Correcting for Plasma Aldosterone Improves the Accuracy of Repeated Timed Urine Sampling for Estimation of Dietary Sodium Intake.

INTRODUCTION: Long-term sodium balance studies show that sodium can be temporarily stored and released in tissues, mediated by circaseptan rhythms of aldosterone and cortisol. This complicates the reliability of a single 24-h urine collection to estimate individual sodium intake. We investigated whether repeated timed urine collection with and without correction for plasma aldosterone is a more accurate alternative for estimating daily sodium intake. METHODS: We conducted a post hoc analysis of a metabolic ward study in which 16 healthy male adults consumed a diet with a fixed sodium content (50 or 200 mmol/day) for 7 days. Each day, urine was collected in 4 intervals (7:00-13:00 h, 13:00-19:00 h, 19:00-23:00 h, and 23:00-07:00 h). Plasma aldosterone was measured at 6:30 h, 12:30 h, and 18:30 h. Sodium intakes were estimated by various formulas using 3 timed urines of day 5-7. RESULTS: During a 200-mmol daily sodium intake, sodium intake estimates based on three repeated timed urine samples and the Toft equation differed 10 [IQR: 3-14], 8 [6-19], 36 [16-49], and 20 [10-43] mmol from the actual intake for intervals 7:00-13:00 h, 13:00-19:00 h, 19:00-23:00 h, 23:00-7:00 h, respectively. These measurements did not significantly differ from a single 24-h urine (20 [12-55] mmol). During a 50-mmol daily sodium intake, repeated timed urine collection performed worse than a single 24-h urine collection. On both diets, correction for plasma aldosterone increased accuracy and sodium intake estimates were significantly more accurate than a single 24-h urine. CONCLUSION: In a controlled environment, repeated timed urine collection corrected for plasma aldosterone is more accurate than a single 24-h urine collection.

Evaluation of three prediction formulas of 24-hour urinary sodium excretion in Chinese residents: a systematic review and meta-analysis.

OBJECTIVE: To determine the appropriateness of three widely used formulas estimating 24-h urinary Na (24hUNa) from spot urine samples in the Chinese population. DESIGN: Systematic review and meta-analysis. SETTING: Literature review was conducted to identify studies for estimating 24hUNa using the Kawasaki, Tanaka and INTERSALT formulas simultaneously in PubMed, Embase and the Cochrane library databases. The mean difference (MD) and correlation coefficients (r) between measures and estimates from different formulas were assessed. PARTICIPANTS: Information extraction and quality assessment were performed in thirteen studies involving 8369 subjects. RESULTS: Two studies which affected the overall robustness were excluded in the 'leave-one-out' sensitivity analyses. Within the final meta-analysis included eleven studies and 7197 participants, 36·07 mmol/d (95 %CI 16·89, 55·25) of MD was observed in the Kawasaki formula, and -19·62 mmol/d (95 %CI -37·37, -1·87) in the Tanaka formula and -35·78 mmol/d (95 %CI -50·76, -20·80) in the INTERSALT formula; a pooled r-Fisher's Z of 0·39 (95 %CI 0·32, 0·45) in the Kawasaki formula, 0·43 (95 %CI 0·37, 0·49) in the Tanaka formula and 0·36 (95 %CI 0·31, 0·42) in the INTERSALT formula. Subgroup analyses were conducted to explore the possible factors affecting the accuracy of the formula estimation from three mainly aspects: population types, Na intake levels and urine specimen types. CONCLUSIONS: The meta-analysis suggested that the Tanaka formula performed a more accurate estimate in Chinese population. Time of collecting spot urine specimens and Na intake level of the sample population might be the main factors affecting the accuracy of the formula estimation.

Spot urinary sodium in CKD patients: correlation with 24h-excretion and evaluation of commonly used prediction equations.

