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Cervical Cancer Screening: the Pap Smear

National Institutes of Health
Consensus Development Conference Statement
July 23-25, 1980

Conference artwork, a woman's profile as multiple offsets from each other.

This statement is more than five years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong. For reliable, current information on this and other health topics, we recommend consulting the National Institutes of Health's MedlinePlus

This statement was originally published as:Cervical Cancer Screening: The Pap Smear. NIH Consens Statement 1980 Jul 23-25;3(4):1-11.

For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used: Cervical Cancer Screening: The Pap Smear. NIH Consens Statement Online 1980 Jul 23-25 [cited year month day];3(4):1-11


A Consensus Development Conference on Cervical Cancer Screening: The Pap Smear was held at the National Institutes of Health on July 23-25, 1980. The purpose of the conference was to examine the scientific basis for screening for cervical cancer and to make recommendations for the medical community and the public on the use of the Pap smear in screening for cancer of the uterine cervix. No attempt was made to provide recommendations related to screening by the Pap smear for other cancers of the female genital tract (i.e., endometrial or ovarian).

Recommendations were based on the accepted definition that screening procedures apply to healthy female populations and not to women identified as patients undergoing gynecologic treatments.

Specific questions addressed at this conference were:

  1. Does screening with a Pap smear affect the mortality from cervical cancer?
  2. Is the Pap smear safe as a screening procedure?
  3. On the assumption that screening is beneficial:
    1. Should the Pap smear be used as a routine screening procedure?
    2. If so,
      • At what age should screening become a regular part of a woman's health evaluation?
      • At what age is screening no longer rewarding?
      • What is the optimal screening frequency at different ages?
      • Should the recommendations made in response to the questions above be modified for certain high- or low-risk groups? If so, what are the groups and what are the modifications?
  4. What critical factors are needed to ensure that the procedure is reliable?
  5. Following screening, what are the responsibilities of those doing the screening for followup, confirmation of findings, and initiation of treatment?

The members of the Consensus Development Panel included epidemiologists, pathologists, obstetricians-gynecologists, practicing physicians, health scientists, a social worker, a lawyer and consumer representatives.

As a framework for developing recommendations, the panel agreed to the following operational definitions:

  • A Pap smear, developed by Dr. George N. Papanicoloaou more than 50 years ago, is a cellular specimen removed from the lower female genital tract which is used in routine screening for cancer. The Pap smear for detection of cervical cancer should include samples of cells from the ectocervix, transformation zone, and endocervical canal.
  • In the United States, most Pap smears are obtained as part of a medical examination by a woman's physician or in the context of a health maintenance program. A cervical cancer screening program refers to the testing of large numbers of women who manifest no symptoms of pathologic changes of the female genital tract, in order to classify them as likely or unlikely to have cervical cancer or its precursors.

In 1980, the incidence estimate of invasive cervical cancer in the United States is 16,000 and the estimate of carcinoma in situ (CIS), or preinvasive cancer, is 45,000. The latest estimate of mortality in 1980 is 7,400 (Silverberg, E., Cancer Statistics, 1980. Ca A Cancer Journal for Clinicians 30:23-44,1980).

Three characteristics of a disease have been cited as requirements for making it suitable for screening. First, the disease should have serious consequences. Second, the disease must have a treatment which, when applied to the screen-detected stage of the disease, is more effective than treatment applied after symptoms have led to a diagnosis. Third, the detectable preclinical phase of the disease should have a high prevalence; otherwise, too few cases would be detected to justify the expense of a screening program. Cancer of the cervix was considered by this conference in the context of these criteria and reaffirmed as a disease highly suitable for screening.

Does Screening With a Pap Smear Affect the Mortality From Cervical Cancer?

Evidence suggests that there is a falling incidence of invasive squamous-cell carcinoma1 and a decreasing mortality from cervical carcinoma. At the same time, carcinoma in situ is being detected with increased frequency. These trends have been noted in association with increased screening for cervical carcinoma and are probably related to early histological diagnosis of cervical neoplasia (abnormal cell growth) in verification of the results of cytological screening.

