audit of reducing sugars requesting chris stockdale
TRANSCRIPT
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• References to test withdrawn from local guideline documents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/