Ozuah PO, Ozuah TP, Stein REK, Burton W, Mulvihill M. Evaluation of a Risk Assessment Questionnaire Used to Target Tuberculin Skin Testing in Children. JAMA. 2001;285(4):451-453. doi:10.1001/jama.285.4.451
Author Affiliations: Department of Pediatrics, Children's Hospital at Montefiore (Drs P. Ozuah, T. Ozuah, and Stein) and Department of Family Medicine (Drs Burton, P. Ozuah, and Mulvihill), Albert Einstein College of Medicine, Bronx, NY.
Context Universal tuberculin skin testing of children has been shown to be costly
and inefficient. In response, several authorities have recommended targeted
screening based on epidemiological risk. In 1996, the New York City Department
of Health (NYCDOH) developed questions to identify children who require a
tuberculin skin test.
Objective To determine the sensitivity, specificity, and predictive validity of
the NYCDOH tuberculosis risk assessment questionnaire.
Design Prospective criterion standard study in which tuberculin skin tests
and the NYCDOH questionnaire were administered simultaneously between August
1996 and January 1998. Specific questions asked about contact with a tuberculosis
case, birth in or travel to endemic areas, regular contact with high-risk
adults, and human immunodeficiency virus infection in the child.
Setting Ambulatory clinic in South Bronx, New York, NY.
Participants Consecutive sample of 2920 children aged 1 to 18 years.
Main Outcome Measures Sensitivity, specificity, positive and negative predictive values of
the questionnaire, and odds ratio (OR) of reactive skin test results.
Results The NYCDOH questionnaire identified 413 children (14%) as having at
least 1 risk factor. Of these, 23 (5.6%) had a positive skin test result;
4 (0.16%) of the 2507 without risk factors had a positive result. Results
for the full NYCDOH questionnaire were sensitivity, 85.2%; specificity, 86.0%;
negative predictive value, 99.8%; positive predictive value, 5.4%; and OR,
35.2 (95% confidence interval, 12.1-102.4).
Conclusion The NYCDOH questionnaire is a valid instrument for identifying children
for tuberculin skin testing.
Surveillance strategies for the prevention of tuberculosis (TB) in children
have alternated between universal screening and targeted screening based on
epidemiological risk. Between 1985 and 1992, there was a reported recrudescence
of TB that accounted for a 35% increase in the number of cases involving children.1- 5
In response, universal Mantoux skin testing using purified protein derivative
(PPD) of tuberculin of all children was advocated by several authorities,
including the Centers for Disease Control and Prevention (CDC) and the American
Academy of Pediatrics (AAP).6- 8
A decline in the prevalence of TB in the mid-1990s coincided with published
reports indicating that universal tuberculin screening of all children was
a costly and inefficient use of limited health care resources.9,10
In February 1996, the AAP's Committee on Infectious Diseases issued updated
guidelines that supported focusing tuberculin skin testing on children who
are at increased risk of acquiring TB.11 In
July 1996, the New York City Department of Health (NYCDOH) also revised its
TB screening policy to allow for targeted screening.12
Both the AAP and NYCDOH identified similar epidemiological risk factors for
TB infection in the pediatric population, including (1) close contact with
an active case of TB; (2) birth in or travel to an endemic region; (3) close
contact with high-risk adults, including those with prolonged incarceration,
human immunodeficiency virus (HIV) infection, homelessness, and intravenous
drug use; and (4) HIV infection. Recently, targeted tuberculin screening based
on similar risk categories has been endorsed by a joint statement of the American
Thoracic Society, the CDC, and the Infectious Diseases Society of America.13 Although the risk categories were based on current
knowledge, no formal analysis of the validity of this approach has been reported.
To our knowledge, no other risk assessment categories have been developed
When any strategy is adopted for targeted screening, an essential question
emerges: Are the risk assessment questions used to identify the need for a
test both sensitive and specific? The present study was designed to determine
the sensitivity, specificity, and predictive validity of the NYCDOH risk assessment
questions used to assess the need for a tuberculin skin test.
We prospectively studied a group of children who lived in the South
Bronx, New York City, NY. In 1996, this area had a reported TB case rate of
38.6 per 100 000, almost 5 times the national average.12
Between August 1996 and January 1998 we recruited a consecutive sample of
children (aged 1-18 years) who were seen for annual health maintenance visits
at the Montefiore Medical Group. All children seen for health maintenance
visits during the study period were considered eligible. Exclusion criterion
was a prior documented positive PPD result. This study was approved by the
institutional review board of Montefiore Medical Center, and written informed
consent was obtained from a parent prior to participation.
Physicians and nurses at the health center had an in-service on the
application of the questionnaire and interpretation of PPD results. The NYCDOH
guidelines were posted in all examination rooms. All children and their caretakers
were asked the following risk assessment questions: (1) Has your child had
any contact with a case of TB? (2) Was any household member including your
child born in or has traveled to areas where TB is common (eg, Africa, Asia,
Latin America, and the Caribbean)? (3) Does your child have regular (eg, daily)
contact with adults at high risk for TB (ie, those who are HIV infected, homeless,
incarcerated, and/or illicit drug users)? (4) Does your child have HIV infection?
Any "yes" response was considered a positive risk factor.
All participants received Mantoux tuberculin skin testing with 0.1 mL
of 5 Tuberculin Units of PPD applied on the volar aspect of the arm to produce
a wheal of at least 6 mm. Patients were instructed to return in 48 hours for
test results, except those tested on a Friday were asked to return in 72 hours.
