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Biomedical subjects

R A Wolfe

Publications and source records attributed to R A Wolfe.

At least 73 records · Page 4Linked to original sources
PubMed1995

Hospitalization among United States dialysis patients: hemodialysis versus peritoneal dialysis.

Measurements of hospitalization in the dialysis population are important because they provide insight into the morbidity and the cost of treatment among dialysis patients. Prior comparisons of hospitalization for different dialysis modalities have had conflicting results. This study was designed to compare hospitalization for patients treated with peritoneal dialysis (PD) versus hemodialysis (HD) using the data from the U.S. Renal Data System 1993 Annual Data Report. The study population included all Medicare dialysis patients prevalent on January 1, 1988 through 1990. Patients were monitored to transplantation, death, or end of the calendar year for a total of 189,654 patient years. Hospital admission rates were computed from the total number of hospital admissions during the year divided by the total number of patient years at risk. Patients were classified by treatment modality (PD, HD), cause of ESRD (diabetes as a cause of ESRD versus all other causes), age (0 to 19, 20 to 44, 45 to 65, +65), and race (black, white). Rate ratios (RR:PD/HD) for hospital admissions per year at risk were estimated, while adjusting for the other factors with Poison regression. On average, hospital admission rates per patient year at risk for dialysis patients treated with PD were 14% higher than for those treated with HD (RR = 1.14; 95% confidence interval (Cl), 1.13 to 1.15) when adjusting for race, age, gender, and cause of ESRD. The excess in the overall adjusted admission rates in PD patients compared with HD patients was higher for black than for white patients (RR:PD/HD = 1.22 versus RR = 1.11; 95% Cl, 1.10 to 1.13).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

A comparison of mortality between patients treated with hemodialysis and peritoneal dialysis.

Patients with ESRD treated with dialysis have a high mortality rate. Controversy exists as to whether this high mortality rate is affected by modality choice. The purpose of this epidemiologic study was to compare mortality in prevalent hemodialysis-treated (HD) and peritoneal dialysis-treated (PD) patients in a large national sample, adjusting for demographic characteristics. Data were obtained from the U.S. Renal Data System for patients prevalent on January 1 of the years 1987, 1988, and 1989, each with 1 yr of follow-up. Patients were censored at transplantation. Death rates per 100 patient years were compared between HD and PD, adjusting for age, race, gender, cause of ESRD (diabetes versus nondiabetes) and < 1 yr or > 1 yr of prior ESRD, by the use of Poisson regression. There were 42,372 deaths occurring over 170,700 patient years at risk. On average, prevalent patients treated with PD had a 19% higher adjusted mortality risk (relative risk (RR) = 1.19; P < 0.001) than did those treated with HD. This risk was found to be insignificant (P > 0.05) and small for ages < 55 and increasingly large and significant for ages > 55 yr. It was accentuated in diabetics (RR = 1.38; P < 0.001) but was also present in nondiabetics (RR = 1.11; P < 0.001). Although present in both males and females, this risk was accentuated in females (RR = 1.30 versus 1.11; both P < 0.001). In this national study of prevalent U.S. dialysis patients, treatment assignment to PD was associated with a 19% higher all-cause mortality rate than HD.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1995

A comparison of cause of death between patients treated with hemodialysis and peritoneal dialysis.

