The effectiveness of cervical screening: a population-based case-control study

Exposure Definition in Case-Control Studies of Cervical Cancer Screening: A Systematic Literature Review

The first step in evaluating the effectiveness of cervical screening is defining exposure to screening. Our aim was to describe the spectrum of screening exposure definitions used in studies of the effectiveness of cervical screening. This systematic review included case-control studies in a population-based screening setting. Outcome was incidence of cervical cancer. Three electronic databases were searched from January 1, 2012 to December 6, 2018. Articles prior to 2012 were identified from a previous review. The qualitative synthesis focused on describing screening exposure definitions reported in the literature and the methodologic differences that could have an impact on the association between screening and cervical cancer. Forty-one case-control studies were included. Six screening exposure definitions were identified. Cervical cancer risk on average decreased by 66% when screening exposure was defined as ever tested, by 77% by time since last negative test, and by 79% after two or more previous tests. Methodologic differences included composition of the reference group and whether diagnostic and/or symptomatic tests were excluded from the analysis. Consensus guidelines to standardize exposure definitions are needed to ensure evaluations of cervical cancer screening can accurately measure the impact of transitioning from cytology to human papillomavirus-based screening and to allow comparisons between programs.

Attendance to a Screening Program for Cervical Cancer in the City of Florence

The study was aimed to assess: a) the proportion of true refusers among non-attenders resulting from residents and screening database matching, b) the typology of refusers compared to attenders, and c) the reasons for non-attendance as stated by refusers. Three hundred and forty-one non-attenders according to computer-produced lists were interviewed: 29 were not evaluable, 148 had had a Pap test, 18 had not attended for valid reasons, and 146 were true refusers; 94 refusers accepted the interview as far a points b) and c) were concerned. Ninety-four attenders, matched by age and residence, were interviewed for comparison. Attendance at private laboratories or incorrect identification of subjects on the screening record accounted for 45 % or 55 % of misclassified cases, respectively. The adjusted true refusal rate in the last 10 years was 18.1 % compared to a computer-assessed non-attendance rate of 40.7 %. Refusal was significantly associated to socioeconomic status (geographic origin, working activity and educational level of both women and husbands), whereas no significant association was observed for sexual history (deliveries, age at first sexual relation, number of partners) or health-related behavior. Attendance and counseling at the gynecologist's office were strongly associated to attendance, and gynecologists should be stimulated to promote opportunistic screening. The belief that screening is useless in the absence of symptoms, the fear of cancer being detected, postponement or laziness were the reasons for non-attendance stated by 80% of refusers. Improving knowledge about the purpose of the Pap test should be the main goal of any action aimed to improve screening attendance.

Cancer screening among a population-based sample of insured women

Purpose

Screening has been shown to lower the morbidity and mortality for breast, cervical, and colorectal cancers. Despite the availability of cancer screening, nearly 70,000 women die each year from these cancers. We conducted a study in 2008 within a privately-insured patient population of women who were members of an integrated health care system in Southeastern Michigan, for whom information on ovarian cancer risk as well as personal and family history of cancer was available.

Methods

We used a population-based, weighted stratified random sample of women from a single health care institution to assess the proportion with up-to-date breast, cervical, and colorectal screening. Multivariable analyses were conducted to identify predictors of screening behavior.

Results

In our study, women reported cervical and breast cancer screening above 90% and colorectal cancer screening above 75%.

Conclusions

The results of our study hold promise that Healthy People 2020 cancer screening objectives might be obtainable as access to health insurance is expanded among US residents.

Application of the Carolina Framework for Cervical Cancer Prevention

OBJECTIVE

The Carolina Framework for Cervical Cancer Prevention describes 4 main causes of cervical cancer incidence: human papillomavirus (HPV) infection, lack of screening, screening errors, and not receiving follow-up care. We present 2 applications of the Carolina Framework in which we identify high-need counties in North Carolina and generate recommendations for improving prevention efforts.

