Variation in Sodium Intake and Intra-individual Change in Blood Pressure in Chronic Kidney Disease.

OBJECTIVE: In the kidney disease clinic setting, higher-than-usual blood pressure is often ascribed to recent dietary sodium indiscretion. While clinical trials demonstrate a clear relationship between salt intake and blood pressure on the population level, it is uncertain whether real-world variation in sodium intake within individual chronic kidney disease (CKD) patients is associated with fluctuations in blood pressure. METHODS: We analyzed data from the Phosphorus Normalization Trial, in which participants with CKD eating their usual diets completed at least three 24-hour urine collections over 9 months, from which we measured sodium. Blood pressure was measured at the time of 24-hour urine collections. For each individual participant, we assessed the slope of the relationship between sodium intake and mean arterial blood pressure (MAP). RESULTS: Among 119 participants (mean age 67 years and mean estimated glomerular filtration rate 31 mL/minute/1.73 m2), there was substantial variation in sodium intake as measured by 24-hour urine collections (mean intake 3,903 mg/day, standard deviation 1037 mg/day). Individual participants had highly variable associations between their sodium intake and their MAP; 47% (n = 56) had inverse associations between sodium and MAP, whereas the remainder had positive (salt-sensitive) associations. CONCLUSIONS: Among CKD patients, there is substantial variation in sodium intake but no predictable relationship between dietary sodium and blood pressure in individuals. The frequent dismissal of elevated blood pressure readings as related to recent sodium intake in clinic may be a misapplication of large-scale population data to explain individual variability and may contribute to clinical inertia regarding high blood pressure treatment.

Spot urine sodium measurements do not accurately estimate dietary sodium intake in chronic kidney disease.

BACKGROUND: Sodium intake influences blood pressure and proteinuria, yet the impact on long-term outcomes is uncertain in chronic kidney disease (CKD). Accurate assessment is essential for clinical and public policy recommendations, but few large-scale studies use 24-h urine collections. Recent studies that used spot urine sodium and associated estimating equations suggest that they may provide a suitable alternative, but their accuracy in patients with CKD is unknown. OBJECTIVE: We compared the accuracy of 4 equations [the Nerbass, INTERSALT (International Cooperative Study on Salt, Other Factors, and Blood Pressure), Tanaka, and Kawasaki equations] that use spot urine sodium to estimate 24-h sodium excretion in patients with moderate to advanced CKD. DESIGN: We evaluated the accuracy of spot urine sodium to predict mean 24-h urine sodium excretion over 9 mo in 129 participants with stage 3-4 CKD. Spot morning urine sodium was used in 4 estimating equations. Bias, precision, and accuracy were assessed and compared across each equation. RESULTS: The mean age of the participants was 67 y, 52% were female, and the mean estimated glomerular filtration rate was 31 ± 9 mL · min(-1) · 1.73 m(-2) The mean ± SD number of 24-h urine collections was 3.5 ± 0.8/participant, and the mean 24-h sodium excretion was 168.2 ± 67.5 mmol/d. Although the Tanaka equation demonstrated the least bias (mean: -8.2 mmol/d), all 4 equations had poor precision and accuracy. The INTERSALT equation demonstrated the highest accuracy but derived an estimate only within 30% of mean measured sodium excretion in only 57% of observations. Bland-Altman plots revealed systematic bias with the Nerbass, INTERSALT, and Tanaka equations, underestimating sodium excretion when intake was high. CONCLUSION: These findings do not support the use of spot urine specimens to estimate dietary sodium intake in patients with CKD and research studies enriched with patients with CKD. The parent data for this study come from a clinical trial that was registered at clinicaltrials.gov as NCT00785629.

Effect of dietary phosphate intake on the circadian rhythm of serum phosphate concentrations in chronic kidney disease: a crossover study.

