Distribution of Tuberculin Skin Test with Purified Protein Derivatives in Children under High Coverage of Bacillus Calmette-Guérin
Date Issued
2007
Date
2007
Author(s)
Chan, Pei-Chun
DOI
en-US
Abstract
Objective: 1) To examine the distribution of reaction to the tuberculin skin test (TST) in Bacillus Calmette-Guérin (BCG) vaccinated children aged from 3 months to 14 years in a country with moderate risk of tuberculosis; and 2) to approximate the proper cutoff point for upper limit of normal size.
Methods: A cross-sectional study of TST with purified protein derivative (PPD RT 23 2TU) was conducted among those children who had received BCG as schedule, and no known immuno-compromised status. The distribution of reaction of TST grouping by different age groups were compared with the standard curve composed by annual risk of infection from pre-vaccination TST evaluation. Goodness of fit was used to check the best cutoff points and were further accessed the sensitivity by a dataset of TST from children with household contact of sputum positive confirmed tuberculosis (TB) case.
Results: 850 eligible data was analyzed. According to distribution of positivity of TST, the effect of BCG on TST decreased after vaccination and the positivity reversed after 7 year-old. The cutoff points for age from 0~7 year-old would be 21, 20,19, 18, 17, 16, 15, 14 mm accordingly to minimize the effect of BCG on TST during this age period and 12 mm for 8 to 14 year-old. From children with household sputum positive contact, the distribution of their TST reaction before age of seven was not age-dependent as general population. On the contrary, it was fairly stable, 10 mm was thus recommended for children with household contact of sputum positive confirmed TB case. These cutoff points provided a specificity of 89.8% in children without known risk of TB infection, clinical TB manifestation and immuno-compromised status, and 27.5% of children with household contact of sputum positive case would be positive.
Conclusions: Before new diagnostic tool for LTBI could be used world-widely, TST is still the most important tool for evaluation of LTBI. The study provided a normal distribution of TST size for BCG vaccinated children in a country with moderate risk of TB. Since it was a bi-modal distribution of TST reaction, using age specific, risk based cut-off value for children was mandatory. Our cutoff points provided high specificity and sensitivity. Risk based, age specific cutoffs can be helpful to select children who need closely follow up or LTBI treatment as a strategy for TB control.
Subjects
皮膚結核菌素測試
幼童及兒童
結核病
tuberculin skin test
infant and children
tuberculosis
SDGs
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-R93842022-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):ac0da72caa54a461e01456fc459b0f72