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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.

Method Name

Gas Chromatography Mass Spectrometry (GC-MS)

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
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

Day(s) Performed

Tuesday, Friday

Report Available

3 to 7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82542