Preventive Medicine in Primary Care Practices
The purpose of screening in clinical practice is to identify the likelihood of a particular disease in asymptomatic persons. Screening differs from case findings in that screening is done in asymptomatic persons based primarily on age and gender. Case findings depend on information about a patient's symptoms and risk for disease. Before a screening test can be effective, certain criteria must be met, including the following: (1) the disease must have serious consequences, a long preclinical phase and effective treatment; (2) the screening test must have high sensitivity and specificity, be low in cost and acceptable to patients; and (3) the risks and costs of false-positive and false-negative results must be low, there must be consensus on management of patients with positive results and there must be a system in place for referral and treatment. Hensrud reviews current screening practices for cancer, hypertension and hyperlipidemia in primary care.
Many organizations have issued recommendations for cancer screening, including the American Cancer Society, the U.S. Preventive Services Task Force and the Institute for Clinical Systems Integration. For a review of their guidelines, see the accompanying table. These guidelines were designed for use in asymptomatic persons and should be modified on the basis of a patient's risk factors.
Guidelines for Cancer Screening in Patients at Average Risk
Site American Cancer Society U.S. Preventive Services Task Force Institute for Clinical Systems Integration Breast Mammography yearly starting at age 40
Breast examination every 3 years at ages 20 to 40; yearly after age 40
Breast self-examination monthly starting at age 20Mammography every one to two years at ages 50 to 69; may start younger if high risk
Breast examination at time of mammographyMammography optional at ages 40 to 49; yearly at ages 50 to 75
Breast examination every three years at ages 20 to 39; yearly at age 40 and olderColorectum Fecal occult blood testing yearly and flexible sigmoidoscopy every five years or double-contrast barium enema every five to 10 years or colonoscopy every 10 years, all starting at age 50
Digital rectal examination at the same time as proceduresAnnual fecal occult blood testing and/or flexible sigmoidoscopy (possible three- to five-year screening interval) starting at age 50 Flexible sigmoidoscopy every five years at ages 50 to 80 or annual fecal occult blood testing or flexible sigmoidoscopy every five years and annual fecal occult blood testing or flexible sigmoidoscopy and barium enema every five years or colonoscopy every five to 10 years Cervix Pap test yearly for three years starting when sexually active or at age 18; after three negative results, then at least once every one to three years Pap test at least every three years starting when sexually active; can discontinue at age 65 if findings have been normal Pap test yearly for three years starting when sexually active or at age 18; at least every three years after three negative results Prostate Digital rectal examination and PSA test offered yearly starting at age 50 NR NR Lung NR NR NR Skin Skin examination every three years at ages 20 to 39; yearly at age 40 and older IE Up to individual medical groups Testicle Testicular examination every three years at ages 20 to 39; yearly at age 40 and older NR IE Ovary Pelvic examination every one to three years at ages 18 to 40; yearly after age 40 NR NR (examination of adnexa at gynecologic examination for other reasons)
NR = not recommended; Pap = Papanicolaou; PSA = prostate-specific antigen; IE = insufficient evidence to recommend for or against screening.
Adapted with permission from Hensrud DD. Clinical preventive medicine in primary care: background and practice: 3. Delivering preventive screening services. Mayo Clin Proc 2000;75:383.Current guidelines for hypertension screening recommend that all adults have a blood pressure check at least every two years. Readings should be repeated annually in patients with systolic readings between 130 and 139 mg Hg or diastolic readings between 85 and 89 mm Hg. Adults whose blood pressure is higher than 140/90 mm Hg should be reevaluated and should have blood pressure rechecked more often, depending on the level of elevation. Primary preventive strategies include weight loss, increased physical activity and, possibly, decreased consumption of sodium and alcohol. One randomized controlled trial also reported impressive results in treatment and prevention of hypertension in patients consuming a low-fat diet that was also high in fruits and vegetables.
Current recommendations for cholesterol screening advise that serum total cholesterol and high-density lipoprotein cholesterol levels be checked every five years. Primary prevention strategies consist of diet and exercise. Initial treatment for high cholesterol levels is the step diet regimen developed by the National Cholesterol Education Program and the American Heart Association.
AMY S. WEICHEL, D.O.
Hensrud DD. Clinical preventive medicine in primary care: background and practice: 3. Delivering preventive screening services. Mayo Clin Proc April 2000;75:381-5.
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