Table of Contents

Component Description

The Family Smoking Prevention and Tobacco Control Act of 2009 gave the Food and Drug Administration regulatory authority over tobacco products. In Section 907(a), the Act states that the Secretary of HHS shall establish tobacco product standards. These product standards shall also include provisions for the testing of the tobacco products. In order to determine the effectiveness of these product standards, it is critical that surveillance systems be in place before the standards are enacted to determine whether they impact exposure of people who continue to use tobacco product. NHANES is an ideal source of human samples for assessing smokers in multiple locations around the country. NHANES will provide the most robust dataset possible for identifying changes in exposure of smokers that should result from enactment of tobacco product standards.

We anticipate that the results of this survey of tobacco exposure biomarkers will be used by FDA, other government agencies, and research institutions. The NHANES data will be used to determine the effectiveness of initial product standards and direct whether further changes to product standards need to be made.

Exposure to volatile organic compounds (VOCs) is ubiquitous. Chronic exposure to extremely high levels of some VOCs can lead to cancer and neurocognitive dysfunction. Urinary metabolites of VOCs can be detectable in urine for a longer period of time than the parent VOCs can be detected in blood.
Nearly 200 air toxics have been associated with adverse health effects in occupational studies or laboratory studies, but have not been monitored in general population groups. Information on levels of exposure to these compounds, as measured by their metabolite levels in urine, is essential to determine the need for regulatory mechanisms to reduce the levels of hazardous air pollutants to which the general population is exposed.

Eligible Sample

Examined participants aged 6 years and older from a one-third sample were eligible. Additionally, to oversample adult smokers, those participants aged 20 years and older, not in the regular one-third subsample, who smoked at least 100 cigarettes in their entire lifetime (SMQ020=1) and now smoke cigarettes every day (SMQ040=1), were also included in this special subsample.

Description of Laboratory Methodology

This method is a quantitative procedure for the measurement of VOC metabolites in human urine using ultra performance liquid chromatography coupled with electro spray tandem mass spectrometry (UPLC-ESIIMSMS) (29). Chromatographic separation is achieved using an Acquity UPLC® HSS T3 (Part no. 186003540, 1.8f µm x 2.1 mm x 150 mm, Waters Inc.) column with 15 mM ammonium acetate and acetonitrile as the mobile phases. The eluent from the column is ionized using an electrospray interface to generate and transmit negative ions into the mass spectrometer. Comparison of relative response factors (ratio of native analyte to stable isotope labeled internal standard) with known standard concentrations yields individual analyte concentrations.

Laboratory Method Files

Laboratory Quality Assurance and Monitoring

Urine specimens are 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 2011-2012 Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–20°C) conditions until they are 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 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 person is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff. 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 CDC and contract laboratories. In the MEC, these methods include performing second examinations on previously examined participants and blind split samples collected on “dry run” sessions.
NCHS developed and distributed a quality control protocol for all the contract laboratories which outlined the Westgard rules (Westgard, et al. 1981) used 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 and Westat 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 CDC/NCEH Tobacco and Volatile Branch quality control and quality assurance performance criteria for accuracy and precision, similar to the Westgard rules (Caudill et al., 2008).


Analytic Notes

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

Subsample Weights

Measures of volatile organic compounds in urine were assessed in a subsample of participants aged 20 years and older. Use the special smoking weights included in this data file when analyzing data. Special sample weights are required to analyze these data properly. Specific sample weights for this subsample are included in this data file and should be used when analyzing these data.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES Demographic Data File contains demographic and 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.

This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier SEQN.

Special Analytic Note: Bias Adjustments Applied to VOC Metabolites in Urine Assay in NHANES 2011–2012 cycle

Adjustments have been applied to the previously published data.

