Complete Urine Collections Research Articles

Abstract P333: The Impact of Sodium on Blood Pressure and Arterial Stiffness is Moderated by Indices of Obesity in People of African Ancestry.

Background: Obesity is on the rise worldwide and like Na + it is associated with blood pressure (BP) and target organ changes. Our study population has a high incidence of obesity (67%) and a dietary sodium intake that is slightly above the recommended threshold. Previous studies conducted in this population have shown no relationship between Na + and both BP and arterial stiffness. With the high incidence of obesity in this population, it is possible that the indices of obesity blunt this relationship. Therefore in this study we investigate whether the relationship between Na + and both BP and PWV is moderated by the indices of obesity. Methods: We recruited 1219 South Africans of African ancestry and measure 24-h ambulatory on 796 participants and 597 had complete 24-hour urine collection. Anthropometric measurements were taken and a standard questionnaire was issued to determine lifestyle habits and history of medication. To assess arterial stiffness we used applanation tonometry to measure pulse wave velocity (PWV). Results: After correcting for covariates, there was an association between Na + and PB in participants with normal BMI but not in obese participants. Similarly there was a relationship between Na + and PWV (p=0.0447) in individuals with normal BMI only. When waist circumference was used as an index of obesity, gender disparities were observed in the relationship between Na + and PWV. There was no relationship between Na + and PWV irrespective the waist circumference in males but a multivariate regression analyses showed a relationship between Na + and PWV in all women (p=0.0142) and in women with a normal waist circumference (p=0.0006). Conclusion: In a population with a high incidence of obesity, the relationship between Na + and both BP and PWV is modified by the indices of obesity.

Feasibility of collecting 24-h urine to monitor sodium intake in the National Health and Nutrition Examination Survey1–3

Twenty-four-hour urine sodium excretion is recommended for monitoring population sodium intake. Because of concerns about participation and completion, sodium excretion has not been collected previously in US nationally representative surveys. We assessed the feasibility of implementing 24-h urine collections as part of a nationally representative survey. We selected a random half sample of nonpregnant US adults aged 20-69 y in 3 geographic locations of the 2013 NHANES. Participants received explicit instructions, started and ended the urine collection in a urine study mobile examination center, and answered questions about their collection. Among those with a complete 24-h urine collection, a random one-half were asked to collect a second 24-h urine sample. Sodium, potassium, chloride, and creatinine excretion were analyzed. The final NHANES examination response rate for adults aged 20-69 y in these 3 study locations was 71%. Of those examined (n = 476), 282 (59%) were randomly selected to participate in the 24-h urine collection. Of these, 212 persons [75% of those selected for 24-h urine collection; 53% (equal to 71% × 75% of those selected for the NHANES)] collected a complete initial 24-h specimen and 92 persons (85% of 108 selected) collected a second complete 24-h urine sample. More men than women completed an initial collection (P = 0.04); otherwise, completion did not vary by sociodemographic characteristics, body mass index, education, or employment status for either collection. Mean 24-h urine volume and sodium excretion were 1964 ± 1228 mL and 3657 ± 2003 mg, respectively, for the first 24-h urine sample, and 2048 ± 1288 mL and 3773 ± 1891 mg, respectively, for the second collection. Given the 53% final component response rate and 75% completion rate, 24-h urine collections were deemed feasible and implemented in the NHANES 2014 on a subsample of adults aged 20-69 y to assess population sodium intake. This study was registered at clinicaltrials.gov as NCT02723682.

Cushing's Syndrome: Screening and Diagnosis.