1 The majority of invasive cancers occur now in women who have not been screened at all, rather than in those screened too infrequently.

Is the Pap Smear Safe as a Screening Procedure?

There are no known adverse effects that have been ascribed to this screening technique. However, if the Pap smear is incorrectly evaluated by the laboratory, or is incorrectly responded to by the clinician, overinterpretation may result in unnecessary procedures and in possible complications.2

2 Surgical conization for elucidation of minor changes in Pap smear cytology can occasionally result in severe hemorrhage or in an incompetent or obstructed cervix.

On the Assumption That Screening is Beneficial:

  1. Should the Pap smear be used as a routine screening procedure?

The Panel agreed that the Pap smear should be used as a routine screening procedure for cervical cancer.

  1. If so,
    • At what age is screening no longer rewarding?
    • What is the optimal screening frequency at different ages?
    • Should the recommendations made in response to the questions above be modified for certain high or low-risk groups? If so, what are the groups and what are the modifications?

For many years, it has been the policy of health care providers in the United States to recommend annual Pap smear screening for women over age 18. It should be recognized that this policy has not been based on the results of well-designed experimental studies, because there have been no rigorous randomized trials of the impact of Pap smear screening on mortality. However, this policy has contributed to a reduction in the ill effects and mortality due to invasive cervical carcinoma. The Panel carefully reviewed the data presented at the Consensus Development Conference to determine whether changes in this general screening policy should be suggested. On the basis of available scientific data and judgment, the Panel made the following recommendations for screening asymptomatic females:

  • Virgins need not be screened for cervical cancer.3
  • All females who have had sexual intercourse should be screened for cervical cancer.
    • Screening should be initiated soon after the beginning of sexual activity.
    • If the first smear is satisfactory and does not indicate evidence suggestive of neoplasia, the smear should be repeated in one year.
    • If the second smear is also satisfactory and negative, rescreening of a majority of healthy females should be repeated at regular intervals of one-to-three years. The decision on precisely how often to rescreen them should be made jointly by the women and their medical care providers. The panel did not agree on precisely how frequently these examinations should be repeated for healthy females of different ages. For healthy females with different assessed risks of developing cervical cancer, it was felt that, in general, the level of risk should not determine the frequency of screening.4 The level of risk referred to in the above paragraph is determined by four factors, three of which are consistently identified with higher than average likelihood of developing cervical cancer in situ, and the fourth of which is consistently identified with almost complete absence of risk of developing invasive squamous-cell cervical cancer. The factors determining high risk are: first intercourse before 18 years of age; a variety of sex partners; and low socioeconomic status. The factor determining low risk is lifelong abstinence from sexual intercourse ("virgin" status).
  • If two negative Pap smears are obtained after the woman reaches age 60, further screening for the detection of cervical cancer appears to be unrewarding. No assessment was made by the Panel of its usefulness in the detection of vaginal, endometrial (pertaining to the lining of the uterus), or ovarian cancer.
  • A female whose Pap smear reveals significant epithelial abnormality should be referred for diagnostic evaluation as described in the answer to Question Five.
  • Unscreened females at risk should be recruited into the screening programs. Recruitment could be aimed at points of contact with medical care, such as neighborhood clinics, emergency rooms, venereal disease clinics, sites of immigration examinations, jails, hospitals, and all physicians' offices. Evidence suggests that education regarding cervical cancer high-risk factors would increase the use of screening.
  • A randomized clinical trial to determine optimal screening intervals is not recommended.

3 There are some notable exceptions, such as females exposed to DES in utero, who may later develop adenocarcinomata of the cervix and vagina.

