Table of Contents

Locator Record

Title: Second Day Exam - Measles, Rubella, and Varicella (L19_2_R )
Contact Number: 1-866-441-NCHS
Years of Content: 2000 - 2000
First Published: September, 2010
Revised: NA
Access Constraints: RDC Only
Use Constraints: RDC Only
Geographic Coverage: National
Subject:Second Day Exam - Measles, Rubella, and Varicella
Record Source: NHANES 2000 - 2000
Survey Methodology: NHANES 2000 - 2000 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

Second Day Exams

See the general documentation on Second Day laboratory exams. See the general documentation on second day laboratory exams. Also, see the documentation for the primary exam data for Laboratory 19.

Measles

Measles is a highly infectious disease targeted for elimination in the United States by the year 1996. The elimination strategy called for vaccination of all susceptible persons at age 12-15 months and at 4-11 years. NHANES will assess age-specific population immunity, taking into account vaccinees who never develop antibodies, persons who may lose immunity over time, and persons who are immune from natural disease. The U.S. measles elimination goal for 1996 came at a time when measles elimination was being considered as an achievable goal worldwide by the World Health Organization. If success can be demonstrated in the U.S. as well as other countries in the hemisphere, worldwide efforts to eliminate measles will be encouraged. The benefit from a study of measles seroprevalence will be to document age-specific immunity that is found following measles elimination efforts and to help judge the levels of immunity that are needed to eliminate measles.

Rubella

Congenital rubella syndrome (CRS) is the term used to describe the serious birth defects that occur among infants born to women infected with rubella while pregnant. A single rubella vaccination, usually given as measles-mumps-rubella (MMR) vaccine, is thought to confer lifelong immunity. Widespread use of the vaccine has resulted in near elimination of CRS in the United States. In recent years, an increasing proportion of rubella cases have been reported among adults, and outbreaks have occurred among persons of Hispanic ethnicity.

Population-based rubella seroprevalence studies will provide valuable
information about specific groups that lack rubella immunity and therefore could be targeted for immunization. Therefore serologic testing of NHANES participants will be conducted to document the level of immunity to rubella by race and ethnicity and allow comparison data from NHANES III.

Varicella

In 1995, a vaccine for prevention of varicella (chicken pox) was licensed for use in persons 1 year of age and older. Wide use of the vaccine may change the epidemiology of the disease with a shift in incidence to older persons who are at higher risk than are younger persons for more severe disease and complications.

Older persons may have severe complications such as encephalitis and/or death if they develop varicella. Additionally, pregnant women can pass on varicella if they develop it in the last weeks of gestation with severe life-threatening consequences to the newborn. NHANES provides a unique opportunity to assess changes in the seroprevalence of immunity to varicella after introduction of the vaccine. Demographic data on immune and susceptible persons will help target vaccination programs toward groups at risk for disease.

Eligible Sample

Participants aged 16-49 years were tested.

Description of Laboratory Methodology

Measles, Rubella, and Varicella

The staff of the Immunoserology Unit of the California State Department of Health Services (CSDHS), Viral and Rickettsial Disease Laboratory (VRDL) developed these EIA tests. The procedures described below are the standardized protocols of the VRDL's in-house EIA tests for serodiagnosis of viral infections. The individual steps in the test are the same for all these viruses, except that production and purification of viral and control antigens used in the assay are different for individual viruses. These assays are approved and routinely monitored by CLIA staff.

In the indirect EIA, a suitable antigen material (i.e., solubilized virus) is coated on the wells of a 96-well microtiter plate, which is subsequently incubated with a diluted test specimen. If the specimen contains antibody to the antigen, the antibody will form complexes with the antigen on the coated plate.

After washing unreacted serum components from the plate, an antibody-enzyme conjugate is added to the wells and incubated. The conjugate consists of antihuman IgG covalently coupled to the enzyme alkaline phosphatase. The conjugate will react with the antigen-antibody complex on the surface of the well resulting in a sandwich of well-antigen-antibody-antibody-enzyme. If the test specimen does not contain IgG antibody to the antigen, the conjugate will not bind to the well surface and will be removed by washing. The presence of enzyme in the complex is determined by adding an enzyme substrate (indicator system) to the well and incubating while a color reaction occurs. The enzyme substrate reaction will result in a yellow colored product, which is measured in a spectrophotometer adjusted to a wavelength of 405 nanometers with a side band adjusted to 630 nanometers.