BACKGROUND: Salt intake in CKD patients can affect cardiovascular risk and kidney disease progression. Twenty-four hour (24h) urine collections are often used to investigate salt metabolism but are cumbersome to perform. We assessed urinary sodium (U-Na) concentration in spot urine samples and investigated the correlation with 24h U-Na excretion and concentration in CKD patients under nephrological care. Further, we studied the role of CKD stage and diuretics and evaluated the performance of commonly used formulas for the prediction of 24h U-Na excretion from spot urine samples. METHODS: One hundred eight patients of the German Chronic Kidney Disease (GCKD) study were included. Each participant collected a 24h urine and two spot urine samples within the same period. The first spot urine sample (AM) was part of the second morning urine. The second urine sample was collected before dinner (PM). Patients were advised to take their medication as usual without changing dietary habits. U-Na concentrations in the two spot urine samples and their average ((AM + PM)/2) were correlated with U-Na concentration and total Na excretion in the 24h urine collections. Correlations were subsequently studied after stratification by CKD stage and diuretic intake. The usefulness of three commonly applied equations to estimate 24h U-Na excretion from spot urine samples (Kawasaki, Tanaka and Intersalt) was determined using Bland-Altman plots, analyses of sensitivity, specificity, as well as positive (PPV) and negative predictive values (NPV). RESULTS: Participants (42 women, 66 men) were on average (± SD) 62.2 (± 11.9) years old, with a mean serum creatinine of 1.6 (± 0.5) mg/dl. 95% had arterial hypertension, 37% diabetes mellitus and 55% were on diuretics. The best correlation with 24h U-Na total excretion was found for the PM spot U-Na sample. We also found strong correlations when comparing spot and 24h urine U-Na concentration. Correction of spot U-Na for U-creatinine did not improve strength of correlations. Neither CKD stage, nor intake of diuretics had significant impact on these correlations. All examined formulas revealed a significant mean bias. The lowest mean bias and the strongest correlation between estimated and measured U-Na excretion in 24h were obtained using the Tanaka-formula. Also, application of the Tanaka-formula with PM U-Na provided best sensitivity, specificity, PPV and NPV to estimate U-Na excretion > 4g/d corresponding to a salt consumption > 10g/d. CONCLUSION: U-Na concentration of spot urine samples correlated with 24h U-Na excretion especially when PM spot U-Na was used. However, correlation coefficients were relatively low. Neither CKD stage nor intake of diuretics appeared to have an influence on these correlations. There was a significant bias for all tested formulas with the Tanaka-formula providing the strongest correlation with measured 24h U-Na excretion. In summary, using spot urine samples together with the Tanaka-formula in epidemiological studies appears feasible to determine associations between approximate salt intake and outcomes in CKD patients. However, the usefulness of spot-urine samples to guide and monitor salt consumption in individual patients remains limited.

Dietary sodium sources according to four 3-d weighed food records and their association with multiple 24-h urinary excretions among middle-aged and elderly Japanese participants in rural areas.

Reducing Na intake is an urgent global challenge, especially in East Asia and high-income Asia-Pacific regions. However, the sources of Na and their effects on urinary Na excretion have not been fully studied. We sought to clarify these sources and their association with urinary Na excretion. We examined four 3-d weighed food records and five 24-h urinary collections from each of 253 participants in Japan, aged 35-80 years, between 2012 and 2013. We compared the levels of Na according to four categories: foods contributing to discretionary or non-discretionary Na intake, the situation in which dishes were cooked and consumed, food groups and types of cuisine. We also conducted regression analysis in which 24-h urinary Na excretion was a dependent variable and the amounts of food intake in the four categories were independent variables. Levels of Na were the highest in discretionary intake (60·6 %) and in home-prepared dishes (84·0 %). Of the food groups, miso soup showed the highest percentage contribution to Na intake (13·3 %) after seasonings such as soya sauce. In the regression analysis, the standardised coefficient for foods of non-discretionary Na sources was larger than that for discretionary sources, whereas that for home-prepared dishes was consistent with the levels of Na in those foods. Pickled products, followed by fresh fish and shellfish, miso soup and rice, were associated with high urinary Na excretion. Thus, discretionary foods (such as miso soup) contribute the most to Na consumption, although non-discretionary intake (such as pickled vegetables) may influence urinary Na excretion.

Validation of spot urine in estimating 24-h urinary sodium, potassium and sodium-to-potassium ratio during three different sodium diets in healthy adults.

