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.

A Wolf in Sheep’s Clothing: Reuse of Routinely Obtained Laboratory Data in Research

Electronic health records (EHRs) contain valuable data for reuse in science, quality evaluations, and clinical decision support. Because routinely obtained laboratory data are abundantly present, often numeric, generated by certified laboratories, and stored in a structured way, one may assume that they are immediately fit for (re)use in research. However, behind each test result lies an extensive context of choices and considerations, made by both humans and machines, that introduces hidden patterns in the data. If they are unaware, researchers reusing routine laboratory data may eventually draw incorrect conclusions. In this paper, after discussing health care system characteristics on both the macro and micro level, we introduce the reader to hidden aspects of generating structured routine laboratory data in 4 steps (ordering, preanalysis, analysis, and postanalysis) and explain how each of these steps may interfere with the reuse of routine laboratory data. As researchers reusing these data, we underline the importance of domain knowledge of the health care professional, laboratory specialist, data manager, and patient to turn routine laboratory data into meaningful data sets to help obtain relevant insights that create value for clinical care.

Real-time monitoring of drug laboratory test interactions: a proof of concept

OBJECTIVES

For the correct interpretation of test results, it is important to be aware of drug-laboratory test interactions (DLTIs). If DLTIs are not taken into account by clinicians, erroneous interpretation of test results may lead to a delayed or incorrect diagnosis, unnecessary diagnostic testing or therapy with possible harm for patients. A DLTI alert accompanying a laboratory test result could be a solution. The aim of this study was to test a multicentre proof of concept of an electronic clinical decision support system (CDSS) for real-time monitoring of DLTIs.

METHODS

CDSS was implemented in three Dutch hospitals. So-called 'clinical rules' were programmed to alert medical specialists for possible DLTIs based on laboratory test results outside the reference range in combination with prescribed drugs. A selection of interactions from the DLTI database of the Dutch society of clinical chemistry and laboratory medicine were integrated in 43 clinical rules, including 24 tests and 25 drugs. During the period of one month all generated DTLI alerts were registered in the laboratory information system.

RESULTS

Approximately 65 DLTI alerts per day were detected in each hospital. Most DLTI alerts were generated in patients from the internal medicine and intensive care departments. The most frequently reported DLTI alerts were potassium-proton pump inhibitors (16%), potassium-beta blockers (11%) and creatine kinase-statins (11%).

CONCLUSIONS

This study shows that it is possible to alert for potential DLTIs in real-time with a CDSS. The CDSS was successfully implemented in three hospitals. Further research must reveal its usefulness in clinical practice.

Automatic quantification of lymphocyte vacuolization in peripheral blood smears of patients with Batten's disease (CLN3 disease)

Quantifying lymphocyte vacuolization in peripheral blood smears (PBSs) serves as a measure for disease severity in CLN3 disease-a lysosomal storage disorder of childhood-onset. However, thus far quantification methods are based on labor-intensive manual assessment of PBSs. As machine learning techniques like convolutional neural networks (CNNs) have been deployed quite successfully in detecting pathological features in PBSs, we explored whether these techniques could be utilized to automate quantification of lymphocyte vacuolization. Here, we present and validate a deep learning pipeline that automates quantification of lymphocyte vacuolization. By using two CNNs in succession, trained for cytoplasm-segmentation and vacuolization-detection, respectively, we obtained an excellent correlation with manual quantification of lymphocyte vacuolization (r = 0.98, n = 40). These results show that CNNs can be utilized to automate the otherwise cumbersome task of manually quantifying lymphocyte vacuolization, thereby aiding prompt clinical decisions in relation to CLN3 disease, and potentially beyond.

Clinical usefulness of drug-laboratory test interaction alerts: a multicentre survey

OBJECTIVES

Knowledge of possible drug-laboratory test interactions (DLTIs) is important for the interpretation of laboratory test results. Failure to recognize these interactions may lead to misinterpretation, a delayed or erroneous diagnosis, or unnecessary extra diagnostic tests or therapy, which may harm patients. The aim of this multicentre survey was to evaluate the clinical value of DLTI alerts.

METHODS

A survey was designed with six predefined clinical cases selected from the clinical laboratory practice with a potential DLTI. Physicians from several departments, including internal medicine, cardiology, intensive care, surgery and geriatrics in six participating hospitals were recruited to fill in the survey. The survey addressed their knowledge of DLTIs, motivation to receive an alert and opinion on the potential influence on medical decision making.

RESULTS

A total of 210 physicians completed the survey. Of these respondents 93% had a positive attitude towards receiving DLTI alerts; however, the reported value differed per case and per respondent's background. In each clinical case, medical decision making was influenced as a consequence of the reported DLTI message (ranging from 3 to 45% of respondents per case).

