Severe undernutrition in children affects tuberculin skin test performance in southern India

Undernutrition impairs immunity to Mycobacterium tuberculosis and is a risk factor for tuberculosis disease (TB). We aim to investigate if severe undernutrition affects the tuberculin skin test (TST) response among household contacts (HHCs) of pulmonary TB cases. We analyzed data from HHCs (> five years) of pulmonary TB cases in Southern India. Undernutrition was defined as per World Health Organization based on body mass index (BMI) for adults (undernutrition 16-18.4 and severe undernutrition <16 kg/m2) and BMI relative to the mean for children (undernutrition 2SD-3SD and severe undernutrition < 3SDs below mean). Univariate and multivariate models of TST positivity (> five mm) were calculated using logistic regression with generalized estimating equations. Among 1189 HHCs, 342 were children (age 5-17 years) and 847 were adults. Prevalence of TST positivity in well-nourished, undernourished and severely undernourished children was 135/251 (53.8%), 32/68 (47.1%), and 7/23 (30.4%) respectively; among adults, prevalence of TST positivity was 304/708 (42.9%), 43/112 (38.4%) and 12/26 (46.2%), respectively. Severe undernutrition in children was associated with decreased odds of TST positivity (adjusted odds ratio 0.3; 95%CI 0.1-0.9). Severe undernutrition in children was associated with decreased odds of TST positivity. False-negative TSTs may result from undernutrition; caution is warranted when interpreting negative results undernourished populations.营养不良会削弱机体对结核分枝杆菌（Mycobacterium tuberculosis）的免疫防御能力，同时也是结核病（TB）的危险因素。本研究旨在探讨重度营养不良是否会影响肺结核患者家庭接触者（HHCs）的结核菌素皮肤试验（TST）反应。本研究分析了印度南部地区肺结核患者家庭接触者（年龄≥5岁）的相关数据。营养不良的判定标准参照世界卫生组织（WHO）：成人采用体重指数（BMI）进行划分，BMI 16~18.4 kg/m²为营养不良，BMI <16 kg/m²为重度营养不良；儿童则采用相对于群体均值的BMI值进行划分，BMI低于均值2~3个标准差为营养不良，低于均值3个标准差以上为重度营养不良。本研究采用广义估计方程（generalized estimating equations，GEE）结合logistic回归，构建结核菌素皮肤试验阳性（硬结直径>5mm）的单因素与多因素分析模型。本次研究共纳入1189名家庭接触者，其中342名为儿童（年龄5~17岁），847名为成人。营养良好、营养不良及重度营养不良儿童的结核菌素皮肤试验阳性率分别为135/251（53.8%）、32/68（47.1%）及7/23（30.4%）；成人组中，该阳性率分别为304/708（42.9%）、43/112（38.4%）及12/26（46.2%）。儿童重度营养不良与结核菌素皮肤试验阳性的比值比降低存在关联（校正后比值比为0.3，95%置信区间：0.1~0.9）。儿童重度营养不良与结核菌素皮肤试验阳性率降低显著相关。营养不良可能导致结核菌素皮肤试验假阴性结果，因此对营养不良人群的试验阴性结果进行解读时需格外谨慎。