Prototype application of a robot in the clinical laboratory enabling fully automated quantification of fecal porphyrins.

ABSTRACT

Unpleasant specimens, sensitive analytes, and a lengthy chromatographic procedure were the main reasons we implemented fecal porphyrin analysis with a laboratory robot. We describe the system in detail and compare it with the same technique performed manually. The day-to-day variation of assays of standards was lower with the robot than with the manual operation 8% (CV) for coproporphyrin I and 11% for protoporphyrin IX. We repeatedly analyzed a specimen from a healthy volunteer and determined that the specimen contained (in nmol/g dry wt) 7.1 (SD 0.7) for coproporphyrin I, 3.0 (SD 0.4) for coproporphyrin III, and 44.4 (SD 4.3) for protoporphyrin IX. Upper reference limits as measured in 20 healthy volunteers were 20 nmol/g dry wt for coproporphyrin I, 12 nmol/g for coproporphyrin III, and 80 nmol/g for protoporphyrin IX. We also present characteristic chromatograms for samples from various different porphyrias that exhibit abnormal fecal porphyrin excretion. Calculations of return on investment show that the robot, working at full capacity, is a profitable tool.