PURPOSE: To evaluate the validity of spot urine assay methods in estimating the 24-h urinary sodium, potassium and sodium-to-potassium ratio during three different sodium diets. MATERIALS AND METHODS: Twelve healthy volunteers were asked to adhere to 3 dietary sodium targets (3.3-5.0g/day,<3.3 g/day and >5.0 g/day) for three consecutive weeks and to measure salt excretion daily in spot urine samples using a self-monitoring device. On day 7 of each week, 24-h urine was collected to compare measured with estimated 24-h salt excretion (by the Kawasaki, Tanaka and INTERSALT equations). RESULTS: Correlation coefficients relating measured and estimated 24-h sodium excretion were low and not significant for Kawasaki and INTERSALT and moderate for the Tanaka equation (τ 0.56-0.64,p<.05). Bland-Altman plots showed considerable differences between estimated and measured sodium excretion across all salt diets. Over 40% of the participants showed an absolute difference between measured and estimated 24-h sodium of more than 1000 mg/day. The correlation coefficients between 24-h and spot Na/K ratio were 0.67, 0.94 and 0.85(p<.05), and mean differences were 0.59, 0.06 and 0.48 for the intermediate, low and high sodium diets, respectively. CONCLUSION: These findings do not support estimation of individual 24-h salt excretion from spot urine by the Kawasaki, Tanaka, or INTERSALT formula. Plain language summaryAccurate monitoring of salt intake is essential to improve BP control. At present, measurement of sodium and potassium excretion in multiple non-consecutive 24-h urinary collections is considered the gold standard for measuring dietary sodium intake. However, this method is burdensome, time-consuming and error prone.Therefore, we assessed and compared the validity of three formula-based approaches to estimate 24-h urinary sodium and potassium excretion and the Na/K ratio from spot urine samples measured by a self-monitoring device under three different sodium diets using 24-h urine collections as the reference.We conclude that use of three commonly used equations that estimate 24-h urinary sodium and potassium excretion result in substantial bias, poor precision and poor accuracy and are therefore not recommended. The Na/K ratio based on multiple casual urine samples may be a useful, low-burden, low-cost alternative method to 24-h urine collection for monitoring daily salt intake.

Feasibility of 24-h urine creatinine clearance as a renal function monitoring tool in spinal cord injury patients.

OBJECTIVE: Renal dysfunction is a major cause of morbidity in patients with spinal cord injury (SCI). A 24-h urine creatinine (Cr) clearance (24-h urine CCr) is cost-effective and easy to implement compared to renal scintigraphy in the evaluation of renal function. This study aimed to verify the feasibility of 24-h urine CCr in the SCI population by assessing the correlation with effective renal plasma flow (ERPF) on renal scintigraphy. METHODS: Data from 245 SCI patients (189 males, mean age: 50.2 years) were used in this retrospective review. Clinical characteristics, 24-h urine CCr, serum Cr, comorbidities, and body composition analyses were assessed for correlation with laboratory parameters including renal scintigraphy. Strong predictors of ERPF were determined by multivariate linear regression analysis. Areas under receiver-operating characteristic curves were calculated to evaluate the discriminating power of 24-h urine CCr to predict ERPF <250 ml/min. RESULTS: Spinal cord injury patients showed tubular dysfunction despite normal serum Cr and 24-h urine CCr. There was a significant correlation between 24-h urine CCr and ERPF, and 24-h urine CCr was one of the strongest predictors for ERPF (area under the curve 0.72, 95% CI 0.64-0.80, p < 0.000) among other parameters such as age, appendicular lean mass index, and body mass index. 24-h urine CCr was an independent predictor of ERPF in subacute (R2 = 0.497, p < 0.001) and chronic SCI patients (R2 = 0.664, p < 0.0001). The optimized 24-h urine CCr cut-off was 139.4 ml/min/1.72 m2 for predicting decreased ERPF <250 ml/min (sensitivity 67.6% and specificity 64.0%). CONCLUSION: 24-h urine CCr is a sensitive indicator for renal function deterioration of SCI patients. Further longitudinal studies with larger numbers of SCI patients are needed to confirm the feasibility of 24-h urine CCr for monitoring this population.

Biomarkers of Fruit Intake Using a Targeted Metabolomics Approach: an Observational Cross-Sectional Analysis of the ELSA-Brasil Study.