4 The assessed risk of a healthy female getting cervical cancer in the future should play a part in decisions about the frequency or repeated screening only when that assessed risk is either extremely high or extremely low. Any healthy female whose risk level is assessed as being at or below the level found in the general female population is considered to have a low risk level. Any healthy female whose risk level is assessed as being five times higher than the risk level found in the general population would be considered to have an extremely high risk level, but application exclusively of the factors determining high risk mentioned in the text has so far not revealed any groups of healthy women with a risk level this high. However, the level of risk should be the criterion used in identifying groups of women for whom intensive and complete recruitment into screening programs is critical.

What Critical Factors Are Needed To Ensure That the Procedure is Reliable?

Key factors affecting reliability include a proper clinical sample, high quality laboratory evaluation, and proper communication between the cytopathologist and the clinician.

The quality of a laboratory's cytopathological technique is of prime importance to any screening program, but high quality is difficult and expensive to attain and to maintain. While certain technical points can be evaluated by federal agencies (such as the Center for Disease Control) the key factors in assuring consistently good cytopathologic practice are the qualifications and continuing education of the personnel as well as the quality assurance program of the laboratory. Quality is best assured if a laboratory meets the accreditation standards of the American Society of Cytology and the College of American Pathologists. There must be adequate staffing to maintain high quality. The standards of the American Society of Cytology (currently, a maximum workload per cytotechnologist of 12,000 cases per annum, for screening) and those recommended in the Canadian Walton Report (currently, three cytotechnologists per 25,000 cases per annum for screening, quality assurance, supervision, etc.) are recommended. The technical staff must be supported by adequate clerical staff and personnel proficient in cytopreparatory techniques.

Accurate and complete reporting between the cytology laboratory and the clinician is of basic importance to proper Pap screening. Poor wording of the report and the use of laboratories at great distances from the clinician can impair proper communication. Use of numerical classification (i.e., Pap I-V) in place of diagnostic terminology is discouraged and should be abandoned in favor of acceptable, standard, clearly understood medical disease nomenclature. Neoplasia of the cervix develops as a progressive spectrum of tissue changes which terminate in lethal invasive carcinoma, with exfoliated (shed) cells showing characteristic neoplastic changes. Any specific changes detected by Pap smear screening are best stated in clear, mutually understood, diagnostic terminology. In this way, the biologic significance and recommendations for diagnostic workup and handling are reported completely and clearly to the clinician, so that the severity of the changes is understood, and the clinician has clear guidance for appropriate action.

Following a Screening What Are the Responsibilities for Followup, confirmation of Findings, and Initiation of Treatment?

The Panel recommends that whenever a clinician receives a Pap smear report suggestive of cervical neoplasia (dysplasia, or cellular anomalies; carcinoma in situ; invasive cancer) the patient in question must undergo thorough diagnostic evaluation. It is the responsibility of the physician, or his designated substitute, to notify the patient of the abnormal result. The objective of the diagnostic investigation is to use the simplest procedure to ensure an accurate diagnosis.

Ideally, diagnostic evaluation should include colposcopic examination and biopsies of representative areas of the cervix usually including an endocervical curettage (scraping of the interior wall of the cervix). Diagnostic conization of the cervix (removal of a cone of tissue) may also be required if the location of the lesion makes colposcopy unsatisfactory, if the diagnosis from an endocervical curettage so indicates, or if the cytologic and histologic findings conflict.

Treatment of neoplastic lesions must be individualized. In certain cases, noninvasive lesions may be treated in outpatient facilities with proper gynecologic oncologic expertise. On the other hand, invasive cervical carcinoma requires the use of hospital facilities in addition to referral to, or consultation with, a physician with expertise in gynecologic oncology. The status of the woman who has been treated for cervical neoplasia should be closely followed.

Further Investigations

The crucial unanswered question is whether carcinoma in situ develops and progresses at different rates in women with different assessed levels of risk. The panel therefore recommends research on the rate of progression of pre-symptomatic disease in high-risk women. The panel also recommends that studies be undertaken to monitor the impact of changes in the Pap smear screening interval on the incidence and mortality rates of cervical carcinoma. Finally, it recommends that a task force be convened within five years to assess all relevant scientific data that may have accumulated since July 1980.

