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Results for “Life Table Method”

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PubMed1988

[Cumulative functional rates of orthoptic dialysis fistulas and interposition grafts].

The function of 221 dialysis shunts was investigated retrospectively in 111 patients of an outpatient haemodialysis centre. The mean age of the patients was 58 years. Of 221 recorded shunts, 171 were direct arteriovenous fistulas, while 50 were interposition grafts. The longest observation period was almost 20 years (227 months). The cumulative function rate was evaluated by the life table method; primary patency (until first revision) was differentiated from total function (revisions included). The direct fistulas as compared to the grafts had a significantly (P less than 0.05) higher primary function rate (median 35 vs. 13 months) and after 36 months also a significantly longer total function (median 76 vs. 28 months). Complications were significantly (P less than 0.05) more frequent in grafts than in fistulas (61/50 vs 120/171). Surgical revisions of fistulas failed significantly more often (P less than 0.05) than revisions of grafts (137/171 versus 26/50). Grafts on the forearm had significantly worse results as compared to grafts or fistulas on the upper arm (P = 0.03). In contrast to age, sex and underlying disease of patients a blood pressure less than 130/70 mmHg was a significant risk factor for shunt failure (P = 0.002). Analysis of primary function shows (clearer than the total patency rate) that a direct fistula is a better vascular access in haemodialysis patients than a graft.

Actuarial Analysis↗

PubMed1975

Reoperation and recurrence in Crohn's colitis and ileocolitis; Crude and cumulative rates.

To determine the risks of reoperation and clinical recurrence in Crohn's disease involving the colon, we analyzed by both crude and actuarial (life-table) methods follow-up data from 160 patients hospitalized with Crohn's colitis or ileocolitis from 1964 through 1973. A total of 100 patients (63 per cent) underwent major operation; of these, 58 required reoperation. By the 15th year after initial operation, there was a cumulative reoperation rate of 89 and an overall clinical recurrence rate of 94 per cent. Crude data implied that the reoperation rate diminished with each succeeding operative procedure, from 58 per cent after the first operation to 47 per cent after the fourth. By contrast, actuarial analysis revealed that at the three-year follow-up point, the cumulative chance of reoperation increased from 37 per cent after the first surgical procedure to 60 per cent after the fourth. The inexorable tendency of Crohn's ileocolitis to require repeated operations is demonstrable by actuarial methods.

Adult↗

PubMed1984

Homologous veins as an arterial substitute: long-term results.

From 1968 through 1982, 129 homologous vein grafts were used in 91 patients in the following positions: 75 in the femoropopliteal, tibial, or peroneal artery; 38 in the aortocoronary artery; 13 in the aortopulmonary artery; and one each in the atrioventricular fistula, carotid-subclavian artery, and brachial-radial artery. In the lower extremity patency ranged from 0 to 121 months (mean 22.4 +/- 4.4 months). All grafts were performed for limb salvage, and 75% of the patients had undergone previous operations. Cumulative patency by the life-table method showed that while 50% of grafts occluded by 1 year, 60% of the remaining grafts continued to be functional for more than 5 years. Fifty percent of the aortocoronary bypass grafts studied were occluded at 1 year. Eight of the 13 systemic pulmonary artery shunts were patent at time of death, revision, or total correction. Multiple revisions and thrombectomies are required to maintain patency of homograft veins. The outcome is variable and unpredictable. The inconsistency is due to the antigenicity of the graft. If one is committed to the necessary efforts required to ensure long-term patency, the homologous saphenous vein is a suitable substitute when autogenous tissue is unavailable.

Arterial Occlusive Diseases↗

PubMed1984

Composite sequential bypasses to the ankle and beyond for limb salvage.

Composite grafts of polytetrafluoroethylene (PTFE) and saphenous vein were used for sequential bypasses to the ankle and foot in 35 men and 19 women (mean age 66.5 years). Presenting symptoms were rest pain (25), digital gangrene (19), and ischemic ulcer (10). Thirty-one tibial and 23 pedal bypasses were done and were followed up to 48 months (mean 26.4 months). The ankle pressure index rose from 0.31 +/- 0.11 preoperatively to 0.77 +/- 0.21 postoperatively. Mean graft flows were 34.8 ml/min. Composite sequential grafts took 51 minutes longer to perform than femoral-tibial vein grafts. Patency rates by the life-table method were 81.4% at 2 years and 72.4% at 4 years. Graft failures after the first 10 weeks usually led to amputation. Use of PTFE as an inflow conduit permits otherwise inadequate lengths of saphenous vein to be used for anastomosis to delicate distal vessels and takes advantage of the vein's ability to tolerate low flows. Our experience suggests that the excellent patency rates make sequential bypasses a reasonable option for limb salvage.