METHODS

We created a cervical cancer prevention need index (CCPNI) that ranked counties on cervical cancer mortality, HPV vaccine initiation and completion, Pap smear screening, and provision of Pap tests to rarely- or never-screened women. In addition, we conducted in-depth interviews with 19 key informants from programs and agencies involved in cervical cancer prevention in North Carolina.

RESULTS

North Carolina's 100 counties varied widely on individual CCPNI components, including annual cervical cancer mortality (median 2.7/100,000 women; range 0.0-8.0), adolescent girls' HPV vaccine initiation (median 42%; range 15%-62%), and Pap testing in the previous 3 years among Medicaid-insured adult women (median 59%; range 40%-83%). Counties with the greatest prevention needs formed 2 distinct clusters in the northeast and south-central regions of the state. Interviews generated 9 recommendations to improve cervical cancer prevention in North Carolina, identifying applications to specific programs and policies in the state.

CONCLUSIONS

This study found striking geographic disparities in cervical cancer prevention need in North Carolina. Future prevention efforts in the state should prioritize high-need regions as well as recommended strategies and applications in existing programs. Other states can use the Carolina Framework to increase the impact of their cervical cancer prevention efforts.

Evaluation of the Cobas 4800 HPV Test for Detecting High-Risk Human Papilloma-Virus in Cervical Cytology Specimens

As new platforms for high-risk strains of human papillomavirus (HR HPV) testing are introduced into the clinical laboratory, it is important to verify their performance and agreement. In this validation study, post-aliquot cervical cytopathology specimens (n = 226) were used to analyze agreement between the Invader HPV ASR assay (Hologic) and the recently FDA-approved Cobas 4800 high-risk HPV assay (Roche). Residual sample from 92 Invader positive and 134 Invader negative samples were analyzed with the Cobas 4800 test. Discordant results were further analyzed by Linear Array HPV genotype testing (Roche). To assess intra- and inter-run precision, 31 Invader positive samples were run in duplicate on the Cobas 4800 by different operators over multiple days and purchased HR HPV DNA control was run in ten replicates. Cross-contamination during cytology processing was evaluated by spiking 6 Invader negative samples with different volumes of Acrometrix HPV High Risk Positive Control and analyzed on the Cobas with 4 negative samples in between. There was significant discordance between the assays (p < 0.001; exact McNemar X² test), with overall agreement of 82%. Of the 92 Invader positive samples, 58 (63%) were positive with the Cobas assay, while 34 (37%) were negative. Of the 134 Invader negative samples, 6 (4%) were positive with the Cobas while 128 (96%) were negative. The observed discordance may be attributed to the previously described false positive rate of the Invader ASR assay. The Cobas 4800 high-risk HPV assay is a viable new tool for use in the clinical setting to identify high-risk HPV.

Trends in cervical cancer in the Netherlands until 2007: has the bottom been reached?

We explored trends in incidence and mortality of cervical cancer by age, stage and morphology, and linked the observed trends to screening activities. Data was retrieved from the Netherlands Cancer Registry during 1989-2007 (incidence) and Statistics Netherlands during 1970-2007 (mortality). Trends were evaluated by calculating the estimated annual percentage change (EAPC). Joinpoint regression analysis was used to detect changes in trends. Cervical intraepithelial neoplasia (CIN) detection rates were calculated by data from "the nationwide network and registry of histo- and cytopathology" during 1990-2006. Total age-adjusted incidence rate (European standardized rate (ESR)) was 7.9 per 100,000 woman years in 2007. During 1989-1998, incidence rates decreased with an EAPC of -1.3% (95% confidence interval (CI) -2.2 to -0.3), during 1998-2001 with -6.7% (95% CI: -16.4 to 4.1), and increased during 2001-2007 with 2.3% (95% CI: 0.4 to 4.2). Total mortality ESR was 1.9 per 100,000 woman years in 2007. Mortality rates decreased during 1970-1994 annually with -4.1% (95% CI: -4.6% to -3.7%), and with -2.6% (95% CI: -3.8% to -1.5%) during 1994-2007. The observed trend in total incidence is similar to the trend in squamous cell carcinomas in age group 35-54 years, suggesting that the observed trends are likely to be associated to changes in the screening program. This is supported by the trend in CINIII detection rates. In conclusion, incidence and mortality overall decreased and leveled off. On top of that there was an extra decrease that was compensated by a following recent increase in incidence, probably resulting from reorganization of the Dutch screening program.