BACKGROUND: Advances in technology have led to the identification of a greater number of metabolites related to diet. Although fruit intake biomarkers have been reported in some studies, these findings require further replication, considering the relevance of fruits for diet quality and health. OBJECTIVES: The aim of this study was to explore the associations of a set of potential urinary biomarkers of diet, assessed using a targeted metabolomics approach, with self-reported fruit intake data in participants of a computer-assisted 24-h dietary recall (GloboDiet software) validation study. METHODS: A total of 93 individuals aged 43-72 y, 54% female, participated in this study. The subjects were a subsample of the Longitudinal Study of Adult Health (ELSA-Brasil). A 24-h dietary recall was obtained with the aid of GloboDiet software matching a 24-h urine sample from each participant. Candidate biomarkers were selected in a literature search and identified in urine by LC coupled to high-resolution MS. Spearman correlation analyses were performed between fruit intake and each biomarker. RESULTS: Spearman correlation analysis showed that total fruits intake was significantly correlated with citric acid (ρ = 0.213, P = 0.041), ferulic acid sulfate I (ρ = 0.240, P = 0.020), hesperetin glucuronide/homoeriodictyol glucuronide (ρ = 0.303, P = 0.003), hydroxyhippuric acid (ρ = 0.239, P = 0.021), homovanillic alcohol sulfate (ρ = 0.339, P = 0.001), methylgallic acid sulfate (ρ = 0.268, P = 0.009), naringenin glucuronide (NG; ρ = 0.278, P = 0.007), proline betaine (PB; ρ = 0.305, P = 0.003), syringic acid sulfate (ρ = 0.210, P = 0.044), and sinapic acid sulfate (ρ = 0.412, P < 0.001). Among them, 3 have been described in literature as promising biomarkers for intake of total fruit, oranges, and citrus fruit: NG, hesperetin glucuronide, and PB. CONCLUSIONS: Associations of total fruits intake with urinary measurements indicate the potential usefulness of dietary biomarkers in the Brazilian population as a complement to self-reported dietary assessments.

Is there a relationship between dietary sodium and potassium intake and clinical findings of a migraine headache?

Few studies have assessed the association between sodium (Na) and potassium (K) and migraine headaches. In this study, we aimed to examine the relationship between 24-hour urine Na and K intakes and clinical findings of migraine in an Iranian sample. In this cross-sectional study, 262 participants, aged 20-50 years, were included with a body mass index (BMI) of 18·5-30 kg/m2 and a diagnosis of migraine. One 24-hour urine sample was collected from each subject to estimate the Na and K intakes. The clinical features of migraine, including frequency, duration, severity, Migraine Headache Index Score (MHIS), and Headache Impact Test (HIT) score, were assessed. Besides, a multiple linear regression analysis was performed, and beta estimates and the corresponding 95% confidence intervals (CIs) were reported. Overall, 224 women and 38 men, with a mean age of 36·10 years and BMI of 25·55 kg/m2 comprised our study population. After controlling for potential confounders, the 24-hour urine Na was positively associated with a longer headache duration (ß = 0·29; 95% CI: 0·06, 0·53) in the group with the highest urine Na levels as compared to the group with the lowest levels. After adjustments for potential confounders, an increase of 13·05 in the MHIS was observed when the 24-hour urine Na level increased from the first to the third tertile (ß = 13·05; 95% CI: 1·70, 24·41). Our findings suggested that a higher 24-hour urine Na level was positively associated with a longer duration of migraine headaches and a higher MHIS.

Accuracy of equations for predicting 24-h urinary potassium excretion from spot urine samples in Chinese children.

Accurate assessments of potassium intake in children are important for the early prevention of CVD. Currently, there is no simple approach for accurate estimation of potassium intake in children. We aim to evaluate the accuracy of 24-h urinary potassium excretion (24UKV) estimation in children using three common equations: the Kawasaki, Tanaka and Mage formulas, in a hospital-based setting. A total of 151 participants aged 5-18 years were initially enrolled, and spot urine samples were collected in the whole 24-h duration to measure the concentrations of potassium and creatinine. We calculated the mean difference, absolute and relative difference and misclassification rate between measured 24UKV and the predicted ones using Kawasaki, Tanaka and Mage formulas in 129 participants. The mean measured 24UKV was 1193·3 mg/d in our study. Mean differences between estimated and measured 24UKV were 1215·6, -14·9 and 230·3 mg/d by the Kawasaki, Tanaka and Mage formulas, respectively. All estimated 24UKV were significantly different from the measured values in all the time point (all P < 0·05), except for the predicted values from Tanaka formula using morning, afternoon and evening spot urine. The proportions with relative differences over 40 % were 87·2%, 32·5% and 47·3 % for Kawasaki, Tanaka and Mage formulas, respectively. Misclassification rates were 91·5 % for Kawasaki, 44·4 % for Tanaka and 58·9 % for Mage formula at the individual level. Our findings showed that misclassification could occur on the individual level when using Kawasaki, Tanaka and Mage formulas to estimate 24UKV from spot urine in the child population.

