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Biomedical subjects

Kevin C Abbott

Publications and source records attributed to Kevin C Abbott.

At least 19 recordsLinked to original sources
PubMed2006

Risk factors for Mycobacterium tuberculosis in US chronic dialysis patients.

BACKGROUND: End-stage renal disease is known to disrupt the cell-mediated immune response that is responsible for the killing of intracellular organisms such as Mycobacterium tuberculosis. Risk factors that contribute to the development of tuberculosis (TB) disease in the US dialysis population have not been studied on a large scale. METHODS: A retrospective cohort study of TB disease in 272,024 patients in the US Renal Data System initiated on dialysis therapy between 1 April 1995 and 31 December 1999 with Medicare or Medicaid as primary payer were analysed. A total of 21 risk factors were analysed. RESULTS: Among the US population studied, there is a 1.2 and 1.6% cumulative incidence of TB in patients undergoing either peritoneal or haemodialysis, respectively. Ten risk factors for TB that proved to be statistically significant included advanced age (P<0.001), unemployment (P<0.001), Medicaid insurance (P<0.001), reduced body mass index (P<0.001), decreased serum albumin (P<0.001), haemodialysis (P=0.019), both Asian (P=0.010) and Native American (P=0.020) race, ischaemic heart disease (P=0.032), smoking (P=0.010), illicit drug use (P=0.018) and anaemia (P=0.028). TB was independently associated with increased mortality, adjusted hazard ratio (AHR) 1.42 (95% CI 1.18-1.70, P<0.001). CONCLUSIONS: The prevalence of TB disease in the US dialysis population is low compared with worldwide rates; however, the disease is associated with increased mortality. Of the 10 significant risk factors identified, five are potentially modifiable.

Aged↗
PubMed2006

Agreement of immunosuppression regimens described in Medicare pharmacy claims with the Organ Procurement and Transplantation Network survey.

The Organ Procurement and Transplantation Network (OPTN) collects intermittent survey data on immunosuppressive medication use that are studied frequently as research measures. Pharmacy billing claims may provide an accurate measure of immunosuppression use over time. Herein is characterized the agreement of Medicare pharmacy claims for immunosuppressive medications with OPTN reports. Data were drawn from the United States Renal Data System. Participants received a kidney transplant in 2000 to 2001 and had an OPTN record and a Medicare pharmacy claim for an immunosuppressive drug at transplant discharge and 6 mo and 1 yr after transplantation. The concordance (kappa) of the OPTN and claims (+/-30 d of survey) for indicated medication use was compared, and sensitivity, specificity, and predictive values for claims were computed, assuming OPTN as a "gold standard." Clinical trial participation and regimen changes were examined as explanations for discordance. A total of 4357 eligible subjects were identified. Concordance over observation ranged from excellent for calcineurin inhibitors (kappa > 0.86) to generally very good for adjunctive agents (kappa = 0.49 to 0.75) to poor for corticosteroids (kappa <0.15). Claims demonstrated high positive predictive values (> or =97%) but low negative predictive values (< or =13%) for OPTN-reported corticosteroid use. Regimen changes (28 to 75%) but not clinical trial participation (< or =21%) were identified frequently among cases with discordant indications of nonsteroid medication use. Close agreement of Medicare billing claims and the OPTN for indicated use of nonsteroid immunosuppressive medications supports both as useful measures of drug exposure. Low detection rates of OPTN-indicated corticosteroid use within claims require further examination.

Data Collection↗
PubMed2006

Infection frequency and profile in different age groups of kidney transplant recipients.