The effect of self-sampled HPV testing on participation to cervical cancer screening in Italy: a randomised controlled trial (ISRCTN96071600)

BACKGROUND

In Italy, cervical cancer screening programmes actively invite women aged 25-64 years. Programmes are hindered by low participation.

METHODS

A sample of non-responder women aged 35-64 years, belonging to three different programmes (in Rome, Florence and Teramo), was randomly split into four arms: two control groups received standard recall letters to perform either Pap-test (first group) or human papillomavirus (HPV) test (second group) at the clinic. A third arm was sent letters offering a self-sampler for HPV testing, to be requested by phone, whereas a fourth group was directly sent the self-samplers home.

RESULTS

Compliance with standard recall was 13.9% (N619). Offering HPV test at the clinic had a nonsignificant effect on compliance (N616, relative risk (RR)=1.08; 95% CI=0.82-1.41). Self-sampler at request had the poorest performance, 8.7% (N622, RR=0.62; 95% CI=0.45-0.86), whereas direct mailing of the self-sampler registered the highest compliance: 19.6% (N616, RR=1.41; 95% CI=1.10-1.82). This effect on compliance was observed only in urban areas, Florence and Rome (N438, RR=1.69; 95% CI=1.24-2.30), but not in Abruzzo (N178, RR=0.95; 95% CI=0.61-1.50), a prevalently rural area.

CONCLUSIONS

Mailing self-samplers to non-responders may increase compliance as compared with delivering standard recall letters. Nevertheless, effectiveness is context specific and the strategy costs should be carefully considered.

Prostate-specific antigen screening and mortality from prostate cancer

BACKGROUND

There is no available evidence from randomized trials that early detection of prostate cancer improves health outcomes, but the prostate-specific antigen (PSA) test is commonly used to screen men for prostate cancer.

OBJECTIVE

The objective of the study is to see if screening with PSA decreases mortality from prostate cancer.

DESIGN, SETTING, AND PARTICIPANTS

This is a case-control study using one-to-one matching on race, age, and time of availability of exposure to PSA screening. Decedents, 380, from New Jersey Vital Statistics 1997 to 2000 inclusive, 55-79 years of age at diagnosis were matched to living controls without metastatic prostate cancer. Medical records were obtained from all providers, and we abstracted information about PSA tests from 1989 to the time of diagnosis in each index case.

MEASUREMENTS

Measurements consist of a comparison of screening (yes, no) between cases and controls. Measure of association was the odds ratio.

RESULTS

Eligible cases were diagnosed each year from 1989 to 1999 with the median year being 1993. PSA screening was evident in 23.2-29.2% of cases and 21.8-26.1% of controls depending on the screening criteria. The unadjusted, matched odds ratio for dying of prostate cancer if ever screened was 1.09 (95% CI 0.76 to 1.60) for the most restrictive criteria and 1.19 (95% CI, 0.85 to 1.66) for the least restrictive. Adjustment for comorbidity and education level made no significant differences in these values. There were no significant interactions by age or race.

CONCLUSIONS

PSA screening using an ever/never tabulation for tests from 1989 until 2000 did not protect New Jersey men from prostate cancer mortality.

Pad - a new self-collection device for human papillomavirus

This study was designed to determine the accuracy and agreement of a self-collection method using pad for human papillomavirus (HPV) DNA. One hundred and thirty-four patients at university hospitals voluntarily participated in the accuracy study, and 314 volunteers participated in the agreement study at local clinics. DNA was extracted and amplified using HPV L1 consensus primers designed for the direct sequencing. In the accuracy study, all samples were probed via histological examinations. With regard to the detection of squamous intraepithelial lesion (SIL), self-collection pad sampling displays sensitivity, of 76.9%, and specificity, of 93.3%. Three hundred and fourteen self-collection pad samples and the concurrent physicians' samples showed a 97.8% agreement, with a Kappa value of 0.9200. A new self-collection pad for the detection of HPV DNA appears to constitute an easy, rapid, and convenient alternative method for the cervical cancer screening of many women with the virtue of being incredible readily accessible.

