Environmental exposure to multiple metals is common. A number of metals cause nephrotoxicity with acute and/or chronic exposure. However, few epidemiologic studies have examined the impact of metal co-exposure on kidney function. Therefore, we evaluated associations of antimony and thallium with kidney outcomes and assessed the impact of cadmium exposure on those associations in lead workers.
Multiple linear regression was used to examine associations between ln-urine thallium, antimony and cadmium levels with serum creatinine- and cystatin-C-based glomerular filtration measures, and ln-urine N-acetyl-β-D-glucosaminidase (NAG).
In 684 participants, median urine thallium and antimony were 0.39 and 0.36 μg/g creatinine, respectively. After adjustment for lead dose, urine creatinine, and kidney risk factors, higher ln-urine thallium was associated with higher serum creatinine- and cystatin-C-based estimates of glomerular filtration rate (eGFR); associations remained significant after adjustment for antimony and cadmium (regression coefficient for serum creatinine-based eGFR = 5.2 mL/min/1.73 m2; 95% confidence interval = 2.4, 8.0). Antimony associations with kidney outcomes were attenuated by thallium and cadmium adjustment; thallium and antimony associations with NAG were attenuated by cadmium.
Urine thallium levels were significantly associated with both serum creatinine- and cystatin-C-based glomerular filtration measures in a direction opposite that expected with nephrotoxicity. Given similarities to associations recently observed with cadmium, these results suggest that interpretation of urine metal values, at exposure levels currently present in the environment, may be more complex than previously appreciated. These results also support multiple metal analysis approaches to decrease the potential for inaccurate risk conclusions.
antimony; cadmium; creatinine; kidney function; thallium
Glomerular filtration rate (GFR) is considered the best measure of kidney function, but repeated assessment is not feasible in most research studies.
Cross-sectional study of 1,433 participants from the Chronic Renal Insufficiency Cohort (CRIC) Study (i.e., the GFR subcohort) to derive an internal GFR estimating equation using a split sample approach.
Setting & Participants
Adults from 7 US metropolitan areas with mild to moderate chronic kidney disease; 48% had diabetes and 37% were black.
CRIC GFR estimating equation
Reference Test or Outcome
Urinary 125I-iothalamate clearance testing (measured GFR)
Laboratory measures including serum creatinine and cystatin C, and anthropometrics
In the validation dataset, the model that included serum creatinine, serum cystatin C, age, gender, and race was the most parsimonious and similarly predictive of mGFR compared to a model additionally including bioelectrical impedance analysis phase angle, CRIC clinical center, and 24-hour urinary creatinine excretion. Specifically, the root mean square errors for the separate model were 0.207 vs. 0.202, respectively. The performance of the CRIC GFR estimating equation was most accurate among the subgroups of younger participants, men, non-blacks, non-Hispanics, those without diabetes, those with body mass index <30 kg/m2, those with higher 24-hour urine creatinine excretion, those with lower levels of high-sensitivity C-reactive protein, and those with higher mGFR.
Urinary clearance of 125I-iothalamate is an imperfect measure of true GFR; cystatin C is not standardized to certified reference material; lack of external validation; small sample sizes limit analyses of subgroup-specific predictors.
The CRIC GFR estimating equation predicts measured GFR accurately in the CRIC cohort using serum creatinine and cystatin C, age, gender, and race. Its performance was best among younger and healthier participants.
glomerular filtration rate (GFR); kidney function; GFR estimation
Data are scant regarding access to health care in patients with chronic kidney disease (CKD). We performed descriptive analyses using data from the National Kidney Foundation’s Kidney Early Evaluation Program (KEEP), a nationwide health screening program for adults at high risk of CKD.
From 2000–2010, a total of 122,502 adults without end-stage renal disease completed KEEP screenings; 27,927 (22.8%) met criteria for CKD (10,082, stages 1–2; 16,684, stage 3; and 1,161, stages 4–5). CKD awareness, self-rated health status, frequency of physician visits, difficulty obtaining medical care, types of caregivers, insurance status, and medication coverage and estimated costs were assessed.