Endogenous Cushing's syndrome (CS) is a rare disease, and usually characterized by hypertension, diabetes, obesity, osteoporosis, facial rounding, dorsocervical fat pad, thin skin, purple striae, hirsutism, and mood disorders. Efficient diagnostic and screening strategies lead to the diagnosis of a significantly higher number of cases of CS. As a screening test for CS, the Endocrine Society's Clinical Practice Guidelines recommend a single test with a high diagnostic accuracy, among the 1-mg dexamethasone suppression test (1-mg DST), late night salivary cortisol (LNSC), and 24h urinary free cortisol (UFC). In normal subjects, administering a higher than physiological dose of glucocorticoids prompts the suppression of cortisol secretion. The 1-mg DST explores this normal feedback reaction from the hypothalamic-pituitary-adrenal axis (HPA). It is a simple dynamic test, usually performed in outpatients. A morning serum cortisol level <50nmol/L suffices to exclude CS, unless there is a strong clinical suspicion to suggest otherwise. The HPA axis reaches a nadir just after a person has fallen asleep, but its circadian rhythm is impaired in CS patients, who feature higher cortisol values at night, which are easy to measure in saliva (the LNSC assay). Saliva collection is also suitable for outpatients since cortisol is stable at room temperature and the collection device can be mailed to the laboratory for analysis. UFC levels reflect the integrated tissue exposure to free cortisol over 24h, and thus provide a particular picture of endogenous hypercortisolism. In most cases, high UFC levels coincide with severe hypercortisolism. UFC is used not only to diagnose CS, but also to monitor its response to medical treatment. All screening tests have procedural snares: some drugs can interfere with the DST; false-positive or false-negative LNSC results may be due to an inadequate soaking of the device or to cyclic CS; and in the case of UFC it is important to ensure that patients provide complete urine collections with appropriate total volumes. Measuring cortisol with antibody-based immunoassays can also generate false-positive results due to cross-reactivity between cortisol, cortisone and other metabolites. Structurally-based assays, such as liquid chromatography with tandem mass spectrometry, only measure cortisol and have only recently become available for use in routine clinical practice. This review summarizes the recent literature on the clinical and biochemical aspects of CS diagnostics with a view to helping physicians choose the best screening test for diagnosing endogenous hypercortisolism.

Sodium and potassium urinary excretion and dietary intake: a cross-sectional analysis in adolescents

BackgroundHypertension is the leading cause for heart disease and stroke, for mortality and morbidity worldwide, and a high sodium-to-potassium intake ratio is considered a stronger risk factor for hypertension than sodium alone.ObjectiveThis study aims to evaluate sodium and potassium urinary excretion, and assess the food sources of these nutrients in a sample of Portuguese adolescents.DesignA cross-sectional study with a sample of 250 Portuguese adolescents. Sodium and potassium excretion were measured by one 24-h urinary collection, and the coefficient of creatinine was used to validate completeness of urine collections. Dietary sources of sodium and potassium were assessed using a 24-h dietary recall.ResultsValid urine collections were provided by 200 adolescents (118 girls) with a median age of 14.0 in both sexes (p=0.295). Regarding sodium, the mean urinary excretion was 3,725 mg/day in boys and 3,062 mg/day in girls (p<0.01), and 9.8% of boys and 22% of girls met the World Health Organization (WHO) recommendations for sodium intake. Concerning potassium, the mean urinary excretion was 2,237 mg/day in boys and 1,904 mg/day in girls (p<0.01), and 6.1% of boys and 1.7% of girls met the WHO recommendations for potassium intake. Major dietary sources for sodium intake were cereal and cereal products (41%), meat products (16%), and milk and milk products (11%); and for potassium intake, main sources were milk and milk products (21%), meat products (17%), and vegetables (15%).ConclusionsAdolescents had a high-sodium and low-potassium diet, well above the WHO recommendations. Health promotion interventions are needed in order to decrease sodium and increase potassium intake.

High salt intake: independent risk factor for obesity?

High salt intake is the major cause of raised blood pressure and accordingly leads to cardiovascular diseases. Recently, it has been shown that high salt intake is associated with an increased risk of obesity through sugar-sweetened beverage consumption. Increasing evidence also suggests a direct link. Our study aimed to determine whether there was a direct association between salt intake and obesity independent of energy intake. We analyzed the data from the rolling cross-sectional study-the UK National Diet and Nutrition Survey 2008/2009 to 2011/2012. We included 458 children (52% boys; age, 10±4 years) and 785 adults (47% men; age, 49±17 years) who had complete 24-hour urine collections. Energy intake was calculated from 4-day diary and misreporting was assessed by Goldberg method. The results showed that salt intake as measured by 24-hour urinary sodium was higher in overweight and obese individuals. A 1-g/d increase in salt intake was associated with an increase in the risk of obesity by 28% (odds ratio, 1.28; 95% confidence interval, 1.12-1.45; P=0.0002) in children and 26% (odds ratio, 1.26; 95% confidence interval, 1.16-1.37; P<0.0001) in adults, after adjusting for age, sex, ethnic group, household income, physical activity, energy intake, and diet misreporting, and in adults with additional adjustment for education, smoking, and alcohol consumption. Higher salt intake was also significantly related to higher body fat mass in both children (P=0.001) and adults (P=0.001) after adjusting for age, sex, ethnic group, and energy intake. These results suggest that salt intake is a potential risk factor for obesity independent of energy intake.