Cancer screening: the importance of outcome measures

Cancer screening is attracting greater attention as a growing number of studies and practice guidelines exhort physicians to screen for an increasing number of malignancies. Central to the evaluation of these studies is both the quality of the evidence and the impact of screening upon clinically relevant outcomes. Although much has been written about the optimal study design for screening studies, surprisingly little has been written about evaluating specific outcome measures employed in such studies. This paper reviews the strengths and limitations of common outcomes employed in cancer screening studies. The relationship between study design and outcome measure is explored. Three key biases (lead-time, length-time, and volunteer) associated with screening studies and methods to minimize them are also reviewed. Potential harms associated with screening are outlined. Although disease-specific mortality may be the most robust and relevant traditional outcome measure, increasing attention is being paid to composite health outcome measures for older populations, including quality of life and cost-based measures.

Characteristics of Participation in Cervical Cancer Screening

Although Papanicolaou test screening rates are reportedly high, a significant proportion of women remain unscreened. With recent revision of Papanicolaou test guidelines, it is critical that interventions and programs for cervical cancer directed toward low participating groups or individuals be developed. The purpose of the study was to examine factors that influence participation in cervical cancer screening by quantifying characteristics of women who engage in Papanicolaou test screening in a 12-month period. Using the 2000 National Health Interview Survey and Cancer Topical Module, the sample (N = 18,388) consisted of women who were older than 18 years. The dependent variable was nominally identified as whether a woman had had a Papanicolaou test in the last 12 months. Independent variables examined were insurance, level of education, place for care, age, race, employment, place of residence, and income level. Using logistic regression, all variables except race and income level were found to be significant for participation in cervical cancer screening (P < .000). Each variable is discussed within the framework of the Institute of Medicine model of access to personal healthcare services. Study findings provide insight and guidance for the development and implementation of methods for accessing women who have lower participation rates.

Epidemiological and clinical aspects of human papillomavirus detection in the prevention of cervical cancer

Cervical cancer is a major cause of death, and the second most frequent cancer in women worldwide. Many studies have indicated a causal relation between genital human papillomavirus (HPV) infections and cervical cancer. High-risk HPV genotypes have been detected in almost 100% of all cervical cancers, and the process of HPV mediated carcinogenesis has been partly clarified. The concept that HPV is a obligatory cause in cervical cancer development has lead to extensive research regarding the incorporation of HPV detection in (1) cervical cancer prevention programs, (2) triage of women with abnormal cervical scrapes in the screening program, and (3) follow-up of patients treated for cervical intraepithelial neoplasia (CIN). Epidemiological studies indicate that 50% of women becoming sexually active contract a genital HPV infection within 2 years. The lifetime risk of a genital HPV infection is estimated to be 80%, but very few of these women will develop cervical cancer. Several studies have shown that the persistence of genital HPV infections is especially related to the development of cervical cancer. As a result, HPV detection at a single moment was shown to be of limited clinical value in the triage of patients with abnormal cervical scrapes, or during follow-up after treatment for CIN. Furthermore, major variations in the sensitivity of different HPV detection methods, as well as differences in HPV detection related to the menstrual cycle, have shown that many facts regarding HPV transmission, replication, and detection need to be clarified, before HPV detection can be of clinical value.