Participants with CKD were more likely to report fair/poor health status than those without CKD. Health care utilization increased at later CKD stages; ~95% of participants at stages 3–5 had visited a physician during the preceding year compared with 83.7% of participants without CKD. More Hispanic and African American than white participants at all CKD stages reported not having a physician. Approximately 40% of participants younger than 65 years reported fair/poor health status at stages 4–5 compared with ~30% who were 65 years and older. Younger participants at all stages were more likely to report extreme or somewhat/moderate difficulty obtaining medical care. Comorbid conditions (diabetes, hypertension, and prior cardiovascular events) were associated with increased utilization of care. Utilization of nephrology care was poor at all CKD stages; <6% of participants at stage 3 and <30% at stages 4–5 reported ever seeing a nephrologist.
Lack of health insurance and perceived difficulty obtaining medical care with lower health care utilization, both of which are consistent with inadequate access to health care, are more likely for KEEP participants who are younger than 65 years, nonwhite, and without previously diagnosed comorbid conditions. Nephrology care is infrequent in elderly participants with advanced CKD who are nonwhite, have comorbid disease, and have high-risk states for cardiovascular disease.
Chronic kidney disease; health care access; health insurance; medication payment; socioeconomic status; educational status
Cadmium is a well known nephrotoxicant; chronic exposure increases risk for chronic kidney disease. Recently, however, associations between urine cadmium and higher creatinine-based estimated glomerular filtration rate (eGFR) have been reported. Analyses utilizing alternate biomarkers of kidney function allow evaluation of potential mechanisms for these observations. We compared associations of urine cadmium with kidney function measures based on serum cystatin C to those with serum creatinine in 712 lead workers. Mean (standard deviation) molybdenum-corrected urine cadmium, Modification of Diet in Renal Disease (MDRD) eGFR and multi-variable cystatin C eGFR were 1.02 (0.65) μg/g creatinine, and 97.4 (19.2) and 112.0 (17.7) mL/min/1.73 m2, respectively. The eGFR measures were moderately correlated (rs = 0.5; p less than 0.001). After adjustment, ln(urine cadmium) was not associated with serum cystatin-C-based measures. However, higher ln(urine cadmium) was associated with higher creatinine-based eGFRs including the MDRD and an equation incorporating serum cystatin C and creatinine (beta-coefficient = 4.1 ml/min/1.73 m2; 95% confidence interval =1.6, 6.6). Urine creatinine was associated with serum creatinine-based but not cystatin-C-based eGFRs. These results support a biomarker-specific, rather than a kidney function, effect underlying the associations observed between higher urine cadmium and creatinine-based kidney function measures. Given the routine use of serum and urine creatinine in kidney and biomarker research, additional research to elucidate the mechanism(s) for these associations is essential.
cadmium; cystatin C; kidney function; serum creatinine; urine creatinine
Residual kidney function (RKF) is associated with improved survival in peritoneal dialysis patients but its role in hemodialysis patients is less well known. Urine output may provide an estimate of RKF. The aim of our study was to determine the association of urine output with mortality, quality of life (QOL) and inflammation in incident hemodialysis patients.
Nationally representative prospective cohort study
Setting & Participants
734 incident hemodialysis participants treated in 81 clinics; enrollment, 1995-1998, follow-up until December 2004.
Urine output, defined as producing at least 250 mL (1 cup) of urine daily, ascertained by questionnaires at baseline and year 1.
Outcomes & Measurements
Primary outcomes were all-cause and cardiovascular (CVD) mortality, analyzed using Cox regression adjusted for demographic, clinical and treatment characteristics. Secondary outcomes were QOL, inflammation (CRP and interleukin-6 [IL-6] levels) and erythropoietin (EPO) requirements.
617/734 (84%) participants reported urine output at baseline and 163/579 (28%) at year 1. Baseline urine output was not associated with survival. Urine output at year 1, indicating preserved RKF, was independently associated with lower all-cause mortality (Hazard Ratio [HR], 0.70; 95% Confidence Interval [CI], 0.52-0.93; p=0.02) and a trend towards lower CVD mortality (HR, 0.69; 95% CI, 0.45-1.05; p=0.09). Participants with urine output at baseline reported better QOL and had lower CRP (p=0.02) and IL-6 (p=0.03) levels. Importantly, EPO dose was 12,000 units/week lower in those with urine output at year 1 compared with those without (p=0.001).
Urine volume was measured in only a subset of patients (42%) but was in agreement with self-report (p<0.001).
RKF in hemodialysis patients is associated with better survival and QOL, lower inflammation and significantly less EPO use. RKF should be monitored routinely in hemodialysis patients. Development of methods to assess and preserve RKF is important and may improve dialysis care.