Mortality rates associated with peritoneal dialysis (PD) have been found to be higher than those associated with hemodialysis (HD) among prevalent U.S. patients over the age of 55 in the preceding study. Given the substantial technical differences between PD and HD, causes of death might also be expected to differ between these dialytic modalities. In order to help elucidate the relative contributions of these technical differences and to further the understanding of the excess mortality observed among PD-treated dialysis patients, this epidemiologic study compared cause of death in prevalent HD- and PD-treated patients in a large national sample, adjusting for demographic characteristics. Data for patients prevalent on January 1 of the years 1987, 1988, and 1989, each with 1 yr of follow-up, were obtained from the U.S. Renal Data System. Patients were censored at transplantation. Death rates per 100 patient years for seven cause-of-death categories were compared between HD and PD, adjusting for age, race, gender, cause of ESRD (diabetes versus nondiabetes), and < 1 yr or > 1 yr of prior ESRD, by use of the Poisson regression. There were 42,372 deaths occurring over 170,700 patient years at risk. There was a significantly increased mortality risk for PD compared with HD for all cause-of-death categories, except malignancy, for which there was a higher mortality risk for HD. The excess all-cause mortality observed in PD-treated patients can be accounted for, in decreasing order, by infection (35%), acute myocardial infarction (24%), other cardiac causes (16%), cerebrovascular disease (8%), withdrawal (8%), and malignancy (-6%).(ABSTRACT TRUNCATED AT 250 WORDS)

Cause of Death↗
PubMed1994

The impact of HLA mismatches on the survival of first cadaveric kidney transplants.

BACKGROUND: The benefits of HLA-A, B, and DR matching of cadaveric kidney grafts and recipients remain controversial when viewed from the perspective of social equity and graft survival. METHODS: We estimated graft survival using proportional-hazards techniques, adjusting for patient and donor characteristics, for a series of 30,564 Medicare patients receiving a first cadaveric kidney transplant between 1984 and 1990. The effects of minimal achievable HLA mismatches and maximal matching on graft survival were estimated by simulated allocation of a sample of organs to a sample of 20,000 candidates for transplantation. RESULTS: The adjusted one-year graft survival was 84.3 percent for grafts with no mismatches and 77.0 percent for grafts with four mismatches. National rationing of donor organs to achieve minimal mismatching and maximal matching could potentially decrease the average number of HLA mismatches from 3.6 to 1.2, with a corresponding increase in the number of matches. As a consequence, projected five-year graft survival could potentially increase from 58.5 percent to 62.9 percent. This would be associated with a decrease in the proportion of kidneys allocated to black recipients from 22.2 to 15.0 percent. CONCLUSIONS: Under ideal circumstances, a policy of maximal matching of cadaveric renal transplants would increase five-year graft survival by a comparatively small 4.4 percentage points, but the actual benefit is likely to be smaller.

Adolescent↗
PubMed1994

Analysis of the association of dialyzer reuse practices and patient outcomes.

This historic prospective study assessed the relationship between dialyzer reuse practices and hemodialysis patient mortality through 1 year of follow-up. Medicare patient demographic and survival data were combined with dialyzer reuse data from the Centers for Disease Control and Prevention's annual survey of dialysis-related diseases. Data were analyzed for the US Medicare hemodialysis population of never transplanted patients prevalent on January 1, 1989, and January 1, 1990, who were treated in freestanding dialysis units that used primarily conventional (not high-flux) dialyzers. Time to mortality, or transplant, and other censoring on December 31st of each year was regressed with proportional hazards models on patient, dialysis unit, and reuse measures. Age-, race-, and diagnosis-standardized mortality ratios for dialysis units were also regressed with weighted least squares techniques against dialysis unit and reuse measures. The results showed that patients treated in dialysis units that disinfected dialyzers with a peracetic acid, hydrogen peroxide, acetic acid mixture, or glutaraldehyde experienced higher mortality than patients treated in units that used formalin or in units that did not reuse dialyzers. The relative risk of mortality, compared with patients treated in nonreuse dialysis units, was 1.17 (P = 0.010) for glutaraldehyde and 1.13 (P < 0.001) for the peracetic acid mixture. The relative risk for formalin compared with the reference group of nonreuse was 1.06 (P = 0.088). With adjustment for several patient and dialysis unit characteristics, dialyzer reuse with certain germicides was associated with a significantly elevated mortality risk. This elevated risk, the etiology of which is currently not known, may represent a large number of potentially avoidable deaths per year. Only a large, nationally based analysis of this type has sufficient sample size to detect mortality risks such as these.