During routine review, several systematic biases were discovered in measurements of certain urinary VOC metabolites in the 2005 – 2006 and 2011 – 2012 NHANES cycles. The systematic nature of these biases permitted retrospective adjustment through a statistical approach based on linear regression modeling where adjusted measurements are predicted from unadjusted measurements using suitable data. The “statistical recalibrations” implemented here have the general form of a univariate linear regression equation (accounting for dilution factors routinely used during measurement):

where exp[·] and ln(·) are the natural exponential and natural logarithm functions, respectively. Natural log-transformation of both the un-adjusted and adjusted measurements moderated adverse influence on model fit from extreme measurements. The estimated regression slope and intercept are m and b, respectively, which are tabulated below for each analyte. The dilution factor was accounted for only once for each analyte that underwent more than one statistical recalibration (e.g., URXMB3). Statistical recalibration for the mass fraction of salt (URXHP2, URXGAM) only required a regression slope (i.e., b=0).

The explanatory power of the linear regressions was excellent (R2≥0.95), and residuals exhibited distributions with good approximation to normality, as well as stable variance over the observed range of measurements. These favorable diagnostics demonstrate the efficacy of statistical recalibration for the retrospective amelioration of systematic bias.

Correction for Variation in Preparation of Neat Native Metabolites Standards

During the 2005–2006 and 2011–2012 NHANES cycles, calibrators were prepared from a multi-analyte stock solution formulated from neat materials in-house. Beginning with the NHANES 2015–2016 cycle, calibrators and the multi-analyte stock solution were prepared externally. A systematic bias between the cycles that used in-house calibration materials and the cycle using externally prepared calibration materials was observed for analytes listed in the table below. Further validation of the externally prepared calibrators suggested that the in-house calibrators were inaccurate due to special requirements for handling and preparing accurate solutions from neat materials, some of which are highly hygroscopic.

Analyte Code m used in correction b used in correction
URXAMC 0.99687 0.12843
URXCEM 1.01462 -0.13642
URXDHB 0.99654 0.04687
URXHEM 1.00947 0.30195
URXHPM 0.98949 -0.23802
URXMAD 1.00736 -0.18993
URXTTC 1.03057 -0.0746
URXMB3 0.97491 -0.43202
URX2DC 1.00155 -0.32374

Correction for Mass Fraction of Salt in Neat Compound Standard

During the 2005–2006 and 2011–2012 NHANES cycles, calibrators were prepared from a multi-analyte stock solution formulated from neat materials in-house. Beginning with the NHANES 2015–2016 cycle, calibrators and the multi-analyte stock solution were prepared externally. A systematic bias between the cycles that used in-house calibration materials and the cycle using externally prepared calibration materials was observed for analytes listed in the table below. Further validation confirmed that the large mass fraction of salt in the neat materials was not accounted for during formulation of in-house calibration materials. This discrepancy between the calculated concentration of the calibrators and the actual concentration led to a systematic bias in results for URXHP2 and URXGAM.

Analyte Code m used in correction
URXHP2 0.54711990
URXGAM 0.57755045

 Correction for Stereoisomerism in Urine Samples

UXMB3 occurs in human urine predominantly in the cis isomer, but quantitation in the NHANES 2005–2006 and NHANES 2011–2012 cycles used standards containing the trans isomer. This discrepancy led to a systematic bias in the URXMB3 results. Neat material that is purely cis isomer cannot be readily obtained, but a predictive regression equation can account for these quantitative differences.

Analyte Code m used in correction used in correction
URXMB3 0.97741 -0.18775

Detection Limits

The detection limits were constant for the analytes in the data set. Two variables are provided for each of these analytes. The variable named ending in “LC” (ex., URDAAMLC) 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., URDAAMLC=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 URX (ex., URXAAM) provides the analytic result for the analyte.