Dietary protein and urinary nitrogen in relation to 6-year changes in fat mass and fat-free mass.

In contrast to the physiological expectation, observational studies show that greater protein intake is associated with subsequent body weight (BW) gain. An increase in fat-free mass (FFM) due to the anabolic effects of protein could explain this. To examine associations between protein intake and subsequent changes in fat mass (FM) and FFM in longitudinal, observational data. A health examination, including measures of FM and FFM by bioelectrical impedance at baseline and follow-up 6 years later, was conducted. Diet history interviews (DHI) were performed, and 24-h urinary nitrogen collection at baseline was done. In total, 330 participants with DHI, of whom 227 had validated and complete 24-h urine collection data, were analyzed. Macronutrient energy substitution models were used. Mean estimated protein intake was 14.6 E% from DHI and 11.3 E% from urinary nitrogen. Estimated from DHI, FM increased 46 g per year, with every 1 E% protein substituted for fat (95% confidence interval (CI) = 13, 79; P = 0.006), and FFM increased 15 g per year (1, 30; P = 0.046). Results were similar in other substitution models. Estimated from urinary nitrogen, FM increased 53 g per year, with 1 E% protein substituted for other macronutrients (24, 81; P < 0.0005), and FFM increased 18 g per year (6, 31; P = 0.004). Within a habitual range, a greater protein intake was associated with BW gain, mostly in FM. This is in contrast to the expectations based on physiological and clinical trials, and calls for a better understanding of how habitual dietary protein influences long-term energy balance, versus how greater changes in dietary proteins may influence short-term energy balance.

Estimation of salt intake by 24-hour urinary sodium excretion: a cross-sectional study in Yantai, China

BackgroundHigh levels of dietary sodium are associated with raised blood pressure and adverse cardiovascular health. To determine baseline salt intake, we investigated the average dietary salt intake from 24-hour urinary sodium excretion with a small sample of Yantai adults in the Shandong province of China.MethodsOne hundred ninety one adults aged 18–69 years were randomly selected from the Yantai adult population. Blood pressure, anthropometric indices and sodium excretion in a 24-hour urine collection were measured. Consumption of condiments was derived from 3-day weighted records. Completeness of urine collections was verified using creatinine excretion in relation to weight.ResultsThe mean Na and K outputs over 24 hours were 201.5 ± 77.7 mmol/day and 46.8 ± 23.2 mmol/day, respectively (corresponding to 11.8 g NaCl and 1.8 g K). Overall, 92.1% of the subjects (96.9% of men and 87.1% of women) had intakes of over 6 g salt (NaCl)/d. The main sources of salt intake from weighed condiments records were from home cooking salt (74.7%) followed by soy sauce (15.0%). Salt intake from condiments and salt excretion were weakly correlated((r = 0.20, p = 0.005).A positive linear correlation between salt intake was associated with systolic blood pressure in all adjusted and unadjusted model (r = 0.16, p = 0.01). Each 100 mmol/day increase in sodium intake was associated with a 4.0 mmHg increase in systolic blood pressure.ConclusionDietary salt intake in Yantai adults was high. Reducing the intake of table salt and soy sauce used in cooking will be an important strategy to reduce sodium intake among Yantai adults.

Salt and fluid restriction is effective in patients with chronic heart failure

European and American guidelines have recommended salt and fluid restriction for patients with chronic heart failure (CHF) despite scarce scientific evidence. Therefore, we investigated the effects of salt and fluid restriction in patients with CHF. Ninety-seven stable patients in NYHA class II-IV, on optimal medication, with previous signs of fluid retention, treated with either >40 mg (NYHA III-IV) or >80 mg (NYHA II-IV) of furosemide daily were randomized to either individualized salt and fluid restriction or information given by the nurse-led heart failure clinics, e.g. be aware not to drink too much and use salt with caution, and followed for 12 weeks. Fluid was restricted to 1.5 L and salt to 5 g daily, and individualized dietary advice and support was given. The 24 h dietary recall procedure, urine collection on three consecutive days, and para-aminobenzoic acid 80 mg t.i.d. was used to assess adherence to diet and completeness of urine collection. The primary endpoint was a composite variable consisting of NYHA class, hospitalization, weight, peripheral oedema, quality of life (QoL), thirst, and diuretics. Results After 12 weeks, significantly more patients in the intervention than in the control group improved on the composite endpoint (51% vs. 16%; P < 0.001), mostly owing to improved NYHA class and leg oedema. No negative effects were seen on thirst, appetite, or QoL. Individualized salt and fluid restriction can improve signs and symptoms of CHF with no negative effects on thirst, appetite, or QoL in patients with moderate to severe CHF and previous signs of fluid retention.

