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 Cystinosis |
5ml HEP |
Willink no longer offer this service.
MFT Users: Please avoid collecting sample on a |
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.