Type of vascular access and mortality in U.S. hemodialysis patients.

BACKGROUND: Vascular access (VA) complications account for 16 to 25% of hospital admissions. This study tested the hypothesis that the type of VA in use is correlated with overall mortality and cause-specific mortality. METHODS: Data were analyzed from the U.S. Renal Data System Dialysis Morbidity and Mortality Study Wave 1, a random sample of 5507 patients, prevalent on hemodialysis as of December 31, 1993. The relative mortality risk during a two-year observation was analyzed by Cox-regression methods with adjustments for demographic and comorbid conditions. Using similar methods, cause-specific analyses also were performed for death caused by infection and cardiac causes. RESULTS: In diabetic mellitus (DM) patients with end-stage renal disease, the associated relative mortality risk was higher for those with arteriovenous graft (AVG; RR = 1.41, P < 0.003) and central venous catheter (CVC; RR = 1.54, P < 0.002) as compared with arteriovenous fistula (AVF). In non-DM patients, those with CVC had a higher associated mortality (RR = 1.70, P < 0.001), as did to a lesser degree those with AVG (RR = 1.08, P = 0.35) when compared with AVF. Cause-specific analyses found higher infection-related deaths for CVC (RR = 2.30, P < 0.06) and AVG (RR = 2.47, P < 0.02) compared with AVF in DM; in non-DM, risk was higher also for CVC (RR = 1.83, P < 0.04) and AVG (RR = 1.27, P < 0.33). In contrast to our hypothesis that AV shunting increases cardiac risk, deaths caused by cardiac causes were higher in CVC than AVF for both DM (RR = 1.47, P < 0.05) and non-DM (RR = 1.34, P < 0.05) patients. CONCLUSION: This case-mix adjusted analysis suggests that CVC and AVG are correlated with increased mortality risk when compared with AVF, both overall and by major causes of death.

Mortality risk by hemodialyzer reuse practice and dialyzer membrane characteristics: results from the usrds dialysis morbidity and mortality study.

Hemodialyzer reuse is commonly practiced in the United States. Recent studies have raised concerns about the mortality risk associated with certain reuse practices. We evaluated adjusted mortality risk during 1- to 2-year follow-up in a representative sample of 12,791 chronic hemodialysis patients treated in 1,394 dialysis facilities from 1994 through 1995. Medical record abstraction provided data on reuse practice, use of bleach, dialyzer membrane, dialysis dose, and patient characteristics and comorbidity. Mortality risk was analyzed by bootstrapped Cox models by (1) no reuse versus reuse, (2) reuse agent, and (3) dialyzer membrane with and without the use of bleach, while considering dialysis and patient factors. The relative risk (RR) for mortality did not differ for patients in reuse versus no-reuse units (RR = 0.96; 95% confidence interval [CI], 0.86 to 1.08; P > 0.50), and similar results were found with different levels of adjustment and subgroups (RR = 1.01 to 1.05; 95% CI, lower bound > 0.90, upper bound < 1.19 each; each P > 0.40). The RR for peracetic acid mixture versus formalin varied significantly by membrane type and use of bleach during reprocessing, achieving borderline significance for synthetic membranes. Among synthetic membranes, mortality was greater with low-flux than high-flux membranes (RR = 1.24; 95% CI, 1.02 to 1.52; P = 0.04) and without than with bleach during reprocessing (RR = 1.24; 95% CI, 1.01 to 1.48; P = 0.04). Among all membranes, mortality was lowest for patients treated with high-flux synthetic membranes (RR = 0.82; 95% CI, 0.72 to 0.93; P = 0.002). Although mortality was not greater in reuse than no-reuse units overall, differences may exist in mortality risk by reuse agent. Use of high-flux synthetic membrane dialyzers was associated with lower mortality risk, particularly when exposed to bleach. Clearance of larger molecules may have a role.

Prescription of twice-weekly hemodialysis in the USA.