End-stage Renal Disease; Hemodialysis; Residual Kidney Function; Mortality; Quality of Life; Inflammation
Low-level cadmium exposure, e.g., urinary cadmium < 2.0 μg/g creatinine, is widespread; recent data suggest nephrotoxicity even at these lower levels. Few studies have examined the impact of low-level cadmium exposure in workers who are occupationally exposed to other nephrotoxicants such as lead.
We evaluated associations of urine cadmium, a measure of cumulative dose, with four glomerular filtration measures and N-acetyl-β-D-glucosaminidase (NAG) in lead workers. Recent and cumulative lead dose was assessed via blood and tibia lead, respectively.
In 712 lead workers, mean (SD) blood and tibia lead, urine cadmium, and estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease equation were 23.1 (14.1) μg/dl, 26.6 (28.9) μg Pb/g bone mineral, 1.15 (0.66) μg/g creatinine, and 97.4 (19.2) ml/min/1.73m2, respectively. After adjustment for age, sex, body mass index, urine creatinine, smoking, alcohol, education, annual income, diastolic blood pressure, current or former lead worker job status, new or returning study participant, and blood and tibia lead, higher ln-urine cadmium was associated with higher calculated creatinine clearance, eGFR (β = 8.7 ml/min/1.73 m2; 95% CI = 5.4, 12.1) and ln-NAG but lower serum creatinine.
Potential explanations for these results include a normal physiologic response in which urine cadmium levels reflect renal filtration; the impact of adjustment for urine dilution with creatinine in models of kidney outcomes; and cadmium-related hyperfiltration.
cadmium; kidney function; lead exposure; urine creatinine
Inpatient initiation of chronic hemodialysis is considered undesirable because of cost and possible harms of hospitalization. We examined the patient characteristics and outcomes associated with inpatient initiation.
In a prospective cohort study of incident dialysis patients, the independent association of inpatient hemodialysis initiation with patient outcomes was assessed in multivariable analyses with adjustment for patient characteristics and propensity for inpatient initiation.
A total of 410 of 652 (63%) hemodialysis patients began as inpatients; uremia and volume overload were the most commonly documented reasons. Compared to outpatients, inpatients were more likely to be unmarried, report less social support, have multiple comorbidities and be referred to a nephrologist 4 months or less prior to initiation. Inpatient initiation was protective for subsequent all-cause hospitalization (incidence rate ratio (IRR) = 0.92, confidence interval (CI) 0.89–0.94); this was most pronounced among those who had the highest propensity for inpatient initiation (IRR = 0.66, CI 0.56–0.78), including those referred late to nephrology. Similar results were found for infectious hospitalization. Mortality [hazard ratio = 1.03, CI 0.82–1.30] and cardiovascular events were not significantly different for inpatients versus outpatients.
Inpatient hemodialysis initiation has a protective association with hospitalization among those patients referred late to nephrology, with multiple comorbidities and/or little social support.
End-stage renal disease; Hospitalization; Late referral; Mortality; Social support
Primary care providers' suboptimal recognition of the severity of chronic kidney disease (CKD) may contribute to untimely referrals of patients with CKD to subspecialty care. It is unknown whether U.S. primary care physicians' use of estimated glomerular filtration rate (eGFR) rather than serum creatinine to estimate CKD severity could improve the timeliness of their subspecialty referral decisions.
We conducted a cross-sectional study of 154 United States primary care physicians to assess the effect of use of eGFR (versus creatinine) on the timing of their subspecialty referrals. Primary care physicians completed a questionnaire featuring questions regarding a hypothetical White or African American patient with progressing CKD. We asked primary care physicians to identify the serum creatinine and eGFR levels at which they would recommend patients like the hypothetical patient be referred for subspecialty evaluation. We assessed significant improvement in the timing [from eGFR < 30 to ≥ 30 mL/min/1.73m2) of their recommended referrals based on their use of creatinine versus eGFR.
Primary care physicians recommended subspecialty referrals later (CKD more advanced) when using creatinine versus eGFR to assess kidney function [median eGFR 32 versus 55 mL/min/1.73m2, p < 0.001]. Forty percent of primary care physicians significantly improved the timing of their referrals when basing their recommendations on eGFR. Improved timing occurred more frequently among primary care physicians practicing in academic (versus non-academic) practices or presented with White (versus African American) hypothetical patients [adjusted percentage(95% CI): 70% (45-87) versus 37% (reference) and 57% (39-73) versus 25% (reference), respectively, both p ≤ 0.01).
