Use

The test is useful for evaluating patients with a clinical suspicion of arginine:glycine amidinotransferase deficiency, guanidinoacetate methyltransferase deficiency, and creatine transporter deficiency using plasma specimens. Depletion of cerebral creatine occurs in these conditions, and measurement of guanidinoacetate, creatine, and creatinine, along with associated analyte ratios in plasma and urine, aids in distinguishing the types of creatine deficiency syndromes. Treatment with oral creatine supplementation is effective in some cases and can impact test results.