Table of Contents

Locator Record

Title: Tuberculosis (TB )
Contact Number: 1-866-441-NCHS
Years of Content: 1999 - 2000
First Published: June, 2005
Revised: January, 2008
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:tuberculosis
Record Source: NHANES 1999 - 2000
Survey Methodology: NHANES 1999 - 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

TB skin testing was added to the NHANES 1999–2000 examination to provide comprehensive data about the extent of tuberculosis infection in the United States. To determine the prevalence of TB infection, NHANES participants 1 year of age and older who consented to this component were skin tested with a tuberculin-purified protein derivative (PPD) product, PPD S-1, the standard antigen. To help distinguish reactions due to Mycobacterium tuberculosis infection from cross reactions due to nontuberculous mycobacterial infection, participants were also skin tested with nontuberculous mycobacterial antigen PPD-B (Battey strain lot 100616, also called the Boone strain of Mycobacterium intracellulare). The two products used are not commercially licensed; therefore, CDC received Investigational New Drug (IND) approval (BB-IND-7596) from the Food and Drug Administration.

To aid in the interpretation of skin test results and provide for risk factor analysis, participants were asked questions about TB skin testing, disease, exposure to and treatment for Mycobacterium tuberculosis. These questions were asked in the household interview.

Eligible Sample

Eligibility

Sample persons aged 1 year and over who do not meet the exclusion criteria were eligible.

Exclusion Criteria

Survey Staff

The staff was composed of a certified phlebotomist to place the TB antigens and six trained, full-time skin test readers and six part-time readers.

Protocol and Procedure

For each participant, a randomized computer program selected a different forearm for application of each of the two PPDs. Trained NHANES phlebotomists injected 0.1 ml (5 international units) of the designated PPD intradermally to the volar surface of the designated forearm using the Mantoux method. Phlebotomists were blinded to PPD type. Reactions were measured 48–72 hours later by trained NHANES TST readers who had no knowledge of which PPD had been applied to either arm. TB readers were not aware of the participant’s medical history or any history of contact with TB. To improve return rates for TST reaction measurement, extra remuneration was offered, and readings were performed offsite, in homes, or workplaces, as necessary.

TST measurements were performed for each participant by at least one trained reader. Training and supervision was conducted by four experienced “gold standard” TST readers. To standardize their own practice, gold standard readers performed quarterly blinded sequential comparison readings of at least 20 TB clinic patients’ TST reactions to confirm that they were reading within 2 mm of one another.

Study protocol dictated that two separate readers blinded to one another’s measurements would measure TST reactions of > 25% of participants. Readers worked in separate rooms and recorded measurements in a computer database; measurements recorded on the first screen were not accessible to the second reader. The induration, if any, was palpated. Using non-smearing eyebrow pencil, a dot was made on either side of the widest point of the induration border transverse to the long axis of the forearm. Measurements between the dots were made with a transparent ruler. Markings were removed with cotton and hypoallergic makeup remover or baby oil. The forearm was wiped with makeup remover or baby oil by the first reader regardless of whether a palpable reaction was found and marked.

41.2% of participants had measurements recorded separately by at least two readers who remained unaware of one another’s measurements.

Inspection of the Volar Surface of Each Forearm for Adverse Reactions

Measurement of Induration

Ulceration refers to sloughing of damaged skin or a raw, open sore. Necrosis is the death of cells because of damage or disease.

Quality Assurance & Quality Control

The mean TST reaction and PPD-B reaction were used for the 41.2% of participants who had TST reactions read by two or more readers. Distributions based on the readings of any reader who read more than 300 reactions were similar. TBI prevalence based on the findings of any reader who read more than 300 reactions did not differ statistically from the prevalence based on the mean TST reactions.

Data Processing and Editing

The sequence number links these data to all other data collected during 1999–2000 survey years.

The following variables were derived.

  1. TBDPPDS: the mm of induration for PPDS. This variable combines the measurement for left and right arms since the antigen was randomly placed to blind the reader to the skin test being read.
  2. TBDPPDB: the mm of induration for PPDS. This variable combines the measurement for left and right arms since the antigen was randomly placed to blind the reader to the skin test being read.
  3. TBDPPDSV: an indication if vesiculation was present or absent for PPDS.
  4. TBDPPDBV: an indication if vesiculation was present or absent for PPDB.
  5. TBDPPDSU: an indication if ulceration was present or absent for PPDS.
  6. TBDPPDB: an indication if ulceration was present or absent for PPDB.