The lower limit of detection (LLOD, in µg/L) for urinary VOC metabolites:

VARIABLE Analyte LLOD
URXAAM Urinary N-Acetyl-S-(2-carbamoylethyl)-L-cysteine 2.20
URXAMC Urinary N-Acetyl-S-(N-methylcarbamoyl)-L-cysteine 6.26
URXATC Urinary 2-Aminothiazoline-4-carboxylic acid 15.0
URXBMA Urinary N-Acetyl-S-(benzyl)-L-cysteine 0.500
URXBPM Urinary N-Acetyl-S-(n-propyl)-L-cysteine 1.20
URXCEM Urinary N-Acetyl-S-(2-carboxyethyl)-L-cysteine 6.96
URXCYM Urinary N-Acetyl-S-(2-cyanoethyl)-L-cysteine 0.500
URX1DC Urinary N-Acetyl-S-(1,2-dichlorovinyl)-L-cysteine 12.6
URX2DC Urinary N-Acetyl-S-(2,2-dichlorovinyl)-L-cysteine 4.70
URXDHB Urinary N-Acetyl-S-(3,4-dihydroxybutyl)-L-cysteine 5.25
URXDPM Urinary N-Acetyl-S-(dimethylphenyl)-L-cysteine 0.500
URXGAM Urinary N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine 9.40
URXHEM Urinary N-Acetyl-S-(2-hydroxyethyl)-L-cysteine 0.791
URXHPM Urinary N-Acetyl-S-(3-hydroxypropyl)-L-cysteine 13.0
URXHP2 Urinary N-Acetyl-S-(2-hydroxypropyl)-L-cysteine 5.30
URXPMM Urinary N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-cysteine 2.00
URXMAD Urinary Mandelic acid 12.0
URX2MH Urinary 2-Methylhippuric acid 5.00
URX34M Urinary 3- and 4-Methylhippuric acid 8.00
URXMB1 Urinary N-Acetyl-S-(1-hydroxymethyl-2-propenyl)-L-cysteine 0.700
URXMB2 Urinary N-Acetyl-S-(2-hydroxy-3-butenyl)-L-cysteine 0.700
URXMB3 Urinary N-Acetyl-S-(4-hydroxy-2-butenyl)-L-cysteine 0.600
URXPHE Urinary N-Acetyl-S-(phenyl-2-hydroxyethyl)-L-cysteine 0.700
URXPHG Urinary Phenylglyoxylic acid 12.0
URXPMA Urinary N-Acetyl-S-(phenyl)-L-cysteine 0.600
URXTCV Urinary N-Acetyl-S-(trichlorovinyl)-L-cysteine 3.00
URXTTC Urinary 2-Thioxothiazolidine-4-carboxylic acid 11.2

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 20 YEARS - 150 YEARS

WTFSM - Two year smoking weights

Variable Name:
WTFSM
SAS Label:
Two year smoking weights
English Text:
Two year smoking weights
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
5682.47 to 700606.65 Range of Values 2272 2272
0 No Lab Result 77 2349
. Missing 0 2349

URXUCR - Creatinine, urine (mg/dL)

Variable Name:
URXUCR
SAS Label:
Creatinine, urine (mg/dL)
English Text:
Creatinine, urine (mg/dL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4 to 800 Range of Values 2271 2271
. Missing 78 2349

URX1DC - N-Acel-S-(1,2-dichlorovinl)-L-Cys(ng/mL)

Variable Name:
URX1DC
SAS Label:
N-Acel-S-(1,2-dichlorovinl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(1,2-dichlorovinyl)-L-Cysteine (ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8.9 to 90.4 Range of Values 2240 2240
. Missing 109 2349

URD1DCLC - N-Acel-S-(1,2-dichlorovinl)-L-Cys comt

Variable Name:
URD1DCLC
SAS Label:
N-Acel-S-(1,2-dichlorovinl)-L-Cys comt
English Text:
N-Acetyl-S-(1,2-dichlorovinyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 4 4
1 Below lower detection limit 2236 2240
. Missing 109 2349

URX2DC - N-Acel-S-(2,2-Dichlorvinyl)-L-Cys(ng/mL)

Variable Name:
URX2DC
SAS Label:
N-Acel-S-(2,2-Dichlorvinyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(2,2-Dichlorovinyl)-L-Cysteine (ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.32 to 19.4 Range of Values 2240 2240
. Missing 109 2349

URD2DCLC - N-Acel-S-(2,2-Dichlorvinyl)-L-Cys comt

Variable Name:
URD2DCLC
SAS Label:
N-Acel-S-(2,2-Dichlorvinyl)-L-Cys comt
English Text:
N-Acetyl-S-(2,2-Dichlorovinyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 6 6
1 Below lower detection limit 2234 2240
. Missing 109 2349

