Showing papers on "Mass screening published in 1987"
TL;DR: The reduction in the rate of advanced cancers and of breast cancer mortality in the group allocated to screening when compared to the control group has accelerated with a further year of follow-up, and the implications for screening policy, including the interscreening interval are discussed.
Abstract: Further results are presented from the Swedish two-county breast cancer screening trial. The reduction in the rate of advanced cancers and of breast cancer mortality in the group allocated to screening when compared to the control group has accelerated with a further year of follow-up. Mortality due to other causes and the rate of other cancers remains similar in the two groups. Attention has been focused on the rate at which cancers start re-emerging among women with negative mammograms. Among women over 50 years of age at entry to the study, relatively few interval cancers are seen in the first two years after a screening test; in the third year the rate rises to nearly 50% of the comparable rate in the control group. Among women aged 40-49 years at entry, by contrast, the rate of interval cancers even in the first post screening year is nearly 40% of that in the controls and in the second year nearly 70%. In older women in the group allocated to screening, much of the breast cancer mortality comes from the refusers and little from the interval cancers; in younger women the picture is reversed. The implications for screening policy, including the interscreening interval are discussed.
310 citations
TL;DR: An advanced cochlear echo test technique has been specially developed to tackle some specific problems associated with measurements from infants and has greatly improved noise immunity and given very reliable results on poorly co-operating children.
Abstract: An advanced cochlear echo test technique has been specially developed to tackle some specific problems associated with measurements from infants. The test procedure and data processing combination has greatly improved noise immunity and has given very reliable results on poorly co-operating children. Technical details are given and the results of a study of 105 ears from 55 children are presented. The potential of the advanced technique as a screening test is discussed.
304 citations
TL;DR: A retrospective study of 58 patients with gastric cancer and 162 cancer-free patients showed that a PG I/PG II ratio identified 86.2% of all carcinomas and 87.5% of early carcinomas.
Abstract: The serum level of pepsinogen I (PG I) and pepsinogen II (PG II), and the PG I/PG II ratio were compared with the surface area of the fundic mucosa, as determined endoscopically by the Congo red staining method. Reduction in the area of the fundic mucosa due to gastritis was associated with stepwise reduction in the PG I levels and the PG I/PG II ratios. Reduction in the area of the fundic mucosa was also associated with decreases in the basal acid output, maximal acid output (MAO), the basal pepsin output and the stimulated pepsin output. The best sensitivity and specificity levels for the diagnosis of normal mucosa and severe gastritis were obtained with the PG I/PG II ratio and the MAO. A retrospective study of 58 patients with gastric cancer and 162 cancer-free patients showed that a PG I/PG II ratio identified 86.2% of all carcinomas and 87.5% of early carcinomas. Although this test gave a positive rate of 36% among the cancer-susceptible age group controls, its use would lower the cost of mass screening by targeting a smaller test population.
296 citations
TL;DR: The results were incorporated into a four-part screening protocol designed to reduce the excessive error rates associated with screening strategies that rely exclusively on tympanometry.
Abstract: Tympanograms were obtained from normal preschool and adult subjects with a prototype hand-held tympanometer to obtain normative values for four tympanometric variables: static admittance, equivalent ear canal volume, tympanometric peak pressure, and gradient. Effects of age group, sex, and pump speed (200 or 400 daPa/s) were determined. The results were incorporated into a four-part screening protocol (history, visual inspection, audiometry, and tympanometry) designed to reduce the excessive error rates associated with screening strategies that rely exclusively on tympanometry.
189 citations
TL;DR: The data suggest that HIV infection of inner-city parturients is a significant problem that warrants broadly implemented health strategies and that if risk factor information elicited by physicians is used to initiate HIV antibody counseling and testing of pregnant women, a significant number of seropositive parturient is missed.
