• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Method Files
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • URID - Urine sequence number
  • UR2UCSTS - Urine collection status
  • UR2DAZ - Daidzein, Urine 2nd collection (ng/mL)
  • URDDA2LC - Daidzein, Urine 2nd Comment Code
  • UR2DMA - o-Desmethylangolensin, Urine 2nd (ng/mL)
  • URDDM2LC - o-Desmethylangolensin, Urine 2nd Comment
  • UR2EQU - Equol, Urine 2nd Collection (ng/mL)
  • URDEQ2LC - Equol, Urine 2nd Collection Comment Code
  • UR2ETD - Enterodiol, Urine 2nd Collection (ng/mL)
  • URDET2LC - Enterodiol, Urine 2nd Collection Comment
  • UR2ETL - Enterolactone, Urine 2nd Collect (ng/mL)
  • URDEL2LC - Enterolactone, Urine 2nd Collection Comt
  • UR2GNS - Genistein, Urine 2nd Collection (ng/mL)
  • URDGN2LC - Genistein, Urine 2nd Collection Comment
  • UR2CR - Creatinine, Urine 2nd Collection (mg/dL)
  • VPSU - Variance PSU
  • VSTRA - Variance stratum
  • WT1YUR - 1 year urine weight
  • WT1YUR01 - 1 year urine weight - Jackknife 01
  • WT1YUR02 - 1 year urine weight - Jackknife 02
  • WT1YUR03 - 1 year urine weight - Jackknife 03
  • WT1YUR04 - 1 year urine weight - Jackknife 04
  • WT1YUR05 - 1 year urine weight - Jackknife 05
  • WT1YUR06 - 1 year urine weight - Jackknife 06
  • WT1YUR07 - 1 year urine weight - Jackknife 07
  • WT1YUR08 - 1 year urine weight - Jackknife 08
  • WT1YUR09 - 1 year urine weight - Jackknife 09
  • WT1YUR10 - 1 year urine weight - Jackknife 10
  • WT1YUR11 - 1 year urine weight - Jackknife 11
  • WT1YUR12 - 1 year urine weight - Jackknife 12
  • WT1YUR13 - 1 year urine weight - Jackknife 13
  • WT1YUR14 - 1 year urine weight - Jackknife 14
  • WT1YUR15 - 1 year urine weight - Jackknife 15
  • VPSUBRR - Variance PSU for BRR
  • VSTRABRR - Variance stratum for BRR
  • WT1YUB01 - 1 year urine weight - Fay's BRR 01
  • WT1YUB02 - 1 year urine weight - Fay's BRR 02
  • WT1YUB03 - 1 year urine weight - Fay's BRR 03
  • WT1YUB04 - 1 year urine weight - Fay's BRR 04
  • WT1YUB05 - 1 year urine weight - Fay's BRR 05
  • WT1YUB06 - 1 year urine weight - Fay's BRR 06
  • WT1YUB07 - 1 year urine weight - Fay's BRR 07
  • WT1YUB08 - 1 year urine weight - Fay's BRR 08
  • WT1YUB09 - 1 year urine weight - Fay's BRR 09
  • WT1YUB10 - 1 year urine weight - Fay's BRR 10
  • WT1YUB11 - 1 year urine weight - Fay's BRR 11
  • WT1YUB12 - 1 year urine weight - Fay's BRR 12
  • WT1YUB13 - 1 year urine weight - Fay's BRR 13
  • WT1YUB14 - 1 year urine weight - Fay's BRR 14
  • WT1YUB15 - 1 year urine weight - Fay's BRR 15
  • WT1YUB16 - 1 year urine weight - Fay's BRR 16

National Health and Nutrition Examination Survey

2014-2014 Data Documentation, Codebook, and Frequencies

Phytoestrogen- 24-Hour Urine - Second Collection (U2PT_H_R)

RDC Only Data File: U2PT_H_R.xpt

First Published: October 2019

Last Revised: NA

Due to disclosure issues, this dataset is not available publicly. Access may be obtained through the NCHS Research Data Center (https://www.cdc.gov/rdc).

Component Description

The 24-Hour Urine Collection component was added to NHANES in 2014 to: 1) estimate dietary intakes of sodium and potassium; 2) estimate the excretion of microalbumin (albumin and creatinine); and 3) assess measures of kidney markers (phosphorus, magnesium, calcium, oxalate, and urea nitrogen), phytoestrogens, caffeine, volatile organic compounds, and iodine in the U.S. population.

