Introduction

Reviews

Pap Smears

Getting It Done Right

Timothy B. McCall, M.D.

Screening tests, like Pap smears and mammograms, are designed to detect medical conditions before any symptoms develop. Ideally, screening tests should be cheap, safe and reliable. In the case of Pap smears, unfortunately, only two out of three of those conditions are usually met. Here is how to be sure yours is accurate.

Years before cancer develops, Pap smears can detect abnormal cells. The test is not foolproof—it occasionally misses a cancer. There are two main causes for this error: inadequate sampling by the doctor during the exam and incorrect interpretation of the microscope slides in the lab.

Despite all the attention given in the last few years to inaccurate readings by labs, several studies suggest that sampling errors by physicians are a bigger problem. When correctly performed and interpreted the Pap smear appears to be one of the best screening tests available.

In order to take an adequate specimen, the doctor should take at least two specimens and place them on a slide immediately. The slide must be immersed in alcohol or sprayed with fixative within the first few seconds or the specimen deteriorates, lowering the quality. Recent studies suggest that if the doctor uses a small brush to take the specimen instead of a Q-tip, the results are more accurate. When your doctor gives you the results of a Pap, be sure to ask about the adequacy of the specimen, which should be stated right on the report from the lab.

Misreading an abnormal Pap smear, a so-called “false negative” reading, appears especially common in large labs, which churn out thousands of Pap per year. Some of these labs have been faulted for not allowing technicians adequate time to analyze the slides, in their desire to increase profits. Recent improvements in federal law should improve the situation by limiting the number that can be read per day. If no case should a technician read more than 90 per day and 70 or less is optimal. Ask your doctor, where your Pap smear will be sent and why that lab was chosen.

The Pap test can also be abnormal even though no cancer is developing. These false-positive results may lead to unnecessary biopsies and even surgery. If the Pap result is mildly abnormal often the best course of action is to simply repeat the test.

Most authorities recommend women start getting Pap smears at age 18 or when they start sexual activity, although the benefit of starting at 18 instead of say 23 appears to be small. The most important risk factors for cervical cancer are starting sex at an early age and having had multiple sex partners. Smokers have a 50% greater chance than non-smokers. Race is also a factor: Blacks, Latinos and Native Americans are twice as likely as whites or Asians to get it. As long as a woman has previously been screened regularly and had negative smears, the benefit of continuing Pap smears beyond age 65 appears to be minimal.

Ironically, the Pap smear may be one preventive test some doctors have embraced too wholeheartedly. The suggestion that all women get a Pap every year seems excessive, although that’s what most gynecologists recommend. I know an elderly woman who is a virgin—and therefore doesn’t need Pap smears at all—whose gynecologist was bringing her in every six months for the exam, something pretty traumatic for her.

Women who have Pap smears every three years instead of annually get about 96% of the benefit with considerably less hassle and expense. Whether the added security of more frequent Pap is worth it, is a personal choice that should be made by the woman herself and not by the doctor. Women with risk factors for cervical cancer may want to opt for more frequent smears. Ditto for women who are unsure the lab being used is first-rate.

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