Abstract: Although perinatal transmission of the human immunodeficiency virus (HIV) is well documented, seroprevalence rates of HIV in populations of women of reproductive age have not yet been reported. To determine the seroprevalence of HIV in childbearing women from a population with a high incidence of acquired immunodeficiency syndrome, cord blood samples were collected from 602 infants delivered at an inner-city municipal hospital in New York. Demographic and HIV risk factor information was also collected from mothers of these infants. Twelve (2%) of 602 samples (95% confidence interval, 1% to 4%) were positive for HIV on enzyme-linked immunosorbent assay and Western blot analysis. In interviews, seven of 12 seropositive women had risk factors as defined by the Centers for Disease Control, Atlanta; the remaining five seropositive women had no self-identified risk factors. The HIV seroprevalence rate in our hospital (2.0%) is several times higher than that of many other diseases for which screening is already routine. This serosurvey indicates that HIV infection of inner-city parturients is a significant problem that warrants broadly implemented health strategies. Furthermore, the data also suggest that if risk factor information elicited by physicians is used to initiate HIV antibody counseling and testing of pregnant women, a significant number of seropositive parturients is missed. In areas with significant seroprevalence rates of HIV infection, a broader counseling and testing program may be needed. ( JAMA 1987;258:2701-2703)
161 citations
TL;DR: A strong and highly significant inverse association between the number of full-term pregnancies and the risk of breast cancer was observed and the apparent protective effect of high parity was strongest in the groups with an early first birth, and no such effect could be established among women with their first birth at age 35 or later.
Abstract: The relation between childbearing and breast cancer risk was investigated in a prospective study of 63,090 Norwegian women, among whom 1,565 breast cancer cases occurred in a follow-up from 1961 through 1980. The authors observed a strong and highly significant inverse association between the number of full-term pregnancies and the risk of breast cancer. The association was consistently found in all subgroups according to demographic variables and was obtained for all histologic subtypes except for cases classified as Paget's disease. The relation with parity could not be explained by confounding with age at first birth or other reproductive factors. The apparent protective effect of high parity was strongest in the groups with an early first birth, and no such effect could be established among women with their first birth at age 35 or later. The protective effect of multiparity was observed for cancers in all age groups. Uniparous women had, however, higher risk of developing breast cancer under age 60 than nulliparous women. Those who reported at least one abortion had somewhat lower risk than those who did not, but no trend according to the number of abortions was observed.
157 citations
138 citations
TL;DR: The following statements summarize the current knowledge regarding SIDS, apnea, pneumograms, and home monitors:
132 citations
TL;DR: A Danish study allocated at random 30,970 persons to screening with Hemoccult-II and 30,968 as controls to detect a possible reduction in mortality from colorectal cancer of 25% within 5 years after three screenings with intervals of 2 years.
Abstract: A Danish study allocated at random 30,970 persons to screening with Hemoccult-II and 30,968 as controls in a population of 140,000 between 45 and 74 years old. Persons with known colorectal cancer, adenoma, and distant spread from all types of cancer were excluded. The test was completed in 20,672 persons from August 1985 to September 1986, and 215 (1%) were found to be positive. Colonoscopy in 203 and double-contrast barium enema in 6 detected 37 persons with cancer and 86 with adenomas. Dukes A cancer was detected in 19 in the screening group, in contrast to 2 among controls. Synchronous adenomas were found in 23 with a positive test and 10 controls. Interval cancer was found in nine persons within 1-11 months after a negative test. Eighteen persons got cancer before invitation and six defectors as well. In all, colorectal cancer was detected in 70 persons in the screening group and in 38 controls; the figures for adenomas alone were 103 and 38, respectively. The study is designed to detect a possible r...
130 citations
TL;DR: Routine screening after mastectomy detects few recurrences that are not already symptomatic, and the superior survival associated with discovery of occult recurrence may result from the influences of lead time and length bias.
Abstract: Performance of periodic follow-up examinations after mastectomy for breast cancer is standard practice, primarily for early detection and treatment of recurrence. This study was designed to determine whether this routine screening resulted in significant survival benefit for the patient. The medical records of 1,230 women treated for cure of invasive carcinoma of the breast were reviewed, and 248 cases of recurrence were identified for analysis. Only 36% of recurrences were discovered asymptomatically. Asymptomatic recurrence was associated with favorable biologic factors, ie, more frequent estrogen receptor (ER) positivity and initial node negative status, and survival was superior to that of others. This was particularly true for occult local recurrence. However, compliance with a present schedule of examinations did not confer superior survival. It was concluded that (1) routine screening after mastectomy detects few recurrences that are not already symptomatic, and (2) the superior survival associated with discovery of occult recurrence may result from the influences of lead time and length bias.
127 citations
TL;DR: Clear evidence for a hadronic screening spectrum is found, suggesting the presence of hadronic plasma modes, and spectral multiplets, extrapolated to zero quark mass, are consistent with a restoration of the SU(N) x SU( N) chiral symmetry.
