By Dr S Dash (Consultant Obstetrician/Gynaecologist)
What is it and who gets tested?
The Pap test is a screening test for cancerous and pre-cancerous changes of the mouth of the womb. A positive result indicates that there may be a problem and that further diagnostic procedures must be done. The Pap test is not a diagnostic test. It cannot be used to exclude a cancer of the mouth of the womb (also called ‘cervix’) for a person who has symptoms that could be due to a cervical cancer.
Pap tests are done on women who have no symptoms of cancer and have no findings suggesting a cancer. Thus, Pap tests are done only on women who are normal. If the woman has symptoms or findings suggestive of cancer of the cervix, then a diagnostic test must be done to exclude a cancer or to diagnose a cancer. Diagnostic tests are usually biopsies taken with the help of a special instrument. This is the single most important lesson to learn: if you have a symptom or a finding that could be due to a cancer of the cervix, a normal Pap test never excludes the possibility of cancer.
In the vast majority of instances, an abnormal Pap test results in the diagnosis of a minor change on the cervix. Some of these changes will be pre-cancerous, but most will be of minor significance. They will all have to be evaluated, diagnosed and treated, but most will be easily and effectively treated. Occasionally, a real cancer will be present, which is why this is such an important test. Most cancers are visible on examination and can be biopsied as soon as they are seen. Sometimes the cancers are inside the cervix beyond view and the only indication that it is there is the abnormal Pap test.
Pap test screening is recommended for all women beginning at age 18 years or at the onset of sexual activity, if earlier. The screening interval is usually every year, although if there have been no previous abnormal tests, the interval may be extended. The Pap test is performed by gently scraping cells from the cervix, smearing them onto a microscope slide and sending it to a pathology laboratory for evaluation.
Evaluation of an abnormal Pap test
If a Pap test report indicates a cancerous or pre-cancerous condition, the patient is re-examined and the Pap test repeated. The cervix is viewed with a magnifying instrument called a colposcope. Acetic acid (ordinary table vinegar) is applied to the cervix. The cervix is illuminated with light from the colposcope and evaluated.
If the colposcopic evaluation is satisfactory, meaning all the abnormal areas are seen, then the most abnormal areas are biopsied and sent to the pathologist. The pathology report will indicate the diagnosis.
Treatment of precancerous conditions
Once a diagnosis has been established treatment can be performed. Treatment of pre-cancerous conditions is usually simple and almost 100 per cent effective. It is not treated during pregnancy. It need not even be specifically diagnosed during pregnancy. During pregnancy, all that is needed is to be assured that there is no invasive cancer present. This can often be accomplished by careful repeat colposcopic examinations, without a biopsy.
Once a pre-cancerous condition has been treated then the woman should be re-examined every three months for at least a year and have a Pap test done. If all goes well, she should be re-examined annually. If the woman was pregnant when the abnormal Pap test was found and examination at that time was not suggestive of cancer, then her definitive examination and biopsy can be deferred until six weeks postpartum.
The cause of cervical dysplasia
The cause of cervical pre-cancer and cervical cancer is unknown. Current studies strongly implicate the Human Papilloma Virus (HPV), as at least a cofactor in its development. This is the same virus that causes genital warts. There are over sixty sub-types of HPV that have been isolated, only a few of which are associated with cervical cancer. HPV can be transmitted by direct physical contact. Once there is an infection with HPV, it will probably always be in the tissue. Complete obliteration of the virus from the body is not currently feasible and probably not necessary. All of us probably have a multitude of viruses of which we are unaware and which cause us no discernible problem.
If you have been told that your Pap test indicates the presence of HPV, do not be alarmed. If a definite viral change can be seen with the colposcope then it can be obliterated with cryocautery, laser or left alone.
Where did the HPV come from? Who knows, it may have been there for years. The point is that it is unknown; there is no way to find out. Since it is of no demonstrable detriment to your health, it is not worth the time worrying about where it came from. Some studies have demonstrated that about one third of college students have evidence of past or present infection with HPV. It is not unusual to find it reported on Pap tests in women in their seventh decade.
Conclusion
The Pap test is an excellent screening test. It is easy to do, easy to interpret, easy to evaluate when abnormal. Most importantly, one can detect changes before they become cancerous.
