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

Participants aged 6 years and older were tested.

Description of Laboratory Methodology

Participants will be asked to record their time of 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 which depends on the total number of spot urines which are collected in the MEC.

Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Data Processing and Editing

The analytical methods are described in the Description of Laboratory Methodology section above.

Laboratory Quality Assurance and Monitoring

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

Analytic Notes

Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.

The analysis of NHANES 2011-2012 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2011-2012 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).

 Exam sample weights should be used for analyses.

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.

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 446 Range of Values 7650 7650
. Missing 171 7821

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 39 Range of Values 6963 6963
. Missing 858 7821

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 418 Range of Values 1393 1393
. Missing 6428 7821

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 62.333 Range of Values 1392 1392
. Missing 6429 7821

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
0 to 300 Range of Values 64 64
. Missing 7757 7821

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 to 4.348 Range of Values 64 64
. Missing 7757 7821