Patients who did not return in 48 hours were telephoned that day and asked
to come in later in the day or by the next day (within 72 hours). Postcards
were mailed to all nonadherent patients without telephones, instructing them
to return for retesting. We maintained a log of the test date, patient's name,
medical record number, telephone number, and test result(s).
Initial interpretation of PPD results was performed by trained nurses
and documented in the logbook and medical record. Nurses were blinded to the
results of the questionnaire. If a nurse detected an induration or was uncertain,
a physician assessed the patient immediately. All positive results were confirmed
by a physician and measured with a ruler calibrated in millimeters. Parental
reports and self-assessment of results were not accepted.
Positive PPD skin test reactions were defined as indurations >10 mm,
in accordance with the AAP's guidelines.10
Chest radiographs were obtained for all patients with positive results.
Data were entered and analyzed using SPSS (Chicago, Ill). A "yes" response
to any question was considered sufficient to warrant PPD testing. We determined
the sensitivity (the probability that children with a positive PPD result
would be targeted for screening), the specificity (the probability that children
without a positive PPD result would not be targeted for screening), the positive
predictive value (the probability of a positive PPD result among children
targeted for screening), and the negative predictive value (the probability
of children not targeted for screening having a negative PPD result) for each
risk assessment question and for different combinations of the questions.
We calculated the prevalence of positive PPD results and reviewed the
results of chest radiographic studies. To calculate odds ratios (ORs) and
compare risk factors for TB, we classified the children on the basis of test
results into a positive PPD group and a negative PPD group. We assessed differences
in TB risk factors between these groups. Odds ratios for various combinations
of risk factors for TB were calculated by univariate and multivariate analyses.
After initial analyses, children older than 11 years were found to account
for 75% of those with a positive skin test result and no identifiable risk
factor. Hence, we determined the sensitivity, specificity, positive and negative
predictive values, and OR of age older than 11 years as a specific risk factor
and in combination with the results of the NYCDOH questionnaire.
During the study period, 3093 eligible children were seen at the study
site. No parents refused participation. Ten children were excluded because
of a prior positive PPD test result. Of the 3083 who received Mantoux skin
testing, 163 (5.3%) were lost to follow-up, leaving 2920 (94.7%) children.
Fifty-five percent of these children were Hispanic, 44% were African American,
and 50% were female. Forty-four percent of the children had no health insurance
while 47% were covered by Medicaid.
The NYCDOH questionnaire identified 413 children (14%) as having at
least 1 risk factor for TB. None of the children were identified as being
HIV infected; hence, this item was dropped from further analysis. Of the 413
children with risk factors, 23 (5.6%) had positive skin test results, while
of the 2507 children without a risk factor, 4 (0.16%) had a positive result.
Children with at least 1 risk factor for TB were 35 times more likely to have
a positive skin test result than those with no identifiable risk. Overall,
Mantoux results were positive in 27 children (0.9%). Of the 4 children with
positive skin test results not identified by the questionnaire, 3 (75%) were
older than 11 years. Results of chest radiographs showed that none of the
27 children with positive skin test results had evidence of active disease.
The sensitivity, specificity, positive predictive value, negative predictive
value, and OR for each screening question as well as combinations of risk
factors are presented in Table 1.
The full NYCDOH questionnaire had a sensitivity of 85.2%, a specificity of
86.0%, and a negative predictive value of 99.8%. Including age older than
11 years as a risk factor increased the sensitivity to 96.3% but decreased
the specificity to 61.0%.
This is the first report to demonstrate the validity of an instrument
used in determining the need for a tuberculin skin test in children. The NYCDOH
risk assessment strategy had a high sensitivity and negative predictive value
in this cohort. Children with at least 1 identifiable risk factor were 35
times more likely to have a positive skin test result. Using this strategy,
the vast majority of children in our sample would not have required a skin
test, yet very few children with a positive skin test result would have been
Most of the children not identified by the NYCDOH questionnaire but
who later had a positive skin test result were older than 11 years. This may
be because children in that age group, due to their increased mobility, are
at higher risk of exposure to individuals outside of the immediate household.
The NYCDOH questionnaire primarily focuses on household contacts. When we
included this age group as a risk factor, the sensitivity of the questionnaire
increased to 96.3% but the specificity dropped to 61.0%. In our sample, it
would have meant testing an additional 723 children to pick up 3 positive
skin test results. These circumstances may be acceptable to some clinicians.
Obviously, the prevalence of reactive skin tests and TB in a given population
should be considered in making such a decision.
Of note, 10 children with prior positive PPD results were excluded from
this study. A retrospective review indicated that 9 of the 10 children would
have been identified by the questionnaire. Therefore, the exclusion of children
with prior positive tuberculin skin test results biased the results against
the validity of the risk assessment questionnaire.
We did not make any attempts to verify the caretakers' answers to the
risk assessment questions. It is possible that some of the responses may have
been inaccurate. However, in the clinical setting, the truthfulness of these
responses may not be as important as the caretakers' self-identification as
belonging to a high-risk category. For the same reason, we accepted at face
value a response of "no" to the questions. Additional information was obtained
in some instances; for example, we inquired about the specific countries of
The low positive predictive values calculated in this report reflect
the prevalence rate (1%) of positive skin test results. In the clinical setting,
however, the negative predictive values are more relevant for screening tests
in which the vast majority of children do not have the disease. Positive predictive
values are more critical with diagnostic tests such as the PPD. Universal
PPD testing in low prevalence areas yields high false-positive results because
of the direct relationship between positive predictive values and prevalence.
The children in this study were drawn from a community with a high case rate
of TB. Even in this setting, universal skin testing would have yielded high
false-positive rates, based on our findings. While the screening questionnaire
was validated in this setting, this approach should be examined in different
settings with varying prevalence of TB.