BACKGROUND: Previous trials of binders in chronic kidney disease (CKD) stages 3-5 have shown only modest changes in serum phosphate but evaluated morning phosphate. It is unknown whether a circadian pattern of phosphate concentrations exists in CKD and is modifiable by dietary manipulation. OBJECTIVES: We determined the circadian pattern of serum phosphate concentrations in CKD and whether it was modifiable by altering absorbable phosphate. DESIGN: This was a crossover feeding study in 11 CKD participants (estimated glomerular filtration rate: 30-45 mL · min(-1) · 1.73 m(-2)) and 4 healthy control subjects. All subjects received high-phosphate (2500 mg/d), normal-phosphate (1500 mg/d), and low-phosphate (1000 mg/d plus 1000 mg lanthanum carbonate 3 times/d) diets for 5 d followed by a 10-d washout. After each 5-d feed, phosphate and other measurements were made every 4 h over 1 day. RESULTS: In CKD participants who consumed the high-phosphate diet, there were circadian changes in phosphate with lowest concentrations (± SDs) at 0800 (4.2 ± 0.5 mg/dL) and 2 peaks at 1600 and 0400 (4.5 ± 0.8 and 4.4 ± 0.6 mg/dL, respectively), which were similar to those in healthy controls. Results with the normal-phosphate diet were similar. The low-phosphate diet altered the circadian rhythm (P = 0.02) such that 0400 and 1600 peaks were absent. Differences in phosphate for lowest- compared with highest-phosphate diets were smallest at 0800 and largest at 1600 (0.5 compared with 1.0 mg/dL) in CKD. Circadian changes in phosphate were not explained by urine phosphate excretion, parathyroid hormone, or fibroblast growth factor-23. CONCLUSIONS: A circadian pattern of serum phosphate is observed in CKD with lowest concentrations at 0800 and highest at 1600 and 0400. This circadian pattern is modifiable by phosphate intake and most evident at 1600. Future intervention studies targeting intestinal phosphate absorption should consider afternoon phosphate measurements.

Estimation of 24-hour urine phosphate excretion from spot urine collection: development of a predictive equation.

BACKGROUND: The management of hyperphosphatemia in patients with moderate to severe chronic kidney disease (CKD) includes dietary phosphate restriction and/or prescription of phosphate binders. Measuring phosphate intake in CKD is important for monitoring dietary adherence and for the effectiveness of therapeutic interventions. The 24-hour urine collection is the gold standard method for determining phosphate intake; however, timed urine collections are cumbersome and prone to error. We investigated the precision and accuracy of spot urine phosphate measurements, compared to 24-hour urine phosphate (24hUrP) collection. STUDY DESIGN, SETTING, AND PARTICIPANTS: We evaluated simultaneous spot and 24hUrP measurements, collected on multiple occasions, from 143 participants in the Phosphate Normalization Trial, a randomized trial of phosphate binders versus placebo among persons with an estimated glomerular filtration rate between 20-45 mL/minute per 1.73 m2. We used residual analyses and graphical methods to model the functional relationship of spot urine phosphate and creatinine measurements with 24hUrP. We used multiple linear regression to test whether additional covariates improved model prediction, including treatment assignment, age, sex, height, weight, urine collection time, and last meal time. We internally validated results using leave-one-out cross-validation, and externally validated in an independent replication cohort. RESULTS: A log-log relation between the spot urine phosphate-to-creatinine ratio and 24hUrP excretion yielded the best model fit. In addition to spot urine phosphate and creatinine concentrations, inclusion of age, sex, and weight significantly improved prediction of 24hUrP. Compared with a spot urine phosphate-to-creatinine ratio alone (r2 = 0.12, P < .001), the new equation more accurately predicted 24hUrP (leave-one-out validation r2 = 0.43, P < .001, independent validation r2 = 0.39, P < .001). CONCLUSION: We describe a novel equation to predict 24hUrP excretion using spot urine phosphate and creatinine, age, sex, and weight. The equation is more accurate and precise than the urine phosphate-to-creatinine ratio alone, and it provides a simple method for estimating 24hUrP excretion in patients with nondialysis-requiring CKD.

Effect of salivary phosphate-binding chewing gum on serum phosphate in chronic kidney disease.

BACKGROUND/AIMS: Serum phosphate (P) has been linked to adverse events in patients with chronic kidney disease. Salivary phosphate (Psal) has been proposed as a potential target of therapy with a chitosan-containing chewing gum. METHODS: We conducted several pilot studies to characterize Psal and its relationship with kidney function and subsequently conducted two clinical efficacy studies: a double-blind placebo-controlled trial in patients with end-stage renal disease (ESRD) and an open-label trial in those with stage 3-4 CKD. RESULTS: Pilot studies demonstrated no relationship between the level of kidney function and Psal. Mean Psal was approximately 6.46 mmol/l across the entire spectrum of kidney function. Passive saliva collection demonstrated higher Psal concentration as compared to active collection. There was no evidence of diurnal variation in Psal. Twice daily 20 mg chitosan gum over 4 weeks reduced serum P by 0.065 mmol/l in the double-blind, placebo-controlled trial in ESRD (p = NS vs. placebo). In an open-label extension in these subjects, 40 mg chitosan gum three times daily reduced serum P by 0.065 mmol/l (p = 0.03 vs. end of washout). In a 2-week open-label trial in patients with CKD not on dialysis, 20 mg chitosan gum given three times daily reduced serum P by 0.05 mmol/l (p = 0.003 vs. day 1). Neither trial demonstrated any significant change in Psal with chitosan gum. CONCLUSIONS: Psal concentration is approximately 4-5 times that of serum P and is not related to glomerular filtration rate. Chitosan chewing gum resulted in a reduction of serum P by approximately 0.05-0.065 mmol/l but had no effect on Psal concentration.