Adult↗

PubMed1984

Late survival after carotid endarterectomy for transient ischemic attacks.

Two hundred sixty-six consecutive patients with carotid transient ischemic attacks were treated by 310 carotid endarterectomies. The patients were followed up from 30 months to 12 years, and survival was charted by the life-table method. Comparison with an age- and sex-matched population from the same geographic region showed that survival after operation was not impaired unless there were risk factors from disease that was progressive or could not be well controlled. Hypertension and cardiac disease did not adversely affect survival-probably because they were generally well controlled and included the use of nonsynchronous coronary artery grafting when necessary. Those with impaired cardiac function severe enough to threaten perioperative myocardial infarction or acute irreversible cardiac failure during anesthesia were not recommended for operation.

Adult↗

PubMed1986

Carotid endarterectomy for nonhemispheric cerebral symptoms: patient selection with ocular pneumoplethysmography.

Carotid endarterectomy fails to ameliorate nonhemispheric cerebral symptoms in an unacceptably high proportion of patients, specifically those patients with minor, hemodynamically insignificant carotid lesions. Ocular pneumoplethysmography (OPG) has been shown to accurately predict the hemodynamic significance of carotid lesions, but its use has not been applied to the subset of patients with nonhemispheric symptoms. Preoperative OPG studies were obtained in 43 patients with nonhemispheric symptoms. Postoperatively, 72% of patients with OPG suggestive of hemodynamically significant carotid lesions were relieved of symptoms. By contrast, only 32% of patients with normal OPG were asymptomatic after carotid surgery (p less than 0.05, life-table methods, 24-month follow-up). These data suggest that OPG is a useful test to determine which patients with nonhemispheric cerebral symptoms will benefit from carotid revascularization.

Aged↗

PubMed1986

Flow waveform assessment of polytetrafluoroethylene grafts for reconstruction of lower extremity arteries. A preliminary report.

On the basis of our findings that the outcome of reconstructive surgery for lower limbs could well be predicted by flow waveform analysis, we reviewed femoropopliteal arterial bypass operations involving the use of polytetrafluoroethylene (PTFE) grafts for 35 patients. Of 38 grafts, 26 were PTFE alone, and 12 were PTFE/vein composite grafts. Neither ankle pressure index nor angiographic distal runoff was of predictive value as a prognostic indicator. The cumulative patency rate, calculated by the life-table method, revealed the usefulness of flow waveform analysis for prediction of the outcome of PTFE grafts. In type 0 or I flow, the patency rate was 94% at 1 and 2 years and 79% at 3 years. In contrast, in type II flow, the patency rate was 74% at 1 year, 66% at 2 years, and 49% at 3 years, with a statistical significance at 2 and 3 years (p less than 0.05). Comparison of the result of PTFE grafts with that of PTFE/vein composite grafts showed superior results of composite grafts at 3 years after implantation (42% vs. 83%, p less than 0.05). These findings indicate that flow waveform analysis is useful for prediction of the outcome of PTFE grafts and that PTFE/vein composite grafts should probably be used, particularly in cases of abnormal blood flow.

Actuarial Analysis↗

PubMed1988

Aortobifemoral bypass: the operation of choice for unilateral iliac occlusion?

Aortobifemoral bypass (ABF) is the preferred operation for patients with bilateral aortoiliac occlusive disease, but for those with unilateral occlusion without significant stenosis of the contralateral iliac artery, alternative reconstructions, such as femorofemoral (FF) or iliofemoral (IF) bypass have been advocated. We compared the surgical outcome in 96 such patients after ABF (n = 32), FF (n = 47), or IF (n = 17) bypasses, with biplane arteriography and noninvasive laboratory testing used to assess the contralateral iliac artery and runoff status, in particular, patency of the superficial femoral artery (SFA). Graft patencies were assessed by noninvasive criteria and analyzed by the life-table method. The only death occurred after ABF bypass (3.1%). Primary patency rates at 1, 3, and 5 years with an open SFA were 100%, 89% and 89%, respectively, for ABF; 92%, 92%, and 92% for FF; and 71%, 71%, and 36% for IF. When the SFA was occluded, the primary patency rates at 1, 3, and 5 years were 100%, 100%, and 72%, respectively, for ABF; 72%, 53%, and 35% for FF; and 56%, 56%, and 56% for IF bypasses. There were no later occlusions on the contralateral ("good") side after ABF. Significant progression of atherosclerosis in donor iliac artery was observed in 6% of both FF and IF bypasses. We conclude that ABF is the preferred operation for extensive iliac artery occlusive disease that is hemodynamically significant only on the symptomatic side unless specifically contraindicated by prohibitive risk or abdominal disease. This is particularly true in the face of SFA occlusion.