The following variable, TBQ070 (not derived), is also included in this file:

Have you ever had a severe reaction to a tuberculosis (TB) skin test?
1 = Yes
2 = No

TBABCG BCG scar?
1 = Present
2 = Absent
3 = Refused

NHANES medical examiners were trained to recognize BCG scars and to differentiate them from smallpox vaccination scars through supervised examination of photographs and a small number of human volunteers. Visible scars evaluated by examiners as BCG scars were recorded. No validation of these evaluations was included.

Analytic Notes

The basic definition of TB infection (TBI) used in NHANES is a mean TB skin test (TBS) reaction >10 mm. This is the definition used most frequently in U.S. and international surveys. Alternative definitions of TBI can also be used:

  1.  mean TST reaction >15 mm (the clinical definition of TBI most commonly used for adults in the US, except for individuals with special risks, e.g. contacts, children, immunosuppressed persons, etc.), or
  2. either a mean TST reaction >15 mm or a mean TST >5 mm and <15 mm that is at least 2 mm greater than the reaction of PPD-B (Edwards et al.), the definition that utilizes reactions to both mycobacterial antigens used in the survey.

Although TB infection is generally divided into latent TB infection (LTBI) and TB (active tuberculosis) in the U.S., this distinction could not be made in NHANES 1999–2000. No chest x-ray component was included to distinguish LTBI from TB; therefore, no evaluation of relevant signs and symptoms was performed.

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 1 YEARS - 150 YEARS

TBQ070 - Ever had a reaction to TB test?

Variable Name:
TBQ070
SAS Label:
Ever had a reaction to TB test?
English Text:
Have you ever had a severe reaction to a tuberculosis (TB) skin test?
English Instructions:
We are going to do two skin tests to determine if you have been exposed to the bacteria that causes tuberculosis or TB. The first test, the tuberculin test, measures tuberculosis infection. The other test looks for infection with harmless germs related to TB. The second test makes the tuberculin test result easier to understand.
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 0 0
2 No 7613 7613
. Missing 1219 8832

TBABCG - BCG Scar

Variable Name:
TBABCG
SAS Label:
BCG Scar
English Text:
The phlebotomist visually looks at the upper arms and shoulders of the participant to determine if a BCG scar is present or absent.
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Present 619 619
2 Absent 6992 7611
3 Refused 1 7612
. Missing 1220 8832

TBDPPDS - PPDS induration (mm)

Variable Name:
TBDPPDS
SAS Label:
PPDS induration (mm)
English Text:
PPDS induration (mm)
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 32 Range of Values 7386 7386
. Missing 1446 8832

TBDPPDB - PPDB induration (mm)

Variable Name:
TBDPPDB
SAS Label:
PPDB induration (mm)
English Text:
PPDB induration (mm)
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 28 Range of Values 7385 7385
. Missing 1447 8832

TBDPPDSV - PPDS vesiculation

Variable Name:
TBDPPDSV
SAS Label:
PPDS vesiculation
English Text:
PPDS vesiculation
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 vesiculation present - PPDS 31 31
2 vesiculation absent - PPDS 7582 7613
. Missing 1219 8832

TBDPPDSU - PPDS ulceration

Variable Name:
TBDPPDSU
SAS Label:
PPDS ulceration
English Text:
PPDS ulceration
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 ulceration present - PPDS 3 3
2 ulceration absent - PPDS 7610 7613
. Missing 1219 8832

TBDPPDBV - PPDB vesiculation

Variable Name:
TBDPPDBV
SAS Label:
PPDB vesiculation
English Text:
PPDB vesiculation
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 vesiculation present - PPDB 15 15
2 vesiculation absent - PPDB 7596 7611
. Missing 1221 8832

TBDPPDBU - PPDB ulceration

Variable Name:
TBDPPDBU
SAS Label:
PPDB ulceration
English Text:
PPDB ulceration
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 ulceration present - PPDB 5 5
2 ulceration absent - PPDB 7606 7611
. Missing 1221 8832