Metabolic Profile (Urine)

Diagnostic Use

This test includes screening for urine amino acids and purine/pyrimidine disorders, creatine synthesis, and pyridoxine-dependent epilepsy. It compliments urine organic acids and mucopolysaccharide screening. This test may not detect very rare errors of metabolism. If an inborn error is suspected clinically, please contact the metabolic physician on-call.

Purine and Pyrimidines

For patients with suspected disorders of purine or pyrimidine metabolism.  These are rare conditions with variable clinical features.  Developmental delay, gout, renal impairment, recurrent infections, self mutilation, anaemia and uric acid anomalies may be seen.

The urine metabolic profile covers several markers of purines and pyrimidines which screen for Lesch-Nyhan syndrome, xanthine oxidase deficiency, purine nucleoside phosphorylase deficiency, thymidine phosphorylase deficiency, and beta-ureidopropionase deficiency. A full analysis of urine purine and pyrimidine is available as a sendaway test, if required.

Creatine synthesis (Creatine/Creatinine)

This is a test for patients with symptoms suggestive of disorders in creatine metabolism.The creatine/creatine-phosphate system plays an important role in the storage and transmission of phosphate-bound energy. Creatine is synthesised in the liver and pancreas from arginine and glycine with guanidinoacetate methyltransferase (GAMT) and arginine:glycine amidotransferase (AGAT) as enzymes. Intracellular creatine and creatine-phosphate are non-enzymatically cycled to creatinine which is mainly excreted in urine and daily excretion is directly proportional to total body creatine. GAMT deficiency has a wide clinical phenotype ranging from predominance of extrapyramidal encephalopathy and intractable epilepsy to moderate mental retardation. Patients have systemic depletion of creatine and creatine-phosphate due to impairment of de novo creatine biosynthesis but increased guanidinoacetate excretion. Patients with the very rare AGAT deficiency have decreased excretion of creatine, creatinine and guanidinoacetate. Creatine transporter deficiency shows normal guanidinoacetate and creatinine concentration with increased creatine excretion.

Please request a random urine for screening of these disorders. A plasma sample is only required to confirm urine findings.

Pyridoxine-dependent epilepsy (AASA/P6C)

Alpha-aminoadipic semialdehyde (AASA) is the diagnostic marker for pyridoxine dependent epilepsy. The disease is caused by enzyme defect in alpha-aminoadipic-semialdehyde dehydrogenase (encoded by ALDH7A1 gene) in the lysine degradation pathway, leading to accumulation of AASA and piperideine 6-carboxylate (P6C). AASA is in chemical equilibrium with P6C. Pyridoxine dependent epilepsy is characterized by early onset epileptic encephalopathy. The onset is typically in the neonatal period with intractable seizures, status epileptics that are poorly controlled by pharmacological anticonvulsants but response to large dose of pyridoxine.  Despite seizure control most patients have intellectual disability.

Reference Intervals

Results are reported qualitatively as part of urine metabolic profile.