In 2014, a random half sample of non-pregnant participants aged 20-69 years and examined in the mobile examination center (MEC) were asked to collect their urines for a 24-hour period. For the first half of the year, a random half of those who completed the initial 24-hour urine collection were recruited to collect a second 24-hour urine specimen 3 to 10 days later. For the second half of the year, all those who completed the first 24-hour urine collection were recruited to collect a second 24-hour urine specimen. Data processing information from the initial and second 24-hour urine collections were released in two separate datasets (UR1_H_R and UR2_H_R). Each of these two files contains information on the following: total urine volume, length of collection, completeness of the urine collection, number of complete urine specimens, collection day of the week, and responses to questions on the participants’ experience collecting the urine to assess completeness of the specimen. Please see the documentation for these two files for more details.

Separate datasets were produced to include laboratory results of analytes from the 24-hour urine collections. The present file contains analyte data for urine phytoestrogens and creatinine. See Appendix I for the list of data files for the 24-hour urine collection.

Phytoestrogens, which are plant-derived compounds; such as isoflavones, lignans, soumestans and stilbenes; bear similar structure to endogenous estrogens and are capable of estrogen-receptor binding. Diets higher in consumption of phytoestrogens are associated with lower rates of hormone-dependent cancers, such as breast and prostate. 

To reduce the risk of inadvertent disclosure, all data from this 1-year 24-hour urine collection can only be accessed through the NCHS Research Data Center (RDC). Instructions for requesting use of these data are available from the RDC website (https://www.cdc.gov/rdc/).

Eligible Sample

The eligible sample was a random one-half sample of all examined participants aged 20-69 years with a few participants eliminated based on exclusion criteria (e.g., pregnant). For the first half of the year, a random half of those who completed the initial 24-hour urine collection were recruited to collect a second 24-hour urine specimen 3 to 10 days later. For the second half of the year, all those who completed the first 24-hour urine collection were recruited to collect a second 24-hour urine specimen.

Description of Laboratory Methodology

The test principle utilizes high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) for the quantitative detection of genistein, daidzein, equol, O-desmethylangolensin, enterodiol, and enterolactone. Human urine samples were processed using enzymatic deconjugation of the glucuronidated phytoestrogens followed by size-exclusion filtration. Phytoestrogens were then separated from other urine components by reversed phase HPLC, detected by ESI-MS/MS, and quantified by isotope dilution. Assay precision is improved by incorporating carbon-13 labeled internal standards for each of the analytes, as well as a 4-methylumbelliferyl glucuronide, 4-methylumbelliferyl sulfate, and carbon-13 labeled 4-methylumbelliferone to monitor deconjugation efficiency. This selective method allowed for rapid detection of six phytoestrogens in human urine with limits of detection in the low parts per billion (ppb; ng/mL) range.

Refer to the Laboratory Method Files section for a detailed description of the laboratory methods used.

This is a new component in the 2014 survey cycle.

Laboratory Method Files

Phytoestrogen - Urine Lab Procedure Manual (October 2019)

Laboratory Quality Assurance and Monitoring

Urine samples were processed, stored, and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA for analysis.

Detailed instructions on specimen collection and processing are discussed in the NHANES 24-Hour Urine Study Procedures Manual. Vials were stored under appropriate frozen (-30°C) conditions until they were shipped to National Center for Environmental Health, for testing.

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 Laboratory Procedures Manual (LPM).

Mobile Examination Centers (MECs)

Laboratory team performance is monitored using several techniques. NCHS and contract consultants use a structured competency assessment evaluation during visits to evaluate both the quality of the laboratory work and the quality-control procedures. Each laboratory staff member is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff member. Formal retraining sessions are conducted annually to ensure that required skill levels were maintained.

Analytical Laboratories

NHANES uses several methods to monitor the quality of the analyses performed by the contract laboratories. In the MEC, these methods include performing blind split samples collected during “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2% of all specimens.

NCHS developed and distributed a quality control protocol for all CDC and contract laboratories, which outlined the use of Westgard rules (Westgard et al., 1981) when running NHANES specimens. Progress reports containing any problems encountered during shipping or receipt of specimens, summary statistics for each control pool, QC graphs, instrument calibration, reagents, and any special considerations are submitted to NCHS quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.

All QC procedures recommended by the manufacturers were followed. Reported results for all assays meet the Division of Laboratory Sciences’ quality control and quality assurance performance criteria for accuracy and precision, similar to the Westgard rules (Caudill et al., 2008).

