• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • WTSSGP2Y - Surplus specimen AGP 2 year weights
  • SSAGP - Alpha-1-Acid Glycoprotein (g/L)

National Health and Nutrition Examination Survey

2015-2016 Data Documentation, Codebook, and Frequencies

Alpha-1-Acid Glycoprotein - Serum (Surplus) (SSAGP_I)

Data File: SSAGP_I.xpt

First Published: September 2023

Last Revised: NA

Component Description

Alpha-1-acid glycoprotein (AGP; also called orosomucoid) is synthesized in the liver and structurally belongs to the lipocalin superfamily of secretory proteins, such as retinol-binding protein and α1-microglobulin. It is made up of a polypeptide chain having 5 carbohydrate chains N-glycosidically bonded to it (molar mass of 41,000 daltons).

AGP is a sensitive acute phase reactant and its concentration can increase by a factor of 3 within 24-48 hours when inflammation occurs. It can also be used to differentiate between acute phase reactions (elevated serum level) and estrogen effects (normal or decreased serum level); whereas, the serum level of other positive reactants, such as ceruloplasmin and haptoglobin, increases during such reactions. Moderate and isolated increases occur when glomerular filtration is inhibited in the early stages of uremia. The determination is used in the assessment of the activity of acute and recurring inflammations as well as of tumors with cell necrosis (Schmid, 1975).

Eligible Sample

Examined participants aged 1-5 years and females aged 12-49 years were eligible.

Description of Laboratory Methodology

The Tina-quant Roche AAGP2 assay is based on the principle of immunological agglutination. Anti-α1-acid glycoprotein antibodies react with antigen in the sample to form an antigen/antibody complex. Following agglutination, this is measured turbidimetrically (AAGP2 Tina-quant α1-Acid Glycoprotein Gen.2 [package insert]).

Laboratory Quality Assurance and Monitoring

The laboratory and method were certified according to the Clinical Laboratory Improvement Amendment (1988) guidelines (Clinical Laboratory Improvement Amendment, 1988). Either in-house prepared serum quality control (QC) pools at three levels or Roche QC pools at two levels were analyzed in every run in duplicate and evaluated for validity against pre-established means and control limits by use of a multi-rule quality control program (Caudill et. al., 2008).

Performance of QC pools during the study period:

QC Pool	Analyte	n	Mean (g/L)	SD (g/L)	CV (%)	Difference to target (%)
LS17523_b	AGP	74	0.517	0.02	3.8	-0.96
LS17523_c	AGP	39	0.515	0.02	4.8	0.47
MS17524_b	AGP	74	0.945	0.02	2.6	-1.47
MS17524_c	AGP	39	0.938	0.02	2.6	0.30
HS17525_b	AGP	74	2.063	0.03	1.5	-0.66
HS17525_c	AGP	39	2.024	0.04	1.9	-0.62
PNP_50538700	AGP	20	0.682	0.03	3.6	-0.73
PPP_50539400	AGP	20	1.31	0.04	3.1	-4.93

The method achieved satisfactory performance using the Institute for Reference Materials and Measurements (IRMM) lyophilized human serum reference material ERM-DA470k, which has a certified AGP value of 0.617 g/L as measured by various methods using ERM-D470 as calibrant. The mean recovery of AGP in ERM-DA470k spiked into CFAS protein material was 96.8% (1:2 dilution), 94% (1:4 dilution), and 92.5% (1:8 dilution) during 2 measurements performed in 2020 and 2021. This procedure was adopted to avoid matrix effects that were observed when the reference material was diluted with Roche diluent, saline, or water and showed significant under-recovery.

The current project did not use pristine (never thawed) samples, because the laboratory showed that multiple freeze/thawing cycles do not cause a noticeable loss of AGP; and AGP can be assessed in residual serum as long as the specimens have been stored frozen at -70C.

Data Processing and Editing

Data were received after all the laboratory testing was complete. The data were not edited for extreme values.

Analytic Notes

Refer to the 2015-2016 Laboratory Data Overview for general information on NHANES laboratory data.

There are over 800 laboratory tests performed on NHANES participants. However, not all participants provided biospecimens or enough volume for all the tests to be performed. Additionally, availability of specimens for surplus projects is lower than for other laboratory tests performed on NHANES participants. The specimen availability can also vary by age or other population characteristics. Analysts should evaluate the extent of missing data in the dataset related to the outcome of interest as well as any predictor variables used in the analyses to determine whether additional re-weighting for item non-response is necessary.

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

The analytes included in this dataset were measured in a participants aged 1-5 years and females aged 12-49 years. Special sample weights are required to analyze these data properly. Specific sample weights for this subsample, WTSSGP2Y, are included in this data file and should be used when analyzing these data. The sample weights created for this file used the examination sample weight, i.e., WTMEC2YR, as the base weight. The base weight was adjusted for additional nonresponse to these lab tests and re-poststratified to the population total using sex, age, and race/Hispanic origin. Participants who were part of the eligible population but who did not provide a serum specimen, or did not have sufficient volume of biospecimens, or who did not give consent for their specimens to be used for future research are included in the file, but they have a sample weight assigned “0” in their records.

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.

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. No results were below the lower limit of detection. The lower limit of detection (LLOD in g/L) for SSAGP:

Variable Name	Analyte Name	LLOD
SSAGP	Alpha-1-Acid Glycoprotein (g/L)	0.1

References

• AAGP2 Tina-quant α1-Acid Glycoprotein Gen.2 [package insert]. Indianapolis, IN. Roche Diagnostics. 2014-11, V 9.0.
• Caudill S.P., Schleicher R.L., Pirkle J.L. Multi-rule quality control for the age-related eye disease study. Stat. Med. (2008) 27(20):4094-4106.
• Clinical Laboratory Improvement Amendment. Pub. L. 100-578. 1988. (Oct. 31, 1988).
• Schmid K. α1-Acid glycoprotein. In: Putnam FW, ed. The Plasma Proteins, 2nd ed. New York, NY: Academic Press; 1975:183-228.

Codebook and Frequencies