The DONALD study as a longitudinal sensor of nutritional developments: iodine and salt intake over more than 30 years in German children.

PURPOSE: Mild-to-moderate iodine deficiency was present in large parts of Germany up to the beginning 1990s and improved from then on. Current epidemiological data on spot urine iodine measurements in German children strongly suggest the re-occurrence of an impaired iodine status. We thus examined whether this re-occurrence is identifiable in more detail, through iodine analyses of 24-h urine samples of a well-characterized cohort of German children in whom samples have been systematically collected from 1985 onward. As iodized salt is a major source for iodine supply, urinary sodium excretion was additionally studied. METHODS: Daily iodine and sodium excretions were measured in 2600 24-h urine samples collected between 1985 and 2018 by 677 healthy children aged 6-12 years (participants of the DONALD study). These data were compared with 24-h iodine and sodium excretion estimates obtained from spot urine samples collected in the representative German Health Interview and Examination Surveys for Children and Adolescents KiGGS-baseline (2003-2006) and KiGGS-wave-2 (2014-2017). RESULTS: Between 1985 and1992, DONALD participants started with a median daily iodine excretion level of 40.1 µg/d. Then, during 1993-2003, iodine excretions mounted up to an approximate plateau (~ 84.8 µg/d). This plateau lasted until 2012. Thereafter, iodine concentrations started to decrease again resulting in a median iodine excretion of only 58.9 µg/d in 2018. Sodium excretion, however, had increased. The marked decrease in iodine status along with an abundant sodium excretion corresponded closely with nationwide KiGGS data. CONCLUSIONS: As exemplified for the clearly worsening iodine status in German children, longitudinal cohort studies collecting detailed biomarker-based prospective data have the potential to reliably capture health-relevant nutritional changes and trends, applicable on a more comprehensive and even representative population level.

Sodium and potassium intakes and adiposity among Iranian pre-adolescents and adolescents: a cross-sectional study.

BACKGROUND: High sodium and low potassium intakes are associated with the early development of chronic diseases (e.g., hypertension, obesity). Taking into account the limited data on sodium and potassium intakes by 24-h excretion in urine in pre-adolescents and adolescents, we wished to determine baseline salt intake in Iranian subjects aged 11-18 years. METHODS: This was an observational study involving 374 pre-adolescents and adolescents (154 boys and 220 girls). Sodium and potassium intakes were ascertained by measuring sodium and potassium excretion in urine over 24 h. Creatinine level was used to validate the completeness of the urine collections. The association between sodium and potassium intake and adiposity was determined based on body fat percentage. RESULTS: The mean 24-h urine sodium concentration was 3130 ± 2200 mg/day, equal to 7.961 ± 5.596 g/day salt intake. Approximately half of the study participants exceeded the upper limit of Na intake. The mean potassium intake was estimated 1480 ± 1050 mg/day. There was a positive association between urinary sodium excretion and adiposity in crude (OR 1.79; 95% CI: 1.08-2.74) and full adjusted model (OR: 3.15; 95% CI: 2.28-4.63). Also, in subsample analysis, there was a positive correlation between urinary sodium and adiposity in both pre-adolescents (OR: 2.71; 95% CI: 2.29-3.93) and adolescents (OR: 3.55; 95% CI: 2.17-4.74). However, no significant association was found between 24-h urinary potassium and adiposity. CONCLUSION: Sodium intake, as estimated by 24-h urinary excretion, was higher than recommended and it was positively associated with adiposity. Also, this study reported low compliance of potassium intake recommendations in 11-18 years' Iranian pre-adolescents and adolescents. Health promotion interventions are needed in order to broaden public awareness of high sodium intake and potassium inadequacy to reduce chronic diseases.

Dietary sodium estimation methods: accuracy and limitations of old and new methods in individuals at high cardiovascular risk.

