Characteristics of colorectal cancer with false negative result on immunochemical faecal occult blood test

Metabolic profiling analysis for clinical urine of colorectal cancer

AIM

To demonstrate the little-known metabolic changes and pathways in patients with colorectal cancer (CRC).

METHODS

We used gas chromatography time-of-flight mass spectrometry (GC-TOF/MS) to perform metabolic profiling of urine samples from 163 consecutive patients with CRC and 111 healthy controls without history of gastrointestinal tumors. The metabolic profiles were assayed using multivariate statistical analysis and one-way analysis of variance, and further analyzed to identify potential marker metabolites related to CRC. The GC-TOF/MS-derived models showed clear discriminations in metabolic profiles between the CRC group and healthy control group.

RESULTS

We demonstrated that 15 metabolites contributed to the differences. Among them, eleven metabolites were significantly upregulated, while other four metabolites were downregulated in the urine samples of CRC patients compared with healthy controls. Pathway analysis revealed changes in energy metabolism of patients with CRC, which are reflected in the upregulation of glycolysis and amino acid metabolism and the downregulation of lipid metabolism. Our study revealed the metabolic profile of urine from CRC patients and indicated that GC-TOF/MS-based methods can distinguish CRC from healthy controls.

CONCLUSION

GC-TOF/MS-based metabolomics has the potential to be developed into a novel, non-invasive, and painless clinical tool for CRC diagnosis, and may contribute to an improved understanding of disease mechanisms.

Participant-Related Risk Factors for False-Positive and False-Negative Fecal Immunochemical Tests in Colorectal Cancer Screening: Systematic Review and Meta-Analysis

OBJECTIVES

Colorectal cancer (CRC) screening using fecal immunochemical tests (FIT) may reduce CRC-related mortality but its effectiveness is influenced by the limited accuracy of FIT. Identifying individuals at increased risk of a false FIT result could improve screening, but the available evidence is conflicting. We performed a systematic review and meta-analysis on risk factors for false-positive and false-negative FIT results in CRC screening.

METHODS

A systematic search in MEDLINE, EMBASE, and Cochrane Library identified publications (before 29 January 2017) on risk factors (known at time of FIT invitation) associated with false FIT results (presence/absence of advanced neoplasia) in a CRC screening setting. Risk of bias was assessed using QUIPS. In meta-analysis, summary relative risk ratios and corresponding 95% confidence intervals were calculated for each risk factor.

RESULTS

Of 518 records identified, 14 studies with 54,499 participants in total were included for analysis. In meta-analysis, male sex was associated with a significantly lower risk of false-positivity (RR 0.84, CI 0.74-0.94), whereas participants using non-steroidal anti-inflammatory drugs (NSAIDs) had a higher risk (RR 1.16, CI 1.06-1.27). The use of anticoagulants was most frequently studied, without a significant effect on FIT positivity. Males (RR 1.83, CI 1.53-2.19), participants with a family history for CRC (RR 1.61, CI 1.19-2.15), hyperglycemia (RR 1.29, CI 1.02-1.65), hypertension (RR 1.50, CI 1.14-1.98), obesity (RR 1.38, CI 1.11-1.71), and (former) smokers (RR 1.93, CI 1.52-2.45) were all at significantly higher risk for false-negative results. Age was not found to have a systematic effect on either FIT false-positivity or false-negativity in meta-analysis.

CONCLUSIONS

Multiple risk factors, known at time of FIT invitation, are associated with false FIT results in CRC screening. This information can be used to identify populations risking false reassurance after a negative result or unnecessary colonoscopy after a positive result, and to further optimize CRC screening effectiveness.

From guaiac to immune fecal occult blood tests: the emergence of technology in colorectal cancer screening

Colorectal cancer is the second leading cause of cancer deaths in the United States for both men and women. Colorectal cancer screening is an important means for reducing morbidity and mortality. The American Cancer Society recommends five different screening regimens for adults of average risk, age 50 years and older. The optimal effectiveness of a screening program is dependent on the accuracy of the screening test used. An accurate screening test would have high sensitivity (positive) when an adenomatous polyp or cancer is present and high specificity (negative) in their absence. In April 2002, the American Cancer Society Colorectal Cancer Advisory Group concluded that the immunochemical fecal occult blood test has some advantages that merit revision of their guideline statement for fecal occult blood testing, to include the immunochemical fecal occult blood test. The advantages cited were the possibility of improved sensitivity and specificity and the lack of required dietary restrictions, which make it a more patient-friendly test. Several types of immunochemical fecal occult blood tests are discussed in this article, including their advantages and disadvantages compared with those of the traditional guaiac fecal occult blood testing.

Immunochemical fecal occult blood test is not suitable for diagnosis of hemorrhoids

PURPOSE

This study was conducted to clarify the diagnostic value of an immunochemical fecal occult blood test for hemorrhoids.

PATIENTS AND METHODS

In a case-control study, an immunochemical fecal occult blood test with a 2-day method was carried out on 82 subjects with hemorrhoids, on 82 subjects with colorectal cancer, and on 82 healthy subjects. In a population-based cross-sectional study, 29,714 subjects who received an immunochemical occult blood screening with a 2-day method were divided into two groups, according to the results of a questionnaire on hemorrhoids, and the positivity rate of an immunochemical test as well as the predictive value for colorectal cancer were compared in the two groups. Moreover, both an immunochemical occult blood test with a 2-day method and colonoscopy were conducted at the same time on asymptomatic subjects during a medical checkup.

RESULTS

In the case-control study, the test was positive in 13.4% subjects with hemorrhoids, in 84.1% subjects with colorectal cancer, and in 4.9% healthy subjects, respectively, showing a significant difference in the detection rate between the two diseases (P < 0.001). In the population screening program, the test was positive in 6.9% subjects with hemorrhoids and in 6.5% subjects without hemorrhoids, and the predictive value was 3.2% in subjects with and without hemorrhoids, respectively, indicating no significant difference in the positivity rate as well as the predictive value between the two groups. Among 232 subjects in a medical checkup, 28 patients with hemorrhoids and 21 patients with colorectal polyp 1 cm or larger were diagnosed by colonoscopy, and the occult blood test was positive in 16.7% patients with hemorrhoids and in 52.4% patients with colorectal polyp, respectively. There was a significant difference in the sensitivity between the two disease groups (P < 0.05).

CONCLUSIONS

These findings indicate that the immunochemical fecal occult blood is unsuitable for the diagnosis of the patients with hemorrhoids and an examination of the colorectum is necessary in cases where the occult blood test is positive but there is a sign of hemorrhoids.