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Protocol - Sodium

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Description:

Complete 24-hour urine sample is collected from the study participant in a sterile specimen container. Under- and over-collection can bias results. The specimen is transported to a laboratory on ice and frozen at -20°C or colder until analysis. Urinary sodium concentrations are determined by ion-selective electrode assays (ICEs), which have a between-assay coefficients of variation < 3%. Standard reference materials are available from the National Institute of Standards and Technology (NIST).

Protocol:

1. Specimen Collection, Storage, and Handling Procedures; Criteria for Specimen Rejection

A. Urine specimen should be collected in a urine specimen container that is sterile and prescreened for trace sodium contamination. Sodium is stable frozen indefinitely with multiple freeze-thaw cycles and for 45 days at room temperature. Bacterial growth must be avoided.

B. Ensuring 24-hour collection is essential. Sodium excretion varies during a 24-hour time period, so over-collection and under-collection must be avoided. Completeness of collection is assessed through self-reporting, total urine volume, normalization to urinary creatinine, or oral para-amino benzoic acid (PABA) administration and recovery. PABA can be administered prior to urine collection to ensure completeness of collection, as 93% of the dose is recovered in urine within 5 hours of administration. The use of PABA to assess completeness of the urine collection is not recommended for field studies. It requires that each participant take a PABA pill three days prior to the start of collection thereby increasing the risks of non‐compliance and attrition. In addition, laboratory facilities for the testing of PABA in the urine are limited and where they exist, will increase the costs of the study.

C. Sodium and potassium content in the urine may be determined through Ion Selective Electrode. Creatinine content may be determined through the Creatinine (urinary) Jaffe kinetic method.

D. Aside from sodium intake, urinary sodium excretion can be modified by potassium intake, physical activity, climate, chronic disease, hypertension, and renal function.

Protocol Name from Source:

World Health Organization (WHO), Pan American Health Organization (PAHO), Regional Expert Group for Cardiovascular Disease Prevention through Population-wide Dietary Salt Reduction. (2010). Protocol for population level sodium determination in 24-hour urine samples. Washington, DC: Author. http://new.paho.org/hq/dmdocuments/2010/pahosaltprotocol.pdf

Availability:

Publicly available

Personnel and Training Required

Must complete safety training seminars prior to performing any work in laboratory.

Equipment Needs

Highly specialized equipment is necessary to perform accurate sodium measurements.

Requirements
Requirement CategoryRequired
Major equipment No
Specialized training Yes
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration

Bioassay

Life Stage:

Infant, Toddler, Child, Adolescent, Adult, Senior, Pregnancy

Participants:

All ages

Specific Instructions:

There are no special fasting or dietary restrictions for the study participants.

Selection Rationale

24-hour urine sample collection are easy to collect and noninvasive but can be a burden for the participant. This assay is used to achieve rapid and accurate identification of sodium in a urine sample.

Language

English

Standards
StandardNameIDSource
Common Data Elements (CDE) Person Urinary Sodium Concentration Bioassay in Nanograms per Milliliter 5021339 CDE Browser
Derived Variables

None

Process and Review

The Expert Review Panel #1 reviewed the measures in the Anthropometrics, Diabetes, Physical Activity and Physical Fitness, and Nutrition and Dietary Supplements domains.

Guidance from the ERP includes:

• Added a new measure

  • New Data Dictionary

Source

Pfeiffer, C. M., Hughes, J. P., Cogswell, M. E., Burt, V. L., Lacher, D. A., Lavoie, D. J., . . . Pirkle, J. L. (2014). Urine sodium excretion increased slightly among U.S. adults between 1988 and 2010. Journal of Nutrition, 144, 698-705.

World Health Organization (WHO), Pan American Health Organization (PAHO), Regional Expert Group for Cardiovascular Disease Prevention through Population-wide Dietary Salt Reduction. (2010). Protocol for population level sodium determination in 24-hour urine samples. Washington, DC: Author. http://new.paho.org/hq/dmdocuments/2010/pahosaltprotocol.pdf

General References

Cogswell, M. E., Maalouf, J., Loria, C. M., Patel, S., & Bowman, B. A. (In press). Use of urine biomarkers to assess sodium intake-Challenges and opportunities. Annual Review of Nutrition.

Elliott, P., & Stamler, R. (1988). Manual of operations for "INTERSALT", an international cooperative study on the relation of sodium and potassium to blood pressure. Controlled Clinical Trials, 9, 1S-117S.

Rose, G., & Stamler, J. (1989). The INTERSALT study: background, methods and main results. INTERSALT Co-operative Research Group. Journal of Human Hypertension, 3, 283-288.

Stamler, J., Elliott, P., Dennis, B., Dyer, A. R., Kesteloot, H., et al. (2003). INTERMAP: background, aims, design, methods, and descriptive statistics (nondietary). Journal of Human Hypertension, 17, 591-608.

Wang, C. Y., Cogswell, M. E., Loria, C. M., Chen, T. C., Pfeiffer, C. M., et al. (2013). Urinary excretion of sodium, potassium, and chloride, but not iodine, varies by timing of collection in a 24-hour calibration study. Journal of Nutrition, 143, 1276-1282.

Protocol ID:

51401

Variables:
Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
PX051401_Sodium_Container PX051401010000 Was the specimen collection container prescreened for traces of sodium contamination? 4 N/A
PX051401_Sodium_Urinary_Sodium_Concentration PX051401050000 Urinary sodium Concentration from bioassay 4 N/A
PX051401_Sodium_UrineSpecimen_Age PX051401040000 What is the creatinine content as determined through the Creatinine (urinary) Jaffe kinetic method? 4 N/A
PX051401_Sodium_UrineSpecimen_QualityControl PX051401020000 Did the patient take a PABA pill at least three days prior to urine collection? 4 N/A
PX051401_Sodium_UrineSpecimen_Storage PX051401030000 What is the sodium and potassium content in the urine as determined through Ion Selective Electrode? 4 N/A
Research Domain Information
Measure Name:

Sodium

Release Date:

October 1, 2015

Definition

A bioassay to assess concentration (nanograms per milliliter) of urinary sodium.

Purpose

Sodium is an essential element for the regulation of blood volume and blood pressure. Excess sodium intake elevates blood pressure. High blood pressure is a major risk factor for cardiovascular disease. Approximately 50% of daily sodium intake is excreted in the subsequent 18-31 hours.

Keywords

Nutrition and Dietary supplements, WHO, PAHO