URX2MH - 2-Methylhippuric acid (ng/mL)

Variable Name:
URX2MH
SAS Label:
2-Methylhippuric acid (ng/mL)
English Text:
2-Methylhippuric acid (ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.54 to 18200 Range of Values 2240 2240
. Missing 109 2349

URD2MHLC - 2-Methylhippuric acid comment code

Variable Name:
URD2MHLC
SAS Label:
2-Methylhippuric acid comment code
English Text:
2-Methylhippuric acid comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2161 2161
1 Below lower detection limit 79 2240
. Missing 109 2349

URX34M - 3-Methipurc acd & 4-Methipurc acd(ng/mL)

Variable Name:
URX34M
SAS Label:
3-Methipurc acd & 4-Methipurc acd(ng/mL)
English Text:
3-Methylhippuric acid & 4-Methylhippuric acid(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
5.66 to 55000 Range of Values 2240 2240
. Missing 109 2349

URD34MLC - 3-Methipurc acd & 4-Methipurc acid comt

Variable Name:
URD34MLC
SAS Label:
3-Methipurc acd & 4-Methipurc acid comt
English Text:
3-Methylhippuric acid & 4-Methylhippuric acid comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2238 2238
1 Below lower detection limit 2 2240
. Missing 109 2349

URXAAM - N-Ace-S-(2-carbamoylethyl)-L-Cys(ng/mL)

Variable Name:
URXAAM
SAS Label:
N-Ace-S-(2-carbamoylethyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(2-carbamoylethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.56 to 1620 Range of Values 2240 2240
. Missing 109 2349

URDAAMLC - N-Ace-S-(2-carbamoylethyl)-L-Cys comt

Variable Name:
URDAAMLC
SAS Label:
N-Ace-S-(2-carbamoylethyl)-L-Cys comt
English Text:
N-Acetyl-S-(2-carbamoylethyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2238 2238
1 Below lower detection limit 2 2240
. Missing 109 2349

URXAMC - N-Ace-S-(N-methlcarbamoyl)-L-Cys(ng/mL)

Variable Name:
URXAMC
SAS Label:
N-Ace-S-(N-methlcarbamoyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(N-methylcarbamoyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4.43 to 4320 Range of Values 2240 2240
. Missing 109 2349

URDAMCLC - N-Ace-S-(N-methlcarbamoyl)-L-Cys comt

Variable Name:
URDAMCLC
SAS Label:
N-Ace-S-(N-methlcarbamoyl)-L-Cys comt
English Text:
N-Acetyl-S-(N-methylcarbamoyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2237 2237
1 Below lower detection limit 3 2240
. Missing 109 2349

URXATC - 2-Amnothiazolne-4-carbxylic acid(ng/mL)

Variable Name:
URXATC
SAS Label:
2-Amnothiazolne-4-carbxylic acid(ng/mL)
English Text:
2-Aminothiazoline-4-carboxylic acid(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
10.6 to 2420 Range of Values 2240 2240
. Missing 109 2349

URDATCLC - 2-Amnothiazolne-4-carbxylic acid comt

Variable Name:
URDATCLC
SAS Label:
2-Amnothiazolne-4-carbxylic acid comt
English Text:
2-Amnothiazolne-4-carbxylic acid comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2149 2149
1 Below lower detection limit 91 2240
. Missing 109 2349

URXBMA - N-Acetyl-S-(benzyl)-L-Cysteine(ng/mL)

Variable Name:
URXBMA
SAS Label:
N-Acetyl-S-(benzyl)-L-Cysteine(ng/mL)
English Text:
N-Acetyl-S-(benzyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.354 to 1090 Range of Values 2240 2240
. Missing 109 2349

URDBMALC - N-Acetyl-S-(benzyl)-L-Cysteine comt

Variable Name:
URDBMALC
SAS Label:
N-Acetyl-S-(benzyl)-L-Cysteine comt
English Text:
N-Acetyl-S-(benzyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2225 2225
1 Below lower detection limit 15 2240
. Missing 109 2349

