Godoy P, Díaz J M, Alvarez P, Madrigal N, Ibarra J, Jiménez M, Rullán J
Instituto de Salud Carlos III, Centro Nacional de Epidemiologia.
Med Clin (Barc). 1997 Mar 22;108(11):414-8.
The polymorphic length restriction fragment technique (PLRF) complements epidemiologic investigations. The aim of this study was to present an outbreak of tuberculosis in which the risk factors of infection and disease were studied.
A descriptive study was carried out in cases of tuberculosis. The isolated strains of Mycobacterium tuberculosis were typed by the PLRF technique. A study of the prevalence of infection was carried out among the 61 classmates of two classrooms (A and B) which the index case attended. An historical cohort study was thereafter performed among the cases with infection. The association of the dependent variable (infection or tuberculosis disease) with the remaining variables was determined by the odds ratio (OR).
The incidence of disease was 9.8% (6/61). The strains isolated in 5 patients presented the same PLRF pattern. The prevalence study detected 28 infections (45.9%). Five cases (17.9%) were detected on the second tuberculin test. By multivariate analysis showed that the hours of exposure (1.8-3.2 hours, OR = 2.0; > 3.2 hours; OR = 10.2) were the risk factor for infection. The BCG vaccine, the intensity of the reaction to the tuberculin test and age could be associated with the risk of disease.
The focus of the outbreak was confirmed by the PLRF technique. The importance of repeating the tuberculin test in whom the test was negative on the first test is of note. To evaluate the risk of infection the time of exposure is more important than the proximity to the index case.
多态性长度限制片段技术（PLRF）辅助流行病学调查。本研究旨在呈现一场结核病暴发，并对感染和发病的危险因素进行研究。
对结核病病例进行描述性研究。采用PLRF技术对分离出的结核分枝杆菌菌株进行分型。对首例病例所在的两个教室（A和B）的61名同学进行感染率研究。此后，对感染病例进行历史性队列研究。通过比值比（OR）确定因变量（感染或结核病）与其他变量之间的关联。
发病率为9.8%（6/61）。5例患者分离出的菌株呈现相同的PLRF模式。患病率研究检测到28例感染（45.9%）。在第二次结核菌素试验中检测到5例（17.9%）。多因素分析显示，暴露时间（1.8 - 3.2小时，OR = 2.0；> 3.2小时，OR = 10.2）是感染的危险因素。卡介苗、结核菌素试验反应强度和年龄可能与发病风险相关。
PLRF技术证实了此次暴发的源头。首次结核菌素试验阴性者重复进行该试验的重要性值得关注。评估感染风险时，暴露时间比与首例病例的接近程度更重要。
