Targeted testing of children for tuberculosis: validation of a risk assessment questionnaire

Abstract

Objective: Given the directive of the American Academy of Pediatrics to test children for tuberculosis (TB) only if they are at high risk for the disease, we sought to determine how well a risk assessment questionnaire can predict a positive tuberculin skin test (TST) result among children seen in a medical office setting.

Methods: In a prospective observational study, we identified 31 926 children who received well-child care in 18 pediatric offices of the Kaiser Permanente Northern California Region from August 1996 through November 1998 and who were due to receive a routine TST (Mantoux method) as part of universal screening. Parents were asked to complete a questionnaire about risk factors for TB infection that included demographic information. The TST result at 48 to 72 hours was compared with questionnaire responses to identify responses that were most highly associated with a positive TST result at both the 10-mm and 15-mm cutoffs. A concurrent study was conducted to determine whether parents can recognize induration.

Results: This population was diverse in age (range: 0-18 years), race/ethnicity (white: 37%; Hispanic: 26.4%; Asian: 15.0%; black: 11.8%; other: 8.4%; not stated by parent: 1.6%), and household annual income (range: $10 524-$175 282). Overall incidence of positive TST results was 1.0% at the 10-mm cutoff and 0.5% at the 15-mm cutoff. Positive predictive value of selected individual risk factors at the 10-mm cutoff were: child born outside the United States, 10.4%; history of receiving bacille Calmette-Guérin vaccine, 5.5%; and child having lived outside the United States, 5.3%. Using multivariate analysis, we selected a subset of risk factors that were independently and significantly associated with a positive TST result >/=10 mm: history of receiving bacille Calmette-Guérin vaccine (odds ratio [OR]: 2.31; 95% confidence interval [CI]: 1.70-3.13); household member with history of positive TST result or TB disease (OR: 1.53; 95% CI: 1.14-2.04); child born outside the United States (OR: 8.63; 95% CI: 6.16-12.09); child having lived outside the United States (OR: 2.06; 95% CI: 1.49-2.85); and race/ethnicity reported by parent as Asian (OR: 2.28; 95% CI: 1.59-3.27) or Hispanic (OR: 1.57; 95% CI: 1.09-2.26). Several factors were not statistically significant predictors of a positive TST result: age, sex, household annual income, household member infected with human immunodeficiency virus or who had stayed in a homeless shelter, and being an adopted or foster child. Overall sensitivity of the 9 main items on the questionnaire was 80.9%; when a subset of 4 of these questions plus the race/ethnicity questions were used, sensitivity of responses was 83.5%. Parents failed to recognize positive TST results at a rate of 9.9% (for the 10-mm cutoff) and 5.9% (at the 15-mm cutoff).

Conclusion: A 5-question risk assessment questionnaire completed by parents can be used to accurately identify risk factors associated with TB infection in children. In our population, some risk factors suggested by the American Academy of Pediatrics could not be validated. Parents cannot be relied on to read TST results accurately. Screening for TB can be enabled by using a standardized, validated questionnaire to identify children who should be given tuberculin skin testing.