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.

Capillary Microfluidics for Monitoring Medication Adherence

Medication adherence is a medical and societal issue worldwide, with approximately half of patients failing to adhere to prescribed treatments. The goal of this Minireview is to examine how recent work on microfluidics for point-of-care diagnostics may be used to enhance adherence to medication. It specifically focuses on capillary microfluidics since these devices are self-powered, easy to use, and well established for diagnostics and drug monitoring. Considering that an improvement in medication adherence can have a much larger effect than the development of new medical treatments, it is long overdue for the research communities working in chemistry, biology, pharmacology, and material sciences to consider developing technologies to enhance medication adherence. For these reasons, this Minireview is not meant to be exhaustive but rather to provide a quick starting point for researchers interested in joining this complex but intriguing and exciting field of research.

Reducing salt intake by urine chloride self-measurement in non-compliant patients with chronic kidney disease followed in nephrology clinics: a randomized trial

BACKGROUND

Adherence to low salt diets and control of hypertension remain unmet clinical needs in chronic kidney disease (CKD) patients.

METHODS

We performed a 6-month multicentre randomized trial in non-compliant patients with CKD followed in nephrology clinics testing the effect of self-measurement of urinary chloride (69 patients) as compared with standard care (69 patients) on two primary outcome measures, adherence to a low sodium (Na) diet (<100 mmol/day) as measured by 24-h urine Na (UNa) excretion and 24-h ambulatory blood pressure (ABPM) monitoring.

RESULTS

In the whole sample (N = 138), baseline UNa and 24-h ABPM were143 ± 64 mmol/24 h and 131 ± 18/72 ± 10 mmHg, respectively, and did not differ between the two study arms. Patients in the active arm of the trial used >80% of the chloride strips provided to them at the baseline visit and at follow-up visits. At the third month, UNa was 35 mmol/24 h (95% CI 10.8-58.8 mmol/24 h; P = 0.005) lower in the active arm than the control arm, whereas at 6 months the between-arms difference in UNa decreased and was no longer significant [23 mmol/24 h (95% CI -5.6-50.7); P = 0.11]. The 24-h ABPM changes as well as daytime and night-time BP changes at 3 and 6 months were similar in the two study arms (Month 3, P = 0.69-0.99; Month 6, P = 0.73-0.91). Office BP, the use of antihypertensive drugs, estimated Glomerular Filtration Rate (eGFR) and proteinuria remained unchanged across the trial.

CONCLUSIONS

The application of self-measurement of urinary chloride to guide adherence to a low salt diet had a modest effect on 24-h UNa and no significant effect on 24-h ABPM.

Urine chloride self-measurement to monitor sodium chloride intake in patients with chronic kidney disease

Background Excessive sodium intake is a risk factor for hypertension, cardiovascular disease and the risk for kidney failure in chronic kidney disease (CKD) patients. Methods We tested the diagnostic performance and the feasibility of an inexpensive method based on urine chloride strips for self-monitoring sodium intake in a series of 72 CKD patients. Results Twenty-four hour urinary chloride as measured by the reactive strips and 24 h urinary sodium were interrelated (r=0.59, p<0.001). Forty-nine out of 72 patients (78%) had a 24 h urinary sodium >100 mmol/24 h, i.e. the upper limit recommended by current CKD guidelines. The strip method had 75.5% sensitivity and 82.6% specificity to correctly classify patients with urine sodium >100 mmol/24 h. The positive and the negative predictive values were 90.2% and 61.3%, respectively. The overall accuracy (ROC curve analysis) of urine chloride self-measurement for the >100 mmol/24 h sodium threshold was 87% (95% CI: 77%-97%). The large majority of patients (97%) perceived the test as useful to help compliance with the prescribed dietary sodium and considered the test as simple and of immediate application (58%) or feasible but requiring attention (39%). Conclusions A simple and inexpensive test for urine chloride measurement has a fairly good performance for the diagnosis of excessive sodium intake. The test is feasible and it is perceived by CKD patients as helpful for enhancing compliance to the dietary sodium recommendations. The usefulness of this test for improving hypertension control in CKD patients will be tested in a clinical trial (Clinicaltrials.gov RF-2010-2314890).