Abstract: In an effort to characterize the large-scale structure and composition of the QCD plasma at zero baryon-number density in the vicinity of the high-temperature phase transition, we have carried out a numerical simulation in SU(3) lattice gauge theory with four flavors of low-mass staggered fermions on a 6\ifmmode\times\else\texttimes\fi{}${10}^{3}$ lattice. A small data sample was also collected on 6\ifmmode\times\else\texttimes\fi{}${10}^{2}$\ifmmode\times\else\texttimes\fi{}20 lattices. The simulation uses the Illinois hybrid microcanonical algorithm, adapted for measurements of hadronic screening lengths. Measurements were carried out at three values of the gauge coupling \ensuremath{\beta} and at three values each of the bare quark mass. The principal quantities measured are the static screening masses in several color-singlet channels with quark valence qq\ifmmode\bar\else\textasciimacron\fi{} and qqq. Clear evidence for a hadronic screening spectrum is found, suggesting the presence of hadronic plasma modes. The spectral multiplets, extrapolated to zero quark mass, are consistent with a restoration of the SU(N)\ifmmode\times\else\texttimes\fi{}SU(N) chiral symmetry.
TL;DR: The prevalence and mode of inheritance of major genetic eye diseases have been investigated in China since the establishment of the Section of Ophthalmic Genetics of the Chinese Society of Genetics as mentioned in this paper.
Abstract: The prevalence and mode of inheritance of major genetic eye diseases have been investigated in China since the establishment of the Section of Ophthalmic Genetics of the Chinese Society of Genetics. Mass screening of genetic eye diseases has been undertaken in many districts in China, covering more than 700,000 people, and more than 5000 pedigrees of genetic eye diseases have been collected and analysed all over China. Based on these data, the prevalence and mode of inheritance of dyschromatopsia, degenerative myopia, retinitis pigmentosa, congenital ptosis, congenital microphthalmos, congenital cataract, congenital glaucoma, Leber's optic atrophy, corneal dystrophy, congenital nystagmus, coloboma of the eye, congenital aniridia, retinoblastoma, macular dystrophy, simple myopia, primary glaucoma, and strabismus have been investigated, and the results are presented.
TL;DR: The complete blood count and leukocyte differential count have no value in screening asymptomatic members of the general population and are appropriate to obtain when a hematologic or infectious disorder is suspected, but they may not affect decision making if the diagnosis is clinically evident.
Abstract: The complete blood count and leukocyte differential count have no value in screening asymptomatic members of the general population. The complete blood count may be useful for screening infants in the first year of life, institutionalized elderly persons, pregnant women, and recent immigrants from Third World countries, if poor nutrition or inadequate iron intake is suspected. These tests are not useful for hospitalized patients, unless an abnormality is suspected or surgery with major blood loss is anticipated. It is appropriate to obtain the tests when a hematologic or infectious disorder is suspected, but they may not affect decision making if the diagnosis is clinically evident. The leukocyte differential count is unnecessary to confirm an infection in most cases in which leukocytosis is present. Repeat tests should be limited to situations where the clinical course is unclear, and at intervals long enough such that the results might affect clinical decision making.
TL;DR: In this article, the authors used the Clinical Interview Schedule (CIS) as a criterion for assessing the presence of psychiatric disturbances on a 5-point scale and interviewed by a psychiatrist.
Abstract: Ninety consecutive patients aged 14 and above attending a general practice in Verona completed the 30-item General Health Questionnaire (GHQ), were assessed by the general practitioner for the presence of psychiatric disturbances on a 5 point scale, and interviewed by a psychiatrist using the Clinical Interview Schedule (CIS). The Italian versions of both the GHQ and the CIS were confirmed as feasible instruments for general practice studies in Italy. Taking the Overall Severity Rating made by the psychiatrist (Psy-OSR) at the end of the CIS as the criterion, the best CIS threshold in discriminating between “cases” and “non cases” was 12/13, while the GHQ cut off point of 5/6 gave the best results in terms of balance between sensitivity (81%) and specificity (71%). According to this cutting score, 47.8% of patients were high scorers. The corresponding figures of sensitivity and specificity for a GHQ cut off 4/5 were 89% and 65%. A comparison of the performance of the GHQ-30, GHQ-12 and C-GHQ (Goodchild and Duncan-Jones method of scoring), obtained in the usual way, as well as using ROC analysis showed that the C-GHQ gave the best overall results, but the difference was not significant. Using the Psy-OSR ≥2 or the CIS Total Weighted Score ≥13 as indicators, the prevalence of “true” cases in this sample was 35.5% and 38.8% respectively, a rate lower than that reported by Fontanesi et al. (1985) in another general practice study in Italy.