Comparison and validation of 2 analytical methods for measurement of urinary sucrose and fructose excretion

Urinary sugars excretion has been proposed as a potential biomarker for intake of sugars. In this study, we compared 2 analytical methods (gas chromatography [GC] and enzymatic reactions—UV absorption) for quantifying urinary fructose and sucrose using 24-hour urine samples from a randomized crossover controlled feeding study. All samples were successfully quantified by the GC method; however, 21% and 1.9% of samples were below the detection limit of the enzymatic method for sucrose and fructose, respectively. Although the correlation between the 2 methods was good for fructose (Pearson correlation, 0.71), the correlation was weak for sucrose (Pearson correlation, 0.27). We favor the GC method because of its better sensitivity, simplicity, and the ability to quantify fructose and sucrose directly in the same run. Of the 106 samples from 53 participants with complete urine collection after 2 study diets, 24-hour urinary fructose excretion was significantly associated with fructose intake. The sum of 24-hour urinary fructose and sucrose was significantly associated with total sugars consumption. However, variation in intakes of sugars explained only a modest amount of variation in urinary sugars excretion. In the unadjusted models, fructose intake explained 24.3% of urinary fructose excretion, and intake of total sugars explained 16.3% of the sum of urinary fructose and sucrose. The adjusted models explained 44.3% of urinary fructose excretion and 41.7% of the sum of urinary fructose and sucrose. Therefore, we caution using these biomarkers to predict sugars consumption before other factors that determine urinary sugars excretion are understood.

Estimating salt intake in a Caucasian population: can spot urine substitute 24-hour urine samples?

A simple and valid alternative for 24-hour urine collection to estimate populational 24-hour urinary sodium excretion would be desirable for monitoring sodium intake in populations. To assess the validity of the predicted 24-hour urinary sodium excretion using spot urine and two different prediction methods in a Danish population. Overall, 473 Danish individuals provided a para-aminobenzoic acid-validated complete 24-hour urine collection and a spot urine sample. Data were collected in the DanThyr study (248 women aged 25-30 years and 60-65 years) and the Inter99 study (102 men and 113 women aged 30-60 years), respectively. The measured 24-hour urine sodium excretion was compared with the predicted 24-hour sodium excretion from a causal urine specimen, using both the Tanaka prediction method and a prediction model developed in a Danish population. The measured 24-hour sodium excretion (median, 5th to 95th percentile) was men 195 (110 to 360) and women 139 (61 to 258), whereas the predicted 24-hour sodium excretion for the Tanaka model was men 171 (117 to 222) and women 153 (92 to 228) and for the Danish model was men 207 (146 to 258); women 134 (103 to 163). The Spearman correlation between predicted and measured 24-hour sodium excretion was 0.39 and 0.49 for the Tanaka and the Danish model, respectively. For both prediction models, the proportion of individuals classified in the same or adjacent quintile was 74% for men and 64% for women. Both prediction models gave a reasonable classification of individuals according to their sodium excretion. However, the median daily sodium intake was estimated more precisely by the Danish model, especially among men.

