Colorectal Cancer Screening (PDQ®): Screening - Health Professional Information [NCI] - Evidence of Benefit
Table 3. Randomized Controlled Screening Trials: Fecal Occult Blood Testing continued...
Potential false-positive test results due to an increased risk of upper GI bleeding are of concern with FOBT testing and pretest protocols, therefore; low-dose aspirin regimens should be discontinued for a week or more prior to FOBT. The performance of iFOBT was tested in an ongoing diagnostic study (2005–2009) at 20 internal medicine GI practices in southern Germany. Nineteen hundred seventy-nine patients (233 regular low-dose aspirin users and 1,746 never users) were identified in the records for inclusion in the analysis. All patients provided one stool sample taken within a week before colonoscopy preparation, which was collected according to instructions in a container that was kept refrigerated or frozen until rendered to the clinic on the day of colonoscopy, and the patients agreed to complete a standard questionnaire regarding the use of analgesics and low-dose aspirin (for prevention of cardiovascular disease). Stool samples were thawed within a median of 4 days after arrival at the central laboratory (shipped frozen from the recipient clinics). Fecal occult blood levels were measured by two automated iFOBT tests according to the manufacturer's instructions (RIDASCREEN Haemoglobin and RIDASCREEN Haemo-/Haptoglobin Complex, r-biopharm, Bensheim, Germany) following clinical procedures and blinded to colonoscopy results. Advanced neoplasms were found in 24 aspirin users (10.3%) and in 181 nonusers (10.4%). At the cut-point recommended by the manufacturer, sensitivities for the two tests were 70.8% (95% CI, 48.9%–87.4%) for users compared with 35.9% (95% CI, 28.9%–43.4%) for nonusers and 58.3% (95% CI, 36.6%–77.9%) for users compared with 32% (95% CI, 25.3%–39.4%) for nonusers (P = .001 and P = .01, respectively). Specificities were 85.7% (95% CI, 80.2–90.1%) for users compared with 89.2% (95% CI, 87.6%–90.7%) for nonusers and 85.7% (95% CI, 80.2%–90.1%) for users compared with 91.1% (95% CI, 89.5%–92.4%) for nonusers (P = .13 and P = .01, respectively). For these iFOBTs, sensitivity for advanced neoplasms was notably higher with the use of low-dose aspirin while specificity was only slightly reduced, suggesting that there might be an advantage to aspirin use to increase sensitivity without much decrease in specificity.
The flexible fiberoptic sigmoidoscope was introduced in 1969. The 60 cm flexible sigmoidoscope became available in 1976. The flexible sigmoidoscope permits a more complete examination of the distal colon with more acceptable patient tolerance than the older rigid sigmoidoscope. The rigid instrument can discover 25% of polyps, and the 60 cm scope can find as many as 65%. The finding of an adenoma by FS may warrant colonoscopy to evaluate the more proximal portion of the colon.[38,39] The prevalence of advanced proximal neoplasia is increased in patients with a villous or tubulovillous adenoma distally and is also increased in those aged 65 years or older with a positive family history of CRC and with multiple distal adenomas. Most of these adenomas are polypoid, flat and depressed lesions, which may be somewhat more prevalent than previously recognized.