Formaldehyde (FA) is an environmental chemical occurring in tobacco smoke, building materials, and furniture, among other sources (Pala et. al., 2008). FA was classified as carcinogenic to humans by the International Agency for Research in Cancer (IARC, 2006 and Cogliano et. al., 2005). People exposed to high levels of FA are at increased risks of nasopharyngeal cancer and lymphohematopoietic cancer, specifically myeloid leukemia (Clinical Chemistry Branch, 2019). FA is also produced by most living organisms as part of regular metabolic activities.
FA is highly reactive towards biomolecules and can react with proteins to form so called “adducts” (Metz et. al., 2004). Adducts with hemoglobin have successfully been used as biomarkers of exposure for a range of environmental chemicals (Osterman-Golkar et. al., 1976).
Examined participants aged 6 years and older from a one-third subsample were eligible.
This procedure describes a method to measure N-terminal hemoglobin adducts of Formaldehyde in human erythrocytes. It consists of 5 parts:
Because results are reported in nanomol adduct per gram of hemoglobin used in the measurement, the amount of hemoglobin used for this analysis needs to be determined. Therefore, this procedure includes a commercial method for measuring total hemoglobin in clinical samples (Eilers, 1967).
Refer to the Laboratory Method Files section for a detailed description of the laboratory methods used.
There were no changes to the lab method, lab equipment, or lab site for this component in the NHANES 2015-2016 cycle.
Formaldehyde Lab Procedure Manual (January 2020)
Washed-packed red blood cell specimens 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 Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–30°C) conditions until they are shipped to the 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 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 on “dry run” sessions. In addition, contract
laboratories randomly perform repeat testing on 2% of all specimens.
NCHS developed and distributed a QC protocol for all the 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’ QA/QC performance criteria for accuracy and precision, similar to the Westgard rules (Caudill et. al., 2008).
The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.
Refer to the 2015-2016 Laboratory Data Overview for general information on NHANES laboratory data.
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.
Subsample Weights
Formaldehyde was measured in a one-third subsample of participants 6 years and
older. 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 using the appropriate
survey design and demographic variables. The NHANES 2015-2016 Demographics File contains
demographic data, health indicators, and other related information collected
during household interviews as well as the 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.
The Fasting Questionnaire File includes auxiliary information, such as fasting status, length of fast, and the time of venipuncture.
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 named ended
“LC” (ex., LBDFORLC) 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. The
other variable prefixed LBX (ex., LBXFOR) provides the analytic result for that
analyte. For analytes with analytic results below the lower limit of detection
(ex., LBDFORLC =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 lower limit of detection (LLOD, in nmol/g HB) for FA is:
|
Variable Name |
Analyte Description |
LLOD |
|
LBXFOR |
Formaldehyde |
0.67 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 16357.767797 to 708844.24678 | Range of Values | 2644 | 2644 | |
| 0 | No Lab Result | 48 | 2692 | |
| . | Missing | 0 | 2692 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 57.7 to 228 | Range of Values | 2372 | 2372 | |
| . | Missing | 320 | 2692 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0 | at or above the limit of detection | 2372 | 2372 | |
| 1 | below limit of detection | 0 | 2372 | |
| . | Missing | 320 | 2692 |