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Test Code SORBU Sorbitol and Mannitol, Quantitative, Random, Urine


Ordering Guidance


This is the preferred test for monitoring effectiveness of treatment in patients with phosphomannomutase 2 deficiency (PMM2-CDG). The preferred test for assessing sorbitol dehydrogenase (SORD) deficiency-related peripheral neuropathy is SORD / Sorbitol and Xylitol, Quantitative, Random, Urine



Necessary Information


Patient's age is required.



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 2 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.


Forms

If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Secondary ID

614934

Useful For

Monitoring effectiveness of treatment in patients with phosphomannomutase 2 deficiency (PMM2-CDG)

 

Establishing a baseline level prior to initiating treatment for PMM2-CDG

 

This test is not useful for diagnosing congenital disorders of glycosylation (CDG) in general or PMM2-CDG in particular

Method Name

Gas Chromatography Mass Spectrometry (GC-MS)

Reporting Name

Sorbitol and Mannitol, QN, U

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 28 days
  Frozen  28 days

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Phosphomannomutase 2 deficiency, or PMM2-CDG, is the most common congenital disorder of glycosylation (CDG) accounting for about 50% of known CDG patients.

 

In many patients with PMM2-CDG, the urine polyols, sorbitol and mannitol, are elevated relative to controls. Sorbitol, in particular, has been shown to be positively correlated with severely affected patients in contrast to patients in the mild or moderate categories. It is also higher in patients with moderate peripheral neuropathy. Both mannitol and sorbitol were increased in patients with mild liver dysfunction.(1) Treatment options for PMM2-CDG remain limited however; current literature reports that the aldose reductase inhibitor, epalrestat, can correct the underlying enzyme deficiency in a majority of patients with PMM2-CDG.(2) Recent trials suggest that treatment with epalrestat, in addition to other therapeutic benefits, resulted in nearly normalized levels of sorbitol and mannitol relative to controls.(1)

Reference Values

Mannitol: <97 mmol/mol creatinine

Sorbitol: <35 mmol/mol creatinine

Interpretation

The quantitative results of sorbitol and mannitol are reported without added interpretation.

Day(s) Performed

Tuesday, Friday

Report Available

3 to 7 days

Specimen Retention Time

3 months

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

82542

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SORBU Sorbitol and Mannitol, QN, U 74447-4

 

Result ID Test Result Name Result LOINC Value
614936 Mannitol 47698-6
614935 Sorbitol 48152-3
614937 Interpretation 59462-2
614938 Reviewed By 18771-6