Prevention of advanced colorectal cancer by screening using the immunochemical faecal occult blood test: a case-control study

To evaluate colorectal cancer screening with faecal occult blood testing (FOBT) in terms of prevention of advanced cancers, we conducted a case-control study in the areas where an annual screening programme with immunochemical FOBT has been offered to all inhabitants aged 40 years or over. Cases were 357 consecutive patients in the study areas clinically diagnosed as having advanced colorectal cancer or a tumour invading the muscularis propriae or deeper, that is, T(2)-T(4) in TNM classification. Three controls were selected for each case matched by gender, age, residential area and exposure status to screening within 1 year before case diagnosis. The odds ratios (ORs) of developing advanced cancer were calculated using conditional logistic regression analyses. The OR for those screened within 3 years before the diagnosis vs those not screened was 0.54 (95% confidence interval (CI) 0.29-0.99). The ORs were lower for rectum than for colon (0.32-0.73 and 0.84-1.18 for rectum and colon, respectively). For those screened within the past 3 years, OR of developing advanced cancer in the rectum was 0.32 ( 95%CI: 0.12-0.84). A screening programme with immunochemical FOBT can be effective for prevention of advanced colorectal cancer. Risk reduction appears to be larger for rectal than for colon cancer. British Journal of Cancer (2003) 89, 23-28. doi:10.1038/sj.bjc.6601002 www.bjcancer.com

Low risk of cervical cancer during a long period after negative screening in the Netherlands

A condition for effective cervical cancer screening is a low incidence of cervical cancer after negative screening compared to that in the absence of screening. This relative risk was studied for the period 1994-1997 in the Netherlands and compared with previous studies. All cases of invasive cervical cancer diagnosed from 1994 to 1997 in the Netherlands were related to woman-years at risk, stratified by age, number of preceding negative screenings and time since the preceding negative screening. These incidence rates were compared with that before screening started in the Netherlands. The relative risk increases from 0.13 in the first year after screening to 0.24 after more than 6 years after screening for women with one previous negative screening. These figures reduce to 0.06 and 0.18, respectively, for women with two or more previous screenings. However, these estimates are less favourable when account is taken of the likely decrease in risk for cervical cancer in the period studied. Our data show a low relative risk of cervical cancer for several years following the last negative Pap smear. However, the denominator of the relative risk, that is, the incidence without screening, may have been overestimated. This applies also to the IARC multicountry study, and may have caused too optimistic expectations about the effectiveness of cervical cancer screening.

Primary screening for high risk HPV by home obtained cervicovaginal lavage is an alternative screening tool for unscreened women

BACKGROUND/AIMS

Self sampling is considered an adjuvant tool to facilitate the participation of women in cervical cancer screening programmes. This study aimed to evaluate whether cervicovaginal lavage could be an alternative for the cervical smear in cytology and human papillomavirus (HPV) testing and to assess the acceptance of the self sampling device by women.

METHODS

Fifty six women with abnormal cervical cytology (very mild dyskaryosis or worse) and 15 women with normal cervical cytology obtained a self collected cervicovaginal lavage at home and filled in a questionnaire on the use of the device. At the colposcopy clinic the gynaecologist performed the same procedure followed by a cervical smear for cytology and HPV DNA testing.

RESULTS

The self sampling device was acceptable to 88% of the women. The concordance between the cytology results in the smear and the lavage by the doctor and the patient was 54% and 41%, respectively (kappa = 0.28 and 0.14). The concordance between high risk HPV detection in the smear and the lavage by the doctor and the patient was 93% and 78%, respectively (kappa = 0.82 and 0.53). Ninety one per cent of the women with high grade cervical intraepithelial neoplasia (CIN) had a high risk HPV positive test in the smear, compared with 91% and 81% in the lavages taken by the doctor and the patient, respectively.

CONCLUSIONS

HPV DNA testing by home obtained samples is useful as a screening tool for cervical cancer, whereas cervical cytology by self sampling is not. Although the sensitivity for high grade CIN by high risk HPV testing in the lavage by the patient is not significantly lower than that in the cervical smear, self sampling for HPV DNA is a feasible alternative method in women who decline to participate in population based cervical cancer screening programmes. However, participation in the screening programme remains the best option.

Has the use of pap smears reduced the risk of invasive cervical cancer in Guadalajara, Mexico?