Dialysis↗
PubMed1994

Comparative mortality risks of chronic dialysis and cadaveric transplantation in black end-stage renal disease patients.

In view of the relatively low mortality risk on dialysis and the high risk of allograft loss among black compared with white end-stage renal disease (ESRD) patients, we studied the relative mortality risks of all black renal transplant candidates in Michigan from 1984 to 1989. There were 770 black ESRD patients followed from wait-listing for cadaveric (CAD) kidney transplantation until the time of transplantation, death, or December 31, 1989. The time on dialysis prior to wait-listing exceeded 1 year in 24% of these patients. Black diabetic patients on the waiting list have more than twofold relative mortality risk (RR) compared with nondiabetic individuals (RR = 2.73, P < 0.001) while the RR by diabetes status among CAD transplant recipients was small. Overall, CAD transplantation was associated with elevated risk of mortality in the first month posttransplantation (RR = 3.39, P < 0.03). Cadaveric donor transplant and wait-listed dialysis patients have equal death rates 112 days after transplantation. Thereafter, death rates were lower for transplant recipients compared with transplant candidates on dialysis. One year after transplantation, CAD transplant recipients on the average have approximately half the risk of death compared with dialysis patients who remain on the waiting list (RR = 0.49, P < 0.03). The cumulative survival probabilities are superior in transplant recipients just beyond 1 year after transplantation. Therefore, CAD transplantation in black ESRD patients is associated with a high risk of mortality in the early period after transplantation. Beyond 1 year, black transplant recipients have a substantial survival advantage over corresponding dialysis patients on the waiting list.

Adolescent↗
PubMed1994

The standardized mortality ratio revisited: improvements, innovations, and limitations.

Evaluation of patient outcome for end-stage renal disease patients is an important component of the comparison of treatment protocols. End-stage renal disease mortality comparisons are facilitated by availability of the relevant data in administrative databases. The standardized mortality ratio has been widely used by the renal community for such evaluation. Accurate methods for evaluating adjusted mortality with the standardized mortality ratio are shown, even when there are few deaths expected. Both confidence interval and probability value calculations are shown. Classification errors for the identification of elevated mortality will occur even with accurate calculations. Criteria for choosing adjustment factors are reviewed. Only those factors that result in unavoidable variation in mortality should be adjusted for. Analysts using the US Renal Data System death rate tables for standardized mortality ratio computations must calculate mortality and patient follow-up with the same methods used by the US Renal Data System. In particular, patient follow-up must include postwithdrawal and posttransfer data but not data for the first 90 days of end-stage renal disease. Methods for comparison to a regional norm are presented.

Databases, Factual↗
PubMed1994

Socioeconomic status and end-stage renal disease in the United States.

The incidence of treated end-stage renal disease (ESRD) varies markedly according to age, race, sex, and geographic characteristics of the population. We asked whether some of the variability in the incidence of treated ESRD (t-ESRD) was associated with differences in socioeconomic status and whether socioeconomic status could explain some of the effects of race on t-ESRD incidence. Demographic characteristics of incident cases of t-ESRD from the years 1983 to 1988 were obtained from the U.S. Renal Data System, which registers most treated cases of ESRD. The average race specific, per capita income of the county of residence, as determined from the Bureau of Health Professions Area Resource File, was used as a surrogate measure of socioeconomic status. the incidence of t-ESRD for individuals < 60 years of age was modeled as a log-linear function of socioeconomic and demographic factors, including age, sex, the urban fraction of the county of residence, and the census geographic region. For both Whites and Blacks, the incidence of t-ESRD was higher for males and older age groups, as expected. In general, the incidence of t-ESRD was inversely related to income level. For Whites, the relative risk was 1.21 for income of $0 to 10.000, 1.11 for $10,000 to 15,000, 1.00 for $15,000 to 20,000 (reference), 0.89 for $20,000 to 25,000, and 0.77 for income > $25,000. For Blacks, the relative risk was 1.10 for income of $0 to 10,000, 1.20 for $10,000 to 15,000, 1.00 for $15,000 to 20,000 (reference), 0.81 for $20,000 to 25,000, and 0.69 for income > $25,000.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Continuous ambulatory peritoneal dialysis and hemodialysis: comparison of patient mortality with adjustment for comorbid conditions.

