Is it Worthwhile to do a Single Fecal Occult Blood Test?
Abstract & Commentary
Synopsis: A single fecal occult blood test cannot be recommended as the only screening test for colorectal neoplasia.
Source: Collins JF, et al. Ann Intern Med. 2005;142:81-85.
Fecal occult blood tests (fobts) were performed on samples from digital rectal examinations in 2665 average-risk asymptomatic adults. In addition, each patient had 6-sample at-home FOBTs done. Colonoscopy was also completed in each subject. Specificities for the 6-sample FOBT and the single-digital FOBT were 93.9% and 97.5% respectively among the 1656 patients with no neoplasia. Sensitivities for detection of advanced neoplasia (defined as tubular adenomas 10 mm or greater, adenomas with villous histology or high-grade dysplasia, or invasive cancer) in 284 patients were 23.9% for the 6-sample FOBT and 4.9% for the digital FOBT.
Collins and associates conclude that the single digital FOBT is a poor screening method for colorectal neoplasia. They suggest that a negative result performed as part of regular primary care screening does not decrease the odds of advanced neoplasia. They recommend that patients should be offered an at-home, 6-sample FOBT or an alternative screening test.
Comment by Frank W. Ling, MD
I certainly hope you don’t think I am fixated on screening for colon cancer. I wanted to include this article even though in a previous commentary; we reviewed the usefulness (or lack thereof) of virtual colonoscopy. This particular report addresses the issue of real-life office practice in which the diligent practitioner is trying to screen for neoplasias in the best ways possible. The results here call into question the many expert panels that recommend screening for colon cancer in asymptomatic adults older than age 50. More to the point, we need to determine whether it is worth it to do a single digital FOBT for our patients in the course of our practices.
Admittedly, you can question the study sample in this study. The patients are 97% male. In fairness, there is no reason to expect the results to be any different in women, so I suggest you read on.
Previous studies have shown that screening with FOBT can reduce colon cancer mortality when positive results are followed with colonoscopy. All those studies used the 6-sample FOBT. This is the first report of the sensitivity and specificity of the office-based single digital FOBT. It would appear that the guaiac tests that we are doing should no longer be relied upon to predict neoplasms.
Since all the patients had colonoscopy by experienced endoscopists following the FOBT screening, there is good reason to believe that the sensitivity and specificity of each technique has been represented appropriately. Based on these results, if we continue to do a single digital FOBT, a positive test should, as in the past, lead to colonoscopy whereas a negative finding should result in the patient being given a 6-sample FOBT kit.
What are you doing in your practice? Is it a study that should be causing you to change your practice style? Are you accepting a negative single-digital FOBT? I don’t expect every reader to change what is done in his/her office, but you can say that you heard about it here if the staff wants to know why you’re changing your modus operandi. If you don’t change, at least be watching to see if new recommendations by expert panels change their positions.
Frank W. Ling, MD, Women’s Health Specialists, PLLC, Memphis, Tennessee is Editor for OB/GYN Clinical Alert.