Actuarial Analysis↗

PubMed1991

Laser angioplasty in peripheral vascular disease: symptomatic versus hemodynamic results.

Most early reports on the efficacy of laser angioplasty have used subjective symptoms rather than objective hemodynamic parameters to evaluate clinical results. We reviewed our experience with hot tip laser-assisted balloon angioplasty in 99 occluded or stenotic arterial segments during 80 procedures in 71 patients, ranging from the aortic bifurcation to the tibial-peroneal trunk. Initial failure to successfully recanalize occluded or stenotic segments occurred in 13 instances (16%). Forty-one procedure-related complications occurred in 31 patients (39%). Functional results were evaluated by use of life-table methods on the basis of symptomatic versus hemodynamic improvement. Cumulative patency rates for symptomatic and hemodynamic improvement were 91% and 64% at 1 month, 71% and 48% at 6 months, and 57% and 34% at 1 year, respectively. These data suggest that symptomatic improvement alone gives a misleadingly high estimate of the efficacy of laser angioplasty when compared with more objective hemodynamic criteria (p less than 0.005). Hemodynamic success was more likely in aortoiliac lesions than femoropopliteal lesions (58% vs 18% at 1 year, p less than 0.01). Hemodynamic parameters should be used to evaluate the success of laser angioplasty, which in its present form, is associated with frequent complications and poor long-term success.

Adult↗

PubMed1990

Overview of radiation-induced skin cancer in humans.

There are about a dozen studies of the incidence of skin cancer among irradiated populations with known skin doses that are available for estimating the risk of radiation-induced skin cancer. It is of note that they provide no evidence for a dose threshold and are compatible with a linear dose-response relationship, at least for ultraviolet radiation exposed skin. The studies also provide varying amounts of evidence concerning a number of other important issues in assessing skin cancer risk: types of skin cancer induced by ionizing radiation, the appropriateness of relative risk vs absolute risk models, combined effects of ionizing and UV radiations, and variations in sensitivity to skin cancer induction among demographic and genetic subgroups. Little epidemiological information is available on several factors, such as the RBE for high-LET radiation, the effects of dose protraction or fractionation, or variations in risk by age at irradiation. A reasonable estimate of skin cancer lethality was 0.2 per cent when weighted for the relative proportions of squamous cell and basal cell skin cancers. Average risk estimates of radiation-induced skin cancer incidence were: absolute risk (AR) of 8.5 X 10(-4) person-year-Sv and excess relative risk (RR) of 52 per cent/Sv. Lifetime skin cancer risk was calculated by life-table methods for males from exposures spread out over ages 20-60 years. The estimates for excess skin cancer incidence were 2 per cent and 11 per cent per Sv under the AR and RR models, respectively, while the corresponding mortality risks were 4 X 10(-5) and 2 X 10(-4) per Sv.

Environmental Exposure↗

PubMed1996

Quantitative immunocytochemical assays on frozen sections of p53: correlation to the follow-up of patients with breast carcinomas.

A series of 222 tumor samples stored at -80 degrees C in the authors' tumor library were investigated with anti-p53 (PA 1801) and streptavidin-biotin-peroxidase complex. The p53 immunoprecipitates were quantified by densitometry assessed by image analysis of digitized microscopic images. Two parameters, percentage of positive surface and mean optical densities, were compared with the patient's outcome (follow-up = 96.8 months) (life table method, Mantel Cox test, BMDP statistical software). The p53 expression significantly correlated with a poor overall survival (P = .0063), metastasis-free survival (P = .024), and recurrence-free survival (P = .022) at a 20% cutoff point of positive immunoreactive tumor surface. A strong prognostic significance was observed in the node-positive subset of patients but not in the node-negative subset, except for recurrence-free survival (P = .047). The results indicate the clinical relevance p53 evaluated by quantitative immunocytochemistry.

Adult↗

PubMed2003

A trial-based cost-effectiveness analysis of letrozole followed by tamoxifen versus tamoxifen followed by letrozole for postmenopausal advanced breast cancer.