A historical prospective national sample of 1,725 diabetic and 2,411 non-diabetic Medicare end-stage renal disease (ESRD) patients incident from 1986 to 1987 was analyzed for the mortality of patients selected to receive continuous ambulatory peritoneal dialysis (CAPD) or hemodialysis (HD) with adjustment for patient characteristics, including the presence of comorbid conditions at onset of ESRD. Cox proportional hazards analyses were used to compare the mortality of CAPD and HD patients. Patients were followed from 30 days following onset of ESRD until two to four years post-onset. No statistically significant difference in relative mortality risk (RR) was found among non-diabetic patients selected for CAPD compared to HD (RR = 0.84 for CAPD versus HD, P = 0.25), while evidence of higher adjusted mortality for CAPD compared to HD was found among diabetic patients (RR = 1.26, P = 0.03). Mortality analyses adjusted for pre-treatment risk factors suggest that CAPD and HD provide incident non-diabetic ESRD patients with similar expected survival outcomes. Evidence that increased mortality was associated with CAPD among diabetic patients, particularly among elderly patients, suggests the need for further controlled studies of mortality among CAPD patients with diabetes.

Aged↗
PubMed1994

Potential pitfalls in interpreting maps of stabilized rates.

There have been many advances in the mapping of disease mortality and morbidity rates in recent years. An increasingly common approach is to calculate "stabilized" rates for individual geographic areas by incorporating information from the entire set of data. One such method, adopted by the Environmental Protection Agency [corrected] for its mortality maps, is described and applied to national end-stage renal disease data. Some possible difficulties in interpretation are noted, resulting from: (1) insufficient shrinkage, (2) highly skewed rate distributions, (3) different denominator distributions, and (4) variations in population density.

Aged↗
PubMed1994

The association of diabetic status, age, and race to withdrawal from dialysis.

Higher rates of withdrawal from dialysis have been shown among young diabetic patients. This study examined the hypothesis that diabetic status has a joint effect with age as the result of an age-related increase in co-morbid conditions among nondiabetic ESRD patients. Using data collected during the 1980s by the Michigan Kidney Registry, the experience of 4,753 white and 2,988 black Michigan dialysis patients (13,863 patient years) is analyzed. During follow-up, 364 white and 80 black patients withdrew from dialysis. By use of a Cox analysis, adjusted rates of withdrawal were shown to be higher among white than black patients (rate ratio (RR) = 3.34; P < 0.001), without significant differences by diabetic status. Rates increased with age (RR = 7.9 for 80+ versus 20 to 35 yr; P < 0.001), without significantly different patterns by race. Adjusted withdrawal rates among diabetics were 2.3 times that of nondiabetics overall (P < 0.001), with a statistically significant joint effect with age, the RR being highest among young patients. Among white patients, nondiabetics using continuous ambulatory peritoneal dialysis had a lower relative withdrawal rate than those using hemodialysis (RR = 0.73; P = 0.07), whereas diabetics using continuous ambulatory peritoneal dialysis showed slightly higher although statistically insignificant rates than their counterparts using hemodialysis (RR = 1.21; P = 0.50). Between 1980 and 1989, withdrawal rates for white patients aged 20 to 34 yr tended to decrease by 20% per year (P = 0.05), whereas they increased by 11% per year for patients aged 50 to 69 yr (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Causes of death in dialysis patients: racial and gender differences.