BACKGROUND/AIMS: The purpose of this study was to investigate the frequency and characteristics of two hemodialysis sessions/week, to identify factors which influence or predict this prescription, and to examine the outcomes of patients receiving hemodialysis two times/week as compared to the more common treatment of three times/week. METHODS: Data from a national sample of 15,067 adult hemodialysis patients were utilized to compare twice-weekly with thrice-weekly therapy by logistic regression. RESULTS: Patients treated less than one year were more likely to be treated twice-weekly (6.1%) than patients on dialysis for one year or more (2.7%) (AOR = 1.49, p = 0.002). Treatment schedules also varied significantly by geographic region. Factors predictive of twice-weekly hemodialysis (p < 0.05) were older age, Caucasian race, female gender, higher serum albumin, lower serum creatinine levels, and lower body mass index. A higher estimated renal function at the start of ESRD was also predictive of a twice-weekly schedule among incident patients (AOR = 1.05, p = 0.05). In addition, Cox-adjusted survival analysis indicated a lower mortality risk (RR = 0.76, p = 0. 02) for twice-weekly hemodialysis compared to thrice-weekly among prevalent patients. For incident patients, however, the results were not significant when adjusted for GFR at ESRD onset (RR = 0.85, p = 0.31). CONCLUSION: Geographic differences in prescribed treatment remained unexplained by measured characteristics. The survival advantage associated with twice-weekly hemodialysis is likely to be related to patient selection and greater residual renal function.

Survival advantage in Asian American end-stage renal disease patients.

UNLABELLED: Survival advantage in Asian American end-stage renal disease patients. BACKGROUND: An earlier study documented a lower mortality risk for end-stage renal disease (ESRD) patients in Japan compared with the United States. We compared the mortality of Caucasian (white) and Asian American dialysis patients in the United States to evaluate whether Asian ancestry was associated with lower mortality in the United States. METHODS: The study sample from the U.S. Renal Data System census of ESRD patients treated in the United States included 84,192 white or Asian patients starting dialysis during May 1995 to April 1997, of whom 18,435 died by April 30, 1997. Patient characteristics were described by race. Relative mortality risks (RRs) for Asian Americans relative to whites were analyzed by Cox proportional hazards regression models adjusting for characteristics and comorbidities. Population death rates were derived from vital statistics for the United States and Japan by age and sex. RESULTS: Adjusting for demographics, diabetes, comorbidities, and nutritional factors, the RR for Asian Americans was 0.75 (P = 0.0001). Race-specific background population death rates accounted for over half of the race-related mortality difference. For whites, mortality decreased as the body mass index (BMI) increased. For Asians, the relationship between BMI and survival was u-shaped. The ratio of Asian American/white dialysis death rates and the ratio of Asian American/white general population death rates both varied by age in a similar pattern. The population death rates of Asian American and Japanese were also similar. CONCLUSION: Among dialysis patients, Asian Americans had a markedly lower adjusted RR than whites. The effect of BMI on survival differed by race. Compared with the respective general population, dialysis patients had the same relative increase in death rates for both races. The difference in death rates between the United States and Japan does not appear to be primarily treatment related, but rather is related to background death rates.

Predialysis blood pressure and mortality risk in a national sample of maintenance hemodialysis patients.

The role of predialysis blood pressure (BP) as a risk factor for the high mortality in chronic hemodialysis (HD) patients has remained controversial. The objective of the current study was to further explore in a national random sample of 4,499 US hemodialysis patients any relationship of systolic or diastolic and predialysis or postdialysis BP with mortality, while considering subgroups of patients and controlling for other patient characteristics and comorbidities. The main finding of this study is the association of a low predialysis systolic BP with an elevated adjusted mortality risk (relative mortality risk [RR] = 1.86 for systolic BP < 110, P < 0.0001). No association with an elevated mortality risk could be observed for predialysis systolic hypertension (RR = 0.98 to 0.99, not significant [NS]), except for an elevated risk of cerebrovascular deaths. Postdialysis systolic BP was associated with an elevated mortality risk both for low and high BP levels as compared with midrange BP. Further evaluation of the elevated mortality risk associated with low predialysis systolic BP indicated similar patterns for both diabetic and nondiabetic subgroups and for patients with and without congestive heart failure (CHF) or coronary artery disease, although it was more pronounced among those with CHF. The level of predialysis fluid excess did not modify these results substantially. The findings from this historical prospective national study do not argue against the treatment of hypertension and suggest greater attention to postdialysis hypertension. The strikingly elevated mortality risk with low predialysis systolic BP suggests that low predialysis BP needs to be viewed with great concern and avoided where possible.

Noncompliance in hemodialysis: predictors and survival analysis.

