在香港以接種過卡介苗學童的結核菌素反應，來估計每年感染結核病的風險

在香港以接種過卡介苗學童的結核菌素反應，來估計每年感染結核病的風險Tuberculin response in BCG vaccinated schoolchildren and the estimation of annual risk of infection in Hong Kong

背景： Background: 自1980年起，香港已完成普及新生兒卡介苗接種涵蓋率。In Hong Kong there has been nearly universal neonatal BCG vaccination coverage since 1980.

方法： Method: 在一次例行卡介苗復種計劃，有21113位6-9歲的小學生接受一個單位的結核菌素（PPD RT-23）的皮下注射做結核菌素皮膚測試。21 113 schoolchildren aged 6–9 years were skin tested with one unit of tuberculin (PPD RT-23) using the intradermal technique during a routine BCG revaccination programme. 並登錄受測者性別，出生日期，結核菌素試驗日期，並在做結核菌素皮膚測試72小時後檢測皮膚結核菌素反應的大小。Information on sex, date of birth, date of tuberculin testing, and tuberculin reaction size at 72 hours was retrieved. 用三種不同的方法估算每年感染結核病的風險（ARTI）。The annual risk of tuberculous infection (ARTI) was estimated by three different approaches.

結果： Results: 發現在女孩受測者，隨著年齡的增加，結核菌素陽性率有顯著增高在所有常用的皮膚結核菌素反應大小的截止點（5，10，和15毫米）。Significantly higher tuberculin positive rates were found in girls and with increasing age at all commonly used cut-off points (5, 10, and 15 mm). 使用>10毫米皮膚結核菌素反應大小的截止點，和換算公式（12）（1 - 結核菌素陽性率）1 /年齡，估計每年感染結核病的風險（ARTI）：受測女孩每年感染結核病的風險為1.93％（95％CI為1.84〜2.03）；受測男孩每年感染結核病的風險為1.41％（95％CI為1.33〜1.50）。Using a cut-off point of >10 mm and the formula 12 (1 – tuberculin positive rate)1/age, the ARTI was estimated to be 1.93% (95% CI 1.84 to 2.03) for girls and 1.41% (95% CI 1.33 to 1.50) for boys.利用在6-7歲和8-9歲兩個年齡族群間結核菌素陽性率的差異，每年感染結核病的風險(ARTI)：則女孩變更為1.90％（95％CI為1.09〜2.70）和男孩變更為1.84％（95％CI為1.15至2.54）元。Using the differences in the tuberculin positive rate between the 6–7 year and 8–9 year age groups, the ARTI became 1.90% (95% CI 1.09 to 2.70) and 1.84% (95% CI 1.15 to 2.54) for girls and boys, respectively. 當感染的患病率以定位在15毫米為第二波高峰的結核菌素反應分佈曲線做估計，並假設乙對稱分佈反應的大小在這些感染高峰間，相對應的每年感染結核病的風險(ARTI)：在受測女孩會降低到0.52％（95％CI：0.460.59）和在受測男孩會降低到0.43％（95％CI為0.37至0.49），與間接從疾病的患病率估計類似。When the prevalence of infection was estimated by locating a secondary peak of the tuberculin reaction distribution curve at 15 mm and assuming a symmetrical distribution of reaction sizes among those infected around this peak, the corresponding ARTI was much lower at 0.52% (95% CI 0.46 to 0.59) and 0.43% (95% CI 0.37 to 0.49) for girls and boys, similar to that estimated indirectly from the prevalence of disease.

結論： Conclusion: 在接受卡介苗疫苗接種的兒童中，每年感染結核病的風險(ARTI) 如以常規方法估計是出乎意料的高，與預期活動性結核病的年發病率不符。The ARTI as estimated by conventional methods was unexpectedly high among BCG vaccinated children and did not agree with that anticipated from the annual incidence of active disease. 還需要進一步研究解決這些差異，包括卡介苗和其他環境刺激因素的可能交互作用。Further studies are needed to address the discrepancies, including the possible interaction between BCG and other environmental stimuli.

http://thorax.bmj.com/content/60/2/124.full.html