URXBPM - N-Acetyl-S-(n-propyl)-L-Cysteine(ng/mL)

Variable Name:
URXBPM
SAS Label:
N-Acetyl-S-(n-propyl)-L-Cysteine(ng/mL)
English Text:
N-Acetyl-S-(n-propyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.85 to 545 Range of Values 2191 2191
. Missing 158 2349

URDBPMLC - N-Acetyl-S-(n-propyl)-L-Cysteine comt

Variable Name:
URDBPMLC
SAS Label:
N-Acetyl-S-(n-propyl)-L-Cysteine comt
English Text:
N-Acetyl-S-(n-propyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1692 1692
1 Below lower detection limit 499 2191
. Missing 158 2349

URXCEM - N-Acetyl-S- (2-Carbxyethyl)-L-Cys(ng/mL)

Variable Name:
URXCEM
SAS Label:
N-Acetyl-S- (2-Carbxyethyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-Carboxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4.92 to 3230 Range of Values 2240 2240
. Missing 109 2349

URDCEMLC - N-Acetyl-S-(2-Carbxyethyl)-L-Cys comt

Variable Name:
URDCEMLC
SAS Label:
N-Acetyl-S-(2-Carbxyethyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-Carboxyethyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2226 2226
1 Below lower detection limit 14 2240
. Missing 109 2349

URXCYM - N-Acetyl-S-(2-cyanoethyl)-L-Cyst(ng/mL)

Variable Name:
URXCYM
SAS Label:
N-Acetyl-S-(2-cyanoethyl)-L-Cyst(ng/mL)
English Text:
N-Acetyl-S-(2-cyanoethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.354 to 1600 Range of Values 2240 2240
. Missing 109 2349

URDCYMLC - N-Acetyl-S-(2-cyanoethyl)-L-Cyst comt

Variable Name:
URDCYMLC
SAS Label:
N-Acetyl-S-(2-cyanoethyl)-L-Cyst comt
English Text:
N-Acetyl-S-(2-cyanoethyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2087 2087
1 Below lower detection limit 153 2240
. Missing 109 2349

URXDHB - N-Ace-S- (3,4-Dihidxybutl)-L-Cys(ng/mL)

Variable Name:
URXDHB
SAS Label:
N-Ace-S- (3,4-Dihidxybutl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (3,4-Dihidroxybutyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.71 to 2410 Range of Values 2240 2240
. Missing 109 2349

URDDHBLC - N-Ace-S- (3,4-Dihidxybutl)-L-Cys comt

Variable Name:
URDDHBLC
SAS Label:
N-Ace-S- (3,4-Dihidxybutl)-L-Cys comt
English Text:
N-Acetyl-S- (3,4-Dihidroxybutyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2239 2239
1 Below lower detection limit 1 2240
. Missing 109 2349

URXDPM - N-Ace-S-(dimethylphenyl)-L-Cys(ng/mL)

Variable Name:
URXDPM
SAS Label:
N-Ace-S-(dimethylphenyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(dimethylphenyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.354 to 2.27 Range of Values 2240 2240
. Missing 109 2349

URDDPMLC - N-Ace-S-(dimethylphenyl)-L-Cys comt

Variable Name:
URDDPMLC
SAS Label:
N-Ace-S-(dimethylphenyl)-L-Cys comt
English Text:
N-Acetyl-S-(dimethylphenyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 6 6
1 Below lower detection limit 2234 2240
. Missing 109 2349

URXGAM - N-Ac-S-(2-carbmo-2-hydxel)-L-Cys(ng/mL)

Variable Name:
URXGAM
SAS Label:
N-Ac-S-(2-carbmo-2-hydxel)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
6.65 to 171 Range of Values 2240 2240
. Missing 109 2349

URDGAMLC - N-Ac-S-(2-carbmo-2-hydxel)-L-Cys comt

Variable Name:
URDGAMLC
SAS Label:
N-Ac-S-(2-carbmo-2-hydxel)-L-Cys comt
English Text:
N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1145 1145
1 Below lower detection limit 1095 2240
. Missing 109 2349

