Clinical Indications

Plasma amino acids may be abnormal in a variety of amino acid disorders, urea cycle defects and some organic acidurias. If possible, investigations should be carried out on samples taken when the patient is symptomatic.

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's) and Metabolic screening questionnaire

Availability

Analysed by referral laboratory if specific criteria met.

Specific Criteria

Requests must be accompanied by a completed Metabolic screening questionnaire which has been authorised by a Consultant.

Patient Preparation

Plasma amino acids fluctuate widely depending on the protein intake and whether the patient is in a fed or fasted state. Dietary restrictions may cause characteristic amino acid patterns to disappear and result in false negative results. 
Collect sample during acute illness if possible, state feeding and advise if protein has been withdrawn.
If non-acute situation, a fasting sample is preferred (2-3 hrs post feed in infants).

Turnaround Time

2 weeks

Specimen

Plasma

Volume

1.0 ml

Container

Paediatric Lithium Heparin (Orange top) tube

Collection

Samples should be transported to laboratory immediately. (PAA & send; NOUAA & save)

Lab. Handling

Separate into 2 aliquots within 1 hour of collection and freeze at minus 20’C. Send frozen.

Causes for Rejection

Unlabelled sample. Not meeting specific criteria for analysis. 
Delay in sample reaching laboratory. Haemolysed samples are generally unsuitable.