A decade of microchip electrophoresis for clinical diagnostics - A review of 2008-2017

A core element in clinical diagnostics is the data interpretation obtained through the analysis of patient samples. To obtain relevant and reliable information, a methodological approach of sample preparation, separation, and detection is required. Traditionally, these steps are performed independently and stepwise. Microchip capillary electrophoresis (MCE) can provide rapid and high-resolution separation with the capability to integrate a streamlined and complete diagnostic workflow suitable for the point-of-care setting. Whilst standard clinical diagnostics methods normally require hours to days to retrieve specific patient data, MCE can reduce the time to minutes, hastening the delivery of treatment options for the patients. This review covers the advances in MCE for disease detection from 2008 to 2017. Miniaturised diagnostic approaches that required an electrophoretic separation step prior to the detection of the biological samples are reviewed. In the two main sections, the discussion is focused on the technical set-up used to suit MCE for disease detection and on the strategies that have been applied to study various diseases. Throughout these discussions MCE is compared to other techniques to create context of the potential and challenges of MCE. A comprehensive table categorised based on the studied disease using MCE is provided. We also comment on future challenges that remain to be addressed.

Optimization of Tetrapolar Impedance Electrodes in Microfluidic Devices for Point of Care Diagnostics using Finite Element Modeling

Electrophoresis is widely applied in the field of biochemistry and molecular biology. Tetrapolar electrical impedance sensing (TEIS) has been shown capable of replacing the conventional detection technology in order to develop a point of care electrophoretic analyzer. Besides the advantages of reduced influence of electrode polarization, TEIS is affected by sensitivity distribution depending on the electrode design. A well reported practice outside of electrophoresis, systematic investigation of the effects of sensitivity distribution on the TEIS in microfluidic devices has not been conducted. Here we utilize finite element modeling, backed by experimental results, to optimize the sensor design within an electrophoretic separation device. Numerous sensor designs were validated regarding detectability, sensitivity and spatial resolution. The results show, that minimizing the distance between the central/pick-up electrodes increases sensitivity and spatial resolution whereas the distance between the central electrodes and the outer electrode do not influence sensitivity and spatial resolution.

Integrating Internal Standards into Disposable Capillary Electrophoresis Devices To Improve Quantification

To improve point-of-care quantification using microchip capillary electrophoresis (MCE), the chip-to-chip variabilities inherent in disposable, single-use devices must be addressed. This work proposes to integrate an internal standard (ISTD) into the microchip by adding it to the background electrolyte (BGE) instead of the sample—thus eliminating the need for additional sample manipulation, microchip redesigns, and/or system expansions required for traditional ISTD usage. Cs and Li ions were added as integrated ISTDs to the BGE, and their effects on the reproducibility of Na quantification were explored. Results were then compared to the conclusions of our previous publication which used Cs and Li as traditional ISTDs. The in-house fabricated microchips, electrophoretic protocols, and solution matrixes were kept constant, allowing the proposed method to be reliably compared to the traditional method. Using the integrated ISTDs, both Cs and Li improved the Na peak area reproducibility approximately 2-fold, to final RSD values of 2.2–4.7% (n = 900). In contrast (to previous work), Cs as a traditional ISTD resulted in final RSDs of 2.5–8.8%, while the traditional Li ISTD performed poorly with RSDs of 6.3–14.2%. These findings suggest integrated ISTDs are a viable method to improve the precision of disposable MCE devices—giving matched or superior results to the traditional method in this study while neither increasing system cost nor complexity.

Versatile electrophoresis-based self-test platform

Lab on a Chip technology offers the possibility to extract chemical information from a complex sample in a simple, automated way without the need for a laboratory setting. In the health care sector, this chemical information could be used as a diagnostic tool for example to inform dosing. In this issue, the research underpinning a family of electrophoresis-based point-of-care devices for self-testing of ionic analytes in various sample matrices is described [Electrophoresis 2015, 36, 712-721.]. Hardware, software, and methodological chances made to improve the overall analytical performance in terms of accuracy, precision, detection limit, and reliability are discussed. In addition to the main focus of lithium monitoring, new applications including the use of the platform for veterinary purposes, sodium, and for creatinine measurements are included.