Primary care physicians recommended subspecialty referrals earlier when using eGFR (versus creatinine) to assess kidney function. Enhanced use of eGFR by primary care physicians' could lead to more timely subspecialty care and improved clinical outcomes for patients with CKD.
Stroke is the third most common cause of cardiovascular disease death in patients on dialysis; however, characteristics of cerebrovascular disease, including clinical subtypes and subsequent consequences, have not been well described.
Prospective national cohort study, the Choices for Healthy Outcomes in Caring for ESRD (CHOICE) study.
Settings & Participants
1,041 incident dialysis patients treated in 81 clinics, enrolled from 10/95–7/98, followed until 12/31/2004.
Time from dialysis initiation.
Outcomes & Measurements
Cerebrovascular disease events were defined as non-fatal (hospitalized stroke, carotid endarterectomy) and fatal (stroke death) events after dialysis initiation. Stroke subtypes were classified using standardized criteria from the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) system. Incidence of cerebrovascular event subtypes were analyzed using time-to-event analyses accounting for competing risk of death. Clinical outcomes after stroke were abstracted from medical records.
A total of 165 participants experienced a cerebrovascular event with an overall incidence of 4.9 per 100 person-years. Ischemic stroke was the most common (76% of all 200 events) with cardioembolism subtype accounting for 28% of the 95 abstracted ischemic events. The median time from onset of symptoms to first stroke evaluation was 8.5 hours (25th and 75th percentiles 1, 42 hours), with only 56% of patients successfully escaping death, nursing home, or a skilled nursing facility.
Relatively small sample size limits power to determine risk factors.
Cerebrovascular disease is common in dialysis patients, is identified late, and carries a significant risk of morbidity and mortality. Stroke etiologic subtypes on dialysis are multifactorial, suggesting risk factors may change the longer one has ESRD. Further studies are needed to address the poor prognosis through prevention, early identification, and treatment.
Cerebrovascular disease; Stroke; Dialysis; Prognosis; Epidemiology
Clinical practice guidelines were established to improve the diagnosis and management of chronic kidney disease (CKD), but the extent, determinants, and cost implications of guideline adherence and variation in adherence have not been evaluated.
Settings & Participants
Nationally representative sample of 301 U.S. primary care physicians and nephrologists
Provider and patient characteristics
Outcomes & Measurements
Guideline adherence was assessed as present if physicians recommended at least 5 of 6 clinical tests prescribed by the National Kidney Foundation-Kidney Disease Outcomes and Quality Initiative (KDOQI) guidelines for a hypothetical patient with newly identified CKD. We also assessed patterns and cost of additional non-recommended tests for the initial clinical evaluation of CKD.
Most of the 86 family medicine, 89 internal medicine, and 126 nephrology physicians practiced greater than 10 years (54%), were in non-academic practices (76%), spent greater than 80% of their time performing clinical duties (78%), and correctly estimated kidney function (73%). Overall, 35% of participants were guideline adherent. Compared to nephrologists, internal medicine and family physicians had lower odds of adherence for all recommended testing (Odds Ratio (OR) [95% CI]:0.6[0.3–1.1] and 0.3[0.1–0.6], respectively). Participants practicing greater than 10 years had lower odds of ordering all recommended testing compared to participants practicing less than 10 years (OR[95% CI]: 0.5[0.3–0.9]). Eighty-five percent of participants recommended additional tests, which resulted in a 23% increased total per patient cost of the clinical evaluation.
Recommendations for a hypothetical case scenario may differ from that of actual patients.
Adherence to the recommended clinical testing for the diagnosis and management of CKD was poor and additional testing was associated with substantially increased cost of the clinical evaluation. Improved clarity, dissemination, and uptake of existing guidelines are needed to improve quality and decrease costs of care for patients with CKD.
chronic kidney disease; primary care providers; guidelines; KDOQI; cost
Increasing evidence supports a role for cell-mediated immunity in the pathogenesis of cardiovascular disease. Single nucleotide polymorphisms (SNPs) in JAK3, STAT4, and STAT6 of the Janus kinase–signal transducer and activator of transcription (Jak-Stat) signal transduction pathway were examined for association with time to new cardiovascular events in incident dialysis patients from the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease study.