URXHEM - N-Ace-S-(2-Hydroxyethyl)-L-Cys(ng/mL)

Variable Name:
URXHEM
SAS Label:
N-Ace-S-(2-Hydroxyethyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-Hydroxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.559 to 66.7 Range of Values 2240 2240
. Missing 109 2349

URDHEMLC - N-Ace-S-(2-Hydroxyethyl)-L-Cys comt

Variable Name:
URDHEMLC
SAS Label:
N-Ace-S-(2-Hydroxyethyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-Hydroxyethyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1425 1425
1 Below lower detection limit 815 2240
. Missing 109 2349

URXHP2 - N-Ace-S-(2-hydroxypropyl)-L-Cys(ng/mL)

Variable Name:
URXHP2
SAS Label:
N-Ace-S-(2-hydroxypropyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-hydroxypropyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.75 to 9360 Range of Values 2240 2240
. Missing 109 2349

URDHP2LC - N-Ace-S-(2-hydroxypropyl)-L-Cys comt

Variable Name:
URDHP2LC
SAS Label:
N-Ace-S-(2-hydroxypropyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-hydroxypropyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2152 2152
1 Below lower detection limit 88 2240
. Missing 109 2349

URXHPM - N-Ace-S-(3-Hydroxypropyl)-L-Cys(ng/mL)

Variable Name:
URXHPM
SAS Label:
N-Ace-S-(3-Hydroxypropyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (3-Hydroxypropyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
9.2 to 12700 Range of Values 2240 2240
. Missing 109 2349

URDHPMLC - N-Ace-S-(3-Hydroxypropyl)-L-Cys comt

Variable Name:
URDHPMLC
SAS Label:
N-Ace-S-(3-Hydroxypropyl)-L-Cys comt
English Text:
N-Acetyl-S- (3-Hydroxypropyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2239 2239
1 Below lower detection limit 1 2240
. Missing 109 2349

URXMAD - Mandelic acid(ng/mL)

Variable Name:
URXMAD
SAS Label:
Mandelic acid(ng/mL)
English Text:
Mandelic acid(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8.5 to 27500 Range of Values 2240 2240
. Missing 109 2349

URDMADLC - Mandelic acid comment code

Variable Name:
URDMADLC
SAS Label:
Mandelic acid comment code
English Text:
Mandelic acid comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2220 2220
1 Below lower detection limit 20 2240
. Missing 109 2349

URXMB1 - N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys(ng/mL)

Variable Name:
URXMB1
SAS Label:
N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(1-HydroxyMethyl)-2-Propenyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.495 to 2.22 Range of Values 2240 2240
. Missing 109 2349

URDMB1LC - N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys comt

Variable Name:
URDMB1LC
SAS Label:
N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys comt
English Text:
N-Acetyl-S-(1-HydroxyMethyl)-2-Propenyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 45 45
1 Below lower detection limit 2195 2240
. Missing 109 2349

URXMB2 - N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys(ng/mL)

Variable Name:
URXMB2
SAS Label:
N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-hydroxy-3-butenyl)-L-Cysteine (ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.495 to 43.2 Range of Values 2240 2240
. Missing 109 2349

URDMB2LC - N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys comt

Variable Name:
URDMB2LC
SAS Label:
N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-hydroxy-3-butenyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 582 582
1 Below lower detection limit 1658 2240
. Missing 109 2349

URXMB3 - N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys(ng/mL)

Variable Name:
URXMB3
SAS Label:
N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (4-hydroxy-2-butenyl)-L-Cysteine (ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.424 to 248 Range of Values 2240 2240
. Missing 109 2349

URDMB3LC - N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys comt

Variable Name:
URDMB3LC
SAS Label:
N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys comt
English Text:
N-Acetyl-S- (4-hydroxy-2-butenyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2198 2198
1 Below lower detection limit 42 2240
. Missing 109 2349