In Mexico, cervical cancer is the leading cause of death due to cancer among women 35 years of age and older. Although cytologic screening for cervical cancer was introduced as a national program 24 years ago, the mortality rate for this disease has been increasing. A case-control study was undertaken. Cases were women younger than 70, with newly diagnosed invasive cervical cancer (ICC), who had been residing for at least the past year in the metropolitan area of Guadalajara. They were selected from 5 hospitals belonging to the Mexican National Health System. Controls were women without cervical cancer who were treated in the same health center as the corresponding case. Analysis included 143 cases and 311 controls. Information on risk factors for cervical cancer and prior cervical cytologic screening was obtained through a standardized personal interview. Overall, 54% of the cases reported having had a cervical cytology compared with 82% of controls. When compared with unscreened women, those who had ever had a Pap smear had a significantly lower risk of cervical cancer (OR = 0.3, 95% CI 0.2-0.4), and the protective effect persisted for over 5 years. Utilization of Pap smears in the metropolitan area of Guadalajara exerted a protective effect on ICC. Of the 65 women who reported a negative history of Pap smears, 45 would not have contracted cancer if they had ever had a Pap smear.

A novel form of ascertainment bias in case-control studies of cancer screening

In case-control studies of cancer screening, some have generally admonished investigators against case definitions based on diagnosis dates because of lead-time bias. However, perhaps partly due to vagueness, the admonitions have been frequently ignored. A recurrence-time model simulates case ascertainment when diagnosis must occur within a specific calendar period. The model depends on screening test sensitivity and rate, age-specific preclinical incidence rates, and preclinical duration time and survival time distributions. For one study of sigmoidoscopic screening for colorectal cancer, when the true odds ratio is 1, its estimate is 0.50 to 0.75 under plausible assumptions. This bias can affect any observational study wherein case definition depends on diagnosis times (e.g., health-plan enrollment data). To avoid bias in observational investigations of cancer screening wherein the case definition depends on the diagnosis date, one must ensure that both screening and preclinical incidence do not occur before the case definition period.

Relation of human papillomavirus status to cervical lesions and consequences for cervical-cancer screening: a prospective study

BACKGROUND

A relation has been established between infection with high-risk types of human papillomavirus and development of cervical cancer. We investigated a role for testing for human papillomavirus as part of cervical-cancer screening.

METHODS

We monitored by cytology, colposcopy, and testing for high-risk human papillomavirus 353 women referred to gynaecologists with mild to moderate and severe dyskaryosis. The median follow-up time was 33 months. At the last visit we took biopsy samples. Our primary endpoint was clinical progression, defined as cervical intraepithelial neoplasia (CIN) 3, covering three or more cervical quadrants on colposcopy, or a cervical-smear result of suspected cervical cancer.

FINDINGS

33 women reached clinical progression. All had persistent infection with high-risk human papillomavirus. The cumulative 6-year incidence of clinical progression among these women was 40% (95% CI 21-59). In women with end histology CIN 3, 98 (95%) of 103 had persistent infection with high-risk human papillomavirus from baseline. Among women with mild to moderate dyskaryosis at baseline, a second test for human papillomavirus at 6 months predicted end histology CIN 3 better than a second cervical smear.

INTERPRETATION

Persistent infection with high-risk human papillomavirus is necessary for development and maintenance of CIN 3. All women with severe dyskaryosis should be referred to gynaecologists, whereas women with mild to moderate dyskaryosis should be referred only after a second positive test for high-risk human papillomavirus at 6 months.

Low-cost diagnostic technologies and clinical outcomes. The impact of inappropriate utilization

Commodification of low-cost diagnostic technologies (LCDTs) carries the risk of an unintended and potentially worrisome shift in how we conceive of health assessment. Optimizing practice requires a balanced understanding of both the beneficial and harmful impact of the use of LCDTs and the development of system incentives for appropriate use.