CONCLUSIONS

In this multicentre survey, most physicians stated DLTI messages to be useful in laboratory test interpretation. Medical decision making was influenced by reporting DLTI alerts in each case. Alerts should be adjusted according to the needs and preferences of the receiving physicians.

Comparison between coagulation factor VIII quantified with one-stage activity assay and with mass spectrometry in haemophilia A patients: Proof of principle

INTRODUCTION

Haemophilia A is a hereditary bleeding disorder caused by a factor VIII (FVIII) deficiency. As biomarker, FVIII activity is used to classify disease severity and to monitor treatment. The one-stage clotting assay (OSA) is performed to measure FVIII activity, but OSA's limitations may result in misclassification of disease severity or suboptimal monitoring of treatment. Measurement of FVIII plasma concentration with liquid chromatography-tandem mass spectrometry (LC-MS/MS) might overcome these challenges. The objective is to investigate the correlation between FVIII activity and concentration, and determinants for differences between the two methods.

METHODS

In this cross-sectional study, all haemophilia A patients receiving standard-of-care were eligible for inclusion. Within the activity categories of <1 IU/dL, 1-5 IU/dL, >5-40 IU/dL, >40-150 IU/dL and >150-600 IU/dL, we randomly selected 15-20 plasma samples and compared FVIII concentration (LC-MS/MS) to FVIII activity (OSA) with linear regression and Bland-Altman analysis. Potential determinants for differences were analysed with linear regression.

RESULTS

Inclusion was 87 samples. Bland-Altman analysis demonstrated an overall mean difference of -1% with an SD of 64% between the two methods. Large differences were correlated with the presence of anti-FVIII antibodies (133% [95% CI: 81, 185] n = 5) and use of exogenous FVIII products (-37% [95% CI: -65,-9] n = 58), for example plasma-derived and B-domain-modified FVIII products.

CONCLUSIONS

Despite good overall correlation between the two methods, relative differences were large, especially for samples with anti-FVIII antibodies or exogenous FVIII products. These differences may have clinical impact. More research is needed to determine the value of FVIII plasma concentration in comparison with FVIII activity.

Colloid osmotic pressure of contemporary and novel transfusion products

Background and Objectives

Colloid osmotic pressure (COP) is a principal determinant of intravascular fluid homeostasis and a pillar of fluid therapy and transfusion. Transfusion‐associated circulatory overload (TACO) is a leading complication of transfusion, and COP could be responsible for recruiting additional fluid. Study objective was to measure COP of blood products as well as investigate the effects of product concentration and storage lesion on COP.

Materials and Methods

Three units of each product were sampled longitudinally. COP was measured directly as well as the determinants thereof albumin and total protein. Conventional blood products, that is red blood cell (RBC), fresh‐frozen plasma (FFP) and platelet concentrates (PLTs), were compared with their concentrated counterparts: volume‐reduced RBCs, hyperconcentrated PLTs, and fully and partially reconstituted lyophilized plasma (prLP). Fresh and maximally stored products were measured to determine changes in protein and COP. We calculated potential volume load (PVL) to estimate volume recruited using albumin's water binding per product.

Results

Colloid osmotic pressure varies widely between conventional products (RBCs, 1·9; PLTs, 7·5; and FFP, 20·1 mmHg); however, all are hypooncotic compared with human plasma COP (25·4 mmHg). Storage lesion did not increase COP. Concentrating RBCs and PLTs did not increase COP; only prLP showed a supraphysiological COP of 47·3 mm Hg. The PVL of concentrated products was lower than conventional products.

Conclusion

Colloid osmotic pressure of conventional products was low. Therefore, third‐space fluid recruitment is an unlikely mechanism in TACO. Concentrated products had a lower calculated fluid load and may prevent TACO. Finally, storage did not significantly increase oncotic pressure of blood products.

P1690Lab-on-a-chip based self-monitoring device for dietary intake of potassium and sodium: the LAB-CHIPS study

Background

Dietary sodium restriction and upholding adequate potassium intake is an important lifestyle modification strategy advocated in guidelines for the management of hypertension and for lowering cardiovascular risk in the general population. The gold standard for estimating sodium and potassium intake, 24-hour urine collection (24hUc), is time consuming and cumbersome, but most importantly not a good indicator of dietary habit due to day-to-day variation. New lab-on-a-chip technology has been developed to measure urinary sodium, potassium and creatinine excretion in a single drop of urine using microcapillary electrophoreses combined with conductivity analyses. Self-monitoring can be done at home over a longer period of time. Results are readily available.