BACKGROUND: Older transplant recipients have been shown to be at greater risk for infectious death than younger adults, but no study to date has looked at relative risk of infection and infection profile differences for children versus adults, which may be very different from one another. METHODS: Data from primary Medicare renal transplant recipients between 1991 and 1998 (n=64,751), as reported in the United States Renal Data System (USRDS), were analyzed for Medicare claims (both inpatient and outpatient) for infection and type of infection in the first year posttransplant. Cox regression was used to model adjusted hazard ratios (AHR) for infection. RESULTS: Total infections among renal transplant recipients increased significantly in more recent years. Patients transplanted in or after 1995 had a significantly higher adjusted risk for infection compared to those transplanted earlier (AHR 1.34, 95% CI=1.29-1.39). Older adults > or = 51 years of age had the highest percentage of experiencing infection, as compared to adults between 18-50 years and children < or = 17 years (P<0.001). Children were at highest risk of viral infection prior to 1995 but at lowest risk of viral infection after 1995, whereas elderly adults were at highest risk of bacterial infection throughout the study. Children experienced more claims for viral infections, whereas older transplant recipients experienced more claims for bacterial infections. CONCLUSIONS: The two extremes of transplant recipient age display very different risks for infection claim frequency and profile.

Adolescent↗
PubMed2006

Myeloma, Hodgkin disease, and lymphoid leukemia after renal transplantation: characteristics, risk factors and prognosis.

BACKGROUND: Hodgkin disease and myeloma were recently included in the classification of posttransplant lymphoproliferative disorder (PTLD). However, because their incidence is low, not much is known about their particular features. METHODS: The incidence, characteristics, risk, and prognostic factors of myeloma, Hodgkin disease, and lymphoid leukemia using the United States Renal Data System from 1991 to 2000 among 66,159 Medicare patients were analyzed. RESULTS: In all, 1,169 recipients developed a lymphoid disease: 823 (1.2%) non-Hodgkin's lymphomas (NHL), 160 (0.24%) myelomas, 60 (0.1%) Hodgkin lymphomas, and 126 (0.2%) lymphoid leukemias. Older age was associated with an increased risk of myeloma and leukemia. The incidence of hepatitis C virus infection was higher in recipients with myeloma (6.9 vs. 3.9%, P=0.05). Induction therapy was associated with a greater risk of myeloma and leukemia, but not Hodgkin disease. Azathioprine was associated with a lower risk of myeloma, and tacrolimus with a lower risk of Hodgkin disease. According to the type of malignancy, ten-year survival rates were significantly different: 42, 26, 55 and 39% respectively for NHL, myeloma, Hodgkin disease, and leukemia. CONCLUSION: These results support specific features and risk factors related to the occurrence of each type of lymphoid-proliferation and suggest for the first time a possible association between hepatitis C virus and myeloma in kidney transplant recipients.

Adult↗
PubMed2006

Acetylcysteine In Diabetes (AID): a randomized study of acetylcysteine for the prevention of contrast nephropathy in diabetics.

BACKGROUND: Patients with diabetes mellitus (DM) are at increased risk of contrast-associated nephropathy irrespective of their baseline creatinine (Cr). We tested the efficacy of N-acetylcysteine (NAC) relative to hydration in unselected patients (irrespective of baseline Cr) with DM. METHODS: We conducted a randomized open-label study comparing hydration alone (combined oral and rapid intravenous hydration, n = 69) to NAC plus hydration (similar hydration protocol plus NAC 600 mg BID x 4 doses, n = 68) in diabetic patients (mean age 65 +/- 10 years, 65% men) undergoing elective coronary angiography. The primary end point was the mean change in serum Cr measured up to 96 hours postangiography. RESULTS: Baseline Cr was 1.14 +/- 0.43 mg/dL (Cr > or = 1.3 mg/dL in 37 subjects). Baseline characteristics including blood urea nitrogen, Cr, and contrast volume were similar between the 2 groups. The mean Cr change in the NAC group was 0.14 +/- 0.47 versus 0.08 +/- 0.11 mg/dL in the hydration only group (P = NS). Contrast-associated nephropathy, defined as a > or = 0.5 mg/dL increase in Cr, was significantly more common in the NAC group, 9.2% versus 1.4%, P = .043. Similar results were found in the subgroup of participants with either an increased baseline serum Cr (> or = 1.3 mg/dL) or in those receiving high contrast volumes (> 100 mL). CONCLUSIONS: N-Acetylcysteine provides no benefit over an aggressive hydration protocol in patients with DM undergoing coronary angiography.