Noncompliance with hemodialysis (HD), depending on the definition, occurs in 2% to more than 50% of patients. To better understand predictors and outcomes of noncompliance, we evaluated patient characteristics associated with noncompliance and the impact of noncompliance on survival. Using data from two USRDS special studies, we identified 6,251 patients who were on dialysis for more than 1 year for inclusion in this study. Noncompliance was defined in four ways: skipping one or more HD sessions in a month, shortening by 10 or more minutes one or more HD sessions in a month, an interdialytic weight gain (IWG) of more than 5.7% of dry weight, or a serum phosphate (PO4) of greater than 7.5 mg/dL. Sociodemographic predictors of noncompliance were identified using logistic regression. Survival analysis was done using Cox proportional hazards models with adjustments for sociodemographics, comorbid conditions, and dose of HD. Overall, 8.5% of patients skipped HD, 20% shortened HD (7% three or more times), 10% had more than a 5.7% IWG, and 22% had a PO4 greater than 7.5. There was a significant correlation among the measures of noncompliance. Blacks (adjusted odds ratio [AOR] = 2.10), patients aged 20 to 39 years (AOR = 1.62), and smokers (AOR = 1.34) were significantly more likely to skip HD than whites, patients aged 40 to 59 years, and nonsmokers, respectively (P < 0.01 for each). Similar results were seen for the other measures of noncompliance, except for PO4, in which blacks were significantly less likely to be noncompliant (NC) (AOR = 0.85, P < 0.05). Compared with compliant patients, those who skipped one or more HD sessions in a month had a 25% higher risk of death (P < 0.01). Those who had greater than a 5.7% IWG had a 35% higher risk of death (P < 0.001), whereas those with a PO4 > 7.5 had a 13% higher risk of death (P < 0.05). Overall, patients who shortened HD sessions did not have a higher risk of death, but those who shortened three or more in 1 month had a 20% higher risk of death (P < 0.05). Compliance with a medical regimen is a complex issue. Noncompliance in HD often, but not always, is associated with a higher risk of an adverse outcome. This is a US government work. There are no restrictions on its use.

Association of serum phosphorus and calcium x phosphate product with mortality risk in chronic hemodialysis patients: a national study.

Elevated serum phosphorus is a predictable accompaniment of end-stage renal disease (ESRD) in the absence of dietary phosphate restriction or supplemental phosphate binders. The consequences of hyperphosphatemia include the development and progression of secondary hyperparathyroidism and a predisposition to metastatic calcification when the product of serum calcium and phosphorus (Ca x PO4) is elevated. Both of these conditions may contribute to the substantial morbidity and mortality seen in patients with ESRD. We have analyzed the distribution of serum phosphorus in two large national, random, cross-sectional samples of hemodialysis patients who have been receiving dialysis for at least 1 year. Data were obtained from two special studies of the United States Renal Data System, the Case Mix Adequacy Study (1990) and the Dialysis Morbidity and Mortality Study Wave 1 (1993). The relative risk of death by serum phosphorus quintiles is described after adjusting for age at onset of ESRD, race, sex, smoking status, and the presence of diabetes, the acquired immunodeficiency syndrome, and/or neoplasm. Logistic regression analysis is then used to describe the demographic, comorbid, and laboratory parameters associated with high serum phosphorus. Serum phosphorus was similar in these two study populations and averaged 6.2 mg/dL. Ten percent of patients had levels greater than 9 mg/dL and at least 30% of each group had serum phosphorus levels greater than 7 mg/dL. The adjusted relative risk of death by serum phosphorus level was not uniform across all quintiles, being constant below a level of 6.5 mg/dL and increasing significantly above this level. The relative risk of death for those with a serum phosphorus greater than 6.5 mg/dL was 1.27 relative to those with a serum phosphorus of 2.4 to 6.5 mg/dL. This increased risk was not diminished by statistical adjustment for coexisting medical conditions, delivered dose of dialysis, nutritional parameters, or markers of noncompliance. Evaluation of predictors of serum phosphorus greater than 6.5 mg/dL revealed in multivariate analysis that younger age at onset of ESRD, female sex, white race, diabetes, active smoking, and higher serum creatinine levels were all significant predictors. Analysis of serum calcium revealed no correlation with relative risk of death. The Ca x PO4 product, however, showed a mortality risk trend similar to that seen with serum phosphorus alone. Those in the highest quintile of the Ca x PO4 product (>72 mg2/dL2) had a relative mortality risk of 1.34 relative to those with products of 42 to 52 mg2/dL2. The relative mortality risk by log parathyroid hormone (PTH) level was elevated for patients with higher levels, but the mortality risk associated with hyperphosphatemia was independent of PTH. For hemodialysis patients who have been receiving dialysis for at least 1 year, we conclude that a large percentage have a serum phosphorus level above 6.5 mg/dL and that this places them at increased risk of death. This increased risk is independent of PTH. The mechanism(s) responsible for death is unknown, but may be related to an abnormally high Ca x PO4 product. Although mechanisms are not clearly established, this study supports the need for vigorous control of hyperphosphatemia to improve patient survival.