2244 TOPIRAMATE RESULTS IN A RAPID AND PROGRESSIVE DECLINE IN URINARY CITRATE OVER 60 DAYS: A PROSPECTIVE STUDY

INTRODUCTION AND OBJECTIVES: Topiramate is commonly prescribed for migraine headaches and, recently, weight loss. It exerts a well-known hypocitraturic effect. We characterized the time course to hypocitraturia, a risk factor for calcium lithiasis. METHODS: Under IRB approval, headache clinic providers offered participation to adult patients starting topiramate; a titrated dosage regimen reaching 100-200 mg/d within 1 month was prescribed. Patients withheld initiation until a baseline 24-h urine collection could be done. After starting topiramate, patients provided 24-h urine collections at 30 and 60 d for comparison. RESULTS: Twelve patients (M:F, 0.71; 38 y) were recruited from 9/2011-4/2012 and contributed complete 24-h urine collections, confirmed by 24-h urinary creatinine excretion. At baseline, 83% (n 10) were normocitraturic (urinary citrate 581 274 mg/d); 2 patients were mildly hypocitraturic (250 39 mg/d). At 30 d, mean urinary citrate excretion decreased nearly 300 mg and averaged 279 121 mg/d; it continued to decrease through 60 d (218 82 mg/d), at which time, 83% (6 of 7 patients with 24-h urine analyses) were hypocitraturic (196 64 mg/d for 6 with hypocitraturia). Paired t-tests confirmed differences in urinary citrate between baseline and 30-d and between baseline and 60-d (p 0.01 and 0.002, respectively) but not between 30 and 60 d, though the 22% decline in mean urinary citrate excretion from 30 to 60 d is nonetheless clincally relevant. Urine pH increased from 6.1 at baseline to 6.6 and 6.5 at 30and 60-d, respectively (p 0.04 for each comparison), increasing brushite supersaturation of urine. No patients reported stone events in the 6-12 month evaluation period. Of 8 hypocitraturic patients offered potassium citrate therapy (30 mEq/d), 4 agreed to initiate it. In the 1 patient from this group who has thus far completed a follow-up 24-h urine collection, urinary citrate excretion increased 102 mg/d within 2 weeks. CONCLUSIONS: Hypocitraturia from topiramate is rapid and progressive. This should be taken into account when starting therapy, particularly in patients with a history of urolithiasis or with identifiable lithogenic risk factors. Potassium citrate should be considered as adjunctive therapy in select individuals, and urinary citrate excretion should be monitored to ensure therapeutic effect.

Evaluation of spot urine as an alternative to 24 h urine collection for determination of biomarkers of exposure to cigarette smoke in adult smokers

ObjectiveExposure to cigarette smoke in adult smokers (SM) can be determined by measuring urinary excretion of selected smoke constituents or metabolites. Complete 24h urine collections are difficult to achieve in ambulatory clinical studies; therefore spot urine (SU) might be a useful alternative. The objective of this study was to evaluate the optimum time for SU collections, and to predict 24h urine biomarker excretion from SU collections. MethodsSU samples were collected at three time points (early morning, post-lunch and evening) along with 24h collections in 37 healthy adult smokers. Nicotine and its five metabolites (nicotine equivalents, NE), metabolites of NNK (NNAL), pyrene (1-OHP), acrolein (HPMA), benzene (S-PMA) and butadiene (MHBMA) were measured in 24h and SU samples. Correlation and agreement between creatinine-adjusted SU and 24h urine collections were determined from the Pearson product-moment correlation, Bland–Altman and Lin’s concordance correlation analyses. A random effect regression model was used to calculate the 24h biomarker excretion from SU collections. ResultsThere were no significant differences (p>0.05) between the three SU collections for the selected biomarkers of exposure except for 3-HPMA, which showed a diurnal variation. Good correlation and statistical agreements were observed for creatinine-adjusted SU (all three time points) and 24h for most of the selected biomarkers. 24h biomarker excretion could be estimated for most of the biomarkers based on the regression model, with the early morning SU collections giving the best results for tobacco specific biomarkers NE (R2=0.66) and NNAL (R2=0.6). ConclusionsSU is a useful alternative to 24h urine collections for most of the selected biomarkers of exposure to cigarette smoke. The early morning SU appears to be the most feasible and practical option as an alternative to 24h collections.

Checking for completeness of 24-h urine collection using para-amino benzoic acid not necessary in the Observing Protein and Energy Nutrition study

