Are immunochemical fecal occult blood tests sensitive and specific enough to be used for colorectal cancer screening?
Immunochemical fecal occult blood tests (IFOBTs), such as OC-Micro, OC-Sensor, or OC-Light, are moderately sensitive (73% – 89%) and highly specific (92% – 95%) for identifying colorectal cancer. In comparison, Homoccult Sensa has a lower sensitivity (64% – 80%) and specificity (87% – 90%). IFOBTs also have the advantage of requiring only one sample. (LOE = 1c)
Lee JK, Liles EG, Bent S, Levin TR, Corley DA. Accuracy of fecal immunochemical tests for colorectal cancer: systematic review and meta-analysis. Ann Intern Med 2014;160(3):171-181.
|Study Design: Meta-analysis (other)
|Setting: Various (meta-analysis)
These researchers searched 5 databases and the reference lists of included studies, finding 19 eligible studies that evaluated the diagnostic accuracy of IFOBTs. Two authors used the STARD and PRISMA protocols and independently determined study eligibility, extracted the data, and evaluated study quality. They included cohort studies and randomized studies that used colonoscopy or longitudinal follow-up as the gold standard and only included studies published in English. They excluded studies or results that evaluated only the detection of adenomas. Limiting analysis to only currently available IFOBTs found a sensitivity of 82% (95% CI, 73% – 89%) and a specificity of 94% (92% – 95%). These numbers translate into a positive likelihood ratio of 13.10 and a negative likelihood ratio of 0.19. There was no difference in performance among different commercial products, and multiple sampling was no more accurate than a single sample. Heterogeneity among the studies was acceptable when removing products that are not commercially available. There was some evidence of publication bias. There are no head-to-head studies comparing one type of test with another, and no research evaluating the effectiveness of IFOBT testing on cancer-related mortality or all-cause mortality.
Allen F. Shaughnessy, PharmD, MMedEd
Professor of Family Medicine
Does a gastroenterologist’s adenoma detection rate make a difference in the subsequent incidence of colorectal cancer?
There is a consistent, linear, inverse relationship between higher adenoma detection rates and a lower rate of colorectal cancer (CRC) and CRC death. I’ll be asking my gastroenterologist about his detection rate before my next colonoscopy! (LOE = 2b)
Corley DA, Jensen CD, Marks AR, et al. Adenoma detection rate and risk of colorectal cancer and death. N Engl J Med 2014;370(14):1298-1306.
|Study Design: Cohort (retrospective)
|Setting: Outpatient (specialty)
The adenoma detection rate has been proposed as a quality measure, with professional societies recommending a rate of at least 15% for female patients and 25% for male patients. But is this a valid quality measure? These researchers at Kaiser Permanente identified all patients who received colonoscopy between 1998 and 2010 and who had at least 6 months of follow-up. Patients were followed up for 10 years, or until a diagnosis of CRC, or until they left the insurance plan. The population had a median age of 64 years, 52% were women, and 57.4% of the colonoscopies were diagnostic (ie, in a symptomatic patient). Gastroenterologists had to perform 300 or more total colonoscopies (75 or more screening colonoscopies) during the study period to be included, and colonoscopies included screening, surveillance, and diagnostic procedures. The detection rate was defined as the percentage of examinations that found at least one adenoma or adenocarcinoma. There were a total of 264,972 colonoscopies eligible for analysis of interval cancers (cancers diagnosed within 6 months of the index colonoscopy were excluded). They detected 712 interval cancers, 60% of which were proximal, and there was a median interval of 39 months from index colonoscopy to diagnosis of cancer. Adenoma detection rates varied widely among the 136 physicians, from 10% to 60% for male patients and 4% to 46% for female patients. The researchers defined quintiles of adenoma detection rates from 16.6% to 38.9%.They found that the risk of an interval CRC, an advanced stage CRC, and a fatal CRC all declined with increasing adenoma detection rates. For example, compared with the lowest quintile, patients of physicians in the highest quintile had hazard ratios of 0.52 for interval CRC (95% CI, 0.39-0.69) and 0.38 for fatal CRC (0.22 – 0.65).
Mark H. Ebell, MD, MS
University of Georgia