BACKGROUND: Third-generation aromatase inhibitors are being considered as an alternative to tamoxifen as first-line therapy for advanced breast cancer. These newer therapies are more expensive, and will gain greater acceptance if they can demonstrate cost-effectiveness. METHODS: Life table analyses are used to compare the costs and benefits [life years gained and quality-adjusted life years (QALYs) gained] of treating postmenopausal women with advanced breast cancer with first-line letrozole (with the option of second-line tamoxifen) compared with first-line tamoxifen (with the option of second-line letrozole). Patient-level data from a large clinical trial describes the effectiveness of the therapy options, clinicians estimate resource usage and utility values are obtained from the literature. RESULTS: The mean cost of providing first- and second-line hormonal therapy is pound 4765 if letrozole is the first-line therapy and pound 3418 if tamoxifen is provided first (a difference of pound 1347). However, patients receiving letrozole as first-line therapy gain an additional 0.228 life years, or 0.158 QALYs. The cost-effectiveness analysis found that first-line hormonal therapy with letrozole gains additional life years at a cost of pound 5917, whilst the cost per additional QALY gained is pound 8514. CONCLUSION: The strategy of letrozole as first-line hormonal therapy not only provides an opportunity for extending and improving patient's quality of life, but also is highly cost-effective compared with other generally accepted medical treatments.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1988

Medical consequences of a factory closure: illness and disability in a four-year follow-up study.

The effect of a factory shut-down on sick leave and disability pensions was investigated in a four-year controlled follow-up study in a general practice setting. The study population consisted of 85 people, 72 women and 13 men, who lost their jobs when a sardine factory near Bergen in Norway was shut down in 1975. The employees of a nearby sister factory' within the same company were chosen as a control population, consisting of 87 people, 66 women and 21 men. The average amount of sick leave for the study group within the first year of follow-up showed a twofold increase compared to the controls. The rate of disability pensions, estimated by the life table method with appropriate adjustments, was more than three times higher in the study group than in the control group from the second through the fourth year of follow-up. The results of this investigation provide further evidence in support of a causal relationship between job loss and illness.

Adult↗

PubMed1982

Cancer among workers exposed to arsenic and other substances in a copper smelter.

A study of the mortality experience of 2802 men who worked one year or more during the period 1940-4964 at a copper smelter in Tacoma, Washington, where arsenic exposure occurred showed a twofold excess in respiratory cancer deaths. Using a time-weighted measure of exposure, a life table method for accumulating dose, and a 10-year lag period, the excess ranged from 1.5 in the lowest exposure category to 2.5 in the highest exposure category. Neither duration of exposure nor time since first exposure contributed strongly to the respiratory cancer excess. The twofold excess in respiratory cancer deaths held for workers with relatively short exposures (less than 10 years) and with a relatively short latency period (less than 20 years) as well as for those with longer exposure and latent periods. This appeared to be because the respiratory cancer excess tended to disappear with time for workers who terminated employment alive, and because workers in high-exposure jobs tended to terminate more quickly than workers in low-exposure jobs. A somewhat unorthodox analytic method showed a weak relationship between the respiratory cancer excess and exposure duration when exposure intensity was held constant. Here, arsenic exposure intensity made an independent contribution to the respiratory cancer excess.

Adult↗

PubMed1983

The use of life tables and survival analysis in testing genetic hypotheses, with an application to Alzheimer's disease.

Because of the late onset of some neuropsychiatric disorders suspected to be under genetic influence, such as Alzheimer's disease, standard techniques for testing genetic hypotheses are difficult to apply to clinical data. The statistical aspects of life table methods and survival probability estimators which can be used to test such hypotheses have been neglected in the psychiatric literature. Two techniques of this kind, the Weinberg morbidity table and the Kaplan-Meier product limit estimator, are applied to real and simulated data. As estimators of lifetime incidence these methods yield roughly equivalent results for both types of data, although from a theoretical standpoint the original Weinberg estimator appears to suffer from logical defects. Parametric models may offer more definitive results, particularly when an estimator of segregation ratio is required. The clinical data in this report were gathered by interviewing relatives of Alzheimer's disease patients sampled through a nursing home survey in metropolitan Baltimore, Maryland during 1980.

Actuarial Analysis↗

PubMed1987

Long-term risk of hysterectomy after tubal sterilization.