Acetylcysteine↗
PubMed2006

Epidemiology of dialysis patients and heart failure patients.

The epidemiology of maintenance dialysis patients and heart failure patients has striking similarities. Both groups have a high prevalence of comorbid conditions, a high hospitalization rate, a low self-reported quality of life, and an excessively high mortality risk, mostly because of cardiovascular causes. Observational studies in both dialysis and heart failure patients have indicated the lack of a significant association between the traditional cardiovascular risk factors and mortality, or the existence of a paradoxic or reverse association, in that obesity, hypercholesterolemia, and hypertension appear to confer survival advantages. The time discrepancy between the 2 sets of risk factors, that is, overnutrition (long-term killer) versus undernutrition (short-term killer) may explain the overwhelming role of malnutrition, inflammation, and cachexia in causing the reverse epidemiology, which may exist in more than 20 million Americans. We have reviewed the opposing views about the concept of reverse epidemiology in dialysis and heart failure patients, the recent Die Deutsche Diabetes Dialyze study findings, and the possible role of racial disparities. Contradictory findings on hyperhomocysteinemia in dialysis patients are reviewed in greater details as a possible example of publication bias. Additional findings related to intravenous iron and serum ferritin, calcium, and leptin levels in dialysis patients may enhance our understanding of the new paradigm. The association between obesity and increased death risk in kidney transplanted patients is reviewed as an example of the reversal of reverse epidemiology. Studying the epidemiology of dialysis patients as the archetypical population with such paradoxic associations may lead to the development of population-specific guidelines and treatment strategies beyond the current Framingham cardiovascular risk factor paradigm.

Dialysis↗
PubMed2006

Use of beta-blockers and aspirin after myocardial infarction by patient renal function in the Department of Defense health care system.

BACKGROUND: Whether the previously reported underutilization of standard-of-care medications in the management of patients with acute myocardial infarction (AMI) persists in more recent years or differs by ward of admission has not been reported. METHODS: We performed a retrospective cross-sectional study of patients hospitalized with a discharge diagnosis of incident AMI to a Department of Defense hospital (Walter Reed Army Medical Center, Washington, DC) from 2001 through 2004. Use of beta-blockers and aspirin at the time of discharge after AMI was assessed according to Modification of Diet in Renal Disease (MDRD) estimated glomerular filtration rate (eGFR) in milliliters per minute per 1.73 m2, stratified by admission to the coronary care unit (CCU) versus other wards. Adjusted odds ratios for discharge beta-blocker and aspirin therapy were calculated by using logistic regression. RESULTS: Among 431 patients, overall discharge use of beta-blockers was 86.8%, and aspirin, 86.8%, both significantly greater after CCU admission than admission to other wards (93%, aspirin use; 91.7%, beta-blocker use; P < 0.001 and P < 0.001). In logistic regression, CCU admission was the only independent factor associated with either beta-blocker or aspirin use; MDRD eGFR was not associated significantly with beta-blocker and aspirin use regardless of admission to the CCU or non-CCU. CONCLUSION: Future studies of disparities in use of standard-of-care medications after AMI according to renal function should account for the primary site of admission, particularly CCU versus others. In addition, legitimate contraindications to the use of beta-blockers and aspirin may be subtle, including appropriate end-of-life decisions.

Adrenergic beta-Antagonists↗
PubMed2005

New-onset gout after kidney transplantation: incidence, risk factors and implications.

