随机挑选身体健康，无疾病史的大一到大四四个年级共1200名学生，每年级各300名，男女各半。
The objects were 1200 healthy and no the disease history students, 300 for each grade who were selected randomly, boys and girls half and half.
其中一半研究对象是呼吸道病患，另一半则身体健康，无肺部疾病史。
Half were patients in the hospital for respiratory disease, and the other half were healthy with no history of lung ailments.
一份详尽的病史是心血管疾病诊断的基础，是常规或任意的有创性和无创性检测所不能取代的，况且，这些检测既昂贵又无效。
A thorough history is fundamental to the diagnosis of cardiovascular disease and cannot be replaced by routine or random noninvasive and invasive testing which is expensive and inefficient.
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