OBJECTIVE: Accurate and easy to use methods for dietary Na intake estimation in population level are lacking. We aimed at (i) estimating the mean Na intake in the group level using a variety of dietary methods (DM) and urinary methods (UM) and correlating them with 24-h urine collection (24UCol) and (ii) improving the accuracy of the existing DM. DESIGN: The most common DM (three 24-h dietary recalls (24DR) and FFQ) and UM (24UCol and spot urine collection using common equations) were applied. To improve the existing: (i) 24DR, discretionary Na was quantified using salt-related questions or adding extra 15 % in total Na intake and (ii) FFQ, food items rich in Na and salt-related questions were added in the standard questionnaire (NaFFQ). SETTING: National and Kapodistrian University of Athens, Greece. PARTICIPANTS: Totally, 122 high cardiovascular risk subjects (56·0 ± 12·6 years; 55·7 % males). RESULTS: Mean 24 h Na excretion (24UNa) was 2810 ± 1304 mg/d. Spot urine methods overestimated the 24UNa (bias range: -1781 to -492 mg) and were moderately correlated to 24UCol (r = 0·469-0·596, P ≤ 0·01). DM underestimated the 24UNa (bias range: 877 to 1212 mg) and were weakly correlated with 24UCol. The improved DM underestimated the 24UNa (bias range: 877 to 923 mg). The NaFFQ presented the smallest bias (-290 ± 1336 mg) and the strongest correlation with 24UCol (r = 0·497, P ≤ 0·01), but wide limits of agreement in Bland-Altman plots (-2909 mg; 2329 mg), like all the other methods did. CONCLUSIONS: The existing methods exhibit poor accuracy. Further improvement of the newly developed NaFFQ could be promising for more accurate estimation of mean dietary Na intake in epidemiological studies. Additional validation studies are needed.

Validation of salt intake measurements: comparisons of a food record checklist and spot-urine collection to 24-h urine collection.

OBJECTIVE: Monitoring population salt intake is operationally and economically challenging. We explored whether a questionnaire assessment and a prediction of Na intake from spot-urine could replace or complement the recommended measurement of Na in 24-h urine (24-h U). DESIGN: Compare the agreement of a Na-specific food record checklist (FRCL) and a late-afternoon spot-urine measurement (PM-spot) with 24-h U measurement in estimating Na intake at group level. Each participant's use of these methods extended over 3 d. Agreement was assessed using mean (95 % CI) differences, linear regression models and Bland-Altman plots. SETTING: The validation study was part of a 1-year workplace intervention trial to lower salt intake in Switzerland. PARTICIPANTS: Seventy women and 71 men, aged 21-61 years, completed three FRCL, and acceptable PM-spot and 24-h U samples at baseline (April-October 2015). RESULTS: Mean Na intake estimates varied slightly across methods (3·5-3·9 g/d). Mean Na intake differences from 24-h U were 0·2 (95 % CI (0, 0·5)) g/d for FRCL and 0·4 (95 % CI (0·2, 0·6)) g/d for PM-spot. Linear regression models and Bland-Altmann plots more clearly depicted differences by sex and discretionary salt use. CONCLUSIONS: Although 24-h U remains the best reference method for monitoring Na intake at the population level, PM-spot and FRCL might be more practical instruments for frequent, periodic Na intake assessments. Population-specific prediction models to estimate 24-h U could be developed and evaluated.

The effect of acid use as a preservative on the results of biochemical tests measured in 24-h urine.

Twenty-four-hour urine measurements play a crucial role in the diagnosis, follow-up and treatment of various diseases. There are different approaches to the collection of urine in patients who need to collect multiple urine samples at a time, especially in hospitals with heavy workloads. In this study, we compared the sodium, potassium, chloride, amylase, calcium, creatinine, phosphorus, microalbumin, protein, magnesium, urea, uric acid, adrenaline, noradrenaline, dopamine, metanephrine, normetanephrine, vanillylmandelic acid, 5-hydroxyindoleacetic acid and homovanillic acid results of 24-h urine samples analyzed immediately without acid addition, which we accepted as the reference and baseline measurement, with the results of the samples analyzed after waiting for 24 h without acid addition, analyzed immediately with acid addition and analyzed after waiting for 24 h with acid addition. Chloride, microalbumin, amylase and protein tests, which are recommended to be measured in the sample without preservatives, are affected by acid addition. Adrenaline, noradrenaline and dopamine, which are the tests recommended to be measured in acid-added urine are degraded in the samples without acid, and the levels of metanephrine and normetanephrine were not significantly degraded in the absence of preservatives.

Estimation of 24 h Urine Protein Versus Spot Urine Protein Creatinine Ratio in Patients with Kidney Disease.