The orally administered para-amino benzoic acid (PABA) is known to have near 100% excretion in urine and is used as a measure of 24-h urine collection completeness (referred to as PABAcheck). The purpose was to examine the effect of including urine collections deemed incomplete based on PABAcheck in a dietary measurement error study. The Observing Protein and Energy Nutrition (OPEN) study was conducted in 1999-2000 and included 484 men and women aged 40-69 years. A food frequency questionnaire and 24-h dietary recalls were evaluated using recovery biomarkers that included urinary nitrogen and potassium from two 24-h urine collections. Statistical modeling determined the measurement error properties of dietary assessment instruments. In the original analyses, PABAcheck was used as a measure of complete urine collection; incomplete collections were either excluded or adjusted to acceptable levels. The OPEN data were reanalyzed including all urine collections and by using criteria based on self-reported missing voids to assess the differences. Means and coefficients of variation for biomarker-based protein and potassium intakes, and measurement error model-based correlations and attenuation factors were similar regardless of whether PABAcheck or missed voids were considered. PABAcheck may not be required in large population-based biomarker studies. However, until there are more analyses evaluating the necessity of a PABAcheck, it is recommended that PABA be given to all participants, but not necessarily analyzed. Then, PABAcheck could be used selectively as a marker of completeness among the collections in which low levels of biomarker are detected or for which noncompliance is suspected.

Endogenous Markers for Estimation of Renal Function in Peritoneal Dialysis Patients

This method comparison study, conducted at the peritoneal dialysis (PD) outpatient clinic of the Department of Renal Medicine, Aarhus University Hospital, Denmark, set out to evaluate the accuracy and reproducibility of methods for estimating glomerular filtration rate (GFR) based on endogenous markers in PD patients. The 12 consecutive patients included in the study were examined twice while in a stable condition. All patients finished the study. Inclusion criteria were age 18 years or older, ability to collect 24-hour urine, and urine production greater than 300 mL in 24 hours. The methods for estimating GFR using endogenous markers included the average of urinary clearances of creatinine and urea [U-Cl(crea-urea)] and two equations using the serum concentration of cystatin C [eGFR(CysC)]. The resulting GFR estimates were compared with those obtained using urinary and corrected plasma clearances of (51)Cr-EDTA [U-Cl(EDTA) and cP-Cl(EDTA)], the corrected plasma clearance being plasma clearance minus dialysate clearance. Compared with the U-Cl(EDTA), the U-Cl(crea-urea) GFR estimate was 12% higher [95% confidence limits (CL): 3%, 21%]. Although significantly different (p = 0.01), the latter two methods showed the best agreement. The estimates obtained using the eGFR(CysC) methods were skewed from y = x compared with the estimates obtained using other methods, indicating strong bias, probably because of extrarenal elimination. The cP-Cl(EDTA) estimate was 34% (95% CL: 26%, 42%), higher than the U-Cl(EDTA) estimate (p < 0.001). The reproducibility (coefficients of variation) differed significantly between methods: cP-Cl(EDTA), 7%; U-Cl(EDTA), 14%; U-Cl(crea-urea), 18%; and both eGFR(CysC) methods, 3%. In PD patients, GFR may be estimated as U-Cl(crea-urea) when complete urine collection is performed, taking into account an overestimation of approximately 12%. The available equations for eGFR(CysC) seem to be inaccurate; further development and validation is desirable. Omitting the eGFR(CysC) methods, cP-Cl(EDTA) was the most reproducible method and might be useful in certain situations.

Discrepancy between use of lean body mass or nitrogen balance to determine protein requirements for adult cats.

This study was undertaken to contrast the minimum protein intake needed to maintain nitrogen balance or lean body mass (LBM) in adult cats using a prospective evaluation of 24 adult, neutered male cats fed one to three different diets. Following a 1-month baseline period during which all cats consumed a 34% protein diet, cats were fed a 20% (LO), 26% (MOD) or 34% (HI) protein diet for 2 months. During the baseline period and following the 2-month feeding period, nitrogen balance was assessed using a 96-h complete collection of urine and feces, and LBM was assessed using dual energy X-ray absorptiometry. Weight loss increased in a linear manner with decreasing protein intake (P <0.01), despite no significant difference in calorie intake. Linear regression of the data indicated that approximately 1.5 g protein/kg (2.1 g/kg(0.75)) body weight is needed to maintain nitrogen balance, while 5.2 g protein/kg (7.8 g/kg(0.75)) body weight is needed to maintain LBM. This study provides evidence that nitrogen balance studies are inadequate for determining optimum protein requirements. Animals, including cats, can adapt to low protein intake and maintain nitrogen balance while depleting LBM. Loss of LBM and an associated reduction in protein turnover can result in compromised immune function and increased morbidity. Current Association of American Feed Control Officials (AAFCO) and National Research Council (NRC) standards for protein adequacy may not provide adequate protein to support LBM. The minimum daily protein requirement for adult cats appears to be at least 5.2 g/kg (7.8 g/kg(0.75)) body weight, well in excess of current AAFCO and NRC recommendations. Further research is needed to determine the effect, if any, of body condition, age and gender on protein requirements.

