Table of Contents

Component Description

The Urine Flow Rate (or urine excretion rate) is a measurement of the quantity of urine produced in a specified period of time. Urine analyte concentrations from single determinations (spot urines) can vary depending on the water content of the urine. Due to this variation, the urine flow rate is a more accurate calculation used to determine urine analyte concentrations, especially exposure to environmental chemicals. When used to determine urine analyte concentrations, the urine excretion rate (mg/min) is the product of the urine flow rate (mL/min) and the urine analyte concentration (mg/mL).

Eligible Sample

All examined participants aged 6 years and older were eligible.

Description of Laboratory Methodology

Participants will be asked to record the time of their last void before coming to the MEC. Participants will then be asked to void at the MEC where the time of collection and volume of the urine will be recorded. The volume of the urine sample collected at the MEC will be measured and the urine flow rate will be calculated from this information. The urine flow rate is calculated by dividing the total volume of the urine sample collected in the MEC, by the total time between the previous urine sample collection and the urine sample collected in the MEC. There may be a maximum of 3 urine flow rates for a participant but that depends on the total number of spot urines collected in the MEC.

There were no changes to the lab method, lab equipment, or lab site for this component in the NHANES 2013-2014 cycle.

Laboratory Quality Assurance and Monitoring

Detailed instructions on specimen collection and processing are discussed in the NHANES Laboratory Procedures Manual (LPM).

The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES LPM.

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Analytic Notes

Refer to the 2013-2014 Laboratory Data Overview for general information on NHANES laboratory data.

Demographic and Other Related Variables

The analysis of NHANES 2013-2014 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2013-2014 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample weight variables. The demographics file may be linked to the laboratory data file using the unique survey participant identifier (i.e., SEQN).

Detection Limits

Since this data is calculated the use of lower limits of detection (LLODs) isn’t applicable.
This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier (i.e., SEQN).

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 6 YEARS - 150 YEARS

URXVOL1 - The volume of urine collection #1

Variable Name:
URXVOL1
SAS Label:
The volume of urine collection #1
English Text:
The volume of urine collection #1
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 552 Range of Values 8057 8057
. Missing 234 8291

URDFLOW1 - Urine #1 Flow Rate

Variable Name:
URDFLOW1
SAS Label:
Urine #1 Flow Rate
English Text:
Urine #1 Flow Rate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 26 Range of Values 7150 7150
. Missing 1141 8291

URXVOL2 - The volume of urine collection #2

Variable Name:
URXVOL2
SAS Label:
The volume of urine collection #2
English Text:
The volume of urine collection #2
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 452 Range of Values 1856 1856
. Missing 6435 8291

URDFLOW2 - Urine #2 Flow Rate

Variable Name:
URDFLOW2
SAS Label:
Urine #2 Flow Rate
English Text:
Urine #2 Flow Rate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 76.667 Range of Values 1855 1855
. Missing 6436 8291

URXVOL3 - The volume of urine collection #3

Variable Name:
URXVOL3
SAS Label:
The volume of urine collection #3
English Text:
The volume of urine collection #3
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4 to 383 Range of Values 99 99
. Missing 8192 8291

URDFLOW3 - Urine #3 Flow Rate

Variable Name:
URDFLOW3
SAS Label:
Urine #3 Flow Rate
English Text:
Urine #3 Flow Rate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.042 to 10.923 Range of Values 99 99
. Missing 8192 8291