Data Processing and Editing

Blood specimens were processed, stored and shipped to Viral and Rickettsial Disease Laboratory, California State Department of Health Services, Berkeley, California for analysis. Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the LABDOC file for detailed data processing and editing protocols. The analytical methods are described in the Description of the Laboratory Methodology section.

Laboratory Quality Assurance and Monitoring

The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed quality control and quality assurance instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the LABDOC file for detailed QA/QC protocols.

Analytic Notes

The second day exam data was a convenience sample and thus did not have sample weights. The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES Household Questionnaire Data files contain demographic data, health indicators, and other related information collected during household interviews. The Phlebotomy Examination file includes auxiliary information such as the conditions precluding venipuncture. The Household Questionnaire Data file and Phlebotomy Examination file may be linked to the laboratory data file using the unique survey participant identifier SEQN.

LB2RUIU - Rubella International Units

Rubella antibody data are reported both as an optical density index that is converted to International Units using the following formula:
LB2RUIU (Rubella_Units) = ((65.93928)x((Rubella_Index))x(0.177)))+ 1.28060

The Rubella index is calculated by subtracting the absorbance of the control well from the absorbance of the antigen well (AG-NS) and dividing the difference by the cut-off value. The cut-off value is calculated as the mean AG-NS value of duplicate 10 IU standards. The equation used is: O.D. index = (AG-NS)/Cut-off value

International Units are calculated based on a standard curve using a regression analysis of duplicate AG-NS values of 10, 40, & 100 IU standards and their squares. An International Unit value greater than or equal to 10 is considered significant for Rubella.

Interpretation of Results
1. An O.D. Index of >= 1.0 indicates the presence of antibody.
2. An O.D. Index of <1.0 indicates that antibody was not detected.
3. An International Unit value of 10 or greater is considered significant for
    Rubella. 

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 16 YEARS - 49 YEARS

LB2DAY - Days between 1st and 2nd exam

Variable Name:
LB2DAY
SAS Label:
Days between 1st and 2nd exam
English Text:
The number of days between the collection of the first and second exam
Target:
Both males and females 16 YEARS - 49 YEARS
Code or Value Value Description Count Cumulative Skip to Item
6 to 44 Range of Values 193 193
. Missing 1 194

LB2ME - Measles

Variable Name:
LB2ME
SAS Label:
Measles
English Text:
Measles
Target:
Both males and females 16 YEARS - 49 YEARS
Hard Edits:
0 to 99.99
Code or Value Value Description Count Cumulative Skip to Item
0 to 29.24 Range of Values 193 193
. Missing 1 194

LB2RU - Rubella

Variable Name:
LB2RU
SAS Label:
Rubella
English Text:
Rubella
Target:
Both males and females 16 YEARS - 49 YEARS
Hard Edits:
0 to 9999.99
Code or Value Value Description Count Cumulative Skip to Item
0 to 18.14 Range of Values 193 193
. Missing 1 194

LB2RUIU - Rubella antibody (international units)

Variable Name:
LB2RUIU
SAS Label:
Rubella antibody (international units)
English Text:
Rubella antibody (international units)
Target:
Both males and females 16 YEARS - 49 YEARS
Hard Edits:
0 to 9999
Code or Value Value Description Count Cumulative Skip to Item
1 to 213 Range of Values 193 193
. Missing 1 194

LB2VAR - Varicella

Variable Name:
LB2VAR
SAS Label:
Varicella
English Text:
Varicella
Target:
Both males and females 16 YEARS - 49 YEARS
Hard Edits:
0 to 9999.99
Code or Value Value Description Count Cumulative Skip to Item
0 to 29.35 Range of Values 193 193
. Missing 1 194