Effects of phosphate binders in moderate CKD.

Some propose using phosphate binders in the CKD population given the association between higher levels of phosphorus and mortality, but their safety and efficacy in this population are not well understood. Here, we aimed to determine the effects of phosphate binders on parameters of mineral metabolism and vascular calcification among patients with moderate to advanced CKD. We randomly assigned 148 patients with estimated GFR=20-45 ml/min per 1.73 m(2) to calcium acetate, lanthanum carbonate, sevelamer carbonate, or placebo. The primary endpoint was change in mean serum phosphorus from baseline to the average of months 3, 6, and 9. Serum phosphorus decreased from a baseline mean of 4.2 mg/dl in both active and placebo arms to 3.9 mg/dl with active therapy and 4.1 mg/dl with placebo (P=0.03). Phosphate binders, but not placebo, decreased mean 24-hour urine phosphorus by 22%. Median serum intact parathyroid hormone remained stable with active therapy and increased with placebo (P=0.002). Active therapy did not significantly affect plasma C-terminal fibroblast growth factor 23 levels. Active therapy did, however, significantly increase calcification of the coronary arteries and abdominal aorta (coronary: median increases of 18.1% versus 0.6%, P=0.05; abdominal aorta: median increases of 15.4% versus 3.4%, P=0.03). In conclusion, phosphate binders significantly lower serum and urinary phosphorus and attenuate progression of secondary hyperparathyroidism among patients with CKD who have normal or near-normal levels of serum phosphorus; however, they also promote the progression of vascular calcification. The safety and efficacy of phosphate binders in CKD remain uncertain.

Cinacalcet hydrochloride treatment significantly improves all-cause and cardiovascular survival in a large cohort of hemodialysis patients.

Secondary hyperparathyroidism (SHPT) affects a significant number of hemodialysis patients, and metabolic disturbances associated with it may contribute to their high mortality rate. As patients with lower serum calcium, phosphorus, and parathyroid hormone are reported to have improved survival, we tested whether prescription of the calcimimetic cinacalcet to hemodialysis patients with SHPT improved their survival. We prospectively collected data on hemodialysis patients from a large provider beginning in 2004, a time coincident with the commercial availability of cinacalcet hydrochloride. This information was merged with data in the United States Renal Data System to determine all-cause and cardiovascular mortality. Patients included in the study received intravenous (i.v.) vitamin D therapy (a surrogate for the diagnosis of SHPT). Of 19,186 patients, 5976 received cinacalcet and all were followed from November 2004 for up to 26 months. Unadjusted and adjusted time-dependent Cox proportional hazards modeling found that all-cause and cardiovascular mortality rates were significantly lower for those treated with cinacalcet than for those without calcimimetic. Hence, this observational study found a significant survival benefit associated with cinacalcet prescription in patients receiving i.v. vitamin D. Definitive proof, however, of a survival advantage awaits the performance of randomized clinical trials.

Efficacy and safety of SBR759, a new iron-based phosphate binder.

Treatment of elevated serum phosphorus in hemodialysis patients remains challenging due in part to the lack of a well-tolerated, safe, and effective phosphate binder. Here we report the results of a single-center, open-label, phase I clinical trial of 44 hemodialysis patients to show the safety and efficacy of a novel iron-based phosphate binder, SBR759. After establishing its safety at an initial dose of 3.75 g/day, SBR759 was given to successive cohorts in several divided doses of up to 22.5 g/day. The defined measure of efficacy was the average change in serum phosphorus in the cohorts receiving 11.25 and 15.0 g/day, in whom the mean reduction was 2.1 mg/dl. A clinically and statistically significant reduction in serum phosphorus was found across the entire dose range. All patients were able to achieve mean phosphorus levels within K/DOQI target ranges at the end of the first week. SBR759 was well tolerated within the anticipated clinical dose range of 3.75-15 g/day. No treatment-related serious adverse events were observed nor were there clinically relevant changes in iron indices. While these preliminary studies highlight the clinical efficiency and safety of SBR759, its promise of improved therapeutic options for hyperphosphatemia in patients with chronic kidney disease requires further study.

