Amino Acid Disorders

Urgent investigations – organic acid and amino acid disorders

Patients with suspected amino acid or organic acid disorders may require urgent studies in order to implement appropriate treatment. These patients often present in the neonatal period with failure to thrive, vomiting, lethargy, hyperventilation, seizures and hypotonia. There may be metabolic acidosis, respiratory alkalosis, hypoglycaemia, hypocalcaemia and/or deranged liver function tests. Blood ammonia and lactate may be raised.

For organic and amino acid screen, as well as acylcarnitines, please send 10ml fresh urine and 2ml heparinised blood or a blood card with 4 spots of blood. Results should be available the same day assuming samples arrive in good time (before 11am) and the laboratory has been warned of the urgent sample. It is important that full clinical details are given including details of metabolic acidosis, jaundice, blood ammonia and drug history. For disorders of fat oxidation e.g. MCAD deficiency, it is important that urine is collected at the time of hypoglycaemic stress. Urgent investigations will normally only be performed following discussions with one of our consultants.

Test Required specimen & volume Special precautions Turnaround time Reference ranges Section
Urine qualitative amino acid screen* 5ml plain U, no preservative None 3 working weeks Qualitative Metabolites
Quantitative amino acids 3ml HEP or 1ml plain CSF, blood not stained Must be sent on ice or deproteinised with internal standard,
contact lab for procedures. Avoid freezing whole blood.
3 working weeks Quoted on report Metabolites
White cell cystine
5ml HEP

Willink no longer offer this service.
Please contact Metabolic Lab at St James’ Hospital
Tel: 0113 206 4256

MFT Users: Please avoid collecting sample on a
Friday. Next day delivery to Leeds cannot be guaranteed.

n/a n/a Metabolites
Total Homocyst(e)ine 3ml HEP P Plasma must be sent frozen 4 working weeks < 15 µmol/L Metabolites
Orotic acid
Urea cycle defects
2ml plain U None 4 working weeks < 5 µmol/mmol creatinine Metabolites
14C-citrulline incorporation
Citrullinaemia and arginosuccinic aciduria
CC, AFC, CCV Contact lab prior to dispatch to discuss test Dependent on culture time Controls quoted Metabolites
14C-leucine oxidation
Maple syrup urine disease
CC, AFC Contact lab prior to dispatch to discuss test Dependent on culture time Controls quoted Metabolites

* All samples must be accompanied by relevant clinical details. This is particularly imperative for urine amino acids, urine organic acids, urine mucopolysaccharides and all samples for prenatal diagnosis. Reports may be withheld where samples are received without clinical details as an accurate interpretation may not be possible without them.