<p><b>OBJECTIVE</b>To explore the value of
detection of
adenomatous polyposis coli (APC)
gene and
K-ras gene mutations in fecal and
blood samples in
colorectal neoplasm screening.</p><p><b>
METHODS</b>From 84 subjects undergoing colonoscopic examination (including 31 with
colorectal carcinoma, 26 with colorectal
adenoma, and 27
healthy subjects) between October, 2003 and March, 2004, 5 ml of heparinized peripheral
blood and 3-5 g fecal specimens were collected. The
DNA was extracted from the specimens for detecting the
mutation of APC and
K-ras gene using
polymerase chain reaction-single strand conformation polymorphism and the results were analyzed statistically.</p><p><b>RESULTS AND CONCLUSION</b>(1) The
incidence of
APC gene mutation was 41.9% and 57.7% in the
plasma, and 34.8% and 26.8% in the fecal specimens of
colorectal carcinoma patients and
adenoma patients, respectively, both higher than that in normal subjects (P<0.05), suggesting high consistency between fecal and
plasma APC gene mutation detection (K=0.811, P<0.05). (2) The
incidence of
plasma K-
ras mutation was 48.4% in
colorectal carcinoma patients, 3.8% in
adenoma patients and 0% in normal control subjects, and in the
feces, the
incidences were 54.8%, 7.7% and 11.1%, respectively. The
mutation rate was higher in
carcinoma patients than in
adenoma patients and normal subjects (P<0.05). Fecal
K-ras gene mutation detection was consistent with
plasma detection (K=0.662, P=0.000). (3)
APC gene mutation detection showed a low
sensitivity and specificity in the
diagnosis of
colorectal carcinoma, but K-
ras mutation detection showed a high
specificity. The diagnostic
sensitivity increased when combining APC and
K-ras gene detection in the
plasma or fecal specimens, but there was no evidence to suggest that APC and K-
ras mutation detection in the
plasma could be better than
detection in the
feces. (4) For
colorectal carcinoma,
APC gene mutation is associated with lymphoid node
metastasis, but not with the
patient's
gender, age,
tumor location, differentiation, distant organ
metastasis or CEA level (P>0.05), and the
mutation of
K-ras gene is related to the degree of
tumor differentiation.</p>