The risk of death in the dialysis population is high and has previously been shown to be accentuated in male (versus female) and white (versus black) subgroups. To better understand the difference in mortality among these subgroups, the causes of death between males and females as well as between whites and blacks adjusting for age, cause of ESRD (diabetic versus nondiabetic), dialysis modality, and time on dialysis (< 1 yr versus > 1 yr) were compared, with national data obtained from the U.S. Renal Data System. A total of 42,372 deaths occurring over 170,700 patient years at risk were analyzed. Males had a 22% higher risk of death than females (P < 0.001), attributable to a higher risk of death due to acute myocardial infarction (relative death rate ratio (RR) = 1.48; P = 0.001), all other cardiac causes (RR = 1.3; P = 0.001), and malignancy (RR = 1.59; P < 0.001). Whites had a 29% higher risk of death than blacks (P < 0.001), accounted for by an increased risk of death due to acute myocardial infarction (RR = 1.34), all other cardiac causes (RR = 1.30), withdrawal from dialysis (RR = 2.72) (all P < 0.001), and infection (RR = 1.09; P = 0.005). This analysis expands the knowledge and understanding of the excess mortality seen in male and white subgroups, which is a necessary step in designing strategies to reduce the high mortality in dialysis patients.

Black or African American↗
PubMed1994

A two-sample test for stochastic ordering with interval-censored data.

A new class of asymptotically nonparametric two-sample approximate tests for discrete interval-censored data is proposed. This class extends the family developed by Pepe and Fleming (1989, Biometrics 45, 497-507) for right-censored data and is based on an integrated weighted difference in survival function estimates. The tests are sensitive to the alternative of stochastic ordering and use Turnbull's (1976, Journal of the Royal Statistical Society, Series B 38, 290-295) estimator of the survival function. The choice of appropriate weight functions is investigated. Simulation results indicate that for interval-censored data the new procedure, with an appropriate weight function, can be more powerful than an omnibus likelihood ratio test and Mantel's (1967, Biometrics, 23, 65-78) test under a broad range of stochastically ordered alternatives. For small sample sizes (n = 50), with moderate censoring (47% and 70%), the size of the test is close to the nominal size.

Biometry↗
PubMed1993

Comparison of survival probabilities for dialysis patients vs cadaveric renal transplant recipients.

OBJECTIVE: To compare mortality risk among cadaveric renal transplant recipients vs transplant candidates on dialysis in the cyclosporine era. SETTING: Patient mortality risk was analyzed by treatment modality for a completed statewide patient population. PATIENTS: All Michigan residents younger than age 65 years who started endstage renal disease (ESRD) therapy between January 1, 1984, and December 31, 1989, were included. Patients were followed up from ESRD onset (n = 5020), to wait-listing for renal transplant (n = 1569), to receiving a cadaveric first transplant (n = 799), and to December 31, 1989. MAIN OUTCOME MEASURE: Mortality rates. RESULTS: Using a time-dependent variable based on the waiting time from date of wait-listing to transplantation and adjusting for age, sex, race, and primary cause of ESRD, the relative risk (RR) of dying was increased early after transplantation and then decreased to a beneficial long-term effect, given survival to 365 days after transplantation (RR, 0.36; P < .001). This lower long-term risk was most pronounced (RR, 0.25) among diabetic transplant recipients compared with diabetic wait-listed dialysis patients (P < .001) and not observed among patients with glomerulonephritis as cause of ESRD (P > .05). Overall, the estimated times from transplantation to equal mortality risk was 117 +/- 28 days and to equal cumulative mortality was 325 +/- 91 days. CONCLUSIONS: The overall mortality risk following renal transplantation was initially increased, but there was a long-term survival benefit compared with similar patients on dialysis. These analyses allow improved description of comparative mortality risks for dialysis and transplant patients and allow advising patients regarding comparative survival outcomes.

Cadaver↗
PubMed1993

The impact of comorbid and sociodemographic factors on access to renal transplantation.