Sociodemographic factors of Pap smear screening in Taiwan

Substantial evidence exists that regular screening is effective in preventing cervical cancer. However, the existing services are underused by many women in Taiwan. To examine the effects of sociodemographic characteristics on the underuse of Papanicolaou (Pap) smear screening, from September to December 1993 we conducted a questionnaire interview on a sample of 4,400 women aged 20 years and older in Taipei city using multistage sampling with probability proportional to size. Our results indicate that 40% of the women sampled have never had a Pap smear and 86% have not had one in the past year. Age is the strongest factor affecting Pap smear use, particularly for women below age 30 and over the age of 65. In addition, women with lower levels of education, women who are not employed, never-married women and women who live outside the city tend to underuse Pap smear screening. These findings help indicate priority groups which should be targeted to increase screening and consequently reduce cervical cancer. Our data also provides a good baseline for comparison of rates of Pap smear screening by various sociodemographic factors in the future.

Cervical cytology reported as negative and risk of adenocarcinoma of the cervix: no strong evidence of benefit

The relationship between negative cervical cytology reports and risk of adenocarcinoma of the cervix was evaluated in a case-control study of 113 cases and 452 controls. All cases and controls had received at least two negative cytology reports. There was no significant difference between the cases and controls in the number of negative cytology reports or in history of cervical abnormality; while a test for trend in the time since last negative cytology report was significant (P < 0.001), the estimated benefit was very modest. Although the estimates of relative protection were higher in women aged less than 35 years than in women aged 35-69 years, this difference was not statistically significant. These results suggest that cervical screening as practised in the 1970s and 1980s was much less effective in preventing adenocarcinoma than squamous carcinoma of the cervix.

Involving the general practitioner in screening for cervical cancer

In the Leiden region, the cervical cancer screening programme for the age group 35-54 years shifted in 1989 from one in which the smears were taken by specially trained paramedical personnel in health centres to a programme where the general practitioner is the smear taker. Hence, it is possible to compare the results of the two types of screening to evaluate whether involvement of general practitioners leads to better uptake of screening. In the 6 year period evaluated in this paper, the 3-yearly cytological rate per thousand for severe dysplasia or worse increased from 1.00 to 3.40; when stratified by age the positive rates were significantly higher. The histological rate per thousand for severe dysplasia increased from 0.60 to 2.09, and for carcinoma in situ from 0.35 to 1.36. All six invasive carcinomata were detected in the GP programme (0.31%). The general practitioner is clearly more able to attract the 'high-risk' groups.

Selection of neighborhood controls for a study of factors related to the diagnosis of cervical cancer

The level of effort required to generate neighborhood controls for a statewide matched case-control study of cervical cancer was investigated, with the aim of identifying hard-to-reach demographic subgroups. Cross reference telephone directories were used to identify households on the same street as the case. Letters were then sent to the households, followed by 'phone calls. A total of 2920 households were contacted to obtain 147 controls. Overall, 63.6% of age-eligible contacts participated in the study. In 49.3% of all households the major reason for not obtaining a control was "no age-eligible women". Level of effort required to obtain a matched control was greater for black women than for white women--on average 24 letters and 40 'phone calls for black women vs 12 letters and 20 calls for white women. Fewer eligible younger women refused to be interviewed than older. No marked differences were noted when the data were stratified by urban-rural area of residence.

Screening for cervical cancer--should the routine be challenged?

Despite the extensiveness of cervical cancer screening programs, certain major issues are still at stake: (a) substantial false negative rates are common, mostly due to impaired test quality, (b) the optimal length of interval between screenings is uncertain, being a function of available resources and the physicians' attitude, (c) the postmenopausal population, in which incidence is highest, is inadequately tapped. Efforts must be made to optimise the process through more stringent control measures, and a more comprehensive cover of the target population.