This cross-sectional study was undertaken to compare 24-h urine protein estimation with spot urine protein-creatinine ratio (PCR). 72 patients having proteinuria of > 150 mg/day were included in this study. 24-h urine total protein (UTP) test were also asked to give their mid-morning spot urine sample the following day for urine protein-creatinine ratio. The subjects were grouped according to their UTP into Groups as described follows: Group A < 1 g/day, Group B 1-3.5 g/day and Group C > 3.5 g/day. Pearson's correlation (r) and paired Student's T test were done. The paired T test showed no difference in the UTP and PCR in the subgroup having qualitative protein of zero and in group A. There was no agreement between the two methods used for quantitation. In the overtly proteinuric patients, the correlation between the UTP and PCR was positive in group A which was statistically significant (p = 0.05) whereas it was not significant (p = 0.07) in group B. Though there was a negative correlation in the massive proteinuria group C it was not significant (p = 0.65). Our study demonstrates that spot PCR can be reliable parameter for initial diagnostic criterion of proteinuria but for follow-up measurements and for proteinuria > 0.5 gm/day, 24-h UTP is the single most accurate measurement of protein excretion.

Reference range for 24-h urine calcium, calcium/creatinine ratio, and correlations with calcium absorption and serum vitamin D metabolites in normal women.

A study of 959 black and white women shows that the normal range for 24-h urine calcium excretion in white women is 30-300 mg and 10-285 mg in black women. Clinical laboratories use a normal range for 24-h urine calcium excretion of 100-300 mg; there is a need for them to update their age- and race-specific ranges. INTRODUCTION: Recommendations for a normal range for 24-h urine calcium vary from a low of 50 mg to a high of 400 mg; most "laboratory normal ranges" based on older literature are incorrect. The objective of this analysis is to define a normal range for young women age 25-45 years and older women age 55-90 years, white and black, for 24-h urine calcium and calcium/creatinine ratio, and to examine the relationship between 24-h urine calcium, calcium absorption, and vitamin D metabolites. METHODS: Data from 3 studies was collected on 959 normal black and white women, ages 25-87 years, for 24-h urine calcium, creatinine, calcium intake, serum 25-hydroxyvitamin D (25OHD),1,25 dihydroxyvitamin D (1,25(OH)2D), and calcium absorption. Urine calcium and creatinine were measured on an auto-analyzer. Calcium absorption was measured by a single isotope method. Serum 25OHD and 1,25(OH)2D were measured by competitive protein binding assay or radioimmunoassay. Because 24-h urine calcium did not fit a normal distribution, non-parametric methods were used to determine the 95% reference interval (RI) and 90% non-parametric confidence intervals (CI) calculated for groups. RESULTS: The 95% reference intervals for 24-h urine calcium for women were as follows: black older 7-225 mg, black younger 8-285 mg; white older 37-275 mg, and white younger 23-287 mg. In older white women, 24-h urine calcium was significantly correlated with serum 1,25(OH)2 D, r = 0.23, p < 0.001, calcium intake r = 0.12, p = 0.001, and calcium absorption r = 0.18, p = 0.003, but not serum 25OHD r = 0.07, p = 0.06. CONCLUSIONS: The normal reference interval for 24-h urine calcium for black women is lower than white women. Twenty-four-hour urine calcium was correlated with serum 1,25(OH)2 D calcium intake and calcium absorption, but not serum 25OHD. This range will be useful clinically for defining hypercalciuria and for following patients on vitamin D and calcium treatment.

The impact of phone counseling on urinary stone prevention.

OBJECTIVE: We compared the effect of standard office-based consultation (OC) and phone correspondences (PC) on dietary 24-h urinary parameters. METHODS: The medical record of all patients treated between January and April 2019 was reviewed. Only patients who had at least two consecutive 24-h urine collections were included. Linear and logistic regressions were used to investigate the difference between the changes in urinary parameters after OC and PC. RESULTS: Forty-three patients underwent 135 OC and 34 PC. Twenty-one received OC and PC, and 22 had only OC. Gender, age, the distance to stone clinic, the number of previous stone episodes, and baseline urinary parameters were similar between the groups. Patients who had both OC and PC had a longer follow-up time (51.7 vs 18.5 months, p < 0.0001) as well as more consults (Median 5.4 vs 2.5, p < 0.0001). Six (27%) patients who had only OC, and eight (38%) patients who had both OC and PC, experienced stone recurrence during the study period (p = 0.52). Following PC, there was a greater improvement in urine volume in comparison to OC (0.27 l/day vs -0.06 l/day, p = 0.034), but there was no difference in the absolute values after the consults between the groups. CONCLUSION: In established stone-clinic patients, PC was associated with a better adherence with follow-up. The 24-h urine results were similar between PC and OC. PC may be an effective alternative for urinary stone management.