TL;DR: Compared with the young, the group aged 65 years or older is at a greater risk for lung cancer and has a higher proportion of lung cancer initially seen at local stage, which indicates selective screening of high-risk target groups may be beneficial.
Abstract: Lung cancer increases in incidence with increasing age and is the leading cause of cancer death in the United States. While mass screening for lung cancer is not indicated, selective screening of high-risk target groups may be beneficial. We tested the hypothesis that lung cancer is initially seen at a less advanced stage with increasing age using incidence cases (N = 22874) from the Centralized Cancer Patient Data System. The percent of lung cancer patients with local stage disease increased from 15.3% of those aged 54 years or younger, to 19.2% of those aged 55 to 64 years, to 21.9% of those aged 65 to 74 years, and to 25.4% of those aged 75 years or older. The percent with distant stage decreased from 48.7%, to 44.5%, to 40.3%, and to 36.7% for the same age groups, respectively. These age-stage trends persisted in subgroup analysis by sex, race, and histological subtype. Furthermore, analysis of 6332 patients who underwent surgical staging showed a greater likelihood of local stage disease with increasing age. Thus, compared with the young, the group aged 65 years or older is at a greater risk for lung cancer and has a higher proportion of lung cancer initially seen at local stage. The efficacy of selective screening for lung cancer in this target group warrants additional study. (JAMA1987;258:921-926)
TL;DR: In Sapporo City, the capital of Hokkaido Prefecture, the condition of the three parameters improved significantly after the institution of mass screening had not yet been performed, and the improvement was thought to be attributed to the effects of the mass screening.
Abstract: One hundred sixty-seven cases of neuroblastoma in the Registry of Childhood Malignancies in Hokkaido Prefecture from 1969 to 1984 were studied, using the age at diagnosis, the clinical stage at diagnosis, and the survival rate to assess the influence of the mass screening of neuroblastoma performed in Sapporo City since 1981. In Sapporo City, the capital of Hokkaido Prefecture, the condition of the three parameters improved significantly after the institution of mass screening (e.g., the 48-month survival rate improved--from 21.3% to 87.5%). In Hokkaido Prefecture (Sapporo City excluded), however, where the mass screening had not yet been performed, no significant change was observed in any of the three parameters (48-month survival rate changed only from 21.1% to 28.1%). Consequently, the improvement in Sapporo City was thought to be attributable to the effects of the mass screening.
TL;DR: The results show a remarkable decrease in the rate of infection from 53.6 to 0.9%.
Abstract: The human T cell lymphotropic virus type I (HTLV-I) is transmitted by blood transfusions that contain cell components as one of the virus transmission modes. We carried out mass screening of sera from seropositive donors by a gelatin particle agglutination test to prevent the spread of HTLV-I by transfusion. Seroconversion rates were compared before and after screening. The results show a remarkable decrease in the rate of infection from 53.6 to 0.9%. Therefore, it is certain that screening by the agglutination method prevents the spread of HTLV-I transmission in blood transfusions.
TL;DR: During 1985 many drug abusers who lived in Edinburgh were found to be infected with the human immunodeficiency virus (HIV) and an alternative counselling and screening clinic for testing for antibodies to HIV was established for use by drug abusers.
Abstract: During 1985 many drug abusers who lived in Edinburgh were found to be infected with the human immunodeficiency virus (HIV). As a result an alternative counselling and screening clinic for testing for antibodies to HIV was established for use by drug abusers. Four hundred and forty one patients were counselled in the first year, and over 60% were either drug abusers or their sexual contacts. One hundred and fourteen (26%) patients were positive for HIV antibody, and 100 (88%) of these were current or former drug abusers. The HIV seropositivity rate in drug abusers was 52% but was only 7% in their sexual contacts. Services were provided for these people as well as counselling before and after the test. The cost of this counselling service for the first year was 27,000 pounds or 61.22 pounds per patient. The unexpected mobility of 23% of the Edinburgh drug abusers, particularly to other areas of Britain, suggests that similar services need to be set up elsewhere.
TL;DR: In Leek, a small town in the north of the Netherlands, 428 men aged between 30-33 years were invited to take part in a screening test for cardiovascular risk factors, and more than half of the participants were found to have an 'abnormality'--that is they scored on one or more of cigarette smoking, overweight, hypertension, hyperlipoproteinaemia, albuminuna or glucosuria.