A critical examination of trends in outcomes over the last decade.

The past decade has seen substantial improvements in end-stage renal disease (ESRD) outcomes, especially mortality, in the United States. Incidence rates for treated ESRD have doubled for most age groups, probably because of improved survival among high-risk populations, such as patients with diabetes and hypertension. The ESRD patient population is becoming older and has a greater incidence of diabetes because of changes in the types of patients starting treatment. The number of patients added to the waiting list each year for transplants has increased dramatically, whereas the number of transplantations performed annually has remained relatively constant. Although transplantation is consequently less available than before, transplant survival, both of the patient and the graft, has improved dramatically. Length of stay for hospitalizations has decreased. Both dialysis mortality and all ESRD mortality have decreased. It is important to monitor such statistics to try and modify adverse trends in outcomes for patients with ESRD. The ability to monitor patient outcomes through national databases has improved greatly during the last decade. Large-scale population-based studies of practices and outcomes for patients with ESRD offer a potent addition to the previously available arsenal of research tools, which was previously dominated by studies from single or few institutions and more expensive randomized clinical trials.

An analysis of risk factors for withdrawal from dialysis before death.

Withdrawal from dialysis has been a significant cause of mortality among dialysis patients, accounting for 6 to 22% of deaths. Since 1990, a new death notification form has allowed more detailed analyses of withdrawal from dialysis separate from causes of death. Using the U.S. Renal Data System data base, this study examined 116,829 deaths in adult patients from 1990 to 1995. Adjusted odds ratios were calculated for the risk of withdrawal using logistic regression. Adjustments included age at death, ethnicity, gender, cause of death, primary cause of end-stage renal disease, time on dialysis, and dialysis modality. In addition, odds ratios of withdrawal were calculated for deaths in patients who started dialysis after age 65. Death was preceded by withdrawal significantly more frequently in women than in men, more than twice as frequently in Caucasians than in African-Americans or Asians, and more frequently in older than in younger age groups. Patients who died of chronic diseases (e.g., dementia, malignancy) were much more likely to withdraw before death, whereas patients who died from more acute causes (e.g., coronary artery disease) were less likely to withdraw before death. It is concluded that patients who are Caucasian, female, older, or die of chronic or progressive diseases are more likely to withdraw from dialysis before death. The ethnic and gender differences in withdrawal do not appear to have a medical explanation from this analysis. Further research along sociologic lines is needed to better explain the differences in withdrawal from chronic dialysis.

Lod score curves for phase-unknown matings.

For a phase-unknown nuclear family, we show that the likelihood and lod score are unimodal, and we describe conditions under which the maximum occurs at recombination fraction theta = 0, theta = 1/2, and 0 < theta < 1/2. These simply stated necessary and sufficient conditions seem to have escaped the notice of previous statistical geneticists.

Recombination fraction estimate of zero in the presence of apparent recombinants: effects of incomplete penetrance and sporadic cases.

For a fully penetrant trait, apparent recombinants between the trait and marker loci result in an estimate of the recombination fraction theta > 0. Given allowance for reduced penetrance and/or sporadic cases, this no longer need be true. In this short communication, we describe conditions under which theta is estimated to be zero despite the presence of apparent recombinants. We demonstrate that even if a large proportion of unaffected individuals are apparent recombinants and the penetrance is moderately high, the lod score may be maximized at theta = 0. Despite maximization at theta = 0, presence of apparent recombinants reduces the maximum lod score in comparison to its value if no apparent recombinants are present.