Oberholzer V G, Briddon A
Clin Chim Acta. 1978 Aug 1;87(3):411-5. doi: 10.1016/0009-8981(78)90186-9.
3-Amino-2-piperidone, a delta-lactam of ornithine, has been detected in the urine of a number of patients with hyperornithinemia. The distinctive yellow colour formed with a ninhydrin-cadmium reagent should help in the detection of hyperornithinemia by urinary chromatography.