Purpose

To assess agreement between 24hUc and the lab-on-a-chip self-monitoring device for estimating past 24h dietary sodium and potassium intake for single and multiple self-tests by using the Kawasaki, INTERSALT and Tanaka formulae.

Methods

Healthy participants (n=12) were asked to adhere to three different weekly dietary sodium restriction goals. Participants received verbal and written information to aim between 3.3 and 5.0 grams of sodium intake a day during week 1 (“normal”), >3.3<5.0 grams in week 2 (low) and >5.0 grams during week 3 (high). Weekly measurement instructions consisted of one self-test on day 1 through 6 and multiple self-tests (n=3) combined with a 24hUc on day 7. To estimate 24h sodium and potassium intake, Kawasaki, INTERSALT and Tanaka formulas were used. The Bland-Altman method was used to calculate the agreement.

Results

The agreement (mg/day) for sodium between 24hUc and a self-test on first morning urine (fmu) (Kawasaki), was −102±804 (normal), −860±592 (low) and 340±1406 (high). For multiple self-tests (n=3) performed on 24hUc days, using the INTERSALT formula, the agreement was: 577±832 (normal), −701±721 (low) and 1788±911 (high). Any combination of same day single or multiple INTERSALT or Tanaka self-tests and fmu Kawasaki did not result in better agreement. For potassium the agreement between 24hUc and fmu (Kawaksaki) was 1071±966 (normal), 1376±678 (low) and 1654±880 (high). Using the Tanaka formula resulted in further underestimation and thus worse agreement for same day self-tests and fmu.

Conclusion

In this study, agreement between 24hUc and the lab-on-a-chip self-monitoring device for estimating past 24h dietary sodium intake was best for a fmu self-test calculated with the Kawasaki formula. For estimating potassium intake, a fmu self-test with help of the Kawasaki formula overestimated potassium intake considerably. This lab-on-a-chip self-monitoring device has the potential to improve current lifestyle modification strategies.

Diagnostic error as a result of drug-laboratory test interactions

Background Knowledge of possible drug-laboratory test interactions (DLTIs) is important for the interpretation of laboratory test results. Test results may be affected by physiological or analytical drug effects. Failure to recognize these interactions may lead to misinterpretation of test results, a delayed or erroneous diagnosis or unnecessary extra tests or therapy, which may harm patients. Content Thousands of interactions have been reported in the literature, but are often fragmentarily described and some papers even reported contradictory findings. How can healthcare professionals become aware of all these possible interactions in their individual patients? DLTI decision support applications could be a good solution. In a literature search, only four relevant studies have been found on DLTI decision support applications in clinical practice. These studies show a potential benefit of automated DLTI messages to physicians for the interpretation of laboratory test results. All physicians reported that part of the DLTI messages were useful. In one study, 74% of physicians even sometimes refrained from further additional examination. Summary and outlook Unrecognized DLTIs potentially cause diagnostic errors in a large number of patients. Therefore, efforts to avoid these errors, for example with a DLTI decision support application, could tremendously improve patient outcome.

Influence of point-of-care C-reactive protein testing on antibiotic prescription habits in primary care in the Netherlands

BACKGROUND

Bacterial resistance to antibiotics represents a serious global challenge that is associated with high morbidity and mortality. One of the most important causes of this threat is antibiotic overuse. The Dutch College of General Practitioners (DCGP) recommends the use of point-of-care (POC) testing for C-reactive protein (CRP) in two guidelines ('Acute Cough' and 'Diverticulitis') to achieve a more sensible prescription pattern of antibiotics.

OBJECTIVE

To evaluate the use of POC-CRP testing in light of the DCGP guidelines and the effect of CRP measurements on antibiotic prescription policy in primary care.

METHODS

In a prospective observational study, which included 1756 patients, general practitioners (GPs) were asked to complete a questionnaire after every POC-CRP testing, stating the indication for performing the test, the CRP result and their decision whether or not to prescribe antibiotics. Indications were verified against the DCGP guidelines and categorized. Antibiotic prescription was evaluated in relation to CRP concentrations.

RESULTS AND CONCLUSION

Indications to perform POC-CRP test and the prescription pattern of antibiotics based on CRP value varied considerably between GPs. Differences in antibiotic prescription rate were most obvious in patients who presented with CRP values between 20 and 100 mg/l, and could in part be explained by the indication for performing POC-CRP test and patient age. Most GPs followed the DCGP guidelines and used low CRP values to underpin their decision to refrain from antibiotic prescription. Peer-based reflection on differences in POC-CRP usage and antibiotic prescription rate amongst GPs may further nourish a more critical approach to prescription of antibiotics.