Prospective cohort study.
Setting & Participants
764 White (n=518) and Black (n=246) participants from 79 dialysis centers.
SNPs in JAK3, STAT4, and STAT6 selectedusing a pairwise approach to identify a maximally informative set of tag SNPs for populations of European and African descent.
Outcomes and Measurements
Cox proportional hazards models were used to estimate unadjusted and multivariable adjusted hazard ratios (HR) for incident cardiovascular disease events after dialysis initiation associated with each race-specific SNP.
Two European tag SNPs (rs3212780 and rs3213409) were associated with new cardiovascular disease events in White patients in JAK3, with unadjusted HR 1.92 (p<0.001) and 1.82 (p=0.07), respectively. One dual-tag SNP (rs3212752) in JAK3 was associated with new cardiovascular events in White patients with unadjusted HR 2.09 (p<0.001) and in Black patients with HR 2.07 (p=0.007). SNP rs3213409 codes for a valine to isoleucine change at amino acid 722, a potentially functional mutation. SNPs in STAT4 and STAT6 were not associated with cardiovascular events after the initiation of dialysis.
This study does not provide direct evidence for the mechanism of increased risk. Replication in independent cohorts is necessary.
Genetic polymorphisms in the Jak-Stat signaling pathway are associated with an increased risk of new cardiovascular events in incident dialysis patients.
dialysis; cardiovascular diseases; inflammation; genes
Existing research on the lead dose range associated with nephrotoxicity in the occupational setting is inconsistent and primarily cross-sectional in design.
To determine if lead dose predicts change in renal function in a large population of current and former lead workers.
Three evaluations were performed between 1997 and 2001. Lead dose was assessed with blood and tibia lead. Renal outcomes included blood urea nitrogen, serum creatinine, and calculated creatinine clearance. We used generalized estimating equations to model change in renal function between each evaluation in relation to tibia lead at the beginning of each follow-up period and concurrent change in blood lead, while adjusting for baseline lead dose and other covariates.
At baseline, mean (SD) age and duration of occupational lead exposure were 42.0 (9.3) and 8.8 (6.3) years, respectively, in 537 current and former lead workers followed over a mean of 2.1 years. Mean (SD) blood and tibia lead were 31.3 (14.4) μg/dL and 35.0 (37.8) μg/g bone mineral, respectively. Women (25.9%) were older and more likely to be former lead workers than men. In males, serum creatinine decreased and calculated creatinine clearance increased over the course of the study. Mean blood lead was not significantly different between evaluations 1 and 3 in either sex, however, tibia lead decreased in women. Blood and tibia lead were significantly associated with change in renal function. In males, serum creatinine decreases and calculated creatinine clearance increases were greatest in participants whose blood lead declined.
Both acute and chronic occupational lead dose measures were associated with change in renal function measures prospectively.
blood lead; renal function; lead exposure; longitudinal; tibia lead
This Practice Point commentary discusses the findings of Lucas et al.’s longitudinal cohort study of chronic kidney disease (CKD) in African American and white individuals with HIV. The study found that—compared with whites—African Americans had a slightly increased risk of incident CKD, but markedly increased rates of estimated glomerular filtration rate decline and progression to end-stage renal disease. This commentary details the clinical implications and limitations of these findings in the context of known racial differences in CKD prevalence and progression to end-stage renal disease in the general population and highlights the importance of screening high-risk HIV patients for kidney disease. CKD is common among HIV patients, and—as in the general population—has a more-aggressive course among African Americans than whites.
chronic kidney disease; end-stage renal disease; HIV; racial differences; screening
Very few studies have addressed the relationship between number of peritoneal dialysis (PD) patients treated at a clinic (PD clinic size) and clinical outcomes. In a national prospective cohort study of incident PD patients (n=236, from 26 clinics), we examined whether being treated at a larger PD clinic [≥50 PD patients (n=3 clinics) vs. <50 PD patients (n=23 clinics)] was associated with better patient outcomes, including fewer switches to hemodialysis, fewer cardiovascular events, lower cardiovascular mortality, and lower all-cause mortality.
Multivariable Cox models were used to assess relative hazards (RHs) for modality switches, cardiovascular events, cardiovascular deaths, and all-cause deaths by PD clinic size. All models were adjusted for demographics, comorbidities, laboratory values, and clinic years in operation.