Using administrative data for case-control studies: the case of the Papanicolaou smear

Administrative data have not been used extensively for case-control studies. As an example, data from the Manitoba Health Services Commission were used to assess the effectiveness of Papanicolaou (Pap) testing in screening for cancer of the cervix. Case patients were 415 women with invasive cancer (aged 25 to 64 years) from the Manitoba Cancer Registry and control subjects were women aged 25 to 64 years chosen from a random sample of the Manitoba female population (N = 29,926). For 82% of case patients there was information about Pap testing in a prior 5-year period, as compared to 91% of the controls. Since diagnostic tests could not be distinguished from screening tests, data for the year prior to diagnosis were not used. The odds ratios for Pap testing reducing the risk of cancer of the cervix was 0.82 (95% confidence interval [CI]: 0.53, 1.26) for women aged 25 to 34, 0.55 (95% CI: 0.35, 0.85) for women aged 35 to 44, 0.40 (95% CI: 0.23, 0.69) for women aged 45 to 54, and 0.45 (95% CI: 0.26, 0.78) for women aged 55 to 64. The overall 4-year relative odds adjusted for age and number of physician visits was 0.51 (95% CI: 0.43, 0.61). These results were similar to previously published values obtained from interview studies. Selection and recall bias are minimized and using claims avoids the expense of seeking neighborhood control subjects, carrying out interviews, or performing follow-up searches. As well, true population-based controls can be used.(ABSTRACT TRUNCATED AT 250 WORDS)

Preventive Pap-smears: balancing costs, risks and benefits

The pattern of spontaneous screening for cervical cancer by general practitioners and gynaecologists in The Netherlands is compared with an efficient screening policy resulting from a cost-effective study. Spontaneous screening tends to start and stop too early in a woman's life, and leaves too many women overscreened or unprotected. The combination in young age of a low incidence of invasive cancer and a high incidence of regressive lesions explains relative ineffectiveness and harmfulness of present screening practice. When screening would take place between ages 30 and at least 60, with intervals of about 5 years, as many lives could be saved for half the costs and with only 60% of the unnecessary referrals and treatments. Much attention should be paid to the coverage of the target population. Therapeutic follow-up policies for dysplastic lesions should be restrained.

The case-control design and the assessment of the efficacy of cancer screening

Case-control studies have been used in recent years to evaluate the efficacy of cancer screening. However, relatively little work has been done to examine the methodology itself for this purpose. In this paper, it is demonstrated that because of self-selection bias the case-control study can yield a biased estimate of screening efficacy. Further, it is shown how this bias can be assessed using data from a randomized trial. Using data from the HIP breast cancer screening study, the magnitude of the self-selection bias is estimated and is seen to be substantial.

Pap tests of rural black women

Cervical cancer is an important cause of cancer mortality in black women. Pap tests may prevent such deaths, but poor, rural black women are relatively less likely than others to be screened. In order to understand why that is so, the authors surveyed 149 women in three rural North Carolina counties. Thirty-three percent of the women interviewed had not had a Pap test in the preceding three years. Variables independently associated with not having a recent Pap test included: having no identifiable source of medical care; having more than one source of gynecologic care; having an internist provide gynecologic care; and perceiving psychological barriers to Pap tests and pelvic examinations. Income, educational level, and health insurance status were not associated with having a recent Pap test. Although access to care remains a problem for some, better use should be made of the medical care encounters available.

A case-control study of the effectiveness of cervical cancer screening in Osaka, Japan

In the small town of Nose in Osaka, Japan, a population-based screening program for cervical cancer by Papanicolaou smear has been conducted since 1965. In order to evaluate the effectiveness of screening in terms of the reduction of the mortality and the incidence of invasive cervical cancer, two types of case-control studies were carried out. In the first study, the case series consisted of all women who died of cervical cancer under 80 years of age at the time of diagnosis in 1965-1987 (N = 15). For each case, 10 controls were chosen from living residents, matched by year of birth. It showed that the odds ratio (OR) of dying of cervical cancer for screened versus non-screened women was 0.22 (95% CI = 0.03-1.95). In the second study, the case series consisted of all women who were diagnosed as having invasive cancer under 80 years of age at the time of diagnosis in the same period (N = 28). For each case, 10 controls were chosen from living residents without invasive cancer, matched by year of birth and according to whether or not they were screened at the year of the diagnosis of the matched case. It showed that the OR of getting invasive cancer for screened versus non-screened women was 0.41 (95%CI = 0.13-1.29). From these results, it was estimated that 78% of cervical cancer mortality and 59% of invasive cervical cancer incidence among non-screened women could be prevented by cervical cancer screening.