Blood
At least 1 mL of blood in a lithium heparin tube, no gel.
Separate plasma within 1 hour of collection and store and transport frozen.
CSF
0.5 mL of clear CSF, snap frozen on dry ice.
Dried blood spot
Taken from a newborn screening card (Guthrie card).
Air-dry blood spots for at least 3-4 hours, without heat. Wrap Guthrie card in paper towel or bond paper and staple to request form. Do not put sample in plastic specimen bag. Use clean envelope for transport.
Urine - best for monitoring known cystinuric patients.
At least 5 mL of random urine.
Store and transport frozen.
Samples taken during acute episodes are most suitable for diagnosis.
Non-acute samples: ideally collected after at least 3 hour fast (e.g. early morning), or immediately before the next feed. Samples collected post-prandially may show increases in amino acids.
CSF - results are uninterpretable from blood-stained samples. If the sample is bloodstained, it may be possible to rectify this by centrifuging the sample before it is frozen.