Table of Contents

Component Description

Prior to 2013, specimens with a reactive anti-HCV screening test result were tested with a confirmatory recombinant immunoblot assay (RIBA) (Chiron RIBA HCV 3.0 Strip SIA) to confirm the presence of anti-HCV. Results for “confirmed anti-HCV” (LBDHCV) were reported as positive if the RIBA was positive, as indeterminate if the RIBA was indeterminate, and as negative if the RIBA was negative or if the anti-HCV screening test result was negative. RIBA positive and indeterminate specimens were further tested for HVC RNA, and, if RNA positive, for HCV genotype.

As of late 2012, Chiron is no longer producing RIBA kits and thus no confirmatory test for anti-HCV was available for the 2013-2014 NHANES cycle. Because only 67.7% (323 of 477) of NHANES specimens with a reactive anti-HCV screening test result during NHANES 2007-2012 were found to be RIBA positive, reporting all specimens with a reactive anti-HCV screening test result as anti-HCV positive would result in an apparent increase in prevalence of ever having HCV infection due merely to the reporting of screening anti-HCV false-positives as antibody positive. Thus, for NHANES to continue to track trends in prevalence of ever having HCV infection via anti-HCV after the 2011-2012 cycle, it is necessary to employ a new HCV testing algorithm, which can produce a prevalence for ever having HCV infection closer to that obtained using RIBA confirmation than would be obtained if all specimens with a reactive anti-HCV screening test result were reported as antibody positive. Data from serum surplus testing with a second anti-HCV screening assay (sometimes referred to as reflex testing), performed to evaluate potential new HCV testing algorithms for NHANES specimens collected after the 2011-2012 cycle, are reported in this file, along with initial anti-HCV screening test and RIBA results.

Eligible Sample

The eligible samples are those from the 2007-2012 NHANES which had a reactive screening anti-HCV test result and were tested with RIBA. All participants aged 6 years or older were eligible to be tested for anti-HCV during NHANES 2007-2012.

Description of Laboratory Methodology

Four hundred seventy-nine (479) samples were screening anti-HCV reactive when tested during NHANES 2007-2012; 2 did not have sufficient serum remaining for RIBA testing to be performed. Surplus serum was available in the Division of Viral Hepatitis Laboratory for additional testing on 394 of these 477 specimens.

HCV antibody reflex test
Abbott ARCHITECT anti-HCV assay is a chemiluminescent microparticle immunoassay (CMIA) for the qualitative detection of immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies to hepatitis C virus (anti HCV) in human serum and plasma (potassium EDTA, lithium heparin, and sodium heparin). ARCHITECT Anti-HCV has been designed to detect antibodies to putative structural and nonstructural proteins of the HCV genome: HCr43, representing in the first region amino acids 1192 to 1457 (33c) of the HCV sequence, and in the second region-amino acids 1 to 150 (core) of the HCV sequence; and c100-3, representing the putative nonstructural (NS3 and NS4) regions of HCV.

The assay is a two-step immunoassay using CMIA technology with flexible assay protocols, referred to as Chemiflex. Briefly, sample, recombinant HCV antigen coated paramagnetic microparticles, and assay diluent are combined. Anti-HCV present in the sample binds to the HCV coated microparticles. After washing, antihuman IgG/IgM acridinium-labeled conjugate is added in the second step. Following another wash cycle, pre-trigger and trigger solutions are added to the reaction mixture. The resulting chemiluminescent reaction is measured as relative light units (RLUs). A relationship exists between the amount of anti-HCV in the sample and the RLUs detected by the ARCHITECT i optical system. The presence or absence of anti-HCV in the sample is determined by comparing the chemiluminescent signal in the reaction to the cutoff signal determined from an active ARCHITECT Anti-HCV calibration curve. If the chemiluminescent signal of the sample is greater than or equal to the cutoff signal, the sample is considered reactive for anti-HCV.

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

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 Procedures Manual (LPM). Read the General Documentation on Laboratory Data file for detailed QA/QC protocols.

Data Processing and Editing

Read the General Documentation on Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Description of Laboratory Methodology section above.

Analytic Notes

NHANES Survey Design:
The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The Demographic file contains: Status Variables providing core information on the survey participant including examination status, Recoded Demographic Variables including age, gender, race, etc., and Interview and Examination Sample Weight Variables and Survey Design Variables. The Questionnaire Data Files contain socio-economic data, health indicators, and other related information collected during household interviews. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Demographic, Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

The age range and constraints for hepatitis C testing are as follows:

The initial screening hepatitis C antibody test was performed on all examinees 6 years old or older. Surplus serum samples available for specimens from 2007-2012 with an initially reactive anti-HCV screening test result and a RIBA testing result were tested with a second anti-HCV screening assay.

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.

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 6 YEARS - 150 YEARS

 

SSASCR1 - SCR for first test

Variable Name:
SSASCR1
SAS Label:
SCR for first test
English Text:
screen-to-cutoff ratio (SCR) for first test with Abbott assay (surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.05 to 18.79 Range of Values 394 394
. Missing 0 394

 

SSAHCV1 - Interpretation of first test

Variable Name:
SSAHCV1
SAS Label:
Interpretation of first test
English Text:
interpretation of first test with Abbott assay (surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Reactive 305 305
2 Nonreactive 85 390
3 Indeterminate 4 394
. Missing 0 394

 

SSASCR2 - SCR for second test

Variable Name:
SSASCR2
SAS Label:
SCR for second test
English Text:
SCR for second test with Abbott assay (surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.84 to 17.37 Range of Values 263 263
. Missing 131 394

 

SSAHCV2 - Interpretation of second test

Variable Name:
SSAHCV2
SAS Label:
Interpretation of second test
English Text:
interpretation of second test with Abbott assay (surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Reactive 258 258
2 Nonreactive 0 258
3 Indeterminate 5 263
. Missing 131 394

 

SSASCR3 - SCR for third test

Variable Name:
SSASCR3
SAS Label:
SCR for third test
English Text:
SCR for third test with Abbott assay (surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.17 1.17 1 1
. Missing 393 394

 

SSAHCV3 - Interpretation of third test

Variable Name:
SSAHCV3
SAS Label:
Interpretation of third test
English Text:
interpretation of third test with Abbott assay (surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Reactive 1 1
2 Nonreactive 0 1
3 Indeterminate 0 1
. Missing 393 394

 

SSAINIT - SCR for initial test

Variable Name:
SSAINIT
SAS Label:
SCR for initial test
English Text:
SCR for initial anti-HCV screening test with Ortho assay (not surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.01 to 49 Range of Values 394 394
. Missing 0 394

 

SSAHCVI - Interpretation of initial test

Variable Name:
SSAHCVI
SAS Label:
Interpretation of initial test
English Text:
interpretation of initial anti-HCV screening test with Ortho assay (not surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Positive 394 394
2 Negative 0 394
3 Indeterminate 0 394
. Missing 0 394

 

SSRIBA - RIBA Test result

Variable Name:
SSRIBA
SAS Label:
RIBA Test result
English Text:
RIBA test result (not surplus serum testing)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Positive 267 267
2 Negative 83 350
3 Indeterminate 44 394
. Missing 0 394