Kidney Function

Background: Myeloperoxidase (MPO) has been suggested to have a role in atherosclerosis through its strong oxidative capacity. We hypothesized that MPO level may predict clinical outcomes in patients with end-stage renal disease receiving long-term peritoneal dialysis (PD) therapy.Study Design: Prospective cohort study.Setting & Participants: 236 long-term PD patients were recruited from a single regional dialysis unit in Hong Kong between April 1999 and February 2001.Predictor: Level of plasma MPO, analyzed using a sandwich enzyme-linked immunosorbent assay.Outcome & Measurement: Mortality and fatal or nonfatal cardiovascular events at 3 years.Results: The distribution of MPO levels was skewed with a median of 31.8 μg/L (25th-75th percentiles, 24.4-42.7). There were 69 deaths and 81 cardiovascular events. Adjusting for traditional and nontraditional risk factors and C-reactive protein, cardiac troponin T, and N-terminal pro-brain natriuretic peptide levels, a doubling in plasma MPO level was associated independently with a 46% (95% CI, 1.02-2.08; P = 0.04) and 60% (95% CI, 1.17-2.18; P = 0.003) increase in risks of mortality and cardiovascular events, respectively. Log2MPO showed significant additional predictive value for mortality (P = 0.04) and cardiovascular events (P = 0.005) when included in Cox regression models consisting of clinical, demographic, dialysis, echocardiographic, and biochemical parameters, as well as C-reactive protein, cardiac troponin T, and N-terminal pro-brain natriuretic peptide levels.Limitations: MPO was measured at a single time and did not reflect changes over time.Conclusions: These data suggest that plasma MPO level has significant independent and additional prognostic value beyond the standard clinical, biochemical, and echocardiographic parameters and is useful for outcome stratification in long-term PD patients. MPO may be an important mediator of increased cardiovascular risk in patients with end-stage renal disease and warrants further investigation.

Background: To make informed decisions in dosing erythropoiesis-stimulating agents and intravenous iron therapy, clinicians must determine whether differences between current and previous test results for anemia and iron status markers reflect expected variation, a significant change, or an actual trend.Study Design: Prospective observational cohort study.Setting & Participants: 30 patients undergoing thrice-weekly in-center hemodialysis.Predictor: Within-patient biological variations in hemoglobin (Hb) level, hematocrit (Hct), reticulocyte Hb content, transferrin saturation (TSAT), and ferritin level were determined over 12 consecutive treatment days.Outcomes & Measurements: We separately measured same-sample analytical variation and within-patient biological variation (coefficient of variation), then calculated the number of sampling days needed to determine the true or homeostatic value for each analyte with 95% probability. We also evaluated whether results differed among the first, second, and third dialysis days of the week.Results: Biological variation differed by analyte. Hb level (4.0%), Hct (4.0%), and reticulocyte Hb content (4.8%) showed much lower variation than TSAT (38.2%) or ferritin level (15.1%). Analytical variation ranged from 2.0%-6.9% for all analytes. We found that one sample day would be sufficient to establish the true mean Hb level or Hct within a level of closeness ±20% and 95% probability. For the same levels of closeness and probability, one sample day would be needed for reticulocyte Hb content, 15 for TSAT, and 3 for ferritin level. No pairwise comparison for any of the 5 analytes yielded a significant difference between results obtained on the first, second, or third dialysis day of the week.Limitations: These findings may not apply to other patient populations.Conclusions: Low biological variation renders Hb level, Hct, and reticulocyte Hb content, but not TSAT and ferritin level, suitable for trend analysis using results from 2 successive samples. TSAT and ferritin test results, unlike reticulocyte Hb content, have limited value in evaluating changes in iron status within individual hemodialysis patients.

Specific reasons some people may elect not to start dialysis treatment (as they approach end stage renal failure) or choose to stop dialysis (even if they have done well on it in the past) are as follows:

• The presence of development of unrelated disease that causes unrelenting pain and suffering (such as widespread cancer), extreme physical disability (such as severe stroke or multiple amputations), or will cause a difficult death in a very short period of time.
• Such severe dementia that they are unable to relate to others or to understand their own illness and the necessary dialysis treatment (e.g., dementia from Alzheimer’s disease or as a result of multiple strokes)
• The occurrence of such severe brain injury that they are permanently unconscious (e.g., from an automobile accident or from a cardiac or pulmonary arrest).

Fortunately, these various conditions, with rare exception (such as a stroke in a dialysis patient with uncontrolled hypertension or blindness and amputations in a severe diabetic), are no more common in patients with end-stage renal disease. They do occur, however, just as they do in other people or in otherwise healthy individuals, and one should prepare for unexpected as well as for foreseeable problems.