Solid-phase competitive luminescence immunoassay for lysozyme in faeces.
We have developed a new simple solid-phase luminescence immunoassay (LIA) for the determination of faecal lysozyme. The assay utilises a polyclonal capture antibody coated to polystyrene beads and acridinium ester-labelled human lysozyme as tracer. Samples are incubated with polystyrene beads and tracer overnight at 4 degrees C. After a thorough washing step, emitted light is measured by an automated luminometer for 2 seconds. The standard curve uses five standards ranging from 0.025 to 6.4 mg/l. The method has a sensitivity of 0.02 mg/l. Dilution recoveries 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 and a patient sample; interassay CV (n = 16) were 6.7% and 13.1% for the 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 (97.5 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 colitis 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 from those with inflammatory bowel disease and might be a valuable tool for diagnosing or evaluating inflammatory bowel disease.
Gao
P
P
Department of Endocrinology and Oncology, Laboratory Group, Heidelberg, Germany.
John
M R
MR
Schmidt-Gayk
H
H
Arndt
B
B
Scheida
M
M
Theuer
D
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003093:Colitis, Ulcerative / Q000175:diagnosis / Q000201:enzymology; D003424:Crohn Disease / Q000175:diagnosis / Q000201:enzymology; D003937:Diagnosis, Differential; D005243:Feces / Q000201:enzymology*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007202:Indicators and Reagents; D007553:Isotope Labeling; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D009113:Muramidase / Q000032:analysis*; D011863:Radioimmunoassay; D012016:Reference Values
D007074:Immunoglobulin G; D007202:Indicators and Reagents; D009113:Muramidase