URXPHE - N-Ace-S-(phenl-2-hydxyetl)-L-Cys(ng/mL)

Variable Name:
URXPHE
SAS Label:
N-Ace-S-(phenl-2-hydxyetl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(phenyl-2-hydroxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.495 to 550 Range of Values 2240 2240
. Missing 109 2349

URDPHELC - N-Ace-S-(phenl-2-hydxyetl)-L-Cys comt

Variable Name:
URDPHELC
SAS Label:
N-Ace-S-(phenl-2-hydxyetl)-L-Cys comt
English Text:
N-Acetyl-S-(phenyl-2-hydroxyethyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 957 957
1 Below lower detection limit 1283 2240
. Missing 109 2349

URXPHG - Phenylglyoxylic acid(ng/mL)

Variable Name:
URXPHG
SAS Label:
Phenylglyoxylic acid(ng/mL)
English Text:
Phenylglyoxylic acid(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8.5 to 42200 Range of Values 2240 2240
. Missing 109 2349

URDPHGLC - Phenylglyoxylic acid comment code

Variable Name:
URDPHGLC
SAS Label:
Phenylglyoxylic acid comment code
English Text:
Phenylglyoxylic acid comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2221 2221
1 Below lower detection limit 19 2240
. Missing 109 2349

URXPMA - N-Acetyl-S-(phenyl)-L-Cysteine(ng/mL)

Variable Name:
URXPMA
SAS Label:
N-Acetyl-S-(phenyl)-L-Cysteine(ng/mL)
English Text:
N-Acetyl-S-(phenyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.424 to 16.6 Range of Values 2240 2240
. Missing 109 2349

URDPMALC - N-Acetyl-S-(phenyl)-L-Cysteine comt

Variable Name:
URDPMALC
SAS Label:
N-Acetyl-S-(phenyl)-L-Cysteine comt
English Text:
N-Acetyl-S-(phenyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1061 1061
1 Below lower detection limit 1179 2240
. Missing 109 2349

URXPMM - N-A-S-(3-hydrxprpl-1-metl)-L-Cys(ng/mL)

Variable Name:
URXPMM
SAS Label:
N-A-S-(3-hydrxprpl-1-metl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
2.85 to 26700 Range of Values 2240 2240
. Missing 109 2349

URDPMMLC - N-A-S-(3-hydrxprpl-1-metl)-L-Cys comt

Variable Name:
URDPMMLC
SAS Label:
N-A-S-(3-hydrxprpl-1-metl)-L-Cys comt
English Text:
N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2240 2240
1 Below lower detection limit 0 2240
. Missing 109 2349

URXTCV - N-Acetyl-S-(trichlorovinyl)-L-Cys(ng/mL)

Variable Name:
URXTCV
SAS Label:
N-Acetyl-S-(trichlorovinyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(trichlorovinyl)-L-Cysteine(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
2.12 to 9.49 Range of Values 2240 2240
. Missing 109 2349

URDTCVLC - N-Acetyl-S-(trichlorovinyl)-L-Cys comt

Variable Name:
URDTCVLC
SAS Label:
N-Acetyl-S-(trichlorovinyl)-L-Cys comt
English Text:
N-Acetyl-S-(trichlorovinyl)-L-Cysteine comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 4 4
1 Below lower detection limit 2236 2240
. Missing 109 2349

URXTTC - 2-Thoxothazlidne-4-carbxylic acid(ng/mL)

Variable Name:
URXTTC
SAS Label:
2-Thoxothazlidne-4-carbxylic acid(ng/mL)
English Text:
2-Thioxothiazolidine-4-carboxylic acid(ng/mL)
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
7.9 to 4460 Range of Values 2240 2240
. Missing 109 2349

URDTTCLC - 2-thoxothazlidne-4-carbxylic comt

Variable Name:
URDTTCLC
SAS Label:
2-thoxothazlidne-4-carbxylic comt
English Text:
2-thioxothiazolidine-4-carboxylic acid comment code
Target:
Both males and females 20 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 895 895
1 Below lower detection limit 1345 2240
. Missing 109 2349