BACKGROUND: Although cyclosporine use has been associated with an increased risk of new-onset gout after renal transplantation, the incidence and risk factors for new-onset gout have not been reported in the era of modern immunosuppression. METHODS: We conducted a retrospective cohort study of Medicare primary renal transplant patients reported in the United States Renal Data System (USRDS), using Medicare claims data to determine the incidence of new-onset gout. Cox regression analysis was used to calculate adjusted hazard ratios (AHR) for cyclosporine (including separate analysis of Neoral) compared directly with tacrolimus, for the risk of new-onset gout, adjusted for baseline demographic factors and posttransplant renal function. RESULTS: The cumulative incidence of new-onset gout was 7.6% at 3 years posttransplant. The following factors were independently associated with an increased risk of new-onset gout: use of Neoral (vs. tacrolimus, AHR 1.25, 95% CI 1.07-1.47) at discharge, recipient male sex (AHR 1.44, 95% CI 1.25-1.67), older age, higher body mass index, and more recent year of transplant. No other immunosuppressive medications were associated with new-onset gout. Diabetes was associated with a significantly lower risk of new-onset gout. The development of new-onset gout was independently associated with decreased patient survival (AHR 1.26, 95% CI 1.08-1.47) as well as death-censored graft survival. CONCLUSIONS: Cyclosporine is an independent risk factor for new-onset gout after transplantation. The incidence of new-onset gout appears to be increasing even while the use of cyclosporine is decreasing, and the development of new-onset gout was an independent predictor for death and graft loss in this population.

Body Mass Index↗
PubMed2005

Thrombotic microangiopathy in United States long-term dialysis patients.

BACKGROUND: The incidence, risk factors, recurrence rates and prognosis of thrombotic microangiopathy (TMA) among long-term dialysis patients in the United States have not been previously described in a national population. METHODS: 272 024 Medicare primary patients in the United States Renal Data System (USRDS) initiated on end-stage renal disease (ESRD) therapy between 1 April 1995 and 31 December 1999 with Medicare as primary payer were analysed in a retrospective cohort study of USRDS of TMA. Cox regression was used to calculate adjusted hazard ratios (AHR) for risk of TMA and risk of death after TMA. RESULTS: The incidence of TMA in the first year of dialysis was 0.5% overall. Among patients with renal failure due to haemolytic uraemic syndrome (HUS), the incidence of TMA was highest in the first year of dialysis (HUS, 11.3% first year, 4.5% per year thereafter), while among patients without HUS the incidence of TMA was much lower and more constant over time (0.3% per year). In Cox regression analysis, independent risk factors for TMA were renal failure due to HUS (adjusted hazard ratio (AHR) 179, 95% CI 95-338), paediatric age (<or=18 years vs older, AHR 2.59, 95% CI 1.48-4.55), female gender (AHR 1.99, 95% CI 1.43-2.78), and systemic lupus erythematosus (SLE, AHR 3.66, 95% CI 1.49-8.51). One-year survival after TMA was poor at 58% (AHR for mortality 2.04, 95% CI 1.23-3.38). CONCLUSIONS: TMA is an uncommon cause of hospitalization after dialysis, but does recur in patients with HUS at a substantial rate. Younger age and SLE were risk factors for new onset TMA, which was associated with poor survival. Vigilant monitoring of select patients with HUS-related ESRD and higher-risk patients with SLE is warranted in the dialysis population.

Age Distribution↗
PubMed2005

Maintenance immunosuppression use and the associated risk of avascular necrosis after kidney transplantation in the United States.