Being treated at a clinic with ≥50 patients was associated with fewer switches to hemodialysis (RH=0.13, 95% CI, 0.06-0.31) and fewer cardiovascular events (RH=0.62, 95% CI, 0.06-0.98). No associations of PD clinic size with cardiovascular or all-cause mortality were seen.
PD patients that are treated at clinics with greater numbers of PD patients may have better outcomes in terms of technique failure and cardiovascular morbidity. PD clinic size may act as a proxy of greater PD experience, more focus on the modality, and better PD practices at the clinic, resulting in better outcomes.
peritoneal dialysis; clinic size; technique failure; cardiovascular morbidity; mortality
The use of peritoneal dialysis (PD) has declined in the United States over the past decade and technique failure is also reportedly higher in PD compared to hemodialysis (HD), but there are little data in the United States addressing the factors and outcomes associated with switching modalities from PD to HD.
In a prospective cohort study of 262 PD patients enrolled from 28 peritoneal dialysis clinics in 13 U.S. states, we examined potential predictors of switching from PD to HD (including demographics, clinical factors, and laboratory values) and the association of switching with mortality. Cox proportional hazards regression was used to assess relative hazards (RH) of switching and of mortality in PD patients who switched to HD.
Among 262 PD patients, 24.8% switched to HD; with more than 70% switching within the first 2 years. Infectious peritonitis was the leading cause of switching. Patients of black race and with higher body mass index were significantly more likely to switch from PD to HD, RH (95% CI) of 5.01 (1.15–21.8) for black versus white and 1.09 (1.03–1.16) per 1 kg/m2 increase in BMI, respectively. There was no difference in survival between switchers and non-switchers, RH (95% CI) of 0.89 (0.41–1.93).
Switching from PD to HD occurs early and the rate is high, threatening long-term viability of PD programs. Several patient characteristics were associated with the risk of switching. However, there was no survival difference between switchers and non-switchers, reassuring providers and patients that PD technique failure is not necessarily associated with poor prognosis.
Clinical performance targets are intended to improve patient outcomes in chronic disease through quality improvement, but evidence of an association between multiple target attainment and patient outcomes in routine clinical practice is often lacking.
In a national prospective cohort study (ESRD Quality, or EQUAL), we examined whether attainment of multiple targets in 668 incident hemodialysis patients from 74 U.S. not-for-profit dialysis clinics was associated with better outcomes. We measured whether the following accepted clinical performance targets were met at 6 months after study enrollment: albumin (≥4.0 g/dl), hemoglobin (≥11 g/dl), calcium-phosphate product (<55 mg2/dl2), dialysis dose (Kt/V≥1.2), and vascular access type (fistula). Outcomes included mortality, hospital admissions, hospital days, and hospital costs.
Attainment of each of the five targets was associated individually with better outcomes; e.g., patients who attained the albumin target had decreased mortality [relative hazard (RH) = 0.55, 95% confidence interval (CI), 0.41–0.75], hospital admissions [incidence rate ratio (IRR) = 0.67, 95% CI, 0.62–0.73], hospital days (IRR = 0.61, 95% CI, 0.58–0.63), and hospital costs (average annual cost reduction = $3,282, P = 0.002), relative to those who did not. Increasing numbers of targets attained were also associated, in a graded fashion, with decreased mortality (P = 0.030), fewer hospital admissions and days (P < 0.001 for both), and lower costs (P = 0.029); these trends remained statistically significant for all outcomes after adjustment (P < 0.001), except cost, which was marginally significant (P = 0.052).
Attainment of more clinical performance targets, regardless of which targets, was strongly associated with decreased mortality, hospital admissions, and resource use in hemodialysis patients.