Minority opinion - Duncan Neuhauser, Ph.D. (Economics)

Review of the several computer-based, cost-effective decision models does not justify yearly screening unless the risk ratio for high-risk groups is at least 5.0. In the absence of such an elevated risk after two negative tests, screening intervals greater than 3 years could be appropriate. In my opinion, the probability that screening prolongs life ranges from .50 to .99+. These decision models are sensitive to the lower end of this probability range only if the screening interval is long. Therefore, a randomized clinical trial does not seem justified. Computer-based models should be widely available in interactive form allowing providers and patients to vary the assumptions and consider the results. These models should be used in high school courses and in health science museums. On the surface, the controversial issue here is the frequency of screening. However, the real issue is the role of computer models in clinical decision making. These powerful techniques are new to medicine, and not enough physicians are being educated in their use. This Pap smear debate will be viewed as one of the historical landmarks in this transformation in clinical reasoning.

Consensus Development Panel

Maureen M. Henderson, M.D. (Chairman)
University of Washington Health Sciences Center
Seattle, Washington
Katherine F. Carson, M.D., F.A.C.O.G.
San Diego, California
Pelayo Correa, M.D.
Louisiana State University Medical Center
New Orleans, Louisiana
Ellen Flannery, J.D.
Washington, D.C.
John K. Frost, M.D.
Johns Hopkins University School of Medicine
Baltimore, Maryland
Genevieve Hill, M.S.W.
Atlanta University
Atlanta, Georgia
Gerry B. Hill, M.B., Ch.B.
Cross Cancer Institute
Edmonton, Alberta
George B. Hutchison, M.D.
Harvard School of Public Health
Boston, Massachusetts
Raymond H. Kaufman, M.D.
Baylor College of Medicine
Houston, Texas
John J. Mikuta, M.D.
University of Pennsylvania
Philadelphia, Pennsylvania
Duncan vB. Neuhauser, Ph.D.
Case Western Reserve University School of Medicine
Cleveland, Ohio
Kenneth L. Noller, M.D.
Mayo Clinic
Rochester, Minnesota
Estelle Ramey, Ph.D.
Georgetown University School of Medicine
Washington, D.C.
Beverly J. Williams, M.D.
University of Tennessee Center for Health Sciences
Memphis, Tennessee
Ralph M. Richart, M.D.
Columbia University,
served as a consultant to the panel in the discussion of the presentations.