Reliability of endogenous markers for estimation of residual renal function in haemodialysis patients

Residual renal function in haemodialysis patients is of increasing interest. However, reproducibility and agreement between methods to measure and estimate glomerular filtration rate (GFR) require further elucidation. The aim of this study was to evaluate the accuracy and reproducibility of GFR estimates based on endogenous markers in haemodialysis patients. Twelve patients were examined twice. GFR was estimated by (i) urine clearances of creatinine, urea and the average of creatinine and urea clearance [U-Cl(crea-urea)]; (ii) an equation based on serum concentration of cystatin C [eGFR(CysC)]. These were compared to (51) Cr-EDTA clearance in plasma [P-Cl(EDTA)] and urine [U-Cl(EDTA)]. U-Cl(crea-urea) produced results similar to U-Cl(EDTA). eGFR(CysC) had a low week-to-week variability. Visually, eGFR(CysC) differed from y=x when compared to the other methods indicating bias, probably due to extrarenal elimination of cystatin C. Coefficients of variation were significantly different, P<0·001: P-Cl(EDTA), 10%; U-Cl(EDTA), 13%; and U-Cl(crea-urea), 13%. P-Cl(EDTA) was 2·1ml min(-1) 1·73m(-2) higher than U-Cl(EDTA) (mean). Glomerular filtration rate in haemodialysis patients can be estimated from U-Cl(crea-urea) when complete urine collection is performed. The available eGFR(CysC) in haemodialysis patients seemed to be biased, and further development and validation is desirable. P-Cl(EDTA) was the most reproducible method and might be useful in special situations.

This Kinetic, Bioavailability, and Metabolism Study of RRR-α-Tocopherol in Healthy Adults Suggests Lower Intake Requirements than Previous Estimates ,

Kinetic models enable nutrient needs and kinetic behaviors to be quantified and provide mechanistic insights into metabolism. Therefore, we modeled and quantified the kinetics, bioavailability, and metabolism of RRR-α-tocopherol in 12 healthy adults. Six men and 6 women, aged 27 ± 6 y, each ingested 1.81 nmol of [5-14CH3]-(2R, 4'R, 8'R)-α-tocopherol; each dose had 3.70 kBq of14C. Complete collections of urine and feces were made over the first 21 d from dosing. Serial blood samples were drawn over the first 70 d from dosing. All specimens were analyzed for RRR-α-tocopherol. Specimens were also analyzed for 14C using accelerator MS. From these data, we modeled and quantified the kinetics of RRR-α-tocopherol in vivo in humans. The model had 11 compartments, 3 delay compartments, and reservoirs for urine and feces. Bioavailability of RRR-α-tocopherol was 81 ± 1%. The model estimated residence time and half-life of the slowest turning-over compartment of α-tocopherol (adipose tissue) at 499 ± 702 d and 184 ± 48 d, respectively. The total body store of RRR-α-tocopherol was 25,900 ± 6=220αmol (11 ± 3 g) and we calculated the adipose tissue level to be 1.53 αmol/g (657αg/g). We found that a daily intake of 9.2αmol (4 mg) of RRR-α-tocopherol maintained plasmaRRR-a-tocopherol concentrations at 23αmol/L. These findings suggest that the dietary requirement for vitamin E may be less than that currently recommended and these results will be important for future updates of intake recommendations.

Foods contributing to sodium intake and urinary sodium excretion in a group of Australian women.

To identify food sources of Na in a group of community-dwelling women in Adelaide, South Australia. A secondary aim was to measure Na excretion in this group. Survey. Community setting, Adelaide, South Australia. Seventy healthy women (mean age 48.6 (SD 8.1) years, mean BMI 28.6 (SD 6.3) kg/m2) living in metropolitan Adelaide, South Australia and participating in a validation study of an FFQ. Dietary intake was derived from two 4 d weighed food records. Foods from the 4 d weighed food records were grouped according to foods or food groups to establish contributors to Na intake. Na excretion was measured in two 24 h urine samples. Completeness of urine collections was verified using creatinine excretion. Bread alone contributed 19.0% of Na intake, with an overall contribution from the breads and cereals group of 32.5%. Meat products contributed 14.4% of intake, the dairy and eggs group (excluding cheese) 9.6% and combination dishes (e.g. pizza, quiche, sandwiches and stir fry dishes) 8.4%. Na excretion was 126 (SD 42) mmol/d, i.e. approximately 7.6 (SD 2.5) g salt/d. Seventy per cent of participants (n 48) had Na excretion ≥100 mmol/d (146 (SD 34) mmol/d). Effective Na reduction could be achieved by reducing the amount in staple foods such as bread and meat products.