Abstract: In Leek, a small town in the north of the Netherlands, 428 men aged between 30-33 years were invited to take part in a screening test for cardiovascular risk factors. Questionnaires were sent to the 267 men who had participated in the screening test as well as to the 161 non-participants, in order to gain an insight into the participatory behaviour and the experience of those involved. The non-participants gave a diversity of motives for not taking part but did not admit to anxiety about finding abnormal results. More than half of the participants who replied (51%, n = 107) were found to have an 'abnormality'--that is they scored on one or more of cigarette smoking, overweight, hypertension, hyperlipoproteinaemia, albuminuna or glucosuria. The supplementary information provided on nutrition and smoking caused a large proportion of them to claim they had changed to a more healthy life-style after the screening test. Those who were under the impression that they had led healthy lives but were still found to have an 'abnormality' were often very astonished and sometimes worried about the result. The men without 'abnormalities' did not lead significantly healthier lives than the rest in terms of exercise, smoking, diet and so on; for them the result might have a 'certificate of health' effect justifying their not always healthy behaviour.
TL;DR: The MRFIT recruitment was attributed to the previous experience of investigators in screening large numbers of participants for clinical trials and similar epidemiologic investigations, and the identification at each clinic of one or more persons whose specific responsibility was recruitment.
TL;DR: Data show that sensitive detection of coronary calcific deposits accurately predicts the presence of atherosclerotic plaque, and sensitive radiographic techniques such as digital subtraction fluoroscopy need to be developed as screening tests.
Abstract: Although changes in lifestyle may increase the life expectancy of persons at high risk for coronary disease, there is no cost-effective screening test that can select these persons from th...
TL;DR: The laboratory procedures which led to the high sensitivity for the cervical cytodiagnosis were analysed and the number of true positive cases was available, and hence the sensitivity of cervical screening for severe dysplasia, or carcinoma in situ, and invasive carcinoma could be assessed.
Abstract: All women in Nijmegen, The Netherlands, with a histological diagnosis of severe dysplasia, or carcinoma in situ, or invasive carcinoma were investigated to see whether they had participated in a population screening programme. Within two years of diagnosis of a negative cervical smear, 45 women were found to have histologically confirmed severe epithelial abnormality of the cervix. From the same population as these apparently false negative cases, the number of true positive cases was available, and hence the sensitivity of cervical screening for severe dysplasia, or carcinoma in situ, and invasive carcinoma could be assessed. This was found to be 83% after two years. The laboratory procedures which led to the high sensitivity for the cervical cytodiagnosis were analysed. Experienced sample takers and cytotechnologists are very important and can reduce sample and screening errors. A good administrative system is necessary to guarantee proper follow up for women with abnormal findings in their cervical smears.
TL;DR: Although the results indicate that very early diagnosis and treatment have a beneficial effect on outcome, more studies are needed before a definite answer can be given as to whether or not mass neonatal screening should be started.
Abstract: A neonatal screening program for CF by determination of albumin in meconium was performed in the north eastern part of the Netherlands from 1973 to 1979. In this period 94,043 newborns were screened and 116,953 were not. A follow-up study of CF patients in the above cohorts was started in 1980. The purposes of this study were to evaluate the effects of early diagnosis and treatment in CF patients by comparing the outcome in the two groups of patients. Although the results indicate that very early diagnosis and treatment have a beneficial effect on outcome, more studies are needed before a definite answer can be given as to whether or not mass neonatal screening should be started.
TL;DR: The Denver Prescreening Developmental Questionnaire (PDQ) has been revised to extend the age of children who can be screened to those from 6 years down to birth, to make the test items more challenging for children and more informative for parents, and to make it easier for professionals to compare a child's performance with Denver Developmental Screening Test (DDST) norms.
TL;DR: Routine maternal HBsAg screening programs may be needed if transmission of hepatitis B from mother to infant is to be prevented and the sensitivity of historical risk factors for identification for hepatitis B surface antigen (HBsAg)-positive parturients is assessed.
Abstract: To assess the sensitivity of historical risk factors for identification for hepatitis B surface antigen (HBsAg)-positive parturients, 4399 pregnant women were consecutively screened for HBsAg. Information regarding risk for hepatitis B infection was obtained from each HBsAg-positive parturient. Twenty-three HBsAg-positive subjects were identified (5.2/1000 deliveries). The HBsAg carrier rate (18/2231, or 8.1/1000 deliveries) was significantly higher in women of black, Asian, or Hispanic origin than in the remaining ethnic groups (non-Hispanic whites plus all others, 5/2168, or 2.3/1000 deliveries) (chi square, 5.95; p = 0.016). Risk factors for identification of HBsAg-positive women were present in 10 of 22 asymptomatic subjects (sensitivity, 45%; 95% confidence interval, 24% to 68%). Much of the information required to assess one of these risk factors, previous infection, involved detailed questioning and is unlikely to be obtained in the context of conventional obstetrical care. Routine maternal HBsAg screening programs may be needed if transmission of hepatitis B from mother to infant is to be prevented.