Laura Aurelian Ph.D.
Associate Professor, Division of Comparative Medicine
Department of Biochemistry and Biophysics
The Johns Hopkins Medical Institute
Baltimore City Hospital
Baltimore, Maryland
William T. Creasman, M.D.
"Treatment of Cancer Detected by the Pap Smear"
Professor of Obstetrics and Gynecology
Director, Gynecologic Oncology
Duke University Medical Center
Durham, North Carolina
Nicholas Day, Ph.D.
"Summary of European Studies"
Chief of Biostatistics Program
Division of Human and Cancer Field Studies
International Agency for Research on Cancer
Susan Devesa, Ph.D.
"Trends in Cervical Cancer in the United States and Other Countries"
Biometry Branch
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
David M. Eddy, M.D., Ph.D.
"The Evaluation of Cervical Cancer Screening Programs"
Associate Professor, Engineering Economic Systems
Stanford University
Stanford, California
Diane J. Fink, M.D.
"Statements on Cervical Cancer Screening Practices"
Associate Director
Medical Applications of Cancer Research
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
Maureen Henderson, M.C.
"Problem Identification"
"Presentation of Panel Consensus Report"
Associate Vice President for Health Services
University of Washington Health Sciences Center
Seattle, Washington
Barbara Hulka, M.D., M.P.H.
"Risk Factors Related to Cervical Cancer"
Professor, Department of Epidemiology
University of North Carolina
School of Public Health
Chapel Hill, North Carolina
George B. Hutchison, M.D.
"Summary Critique of Meeting Presentations and Discussion"
Professor of Epidemiology
Harvard School of Public Health
Boston, Massachusetts
Eileen B. King, M.D.
"Summary of the Status of the Pap Smear"
Clinical Professor of Pathology
University of California, San Francisco
San Francisco, California
Charles U. Lowe, M.D.
"Introduction and Charge to Panel"
Acting Associate Director
Medical Applications of Research
Office of the Director
National Institutes of Health
Bethesda, Maryland
Ramona Lunt, M.P.H.
"Screening Practices in Other Countries"
Scientist, Cancer Unit
World Health Organization
Ihor J. Masnyk, Ph.D.
"Background for Cervical Cancer Screening"
Associate Director
Extramural Research Program
Division of Cancer Biology and Diagnosis
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
Larry McGowan, M.D.
"Clinical Management in Relation to Cervical Cancer Screening"
Professor and Director
Division of Gynecologic Oncology
George Washington University
Washington, D.C.
Anthony B. Miller, M.D.
"Summary of United States and Canadian Studies"
Epidemiology Unit
National Cancer Institute of Canada
University of Toronto
Toronto, Ontario
Alan S. Morrison, M.D.
"Epidemiologic Issues in Screening Programs"
Associate Professor, Department of Epidemiology
Harvard School of Public Health
Boston, Massachusetts
Stanley F. Patten, Jr., M.D., Ph.D.
"Natural History of Cervical Cancer"
Chairman, Department of Pathology
University of Rochester Medical Center
Rochester, New York
Judith M.S. Prewitt, Ph.D.
"Automated Cytology"
Research Mathematician
Division of Computer Research and Technology
Office of the Director
National Institutes of Health
Bethesda, Maryland
Philip C. Prorok, Ph.D.
"Summary of Data on Peridicity (Frequency) in Cervical Cancer Screening"
Mathematical Statistician
Biometry Research and Analytic Studies Section
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
Alan Rabson, M.D.
"Review of the Pap Smear and Its Role in Cervical Cancer Screening"
Division of Cancer Biology and Diagnosis
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
Seymour Romney, M.D.
Professor of Obstetrics and Gynecology
Albert Einstein College of Medicine
Mamaroneck, New York
Michael B. Shimkin, M.D.
"Review of Studies in Cervical Cancer Screening"
Professor, Community Medicine and Oncology
School of Medicine
University of California, San Diego
La Jolla, California
Margaret H. Sloan, M.D.
"Emerging Technologies Which May Be of Value in Cervical Cancer Management"
Special Assistant for Liaison
Division of Cancer Control and Rehabilitation
National Cancer Institute
National Institutes of Health
Silver Spring, Maryland
Ronald Swanson, M.D.
"Efforts to Evaluate Laboratory Reliability Related to the Pap Smear"
Staff Pathologist
LPT Division
Center for Disease Control
Atlanta, Georgia
William Terry, M.D.
Acting Director
Division of Cancer Control and Rehabilitation
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
George L. Wied, M.D.
"Reliability of the Pap Smear"
"Automated Cytology"
Blum-Riese Professor of Obstetrics and Gynecology and Professor of Pathology
Chief, Section of Cytology
University of Chicago
Lying-In Hospital
Chicago, Illinois
George Wilbanks, M.D.
"Follow-up of Abnormal Pap Smears"
Chairman, Department of Obstetrics and Gynecology
Rush-Presbyterian-St. Luke's Medical Center
Chicago, Illinois
Ann Worth, M.D.
"The Walton Report and Subsequent Canadian Experience"
Head, Anatomic Pathology
Cancer Control Agency of British Columbia
Vancouver, British Columbia

Conference Coordinators

Diane J. Fink, M.D.
National Cancer Institute
Bethesda, Maryland
Philip C. Prorok, Ph.D.
National Cancer Institute
Bethesda, Maryland

Conference Sponsors

National Cancer Institute

National Institute on Aging

National Institute of Child Health and Human Development

National Center for Health Care Technology

Office for Medical Applications of Research

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