Test for GRHPR should be ordered in individuals with a family history of primary hyperoxaluria type 2 when a familial mutation is already known, including prenatal testing when familial mutations in the GRHPR gene have previously been identified.
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  • Full Gene Analysis testing is appropriate to confirm diagnosis of a disorder or the test carrier status of individuals with a family history of a disorder, but no mutation has been identified.
  • Familial Mutation testing should be ordered only when a mutation has been identified in a family member.
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  •  Bidirectional sequence analysis is performed to test for the presence of a mutation in all coding regions and intron/exon boundaries of the GRHPR gene. Additionally, gene dosage analysis (multiplex ligation-dependent probe amplification) is used to test for the presence of large deletions and duplications in this gene.(Unpublished Mayo method)
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  • Whole blood
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Day(s) and Time(s) Test Performed:

  • Performed weekly, varies

Analytic Time:

  • 14 days
brentwestra

brentwestra

Brent Westra is a Marketing Segment Manager at Mayo Clinic Laboratories. He leads marketing strategies for product management and specialty testing along with new media innovations. Brent has worked at Mayo Clinic since 2011.