Journal Article•
TL;DR: Selective screening based on risk factors including maternal age may enhance detection of diabetes early in gestation among patients whose early screening values were elevated and whose initial glucose tolerance tests were normal.
TL;DR: Factor structure of the two brief versions of the Michigan Alcoholism Screening Test was similar to that found in younger alcoholics, suggesting that symptom constellation is not necessarily different in the elderly.
Abstract: Alcoholism in the elderly is often underidentified because of the differences in the presentation and symptom patterns compared to younger individuals. One way to address this problem is through routine use of screening instruments, but up to this time, none of the instruments used to identify alcoholism in younger populations have been shown to be valid in the elderly. We studied the validity of the Michigan Alcoholism Screening Test, scored both with weighted (MAST) and unit scoring (UMAST), and two short versions: the Brief MAST (BMAST) and Short MAST (SMAST) in 52 hospitalized elderly male alcoholics and 33 nonalcoholic controls. The MAST and UMAST showed excellent sensitivity and specificity, while the SMAST was less specific, and the BMAST less sensitive and less specific. Factor structure of the two brief versions was similar to that found in younger alcoholics, suggesting that symptom constellation is not necessarily different in the elderly. We recommend the use of the MAST or UMAST for screening for alcoholism in the elderly.
TL;DR: The authors evaluate current proposals for the compulsory screening of selected populations for antibodies to the human immunodeficiency virus (HIV) as a means of controlling the spread of AIDS and argue that any public health benefit predicated on behavior modification among persons who test positive would be marginal or counterproductive.
Abstract: Mandatory screening for antibodies to the human immunodeficiency virus (HIV) is opposed because it is unlikely to lead to changes in behavior necessary to impede the spread of AIDS and because of the potential for invasion of privacy and discrimination. Support is given to the existing guidelines by the US centers for Disease Control for testing among all members of groups vulnerable to HIV infection with their informed consent. A substantial increase in planning and resources for professional testing education and counseling services is needed if these guidelines are to have any real impact. Testing for the presence of HIV antibodies can provide a clear focus for public education and counseling as a foundation for behavior change. The cost-free and timely availability of professional testing for persons vulnerable to HIV is an essential part of the public health strategy to impede the spread of the infection. In order to protect the privacy of high-risk groups and be fair to clinicians statutory confidentiality protection with specific exceptions for foreseeable harm to others would be an important adjunct to this strategy. General criteria for assessing complusory screening of persons with antibodies to the HIV are put forward. These criteris are then applied to 3 paradigmatic proposals forprograms currently being suggested across the country: premarital screening screening in drug treatment and sexually transmitted disease clinics and general screening in prisons.
TL;DR: The ED can be a useful screening site for hypertension; elevated blood pressure on discharge should ensure referral for follow-up evaluation and therapy.
TL;DR: This paper describes a model for the survival of screen-detected cases, with a hazard function that depends on an individual's lead time, the duration of preclinical disease, and the time since diagnosis, that is, after the unknown date when clinical diagnosis would have occurred in the absence of screening.
Abstract: Early detection of cancer by screening advances the date of diagnosis, but may or may not affect survival. To assess the survival benefit associated with early detection, one must estimate the distribution of time survived post lead-time, that is, after the unknown date when clinical diagnosis would have occurred in the absence of screening. One can then compare the adjusted survival of screen-detected cancer cases to other groups of cases not diagnosed by screening. This paper describes a model for the survival of screen-detected cases, with a hazard function that depends on an individual's lead time, the duration of preclinical disease, and the time since diagnosis. The model is fitted to the ten year survival data from the 132 screen-detected cases of breast cancer in the well-known HIP (Health Insurance Plan of Greater New York) study. Comparison with the survival of several groups of cancer cases not detected by screening (interval cases arising clinically in persons previously screened, cases among persons who refuse screening, and cases among randomized controls not offered screening) yields various estimates of benefit. Use of the interval cases for comparison gives an estimate of about 21 breast cancer deaths prevented among 20,166 women screened in the HIP study; use of the data from the randomized controls gives an estimate of about 25 prevented deaths. The former estimate derives from the screened group of women only, and so the same method of evaluation may also be applied to community screening programmes and other situations that do not entail randomization.