Data Processing and Editing

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

Analytic Notes

Variables with data from 24-hour urine first collection and second collection specimens are denoted with a “UR1” and “UR2” prefix, respectively.

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

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

Subsample weights

NHANES participants were selected on the basis of a national probability design. In order to increase the number of participants for specific demographic groups, a multi-stage, unequal probability of selection design was implemented. In 2014, the sample design included an oversample of certain demographic groups: persons 80 years and older, non-Hispanic black, non-Hispanic Asian, Hispanic, and low income white and other persons. Sample weights are constructed that encompass the unequal probabilities of selection, as well as adjustments for non-participation by selected sample persons. In order to produce national, representative estimates, the appropriate sample weights must be used.

The 24-hour urine collection was conducted in a random one-half subsample of 1,103 persons 20-69 years examined in the mobile examination center in 2014. A special one-year urine sample weight (WT1YUR) is provided for the 827 participants who provided a complete 24-hour urine specimen to obtain representative national estimates based on this first 24-hour urine collection. As with other NHANES subsamples, the 24-hour urine sample weights account for the additional probability of selection into the subsample component as well as the additional nonresponse. This sample weight, along with strata (VSTRA) and PSUs (VPSU) are used to calculate variance estimates based on the Taylor Series Linearization method. In addition, 16 Fay-adjusted balanced repeated replication (Fay’s BRR) weights (WT1YUB01 – WT1YUB16), along with their corresponding strata (VSTRABRR) and PSUs (VPSUBRR), and 15 Jackknife replicate weights (WT1YUR01 – WT1YUR15) that can be used with VSTRA and VPSU are included in the files to obtain variance estimates based on a replication method. The Fay’s BRR weights were created with an adjustment factor of 0.3. There is no separate sample weight provided for use with the data collected for the second 24-hour urine specimen. These data were collected for the purpose of estimating within-person variability and not for obtaining nationally representative estimates based on the second 24-hour urine sample. New sample weights would need to be calculated by the user if any additional analytical efforts were planned for the second collection data.

Demographic and Other Related Variables

The analysis of NHANES 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 sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.

Please see Appendix 1 for the list of data files produced from the 24-hour urine collection.

This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier (i.e., SEQN).

Detection Limits

The detection limits were constant for all of the analytes in the data set. Two variables are provided for each of these analytes. The variable name ending in “1LC” (ex., URDZ42LC) indicates whether the result was below the limit of detection: the value “0” means that the result was at or above the limit of detection, “1” indicates that the result was below the limit of detection. For analytes with analytic results below the lower limit of detection (ex., URDZ42LC=1), an imputed fill value was placed in the analyte results field. This value is the lower limit of detection divided by the square root of 2 (LLOD/sqrt[2]). The other variable prefixed UR1 (ex., URZ42) provides the analytic result for that analyte.

The lower limit of detection (LLOD in ng/mL) for 24-Hour Phytoestrogens – First and Second Collections:

Variable Name	SAS Label	LLOD
UR1DAZ	Diadzein, Urine 1st Collection (ng/mL)	0.1
UR1DMA	o-Desmethylangolensin, Urine 1st Collection (ng/mL)	0.05
UR1EQU	Equol, Urine 1st Collection (ng/mL)	0.1
UR1ETD	Enterodiol, Urine 1st Collection (ng/mL)	0.1
UR1ETL	Enterolactone, Urine 1st Collection (ng/mL)	0.05
UR1GNS	Genistein, Urine 1st Collection (ng/mL)	0.08
UR2DAZ	Diadzein, Urine 2nd Collection (ng/mL)	0.1
UR2DMA	o-Desmethylangolensin, Urine 2nd Collection (ng/mL)	0.05
UR2EQU	Equol, Urine 2nd Collection (ng/mL)	0.1
UR2ETD	Enterodiol, Urine 2nd Collection (ng/mL)	0.1
UR2ETL	Enterolactone, Urine 2nd Collection (ng/mL)	0.05
UR2GNS	Genistein, Urine 2nd Collection (ng/mL)	0.08

References

• Caudill, S.P., Schleicher, R.L., Pirkle, J.L. Multi-rule quality control for the age-related eye disease study. Statist. Med. (2008) 27(20):4094-40106.
• Judkins DR (1990). Fay’s Method for Variance Estimation, Journal of Official Statistics, vol. 6. No. 3, pp. 223-239.
• Westgard J.O., Barry P.L., Hunt M.R., Groth T. A multi-rule Shewhart chart for quality control in clinical chemistry. Clin Chem (1981) 27:493-501.

Codebook and Frequencies