Six screening tests for adults: What’s recommended? What’s controversial?
ABSTRACTThis paper discusses guidelines from the US Preventive Services Task Force (USPSTF) and other recommending bodies for screening for abdominal aortic aneurysm and cancers of the colon, cervix, lung, breast, and prostate.
KEY POINTS
- The USPSTF has stringent standards of evidence and therefore its recommendations tend to be more conservative than those of other organizations that issue guidelines. Recommendations are available at www.uspreventiveservicestaskforce.org.
- Because screening can result in harm as well as benefit, screening should be done after shared decision-making with the patient, especially if the screening is controversial, as is the case with mammography for breast cancer and prostate-specific antigen testing for prostate cancer.
- Screening for lung cancer using low-dose computed tomography is recommended yearly beginning at age 55 for people who have at least a 30-pack-year smoking history.
- In women over age 30, cervical cancer screening with Papanicolaou (Pap) and human papillomavirus (HPV) testing is now recommended every 5 years rather than every 3 years. Testing for HPV infection may soon become the first-line screening test, with Pap testing reserved for patients who have a positive HPV result.
- Although the USPSTF no longer recommends mammography for women ages 40 to 49, other organizations continue to do so.
A 68-year-old man with a history of hyperlipidemia is evaluated during a routine examination. He has a 25-pack-year cigarette smoking history but quit 12 years ago. He has no history of hypertension, diabetes mellitus, or stroke. A review of systems is unremarkable, and he has no family history of heart disease or cancer. He has noted no change in his bowel movements, and his most recent screening colonoscopy, done at age 60, was normal. His only current medication is lovastatin.
Physical examination reveals no abnormalities. His blood pressure is 130/82 mm Hg, and his body mass index is 24 kg/m2. His total cholesterol level is 213 mg/dL, and his high-density lipoprotein level is 48 mg/dL.
Which screening tests, if any, would be appropriate for this patient?
The advent in recent years of several new screening tests, along with changing and conflicting screening recommendations, has made it a challenge to manage this aspect of patient care. This article reviews six common screening tests and presents the current recommendations for their use (Table 1).
SCREENING CAN HARM
Screening is used to detect a disease in people who have no signs or symptoms of that disease; if signs or symptoms are present, diagnostic testing is indicated instead. Ideally, screening allows for early treatment to reduce the risk of illness and death associated with a disease.
Problems with screening relate to lead-time bias (detection of disease earlier in its course without actually affecting survival time), length-time bias (detection of indolent and benign cancers rather than aggressive ones), and overdiagnosis (detection of abnormalities that would not cause a problem in the patient’s lifetime, causing unnecessary concern, cost, or treatment).
The leading advisory groups on screening are the US Preventive Services Task Force (USPSTF),1 which is stringently evidence-based in its recommendations, and subspecialty societies, which often rely on expert opinion.2,3
ULTRASONOGRAPHY FOR ABDOMINAL AORTIC ANEURYSM
In 2005, the USPSTF gave a grade-B recommendation (recommended; benefit outweighs harm) for one-time ultrasonographic screening for abdominal aortic aneurysm in men ages 65 to 75 who have ever smoked at least 100 cigarettes over a lifetime. For men in the same age range who have never smoked, they gave a grade-C recommendation (no recommendation; small net benefit). The USPSTF updated its recommendation in 2014. For women ages 65 to 75 who smoke, the USPSTF thinks the evidence is insufficient to recommend for or against screening (grade-I recommendation).
Our patient described above—male, age 68, and with a 25 pack-year smoking history—is a candidate for screening for abdominal aortic aneurysm.
CT SCREENING FOR LUNG CANCER
In December 2013, the USPSTF gave a B-grade recommendation for annual screening for lung cancer with low-dose computed tomography (CT) for adults ages 55 to 80 who have a 30-pack-year smoking history and currently smoke or have quit within the past 15 years. Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that limits life expectancy or the ability to undergo curative lung surgery.
These recommendations were based on the outcomes of the National Lung Screening Trial.4 However, whereas this trial was in people ages 55 to 74, the USPSTF boosted the upper age limit to 80 based on computer modeling, a decision that was somewhat controversial.
Patz et al5 analyzed data from the National Lung Screening Trial and found that about 18% of lung cancers detected by low-dose CT appeared to be indolent and were unlikely to become clinically apparent during the patient’s lifetime. The authors concluded that overdiagnosis should be considered when guidelines for mass screening programs are developed.
Our 68-year-old patient would not qualify for CT screening for lung cancer, since his smoking history is less than 30 pack-years.
COLORECTAL CANCER SCREENING AND PREVENTION
Unlike other cancer screening tests, colorectal cancer screening can also be a preventive measure; removing polyps found during screening with colonoscopy or sigmoidoscopy is an effective strategy in preventing colon cancer.
The USPSTF last updated its colorectal screening recommendations in 2008, giving a grade-A recommendation (strongly recommended; benefit far outweighs harm) to screening using fecal occult blood testing, sigmoidoscopy, or colonoscopy for adults ages 50 to 75. The risks and benefits of these screening methods vary. For adults ages 76 to 85, the task force recommends against routine screening but gives a grade-C recommendation for screening in that age group in some circumstances. They give a grade-D recommendation for screening after age 85.
The USPSTF concluded that the evidence is insufficient to assess the benefits and harms of CT colonography and fecal DNA testing for colorectal cancer screening.
The American Cancer Society issued similar guidelines in 2013, recommending that starting at age 50, men and women at low risk of colorectal cancer should be screened using one of the following schedules (the first four methods help detect both polyps and cancers, and the others detect only cancer)6:
- Colonoscopy every 10 years
- Flexible sigmoidoscopy every 5 years
- A double-contrast barium enema every 5 years
- CT colonography (“virtual colonoscopy”) every 5 years
- A guaiac-based fecal occult blood test annually
- A fecal immunochemical test annually.
Those at moderate or high risk of colorectal cancer are advised to talk with a doctor about a different testing schedule. (eg, colonoscopy every 5 years in patients with a significant family history of colon cancer).
Our patient last underwent colonoscopy 8 years ago and so does not need to be screened again for another 2 years.