Abstract P362: Validation of a Simple Method to Estimate Populational 24-h Urinary Sodium Excretion Based on a Casual Urine Specimen in an Adult Danish Population

Background: Tanaka et al (J Hum Hypert 2002; 16: 97-103) developed a simple method to estimate populational 24-h urinary sodium excretion using a casual urine specimen. However, this method was developed and validated in a Japanese population and thus this method might not be valid in populations that differ markedly from this population. Hypothesis: We assessed the hypothesis that the 24 hour urinary sodium excretion can be estimated from a casual spot urine using the Tanaka prediction method in a Danish general population. Methods: Overall 473 Danish individuals provided both a 24h urine collection and a spot urine sample. Data were collected in the Danthyr study (248 women aged 25-30 years and 60-65 years) and the Inter99 study (102 men and 113 women aged 30-60 years), respectively. Only participants with complete 24h urine collection (validated by the PABA method) were included. We compared the estimated daily sodium excretion through 24h urine (the gold standard) with the predicted 24 h sodium excretion from a causal urine specimen, using the Tanaka prediction method. Results: The predicted median 24 h sodium excretion (median [5 and 95 percentile]) was 8.6 gram [3.7;17.5] compared with a median measured 24 h sodium excretion of 8.9 [5.4; 13:1]. The mean (sd) residual (measured minus predicted 24 h sodium excretion) was 0.08 (3.7). The correlation (Spearman) between predicted and measured 24 h sodium excretion was 0.39 and the R 2 was 0.17. The proportion of individuals classified in the same or adjacent quintiles was 67%. Gross misclassification was found for 3% of the individuals. However, a Bland-Altman plot indicated a tendency of underestimation the sodium excretion for individuals with a high level of sodium excretion (&gt;14 g per day). Conclusion: The Tanaka prediction model gives a reasonable estimate of sodium intake in a Danish population using casual spot urines. However, the validation study showed a tendency of underestimation of the sodium intake for individuals with a high sodium excretion (&gt;14 g per day).

Prevalence and Metabolic Abnormalities of Vitamin D–inadequate Patients Presenting With Urolithiasis to a Tertiary Stone Clinic

To assess the prevalence and metabolic abnormalities of patients with inadequate vitamin D (VD) presenting with urolithiasis to a tertiary stone clinic in North America. A retrospective review of consecutive patients presenting from August 2009 to January 2010 was performed. Demographic and clinical data were collected together with metabolic stone workup, including 2 24-hour urine collections and serum 25-hydroxy VD [25(OH)D]. VD inadequacy (VDI) included VD deficiency and VD insufficiency defined as 25-(OH) VD levels <20 ng/mL and 21-29 ng/mL, respectively. Of 101 patients, 81 (80.2%) were found to have VDI: 34 (33.7%) were deficient and 47 (46.5%) had insufficient VD. Mean age was 50.4 ± 15.8 years and the mean body mass index was 28.7 ± 5.8 kg/m(2). Forty-two percent were smokers, 51% were recurrent stone formers, and 54% had positive family history of urolithiasis. Hyperparathyroidism was detected in 25.9% of patients, of which 91% of them were secondary to VDI. Hypocalcemia and hyperuricemia were found in 36% and 11% of patients, respectively. Of 81 VDI patients, 69 (85.2%) had complete 24-hour urine collections, of which 92.7% had at least one abnormality. However, only 40% of patients with normal VD had metabolic abnormalities (P <.0001). The most prevalent pattern of urinary abnormalities in VDI patients were suboptimal volume (45%), hypocitaturia (24%), hypocalciuria (33%), hypercalciuria (20%), hyperuricosuria (16%), cystinuria (5%), and hyperoxaluria (7.2%). In this preliminary study, patients presenting with urolithiasis were found to have a high prevalence of inadequate VD associated with abnormalities on metabolic stone work-up.