Previous studies with only short-term follow-up have produced conflicting results on whether a tubal ligation increases a woman's risk for having a hysterectomy. By use of population-based data from the province of Manitoba's universal health insurance plan, all women aged 25-44 years who had a tubal ligation in 1974 (n = 4,374) were identified. As a comparison group, a random sample of 10,000 Manitoba women who were registered with the insurance plan on July 1, 1974 was chosen. Women undergoing hysterectomy prior to July 1, 1974 or a tubal ligation from 1970-1982 were excluded, leaving 6,835 in the comparison group. All health care utilization for two years before tubal ligation or July 1, 1974 (comparison group) was recorded to identify health characteristics of the women. Information was recorded on rate of hysterectomy, dilatation and curettage, all hospitalization, and hospitalization for menstrual disorders for two years after tubal ligation or July 1, 1974. For the longer term analysis, information on hysterectomy up to December 31, 1982 was recorded. At two years there was no increase in adverse gynecologic outcomes between the two groups. Survival curves (life table method) comparing the two groups for up to nine years found higher hysterectomy rates for women aged 25-29 beginning at two years after tubal ligation and increasing with time. Multivariate analysis (Cox's regression model) confirmed that for women aged 25-29, tubal ligation increased the probability of a hysterectomy 1.6 times (1.2-2.3, 95% confidence interval) after controlling for previous gynecologic history, marital status, number of physician visits, and hospitalizations. For women aged 30 and over, tubal ligation was not a risk factor for subsequent hysterectomy in either the short or long term.

Adult↗

PubMed1989

Acquired immunodeficiency syndrome (AIDS)-free time after human immunodeficiency virus type 1 (HIV-1) seroconversion in homosexual men. Multicenter AIDS Cohort Study Group.

To estimate the time interval between human immunodeficiency virus type 1 (HIV-1) seroconversion and acquired immunodeficiency syndrome (AIDS) diagnosis in homosexual men, prospective incident cohorts are difficult to obtain and, if assembled, provide few events owing to the long incubation time. Although seroprevalent cohorts are numerous in size and events, the information is limited due to the unknown times since seroconversion. To combine the information provided by 1,628 seroprevalent men (304 AIDS cases) and 233 seroconverters (12 AIDS cases) being followed in a multicenter study since 1984, the postseroconversion changes in hematologic variables occurring in the incident cohort were used to develop a model that allowed for the imputation of the unknown times since seroconversion for the seroprevalent cohort. Nonparametric life table methods incorporating truncation and censoring were applied for the estimation of the probability distribution of the AIDS-free time after seroconversion. The precision of the estimates was evaluated using bootstrap methods. The analysis suggested that AIDS is unlikely (less than 0.5%) in the first year; 78% of seropositive homosexual men remain AIDS-free 60 months after seroconversion; and the AIDS incidence increases for months 12-36 and levels off at 38 per 1,000 person-semesters for months 42-60. The nonparametric estimate of the incidence rate suggests a median AIDS-free time of 11 years, which is longer than previous estimates based on parametric models.

Acquired Immunodeficiency Syndrome↗

PubMed1985

Prognostic value of symptom limited exercise testing in men with a high prevalence of coronary artery disease.

In order to evaluate the independent prognostic information provided by exercise testing in populations with a high prevalence of coronary artery disease, survival rates were calculated with the life table method in 372 men, mean age 48 years, referred for coronary arteriography. The prevalence of angiographic coronary artery disease was 82%. During a mean follow-up of 29 months (1 to 8 years), 32 patients died and 27 patients had a nonfatal event (acute infarction or hospitalization for disabling angina). Both the history (presence or absence of typical angina pectoris or of a previous myocardial infarction) and the exercise test results (abnormal if angina and/or ST segment changes greater or equal to 0.1 mV occurred) had a significant prognostic value for the 5 year survival rate (P less than 0.001). In patients with a positive history, the 5 year cumulative survival rate was 76% if the exercise test was abnormal versus 94% if it was normal (P less than 0.001). The following 8 noninvasive and 2 invasive variables were submitted to a Cox regression analysis: age, typical angina pectoris, previous myocardial infarction, maximal heart rate and workload, maximal ST segment depression and elevation, angina pectoris during exercise testing, number of diseased vessels, and wall motion score on contrast ventriculography. By univariate analysis, the age and the maximal workload reached during exercise were the only noninvasive predictive variables for survival or cardiac events (P less than 0.05). By multivariate analysis, and combining all noninvasive and invasive variables, survival was predicted by the wall motion score, the presence or absence of 3 vessel disease, and age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