OBJECTIVE: To assess the impact of sociodemographic factors and comorbid conditions on access to renal transplantation for adult US dialysis patients with end-stage renal disease (ESRD). DESIGN: Cohort analytic study. Data on comorbid conditions at onset of ESRD were abstracted from patients' medical records and matched to sociodemographic and ESRD data from the United States Renal Data System database. SETTING: United States Medicare dialysis population. PATIENTS: Random, national sample of ESRD patients starting dialysis in 1986 and 1987 (n = 4118). MAIN OUTCOME MEASURE: Time to first renal transplant (living or cadaver donor) since onset of ESRD regressed with two nested Cox proportional hazards models, first against sociodemographic factors alone, and then against sociodemographic factors and comorbid conditions. RESULTS: Cardiovascular diseases are most predictive of who received a transplant; patients with coronary heart disease, congestive heart failure, or left ventricular hypertrophy showed lower transplantation rates relative to patients without the disease (relative rate [RR] = 0.65 to 0.80, P < .05 each). Obese patients and patients with peripheral vascular disease also showed lower transplantation rates (RR = 0.65 to 0.75, P < .05 each). Previously reported sociodemographic effects of lower transplantation rates for older patients, women, nonwhite patients, and lower income patients were confirmed (P < .01). Sociodemographic effects remained essentially unchanged when adjusted for comorbid conditions. CONCLUSIONS: These findings indicate that sociodemographics have strong independent effects on access to transplantation that cannot be explained away as "surrogate" effects related to comorbid factors. Furthermore, the results suggest that lower mortality rates for transplant recipients relative to dialysis patients are due, in part, to a healthier case mix among patients receiving transplants.

Adult↗
PubMed1993

Median sensory distal amplitude and latency: comparisons between nonexposed managerial/professional employees and industrial workers.

To test for associations between occupation and median nerve dysfunction, measures of median motor and median and ulnar sensory amplitude and distal latency were compared among three populations: control subjects without occupational exposure to highly forceful or repetitive hand exertions (N = 105), industrial workers with hand/wrist symptoms (N = 103), and asymptomatic industrial workers (N = 137). Mean sensory amplitudes were significantly smaller (p < 0.05) and motor and sensory distal latencies were significantly longer (p < 0.001) in the industrial "asymptomatic hand" population compared to the control population. Prolongation of median relative to ulnar latency was significantly longer in the asymptomatic industrial population (p < 0.05). Results were most plausibly explained by differences in checklist identified ergonomic stressors. Median sensory amplitudes were significantly smaller (p < 0.01) and latencies longer (p < 0.05) for industrial workers with exposure to high grip forces compared to those without. Exposure misclassification may have reduced power to detect statistically significant differences between exposed and nonexposed population groups.

Adult↗
PubMed1993

An estimate of the size of the US predialysis population with renal insufficiency and anemia.

With the development of recombinant human erythropoietin, clinicians can now treat the anemia of chronic renal failure patients. Although most attention has focused on patients with end-stage renal disease, erythropoietin is also prescribed to anemic renal patients before the initiation of dialysis therapy. This study presents the first objective estimate of the size of the US population with predialysis renal insufficiency and the fraction of those patients who also have anemia. The study used population-based data from the second National Health Nutrition Examination Survey (NHANES II), conducted between 1976 and 1980. Participants underwent interviews, standardized physical examinations, and blood testing, including hematocrit and serum creatinine (N = 25,286 who were surveyed, 10,453 who underwent laboratory testing). Our estimates were based on the following methodology: (1) selecting predialysis renal insufficiency patients aged 12 to 74 years from the NHANES II survey, (2) adjusting for population changes between 1978 and 1988, (3) adding estimates for pediatric and geriatric populations, (4) projecting results to 1990, and (5) excluding nonanemic patients. The NHANES II survey included 44 patients with serum creatinine values greater than 2.0 mg/dL and less than 8.0 mg/dL. This yielded an estimate of 648,000 to 708,000 persons in 1990 with predialysis renal insufficiency. Data from both the NHANES II survey and the literature demonstrate that the percent of patients with anemia varies by serum creatinine level. All total, the study estimated that in 1990 there were between 68,000 and 75,000 individuals with predialysis renal insufficiency who also had anemia. However, several limitations of the methodology suggest that these values overestimate the true population numbers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