Department of Biochemistry, Faculty of Medicine and Health Sciences, University of Kassala, Kassala, Sudan.
Department of Microbiology, Institute of Tropical Medicine, Ibn Sina University, Khartoum, Sudan.
Int J Mycobacteriol. 2020 Apr-Jun;9(2):200-204. doi: 10.4103/ijmy.ijmy_16_20.
Tuberculin skin test (TST) is widely used for the assessment of Bacillus Calmette-Guérin (BCG) vaccine efficacy and screening of latent TB infection (LTBI). Poor or no data are available on the reactivity of tuberculin in Kassala State. The aim of the present study was to assess the response to the BCG vaccine and to estimate the prevalence of LTBI and the annual rate annual risk of tuberculous infection (ARTI) among vaccinated school children using TST.
School-based cross-sectional study was conducted in three localities of Kassala State during 2016-2018. A cluster random sampling method was used for the enrolment. Five tuberculin units of 0.1 mL were injected intradermally in the left forearm of 2568 school children aged 5-15 years. The test was performed after the assessment of child health, nutrition status, and BCG scar status. Tuberculin reaction size was interpreted after 48-72 h. The collected data were analyzed using SPSS (v 20). The classical method was used to estimate ARTI.
Overall, there was no reaction in 81.5% of children. Only 0.66% of children had induration 10 mm-28 mm, indicating the prevalence of latent TB with an annual risk of 0.1%. Tuberculin reactivity was statistically significant affected by child age, gender, geographical location, and nutrition status (P < 0.05), whereas BCG scar status had no effect (P > 0.05).
The study documented a high proportion of tuberculin nonreactivity irrespective of BCG vaccination status and provides data on the prevalence of latent infection among studied groups. Further studies are needed to address the reasons of low and nonreactivity of tuberculin, and evaluation of the BCG vaccine is recommended.
结核菌素皮肤试验（TST）广泛用于评估卡介苗（BCG）疫苗的效果和筛查潜伏性结核感染（LTBI）。在卡萨拉州，有关结核菌素反应的数据很少或没有。本研究旨在评估 BCG 疫苗的反应，并使用 TST 估计接种疫苗的学龄儿童对结核菌素的反应、LTBI 的流行率以及结核感染的年发病率（ARTI）。
2016 年至 2018 年，在卡萨拉州的三个地区进行了基于学校的横断面研究。采用整群随机抽样方法招募。在 2568 名 5-15 岁的学龄儿童的左前臂皮内注射 0.1 mL 5 个结核菌素单位。在评估儿童健康、营养状况和 BCG 疤痕状况后进行测试。在 48-72 小时后解读结核菌素反应大小。使用 SPSS（v 20）分析收集的数据。使用经典方法估计 ARTI。
总体而言，81.5%的儿童无反应。只有 0.66%的儿童硬结 10-28 毫米，表明 LTBI 的流行率为 0.1%，每年有 0.1%的风险。儿童年龄、性别、地理位置和营养状况对结核菌素反应有统计学意义（P<0.05），而 BCG 疤痕状况无影响（P>0.05）。
该研究记录了无论 BCG 接种状态如何，结核菌素无反应的比例都很高，并提供了研究人群中潜伏感染的流行率数据。需要进一步研究以解决结核菌素低反应和无反应的原因，并建议评估 BCG 疫苗。