BACKGROUND: Avascular necrosis (AVN) after renal transplantation has been largely attributed to the use of corticosteroids. However, other risk factors such as microvascular thrombosis and hyperlipidemia have been well described and may be of increased importance in the era of early steroid cessation and avoidance. We hypothesized that maintenance immunosuppressive medications known to be associated with these risk factors for AVN would also be associated with a higher risk of AVN. METHODS: By using the U.S. Renal Data System database, we studied 27,772 primary patients on Medicare who received a solitary kidney transplant between January 1, 1996, and July 31, 2000. Cox proportional hazards regression models were used to calculate adjusted hazard ratios (AHRs) for patient- and transplant-related factors (including allograft rejection) with Medicare claims for AVN. The intensity and duration of corticosteroid use could not be assessed. RESULTS: Among patients who were prescribed sirolimus at discharge, 3.5% of patients who received the combination of sirolimus-cyclosporine A (CsA) demonstrated AVN, compared with 1.4% of patients who received the combination of sirolimus-tacrolimus (P=0.06 by chi). In Cox regression, CsA use (vs. tacrolimus) (AHR 1.36, 95% confidence interval, 1.09-1.71) was independently associated with an increased risk of AVN. Sirolimus use showed a trend toward significance (AHR 1.59, 95% confidence interval, 0.99-2.56), with no significant interaction with CsA. CONCLUSIONS: Compared with other maintenance immunosuppression, AVN was significantly more common after use of CsA prescribed at the time of discharge for renal transplantation. Whether this increased risk of AVN was directly attributable to hyperlipidemia, microvascular thrombosis, or differences in corticosteroid dosing could not be determined.

Adult↗
PubMed2005

Therapeutic plasma exchange as a nephrological procedure: a single-center experience.

In the United States, therapeutic plasma exchange (TPE) is both performed and requested by a wide range of services, often on an empiric basis (before a diagnosis is established). Whether empiric therapy is beneficial has not been established. Patients were identified from an electronic procedure log that included those patients who received plasmapheresis at Walter Reed Army Medical Center from 1996 to 2003. The clinical indications, referring service, and outcomes (including deaths) that occurred were tabulated. Between March 1997 and August 2003, 568 TPE treatments were performed in 54 patients. The majority of the diagnoses were either neurologic (48%) or hematologic (37%). Thirty-three patients (61%) received TPE for a Category I indication. Twelve cases were performed empirically (without an established diagnosis) at the request of the referring service, most (7) performed for presumed thrombotic thrombocytopenic purpura (TTP). Almost 80% of patients required central venous catheters for treatment. Twelve patients (22%) experienced a major complication including death, and six patients (11%) died. Of the patients who died, 5 (83%) were treated empirically versus one death (17%) among patients not treated empirically, P < 0.001 by Chi Square. Only one of the seven patients treated empirically for TTP died, however. In logistic regression analysis, empiric treatment was the only factor independently associated with death, adjusted odds ratio, 34.2, 95% CI, 3.4, 334.8, P = 0.003. The most common indication for TPE was neurological disease, which also accounted for the highest proportion of complications. With the exception of presumed TTP, performing TPE in the absence of a confirmed diagnosis was not beneficial.

Adult↗
PubMed2005

Differing manifestations of hepatitis C and tacrolimus on hospitalized diabetes mellitus occurring after kidney transplantation.

PURPOSE: Previous studies suggest the association of recipient hepatitis C seropositivity (HCV+) and use of tacrolimus (TAC) with post-transplant diabetes mellitus (PTDM) may differ by manifestations of type I or type II diabetes, but this has not been assessed in the era of current immunosuppression. METHODS: We performed a retrospective cohort study of 10,342 Medicare primary renal transplantation recipients without evidence of diabetes at the time of listing in the United States Renal Data System between January 1, 1998 and July 31, 2000, followed until December 31, 2000. Outcomes were hospitalizations for a primary diagnosis of diabetic ketoacidosis (DKA) or hyperglycemic hyperosmolar syndrome (HHS). Cox regression analysis was used to calculate adjusted hazard ratios (AHR) for time to DKA or HHS, stratified by diabetes status at the time of transplant. RESULTS: In Cox regression analysis, use of TAC at discharge was independently associated with shorter time to DKA (AHR, 1.88; 95% CI, 1.05-3.37, p=0.034) but not HHS. In contrast, recipient HCV+ was independently associated with shorter time to HHS (AHR, 3.90; 1.59-9.60, p=.003), but not DKA. There was no interaction between TAC and HCV+ for either outcome. CONCLUSION: These results confirm earlier findings that TAC and HCV+ may mediate the risk of PTDM through different mechanisms, even in the modern era.