Association between hypertension and 24-h urine composition in adults without urolithiasis in China.

PURPOSE: To explore the association between hypertension and 24-h urine composition in adults without urolithiasis in China. MATERIALS AND METHODS: Blood test and 24-h urine analysis were performed on 958 non-stone formers in six cities to select eligible participants. Eligible participants were divided into hypertension group and non-hypertension group according to WHO guidelines. The 24-h urine compositions between two groups were compared using univariate and multivariate logistic regressions. RESULTS: A total of 584 adults without urolithiasis were included in this analysis. Compared with non-hypertension group, hypertension group had significantly older age, higher BMI, higher prevalence of diabetes mellitus and higher levels of total cholesterol and LDL, but lower eCCr value, lower levels of serum creatinine and serum sodium (all P value < 0.05). In univariable comparisons, hypertension patients had significantly higher level of urine potassium (mean difference [MD] = - 3.89 mmol, 95% confidence interval [CI] - 7.37 to - 0.42, P = 0.014) but lower levels of urine creatinine (MD = 0.80 mmol, 95% CI 0.21-1.39, P = 0.004) and pH (MD = 0.12, 95% CI - 0.01 to 0.25, P = 0.033) than non-hypertension adults. However, no significant difference was found in all 24-h urinary components between two groups (all P value > 0.05) in multivariate Logistic regression analyses. CONCLUSIONS: Our study demonstrated that hypertension did not independently influence the 24-h urine composition in adults without urolithiasis in China; however, we cannot make such an arbitrary conclusion that hypertension was not a risk factor for urolithiasis.

Improving Compliance with 24-H Urine Collections: Understanding Inadequacies in the Collection Process and Risk Factors for Poor Compliance.

PURPOSE OF REVIEW: The purpose of this review paper is to describe the 24-h urine collection in terms of its utility, collection process, and common problems with its acquisition. RECENT FINDINGS: Although 24-h urine collections are standard of care for high-risk stone formers, several nuances in test acquisition including inaccurate urine collections 50% of the time and poor patient compliance limit its potential utility. Compliance in obtaining 24-h urine collections has been shown to be improved in patients who have not undergone surgical treatment of urinary calculi, patients with metabolic stone disease or family history of stone disease, Caucasian ethnicity, and in those with more sedentary occupations. Studies show conflicting data of compliance regarding patient age and gender. Physicians must understand the difficulties regarding 24-h urine collections including patient compliance, variability between collections, and complexities with interpretation to best utilize this tool in guiding clinical management for the treatment of nephrolithiasis.

Effects of COVID-19 pandemics on urinary metabolites in kidney stone patients: our kidney stone prevention clinic experience.

BACKGROUND: The dietary habits and lifestyle changes during the COVID-19 pandemic could affect the urinary risk factors in kidney stone formers. In this study, we investigated the effects of the COVID-19 pandemic on 24-h urine metabolites, as a surrogate for dietary intake, in patients with kidney stones, in Tehran, Iran. METHODS: We evaluated the medical records of all patients with urolithiasis who visited in our stone prevention clinic from the beginning of COVID-19 in Iran to 1 year later (Feb 2020-Feb 2021) and compared it with the patients' medical records in the same period a year before COVID-19 (Feb 2019-Feb 2020). RESULTS: The results of our stone prevention clinic showed a decrease in the number of visits during COVID-19. Twenty-four-hour urine urea, sodium, and potassium were significantly lower, and 24-h urine magnesium was significantly higher during COVID-19. Higher 24-h urine oxalate was only shown in patients with the first-time visit, whereas lower 24-h urine uric acid and citrate were only shown in patients with the follow-up visits. CONCLUSIONS: COVID-19 pandemics may change some of the dietary habits of the patients, including lower salt, protein, and fruit and vegetable intake. Although economic issues, restricted access, or sanitation issues may be the reason for the undesirable dietary changes, the importance of a quality diet should be discussed with all patients, as possible. Since the number of patients visited in the stone clinic was lower during COVID-19, virtual visits could be an excellent alternative to motivate patients with kidney stones.