Recent research suggests that uric acid may be nephrotoxic at lower levels than previously recognized and that it may be one mechanism for lead-related nephrotoxicity. Therefore, in understanding mechanisms for lead-related nephrotoxicity, it would be of value to determine whether genetic polymorphisms that are associated with renal outcomes in lead workers and/or modify associations between lead dose and renal function are also associated with uric acid and/or modify associations between lead dose and uric acid. We analyzed data on three such genetic polymorphisms: δ-aminolevulinic acid dehydratase (ALAD), endothelial nitric oxide synthase (eNOS), and the vitamin D receptor (VDR). Mean (± SD) tibia, blood, and dimercaptosuccinic acid–chelatable lead levels were 37.2 ± 40.4 μg/g bone mineral, 32.0± 15.0 g/dL, and 0.77± 0.86 μg/mg creatinine, respectively, in 798 current and former lead workers. Participants with the eNOS Asp allele had lower mean serum uric acid compared with those with the Glu/Glu genotype. Among older workers (age ≥ median of 40.6 years), ALAD genotype modified associations between lead dose and uric acid levels. Higher lead dose was significantly associated with higher uric acid in workers with the ALAD1-1 genotype; associations were in the opposite direction in participants with the variant ALAD1-2 genotype. In contrast, higher tibia lead was associated with higher uric acid in those with the variant VDR B allele; however, modification was dependent on participants with the bb genotype and high tibia lead levels. We conclude that genetic polymorphisms may modify uric acid mediation of lead-related adverse renal effects.
δ-aminolevulinic acid dehydratase; endothelial nitric oxide synthase; genetic susceptibility factors; kidney function; lead exposure; uric acid; vitamin D receptor
Recent research suggests that both uric acid and lead may be nephrotoxic at lower levels than previously recognized. We analyzed data from 803 current and former lead workers to determine whether lead biomarkers were associated with uric acid and whether previously reported associations between lead dose and renal outcomes were altered after adjustment for uric acid. Outcomes included uric acid, blood urea nitrogen, serum creatinine, measured and calculated creatinine clearances, and urinary N-acetyl-β-d-glucosaminidase (NAG) and retinol-binding protein. Mean (± SD) uric acid, tibia lead, and blood lead levels were 4.8 ± 1.2 mg/dL, 37.2 ± 40.4 μg/g bone mineral, and 32.0 ± 15.0 μg/dL, respectively. None of the lead measures (tibia, blood, and dimercaptosuccinic-acid–chelatable lead) was associated with uric acid, after adjustment for age, sex, body mass index, and alcohol use. However, when we examined effect modification by age on these relations, both blood and tibia lead were significantly associated (β= 0.0111, p < 0.01 and β= 0.0036, p = 0.04, respectively) in participants in the oldest age tertile. These associations decreased after adjustment for blood pressure and renal function, although blood lead remained significantly associated with uric acid (β= 0.0156, p = 0.01) when the population was restricted to the oldest tertile of workers with serum creatinine greater than the median (0.86 mg/dL). Next, in models of renal function in all workers, uric acid was significantly (p < 0.05) associated with all renal outcomes except NAG. Finally, in the oldest tertile of workers, associations between lead dose and NAG were unchanged, but fewer associations between the lead biomarkers and the clinical renal outcomes remained significant (p ≤0.05) after adjustment for uric acid. In conclusion, our data suggest that older workers comprise a susceptible population for increased uric acid due to lead. Uric acid may be one, but not the only, mechanism for lead-related nephrotoxicity.
kidney function; mechanisms; occupational lead exposure; renal early biologic effect markers; uric acid
Retinal vascular and anatomic abnormalities caused by diabetes, hypertension, and other conditions can be observed directly in the ocular fundus and may reflect severity of chronic renal insufficiency. The purpose of this study was to investigate the association between retinopathy and chronic kidney disease (CKD).
In this observational, cross-sectional study, 2605 participants of the Chronic Renal Insufficiency Cohort (CRIC) study, a multi-center study of CKD, were offered participation. Non-mydriatic fundus photographs of the disc and macula in both eyes were obtained in 1936 of these subjects.
Photographs were reviewed in a masked fashion at a central photograph reading center using standard protocols. Presence and severity of retinopathy (diabetic, hypertensive or other) and vessel diameter caliber were assessed by trained graders and a retinal specialist using protocols developed for large epidemiologic studies. Kidney function measurements and information on traditional and non-traditional risk factors for decreased kidney function were obtained from the CRIC study.
Greater severity of retinopathy was associated with lower estimated glomerular filtration rate (eGFR) after adjustment for traditional and non-traditional risk factors. Presence of vascular abnormalities usually associated with hypertension was also associated with lower eGFR. We found no strong direct relationship between eGFR and average arteriolar or venular calibers.
Our findings show a strong association between severity of retinopathy and its features and level of kidney function after adjustment for traditional and non-traditional risk factors for CKD, suggesting that retinovascular pathology reflects renal disease.
