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Interpretive Handbook

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Test 61843 :
Polyols, Quantitative, Urine

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

Polyols are sugar alcohols that have been identified in blood, urine, and cerebrospinal fluid. Characteristic patterns of abnormal polyols may suggest a disorder of the pentose phosphate pathway (PPP) including transaldolase (TALDO) deficiency and ribose-5-phosphate isomerase (RPI) deficiency. Both TALDO and RPI deficiency are recently described disorders of carbohydrate metabolism with multisystem involvement.

 

TALDO deficiency is an autosomal recessive disorder caused by a reduction of the enzyme transaldolase.(1) Clinical manifestations are characterized by severe neonatal liver failure, coagulopathy, low serum protein, hypoglycemia, high ammonia, progressive myocardial hypertrophy, and abnormal lactate dehydrogenase with remarkably normal or low transaminases.

 

Patients may present in the antenatal period with HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) of the mother, hydrops fetalis and oligohydramnios, dysmorphic features, cutis laxa, and hypertrichosis. The clinical course is variable, but acute liver failure with normal transaminases is a common finding. Initially, hepatomegaly is absent, but the spleen may be enlarged. Later, hepatomegaly with liver cirrhosis and mild kidney failure occur.

 

RPI deficiency is an autosomal recessive disorder caused by a deficiency of the enzyme ribose-5-phosphate isomerase.(2) Clinical manifestations include neurological deficits such as slow progressing leukoencephalopathy and neuropathy. Additionally, spasticity, ataxia, epilepsy, regression, and delayed psychomotor development have been described.

 

Polyols analysis in urine is the method of choice for the biochemical diagnosis of TALDO and RPI deficiency. For evaluation for familial inheritance, TALDO can be confirmed by enzyme analysis in erythrocytes and lymphoblasts, and by mutation analysis of the TALDO gene. Currently, there is no confirmatory testing offered for RPI deficiency in the United States.

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

Diagnosis of transaldolase (TALDO) deficiency or ribose-5-phosphate isomerase (RPI) deficiency

Interpretation Provides information to assist in interpretation of the test results

An interpretive report is provided.

 

All profiles are reviewed by the laboratory director and interpretation is based on pattern recognition. A detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, elements of differential diagnosis, recommendations for additional biochemical testing and in vitro confirmatory studies (enzyme assay, molecular analysis), name and phone number of key contacts who may provide these studies at Mayo or elsewhere, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

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

A positive test result is diagnostic of TALDO or RPI; however it is strongly recommended to follow-up with molecular analysis.

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.

 

0-11 months

1-3 years

4-17 years

> or =18 years

Erythritol

<220

<267

<171

<99

Arabinitol

<140

<149

<97

<51

Ribitol

<31

<31

<17

<11

Sedoheptulose

<76

<27

<28

<22

 

Values are expressed in mmol/mol creatinine

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Online Mendelian Inheritance in Man. 606003. National Center for Biotechnology Information. Available at www.ncbi.nlm.nih.gov/Omim

2. Online Mendelian Inheritance in Man. 608611. National Center for Biotechnology Information. Available at www.ncbi.nlm.nih.gov/Omim

3.Verhoeven N, Huck J, Roos B, et al: Transaldolase deficiency: liver cirrhosis associated with a new inborn error in the pentose phosphate pathway. Am J Hum Genet 2001;68:1086-1092

4. Verhoeven N, Wallot M, Huck J, et al: A newborn with severe liver failure, cardiomyopathy and transaldolase deficiency. J Inhert Metab Dis 2005;28:169-179


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