Fecal marker variability in colorectal cancer: calprotectin versus hemoglobin.
BACKGROUND
Blood products like hemoglobin are problematic as markers for colorectal neoplasia because bleeding is intermittent. Levels of calprotectin, a leukocyte-derived protein, are increased in stools from colorectal cancer patients. However, this blood constituent may gain luminal access via interstitial leukocyte migration, which could be a less variable mechanism of entry than bleeding.


METHODS
To correlate the levels of and to compare the variability of fecal calprotectin and hemoglobin, quantitative assays were performed independently on multiple serially collected stools from 14 patients with colorectal cancer. Marker level association was estimated with Pearson's correlation coefficient, and variation estimated with an analysis of variance model.


RESULTS
Fecal calprotectin and hemoglobin levels were discordant in 55 (50%) of 110 matched aliquots, and marker levels failed to correlate. The estimated between-subject correlation was -0.10 (95% CI, -0.60 to 0.46), and mean within-subject correlation -0.27 (95% CI, -0.73 to 0.34). The between-stool coefficient of variation was less for calprotectin (22%) than for hemoglobin (80%).


CONCLUSIONS
In patients with colorectal cancer, the mechanism of luminal calprotectin entry appears to be both different from and less erratic than bleeding.
Division of Gastroenterology, Mayo Clinic, Rochester, Minnesota, USA.
J A
JA
Gilbert
D A
DA
Ahlquist
D W
DW
Mahoney
A R
AR
Zinsmeister
J
J
Rubin
R D
RD
Ellefson
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D014408:Biomarkers, Tumor / Q000032:analysis; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D016001:Confidence Intervals; D004797:Enzyme-Linked Immunosorbent Assay; D005243:Feces; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D039841:Leukocyte L1 Antigen Complex; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D019006:Neural Cell Adhesion Molecules / Q000032:analysis*; D012016:Reference Values; D012680:Sensitivity and Specificity
D014408:Biomarkers, Tumor; D006454:Hemoglobins; D039841:Leukocyte L1 Antigen Complex; D019006:Neural Cell Adhesion Molecules