audit of reducing sugars requesting chris stockdale

Audit of reducing sugars requesting

Chris Stockdale

Reducing sugars

• A sugar which has an aldehyde group capable of reducing Cu(II)

0 0.25 0.5 0.75 1 2% reducing sugar

Sugar TLC

Xylose

GlucoseFructoseGalactoseSucroseMaltoseLactose

• Requests from 30/3/11 to 4/5/11

• 66 faeces requests, 13 urine requests

• Sugar TLC performed on 56 of these (47 faeces, 9 urines)

Analysis of reducing sugars requesting

Urinary reducing sugars

STM

BRHC

Other hospitals

Cause Reducing substances in urine

Diabetes mellitus Glucose

Galactosaemia Galactose (glucose)

Hereditary fructose intolerance Fructose

Essential fructosuria (benign) Fructose

Essential pentosuria (benign) L-xylulose

Alkaptonuria Homogentisic acid

Fanconi syndrome Glucose, galactose

Liver dysfunction Galactose, fructose

Citrin deficiency Galactose

Hereditary tyrosinaemia p-Hydroxyphenylpyruvic acid

Drugs Salicylate, levodopa, cephalosporins

When do reducing substances appear in urine?

Galactosaemia Hereditary fructose intolerance

Enzyme affected Galactose 1 phosphate uridyl transferase (GALT)

Aldolase B

Incidence 1/45k 1/20k

Symptoms Liver & kidney dysfunction, brain damage, hypoglycaemia

Liver & renal tubular dysfunction, hypoglycaemia, avoidance of fructose containing foods

Onset Symptoms in first week of life Symptoms upon weaning

Diagnosis GALT activity assayRBC galactose-1-phosphateUrine galactose/galactitolDNA analysis

Nutritional historyDNA analysis

Reasons for urine requests

0

1

2

3

4

5

6

num

ber o

f req

uest

s

Hyperbilirubinaemia/jaundice

Hypoglycaemia

Renal tubular acidosis

Reducing substances testing recommended by Metbionet and/or local guidelines for investigation of:

• hypoglycaemia

• conjugated hyperbilirubinaemia

• early presenting jaundice

• prolonged jaundice

Reducing sugars testing in galactosaemia and HFI

• False positive results– Other causes of liver dysfunction

• False negative results– Galactosaemia recent blood transfusion

not on regular milk feed

– HFI literature reports of false negative results

‘although determination of reducing substances in the urine can be used as a first simple screening test for classical galactosaemia, this test should not be used either to confirm or to reject a diagnosis’

Action points: urine

• Test no longer available

• Clinicians directed to GALT testing when galactosaemia suspected

• References to test withdrawn from local guideline documents

Faecal reducing substances

Faecal reducing substances

BRHC

STM

GP

Other hospitals

Derriford

Taunton

WestonCheltenham

Bath

Faecal reducing substances

Why?

• If sugar malabsorption is suspected

• Inability to absorb a sugar will lead to its appearance in faeces

Lactose malabsorption

• Clinically the most important form of sugar malabsorption• Lactase deficiency• Lactose accumulation in small intestine• Leads to bloating, pain, flatulence, diarrhoea, FTT, colic• Primary, secondary and developmental forms

Lactose malabsorption

• Clinically the most important form of sugar malabsorption• Lactase deficiency• Lactose accumulation in small intestine• Leads to bloating, pain, flatulence, diarrhoea, FTT, colic• Primary, secondary and developmental forms

0

5

10

15

20

25

30

35

Diarrhoea/loosestool

?Lactose intolerant FTT Colic

num

ber

of r

eque

sts

Reducing substances testing in diagnosis of lactose intolerance

• False negative results– Bacterial metabolism of faecal sugars (can be reduced by freezing samples)

• No significant difference could be established between normal children and children with malabsorption syndromes in terms of faecal pH and sugar chromatography.

Schaub & Lentze (1973) Sugars, lactic acid and pH in feces of children. A useful diagnostical approach for gastrointestinal disorders? Eur J Pediatrics, 115, 141-53.

‘fecal reducing sugars can also be measured and become positive by excretion of a reducing sugar in the stools’

Alternative tests for diagnosis of lactose intolerance

• Hydrogen breath test

• Trial of lactose free diet

Action points: faeces

• Test only available in children up to 16

• Requestors alerted to possibility of false negative results

• Advise freezing of samples from external locations

• Test no longer performed on fully formed stools

• Sugar TLC performed only on samples with 0.5% or above reducing substances

• Reducing substances testing decreased from 79 to 43

Reason Number of samples excluded

Urine 13

Faecal requests on patients >16

4

Fully formed samples 20

Total 37

Reason Number of samples excluded

Urine 9

Faecal requests on patients >16

4

Fully formed samples 11

0.25% reducing substances 20

Total 44

• Sugar TLC testing decreased from 56 to 12

Results of the changes to the availability of these tests

Acknowledgements

• Clinical Biochemistry, BRI– Ann Bowron– Dr Vicki Powers– Dr Janet Stone

• Bristol Royal Hospital for Children– Dr Christine Spray

• Metabolic Biochemistry Network– http://www.metbio.net/