Retinopathy; Retinal Vascular Diameter; Chronic Kidney Disease
Little is known regarding the types of information African American and non-African American patients with chronic kidney disease (CKD) and their families need to inform renal replacement therapy (RRT) decisions.
In 20 structured group interviews, we elicited views of African American and non-African American patients with CKD and their families about factors that should be addressed in educational materials informing patients’ RRT selection decisions. We asked participants to select factors from a list and obtained their open-ended feedback.
Ten groups of patients (5 African American, 5 non-African American; total 68 individuals) and ten groups of family members (5 African American, 5 non-African American; total 62 individuals) participated. Patients and families had a range (none to extensive) of experiences with various RRTs. Patients identified morbidity or mortality, autonomy, treatment delivery, and symptoms as important factors to address. Family members identified similar factors but also cited the effects of RRT decisions on patients’ psychological well-being and finances. Views of African American and non-African American participants were largely similar.
Educational resources addressing the influence of RRT selection on patients’ morbidity and mortality, autonomy, treatment delivery, and symptoms could help patients and their families select RRT options closely aligned with their values. Including information about the influence of RRT selection on patients’ personal relationships and finances could enhance resources’ cultural relevance for African Americans.
Decision-making; Renal replacement therapy; Family members; African American
Evidence is lacking to inform providers’ and patients’ decisions about many common treatment strategies for patients with end stage renal disease (ESRD).
The DEcIDE Patient Outcomes in ESRD Study is funded by the United States (US) Agency for Health Care Research and Quality to study the comparative effectiveness of: 1) antihypertensive therapies, 2) early versus later initiation of dialysis, and 3) intravenous iron therapies on clinical outcomes in patients with ESRD. Ongoing studies utilize four existing, nationally representative cohorts of patients with ESRD, including (1) the Choices for Healthy Outcomes in Caring for ESRD study (1041 incident dialysis patients recruited from October 1995 to June 1999 with complete outcome ascertainment through 2009), (2) the Dialysis Clinic Inc (45,124 incident dialysis patients initiating and receiving their care from 2003–2010 with complete outcome ascertainment through 2010), (3) the United States Renal Data System (333,308 incident dialysis patients from 2006–2009 with complete outcome ascertainment through 2010), and (4) the Cleveland Clinic Foundation Chronic Kidney Disease Registry (53,399 patients with chronic kidney disease with outcome ascertainment from 2005 through 2009). We ascertain patient reported outcomes (i.e., health-related quality of life), morbidity, and mortality using clinical and administrative data, and data obtained from national death indices. We use advanced statistical methods (e.g., propensity scoring and marginal structural modeling) to account for potential biases of our study designs. All data are de-identified for analyses. The conduct of studies and dissemination of findings are guided by input from Stakeholders in the ESRD community.
The DEcIDE Patient Outcomes in ESRD Study will provide needed evidence regarding the effectiveness of common treatments employed for dialysis patients. Carefully planned dissemination strategies to the ESRD community will enhance studies’ impact on clinical care and patients’ outcomes.
Living related kidney transplantation (LRT) is underutilized, particularly among African Americans. The effectiveness of informational and financial interventions to enhance informed decision-making among African Americans with end stage renal disease (ESRD) and improve rates of LRT is unknown.
We report the protocol of the Providing Resources to Enhance African American Patients’ Readiness to Make Decisions about Kidney Disease (PREPARED) Study, a two-phase study utilizing qualitative and quantitative research methods to design and test the effectiveness of informational (focused on shared decision-making) and financial interventions to overcome barriers to pursuit of LRT among African American patients and their families. Study Phase I involved the evidence-based development of informational materials as well as a financial intervention to enhance African American patients’ and families’ proficiency in shared decision-making regarding LRT. In Study Phase 2, we are currently conducting a randomized controlled trial in which patients with new-onset ESRD receive 1) usual dialysis care by their nephrologists, 2) the informational intervention (educational video and handbook), or 3) the informational intervention in addition to the option of participating in a live kidney donor financial assistance program. The primary outcome of the randomized controlled trial will include patients’ self-reported rates of consideration of LRT (including family discussions of LRT, patient-physician discussions of LRT, and identification of a LRT donor).
Results from the PREPARED study will provide needed evidence on ways to enhance the decision to pursue LRT among African American patients with ESRD.
Shared decision-making; Live kidney transplantation; Live kidney donation; Chronic kidney disease; End stage renal disease