Diabetes Mellitus↗
PubMed2005

De novo congestive heart failure after kidney transplantation: a common condition with poor prognostic implications.

BACKGROUND: We aim to describe the risk, predictors, and outcomes associated with de novo congestive heart failure (CHF) after kidney transplantation. METHODS: We used registry data from the US Renal Data System to retrospectively investigate de novo CHF in adult Medicare-insured transplant recipients and wait-listed candidates in 1995 to 2001. Heart failure was ascertained from inpatient and outpatient billing records, and participants were followed up until loss of Medicare or December 31, 2001. We used extended Cox hazards analysis to identify independent correlates of posttransplantation de novo CHF (adjusted hazard ratio [AHR], 95% confidence interval [CI]) and examine de novo CHF as a predictor of death and graft loss after transplantation. RESULTS: In 27,011 transplant recipients, cumulative incidences of de novo CHF were 10.2% (95% CI, 9.8 to 10.6) and 18.3% (95% CI, 17.8 to 18.9) at 12 and 36 months and decreased to less than the demographic-adjusted incidence on the waiting list beyond the early posttransplantation period. Risk factors for de novo CHF included older recipient age, female sex, unemployed status at transplantation, pretransplantation comorbidities (anemia, diabetes mellitus, myocardial infarction, angina, cardiac arrhythmia, and peripheral vascular disease), transplant from older donors, donor cardiovascular death, and delayed graft function. We identified pretransplantation obesity, smoking, and posttransplantation complications, including hypertension, anemia, new-onset diabetes, myocardial infarction, and graft failure, as potentially modifiable correlates of de novo CHF. In separate analyses, de novo CHF predicted death (AHR, 2.6; 95% CI, 2.4 to 2.9) and death-censored graft failure (AHR, 2.7; 95% CI, 2.4 to 3.0). CONCLUSION: Although associations may not reflect causality, identification of potentially mutable de novo CHF risk factors suggests targets for improving outcomes that should be evaluated prospectively.

Adolescent↗
PubMed2005

Survival advantages of obesity in dialysis patients.

In the general population, a high body mass index (BMI; in kg/m(2)) is associated with increased cardiovascular disease and all-cause mortality. However, the effect of overweight (BMI: 25-30) or obesity (BMI: >30) in patients with chronic kidney disease (CKD) undergoing maintenance hemodialysis (MHD) is paradoxically in the opposite direction; ie, a high BMI is associated with improved survival. Although this "reverse epidemiology" of obesity or dialysis-risk-paradox is relatively consistent in MHD patients, studies in CKD patients undergoing peritoneal dialysis have yielded mixed results. Growing confusion has developed among physicians, some of whom are no longer confident about whether to treat obesity in CKD patients. A similar reverse epidemiology of obesity has been described in geriatric populations and in patients with chronic heart failure (CHF). Possible causes of the reverse epidemiology of obesity include a more stable hemodynamic status, alterations in circulating cytokines, unique neurohormonal constellations, endotoxin-lipoprotein interaction, reverse causation, survival bias, time discrepancies among competitive risk factors, and malnutrition-inflammation complex syndrome. Reverse epidemiology may have significant clinical implications in the management of dialysis, CHF, and geriatric patients, ie, populations with extraordinarily high mortality. Exploring the causes and consequences of the reverse epidemiology of obesity in dialysis patients can enhance our insights into similar paradoxes observed for other conventional risk factors, such as blood pressure and serum cholesterol and homocysteine concentrations, and in other populations such as those with CHF, advanced age, cancer, or AIDS. Weight-gaining interventional studies in dialysis patients are urgently needed to ascertain whether they can improve survival and quality of life.

Body Mass Index↗