SOLID-PHASE COMPETITIVE LUMINESCENCE IMMUNOASSAY FOR LYSOZYME IN FECES

We have developed a new simple solid-phase luminescence immunoassay (L IA) for the determination of faecal lysozyme. The assay utilises a pol yclonal capture antibody coated to polystyrene beads and acridinium es ter-labelled human lysozyme as tracer. Samples are incubated with poly styrene beads and tracer overnight at 4 degrees C, After a thorough wa shing step, emitted light is measured by an automated luminometer for 2 seconds. The standard curve uses five standards ranging from 0.025 t o 6.4 mg/l. The method has a sensitivity of 0.02 mg/l. Dilution recove ries for three samples were 88, 104 and 108%. Intraassay coefficients of variation (CV, n = 24) were 10.1% and 11.7% for a healthy control a nd a patient sample; interassay CV (n = 16) were 6.7% and 13.1% for th e same healthy control but another patient sample. The normal range of faecal lysozyme in 80 healthy controls was found to be 0.02-1 mg/l (9 7.5 percentile) with a median of 0.28 mg/l, Fifty-three patients with Crohn's disease had faecal lysozyme values ranging from 0.16 to 100.7 mg/l with a median of 1.75 mg/l, and 30 patients with ulcerative colit is showed levels between 0.09 and 118 mg/l with a median of 1.11 mg/l. The assay has proved useful for differentiating healthy individuals f rom those with inflammatory bowel disease and might be a valuable tool for diagnosing or evaluating inflammatory bowel disease.