ASK DR. BAUGHAN                                             October 2, 1998

ARE NEWER PAP TESTS BETTER?

The Pap test (named for its developer, Dr. Papanicolaou) has been a model of an excellent cancer-screening test for the past 50 years.  It has been the primary reason that deaths from cancer of the cervix have been reduced by 70%.  It is associated with a dialogue as reliably repeated as any commercial jingle:  Doctor - “Now scoot down to the end of the table.”  Patient - “Oh, I just hate this!”  Never has something so beneficial to human health been so consistently disparaged.  Any woman who does not get Pap smears at intervals recommended by her health provider is truly being neglectful of her health.  There are programs for reduced fee tests if finances are limited.

Like everything else in medicine, though, there is room for improvement.  There are several recent developments in Pap testing that are being debated to try to improve results.  A Pap test involves using the flat edge of a wooden spatula and a small conical brush to wipe a thin layer of cells off the surface of the cervix and spread them onto a glass slide that is then examined under a microscope.  The cells are examined for abnormal changes and rated on a six point scale from normal through varying degrees of abnormal up to the last two grades being cancer (localized or invasive).  At several steps along the way, there is room for problems.  In wiping the cervix, not enough cells might be obtained or some bleeding might occur with the blood cells obscuring the cervical cells.  In spreading the cells on the slide, the cells might clump up so they cannot be seen well or they might dry out before being sprayed with preservative so their appearance is altered.  The technician or doctor who looks through the microscope might be rushed, tired, or poorly trained.  Some reviews of Pap results have found that a second reviewer might disagree with the first reading as much as 25% of the time.

The Thinprep process eliminates some of the problems with spreading of cells on the slide.  The brush is shaken in a special fluid, the fluid is agitated, and then a thin layer of cells is spread on a slide, so the clumping and drying problems are much less.  The cells look different that with regular Pap tests, though, so retraining of technicians and doctors is necessary.  The Papnet system uses a computer to scan Pap tests and notes the most abnormal cells, which are then reviewed by human eyes.  The Autopap system reviews normal Paps and selects those most likely to have abnormalities, essentially waving a red flag to say, “Double check these!”

All three techniques have shown an increase in accuracy of Pap tests, so why did the American College of Obstetrics and Gynecology recently not recommend them to replace conventional Paps?  First, money.  For the lab my office uses, it costs $37 to have a Pap read.  It costs $60 to have a Thinprep read, with similar costs for Autopap and Papnet.  A review of Papnet results found 0.03% serious abnormalities missed by Paps.  That’s 3 in 10,000.  If everyone had Papnets, we would need to spend $230,00 dollars more than for regular Paps to find those three.  But we still could not say we had “saved three lives.”  Fortunately, cervical cancer develops and grows slowly, almost always over a period of 5-7 years.  So even if a Pap smear is inaccurate one year, it is very unlikely to be inaccurate three years in a row, still leaving time for effective treatment.  Lower grade abnormalities often improve without treatment, so detecting them more frequently would not necessarily improve health, either.

If the costs come down, these tests may become more widely accepted.  For the present, though, the conventional Pap tests remain quite good if women will get them regularly.