The Pap Test Procedure - Web version
Preface
The screening test for preinvasive and early invasive cervical cancer - the PAP test - is a simple, sensitive, non invasive and low cost method of preventing this disease providing the test is correctly performed. In this booklet we provide guidelines for sampling, processing and analysis of the sample so that smears are of optimal quality and women can be reliably informed of the results of their test. The booklets also recommends screening protocols for women who are most at risk of cervical cancer and some advice on management.
The handbook “THE PAP TEST PROCEDURE” has been prepared at the request of the Leonardo da Vinci programme which is a programme of education and training sponsored by the EU. The aim of the handbook is to make cytopathologists and smear takers aware of the scope and limitations of the PAP test and to help them understand the scientific basis of the test. The booklet is not intended to be a comprehensive review of screening but is designed to heighten awareness of the need for quality standars and to give an overview of what is widely considered to be the best practice.
The guidelines are intended for personnel involved in taking cervical smears and drafts of the guidelines were sent with a questionnaire to training schools and key laboratories in Europe for comment before they were included in the text. We would like to thank all who responded to the questionnaire and wherever possible, comments where included in the text. We have had many favorable comments on the book and plan to publish it in several different languages.
Introduction
Cervical cancer is the second most common cancer in women: cancer Registry data indicate that about 500,000 new cases occur each year worldwide. The incidence varies from country to country, the highest incidence being recorded in the developing countries.(ref 1)
In the European Union, about 13,000 women die each year from cervical cancer.(ref 2) Although cervical cancer accounts for only 4% of all cancer deaths in women, it is one of the most common malignancies in women under 50. The major cause of cancer of the cervix uteri is likely to be a sexually transmitted agent, possibly certain types of human papillomavirus.(ref 3) Secondary prevention by mass screening of precancerous lesions of the cervix leads to a reduced incidence and mortality of cancer of the cervix,(ref 4,6) the best results being obtained when all women in defined age groups are invited personally to participate in community-based screening programmes.(ref 7) The highest rates of cervical cancer are seen in Denmark, Portugal and the United Kingdom; rates about half of those of Denmark prevail in the other Member States.(ref 8)
In view of the fact that death due to cervical cancer is avoidable, it is very discouraging to note that there is still an excessive number of deaths due to cervical cancer in women under 55 in the United Kingdom and Denmark, compared to other EU countries. (ref 9)
Invasive cervical cancer can be prevented by a simple, effective, harmless and inexpensive test: the cervical smear or Pap test developed by George Papanicolaou.(ref 10) The test allows rapid detection of precancerous lesions of the cervix, for which conservative treatment exists which blocks any further development.
IN ORDER TO BE EFFECTIVE, ALL PHASES OF THE PAP TEST MUST BE CARRIED OUT CORRECTLY.
The aim of this booklet (web page) is to help cytologists and smear takers to achieve this goal.
AETIOLOGY AND RISK FACTORS
Our current concept of invasive cancer of the cervix is that the invasive stage of the disease is preceded by a precancerous stage known as cervical intraepithelial neoplasia (CIN) and more recently squamous intraepithelial lesion (SIL).
The Pap test permits detection of these precancerous lesions which can readily be removed thereby preventing progression to invasive cancer.
Cancer of the uterine cervix is considered to be a disease with a multifactorial aetiology; both viral and chemical factors are probably responsible for its development.11
The following correlated factors may, directly or indirectly, promote the development
of cancer:
• sexual intercourse at an early age;
• multiple sex partners;
• first pregnancy at an early age and a high number of births;
• viral infections (particularly high-risk types of HPV Human Papilloma Virus);
• history of sexually transmitted disease;
• low socio-economic status;
• immunodepression (HIV infection, chemo and/or radiotherapy, transplants, dialysis);
• cigarette smoking (20-40 cigarettes a day);
• use of contraceptives that do not act as barriers.However, considering the effectiveness of the Pap test, one can say that the most relevant risk factors are represented by:
• never having had a Pap test;
• not having had a Pap est for a long time (more than 5 years).What is screening?
A MASS SCREENING PROGRAMME is a series of diagnostic and therapeutic services offered actively and free of charge to an apparently healthy population and promoted by a National Health Service with the aim of early diagnosis of the disease, before symptoms appear.
Screening for cervical cancer should ideally take place in the framework of a wellorganized mass screening programme.
Mass screening programmes for cervical cancer should be carried out by mailing letters annually over a three year period, offering a smear test to women in the risk age group, according to the UICC/IARC recommendations, the 25-64 age group,4 living in the chosen areas. Asystematic monitoring of all phases of the screening programme is absolutely necessary to improve the technical procedures of the test (sampling and preparation of the cytological smear, reading, etc.) and also for evaluating and improving women’s participation in the programme.FREQUENCY OF PAP SMEAR SCREENING
Cost-effective analysis suggest the Pap test should be routinely performed every 3 years; it is more important to screen all women than to screen the same women at more frequent intervals.
Some countries have decided to screen every 4 o 5 years in order to concentrate their effort to reach all women, especially the women at risk.(ref 6)
The age range varies from 20 to 69, but most screening programmes recruit women between the ages of 25 to 64.
• Incorrect sampling of cervical epithelium
• Failure of transfer of significant biological material from sampling devices to
the slide
• Incorrect slide processing, administrative and clerical errors
• Incorrect interpretation of the smear at light microscope (reporting error)
• Non desquamating cervical lesions (not amenable to quality improvement)ERRORS OF REPORTING
The main objective of all quality programmes for cytopathological laboratories is to reduce the risk of errors of reporting. The main cause of errors of reporting are due to misinterpretation of the smear by the cytologist. Errors of screening may result in false negative report or false positive report being issued. Afalse negative report may be issued if abnormal cells are present in the smear but are not detected by the cytologist.
False negative reports have a serious impact on patient management. They may give the patient and her doctor a false sense of security by leading them to believe the patient is free of malignant disease. Thus a CIN lesion may remain untreated and develop into invasive cancer which carries a poor prognosis for the survival of the patient. In contrast false positive report may be issued when the report mentions a precancerous or cancerous lesion but no cancerous lesions are present on the cervix.
False positives are less critical, because colposcopic and/or histological confirmation are usually required. However they create unnecessary discomfort and distress and lead to inappropriate further examinations and in some cases to inappropriate treatment.
Other causes of error of reporting are:
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incorrect recording of personal data;
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clerical and administrative errors
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clerical and administrative errors