Cinacalcet use patterns and effect on laboratory values and other medications in a large dialysis organization, 2004 through 2006.

BACKGROUND AND OBJECTIVES: Cinacalcet was introduced in mid-2004 to treat secondary hyperparathyroidism in dialysis patients. We aimed to characterize adult patients who received cinacalcet prescriptions and to determine (1) dosage titration and effects on laboratory values, active intravenous vitamin D use, and phosphate binder prescriptions and (2) percentage who achieved National Kidney Foundation Kidney Disease Outcomes Quality Initiative targets for serum parathyroid hormone, calcium, and phosphorus and experienced biochemical adverse effects. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This observational study evaluated 45,487 prevalent patients from a dialysis organization database linked with the Centers for Medicare and Medicaid Services End-Stage Renal Disease database. Patient characteristics, laboratory values (albumin, parathyroid hormone, calcium, phosphorus), intravenous vitamin D, and oral medication (cinacalcet, phosphate binders) prescriptions were evaluated for cinacalcet patients. RESULTS: By June 2006, almost 32% of patients had received cinacalcet prescriptions. Mean baseline corrected calcium was 9.8 mg/dl and phosphorus was 6.3 mg/dl, and median parathyroid hormone was 577 pg/ml, versus 9.5 mg/dl, 5.3 mg/dl, and 215 pg/ml, respectively, for noncinacalcet patients. Patients with cinacalcet prescriptions for > or =6 mo had corrected calcium reduced by 4.2%, phosphorus by 7.0%, and parathyroid hormone by 29.9% by 12 mo. More cinacalcet patients attained Kidney Disease Outcomes Quality Initiative targets with less hyperparathyroidism, hypercalcemia, and hyperphosphatemia but more hypoparathyroidism and hypocalcemia. Over 12 mo, vitamin D use and use consistency increased, phosphate binder dosages increased, and mean cinacalcet daily dosage reached 55 mg. CONCLUSIONS: Patients with cinacalcet prescriptions exhibited more severe hyperparathyroidism and hyperphosphatemia than noncinacalcet patients. Positive effects were less dramatic than in Phase III clinical trials, possibly as a result of modest, slow dosage titration.

Barriers to enrollment of elderly adults in early-phase cancer clinical trials.

Potential strategies to overcome barriers to enrollment of seniors into early-phase trials.

A phase I and pharmacokinetic study of exisulind and docetaxel in patients with advanced solid tumors.

PURPOSE: Exisulind (sulindac sulfone, FGN-1, Aptosyn) is a sulindac metabolite that induces apoptosis via inhibition of cyclic GMP-phosphodiesterase. This agent demonstrated tumor growth inhibition in rodent models of colon, breast, prostate, and lung carcinogenesis. In an orthotopic model of human non-small-cell lung cancer, the combination of exisulind and docetaxel prolonged survival in athymic nude rats, forming the basis of this phase I combination study. EXPERIMENTAL DESIGN: This study evaluated the toxicity and pharmacokinetics of combining exisulind (150-250 mg) given orally twice daily and docetaxel (30-36 mg/m2) administered intravenously on days 1, 8, and 15 of a 4-week cycle. RESULTS: Twenty patients with a range of advanced solid tumors (median age, 59 years; age range, 35-77 years; median performance status, 1) received a total of 70 courses. Observed adverse events were mild to moderate, and there was no dose-limiting toxicity at any level. Grade 3 gastrointestinal toxicities were present in 10 of the 70 cycles (10%) and included nausea, vomiting, dyspepsia, and elevated alkaline phosphatase. Neutropenia was present in four cycles in patients treated with a docetaxel dose of 36 mg/m2. Pharmacokinetic analysis did not demonstrate a clear effect of exisulind on docetaxel pharmacokinetics and vice versa. Relationships were evident between the plasma concentration of exisulind and the development of grade 2 or greater toxicities. One third of patients maintained stable disease for 3 to 12 cycles, but no objective responses were observed. CONCLUSIONS: The combination of docetaxel (36 mg/m2, weekly) and exisulind (500 mg/d) was reasonably well tolerated, and it is undergoing phase II testing in patients with non-small-cell lung cancer.