[Unusual causes of hyperprolactinaemia]

Pituitary adenoma is the main cause of hyperprolactinaemia; however, physicians should be aware that the pituitary is not always to blame. There are many other physiological and pathological causes for hyperprolactinaemia, and the contribution of stress, medication and the presence of macroprolactin should not be overlooked. We describe three patients - a 19-year-old female, a 28-year-old female and a 20-year-old male - in whom hyperprolactinaemia was due to medication use, physical stimulation of the nipple and a combination of macroprolactianaemia with a microadenoma, respectively. The first two case reports show that conducting a thorough patient history can prevent unnecessary imaging and laboratory costs. The third case illustrates that macroprolactinaemia and true hyperprolactinaemia may coexist. While early screening for macroprolactinaemia in an asymptomatic patient can save money, finding macroprolactinaemia in a symptomatic patient still warrants further workup.

Effects of arsenite and UVA-1 radiation on calcineurin signaling

Calcineurin is a Ca(2+)-dependent serine/threonine phosphatase and the target of the immunosuppressive drugs cyclosporin and tacrolimus, which are used in transplant recipients to prevent rejection. Unfortunately, the therapeutic use of this drugs is complicated by a high incidence of skin malignancy, which has set off a number of studies into the role of calcineurin signaling in skin, particularly with respect to cell cycle control and DNA repair. Both UVA1 radiation and arsenic species are known to promote skin cancer development via production of reactive oxygen species. In light of the well-documented sensitivity of calcineurin to oxidative stress, we examined and compared the effects of UVA1 and arsenite on calcineurin signaling. In this paper, we show that physiologically relevant doses of UVA1 radiation and low micromolar concentrations of arsenite strongly inhibit calcineurin phosphatase activity in Jurkat and skin cells and decrease NFAT nuclear translocation in Jurkat cells. The effects on calcineurin signaling could be partly prevented by inhibition of NADPH oxidase in Jurkat cells or increased dismutation of superoxide in Jurkat and skin cells. In addition, both UVA1 and arsenite decreased NF-κB activity, although at lower concentrations, arsenite enhanced NF-κB activity. These data indicate that UVA1 and arsenite affect a signal transduction route of growingly acknowledged importance in skin and that calcineurin may serve as a potential link between ROS exposure and impaired tumor suppression.

Molecular Diagnostics of Calcineurin-Related Pathologies

BACKGROUND

The Ca2+-dependent protein phosphatase enzyme calcineurin (Cn) (protein phosphatase 3) is best known for its role as director of the adaptive immune response. One of its principal substrates is the nuclear factor of activated T cells (NFAT), which translocates to the nucleus after dephosphorylation to mediate gene transcription. Drugs targeting Cn (the Cn inhibitors tacrolimus and cyclosporin A) have revolutionized posttransplantation therapy in allograft recipients by considerably reducing rejection rates.

CONTENT

Owing primarily to intensive study of the side effects of the Cn inhibitors, the unique importance of Cn and Cn/NFAT signaling in the normal physiological processes of many other cell and tissue types is becoming more evident. During the last decade, it has become clear that an extensive and diverse array of clinical conditions can be traced back, at least in part, to a disturbed Cn-signaling axis. Hence, both diagnostics and therapeutic monitoring could benefit from a technique that conveniently reads out Cn/NFAT operative status.

SUMMARY

This review outlines the current knowledge on the pathologic conditions that have calcineurin as a common denominator and reports on the progress that has been made toward successfully applying Cn and Cn/NFAT activity markers in molecular diagnostics.

UVA1 radiation inhibits calcineurin through oxidative damage mediated by photosensitization

The protein phosphatase calcineurin has been gradually revealing itself as the central controller of our immune response, although it is involved in a wide array of signaling pathways related to cellular development and cell cycle progression. As such, calcineurin is an attractive, yet delicate, therapeutic target for the prevention of allograft rejection and treatment of several inflammatory skin conditions. However, calcineurin activity is not only sensitive to immunosuppressants such as cyclosporin A and tacrolimus, but also subject to modulation by reactive oxygen species. We have recently shown, both in vivo and in vitro, that UVA1 radiation suppresses calcineurin activity. In this paper, we present evidence that this activity loss is due to singlet oxygen and superoxide generated by photosensitization and show that a closely related phosphatase, PP2A, is not affected. Furthermore, a survey of this damage reveals oxidation of several Met and Cys residues as well as an overall conformational change. These findings provide a mechanistic basis for the hypothesis that UVA1 and calcineurin inhibitors both affect the same signal transduction pathway in skin.