Kidney Function

Background: Infection is an important cause of hospitalization and death in patients receiving dialysis. Few studies have examined the full range of infections experienced by dialysis patients. The purpose of this study is to examine types, rates, and risk factors for infection in older persons starting dialysis therapy.Study Design: Retrospective observational cohort study.Setting & Participants: The cohort was assembled from the US Renal Data System and included patients aged 65-100 years who initiated dialysis therapy between January 1, 2000, and December 31, 2002. Exclusions included prior kidney transplant, unknown dialysis modality, or death, loss to follow-up, or transplant during the first 90 days of dialysis therapy. Patients were followed up until death, transplant, or study end on December 31, 2004.Predictors: Baseline demographics, comorbid conditions, and serum albumin and hemoglobin levels.Outcomes & Measurements: Infection-related hospitalizations were ascertained using discharge International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. Hospitalization rates were calculated for each type of infection. The Wei-Lin-Weissfeld model was used to examine risk factors for up to 4 infection-related events.Results: 119,858 patients were included, 7,401 of whom were on peritoneal dialysis therapy. During a median follow-up of 1.9 years, infection-related diagnoses were observed in approximately 35% of all hospitalizations. Approximately 50% of patients had at least 1 infection-related hospitalization. Rates (per 100 person-years) of pulmonary, soft-tissue, and genitourinary infections ranged from 8.3-10.3 in patients on peritoneal dialysis therapy and 10.2-15.3 in patients on hemodialysis therapy. Risk factors for infection included older age, female sex, diabetes, heart failure, pulmonary disease, and low serum albumin level.Limitations: Use of ICD-9-CM codes, reliance on Medicare claims to capture hospitalizations, use of the Medical Evidence Form to ascertain comorbid conditions, and absence of data for dialysis access.Conclusion: Infection-related hospitalization is frequent in older patients on dialysis therapy. A broad range of infections, many unrelated to dialysis access, result in hospitalization in this population.

Background: Serum creatinine is a delayed marker of acute kidney injury (AKI). Our purpose is to discover and validate novel early urinary biomarkers of AKI after cardiac surgery.Study Design: Diagnostic test study.Setting & Participants: Children undergoing cardiopulmonary bypass surgery. The test set included 15 participants with AKI and 15 matched controls (median age, 1.5 year) of 45 participants without AKI. The validation set included 365 children (median age, 1.9 year).Index Tests: Biomarkers identified using proteomic profiling: α1-microglobulin, α1-acid glycoprotein, and albumin.Reference Test: AKI, defined as ≥50% increase in serum creatinine level from baseline within 3 days of surgery.Results: Proteomic profiling using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) showed 3 protein peaks that appeared consistently within 2 hours in children who developed AKI after cardiopulmonary bypass surgery. The proteins were identified as α1-microglobulin, α1-acid glycoprotein, and albumin. Using clinical assays, results were confirmed in a test set and validated in an independent prospective cohort. In the validation set, 135 (37%) developed AKI, in whom there was a progressive increase in urinary biomarker concentrations with severity of AKI. Areas under the curve for urinary α1-microglobulin, α1-acid glycoprotein, and albumin at 6 hours after cardiac surgery were 0.84 (95% CI, 0.79-0.89), 0.87 (95% CI, 0.83-0.91), and 0.76 (95% CI, 0.71-0.81), respectively. Participants with increasing quartiles of biomarkers showed increasing lengths of hospital stays and durations of AKI (P < 0.001).Limitations: Single-center study of children with normal kidney function at recruitment. The SELDI-TOF MS technique has limited sensitivity for the detection of proteins greater than the 20-kDa range.Conclusions: Urinary α1-microglobulin, α1-acid glycoprotein, and albumin represent early, accurate, inexpensive, and widely available biomarkers of AKI after cardiac surgery. They also offer prognostic information about the duration of AKI and length of hospitalization after cardiac surgery.

Background: Predictors for incident albuminuria are not well known in population-based cohorts. The purpose of this study is to identify predictors of incident albuminuria in an unselected middle-aged population.Study Design: Observational cohort study.Setting & Participants: Framingham Offspring Study participants who attended both the sixth (baseline; 1995-1998) and eighth (2005-2008) examination cycles.Predictors: Standard clinical predictors were used. Predictors of incident albuminuria were identified using stepwise logistic regression analysis with age and sex forced into the model.Outcomes & Measurements: Albuminuria was defined as urine albumin-creatinine ratio (UACR) ≥17 mg/g (men) or ≥25 mg/g (women). Individuals with albuminuria at baseline were excluded.Results: 1,916 participants were available for analysis (mean age, 56 years; 54% women). Albuminuria developed in 10.0% of participants (n = 192) during 9.5 years. Age (OR, 2.09; P < 0.001), baseline diabetes (OR, 1.93; P = 0.01), smoking (OR, 2.09; P < 0.001), and baseline log UACR (OR per 1-SD increase in log UACR, 1.56; P < 0.001) were associated with incident albuminuria in a stepwise model. An inverse relationship with female sex (OR, 0.53; P < 0.001) and high-density lipoprotein (HDL) cholesterol level (OR, 0.80; P = 0.007) also was observed. Results were similar when participants with baseline chronic kidney disease (n = 102), defined as estimated glomerular filtration rate <60 mL/min/1.73 m2, were excluded from the model. Age, male sex, low HDL cholesterol level, smoking, and log UACR continued to be associated with incident albuminuria when baseline diabetes (n = 107) was excluded. Age, male sex, and log UACR correlated with incident albuminuria after participants with baseline hypertension were excluded (n = 651).Limitations: Causality may not be inferred because of the observational nature of the study. One-third of participants did not return for follow-up, potentially attenuating the observed risks of albuminuria.Conclusions: The known cardiovascular risk factors of increasing age, male sex, diabetes, smoking, low HDL cholesterol level, and albuminuria within the reference range are correlates of incident albuminuria in the general population.