With observational studies producing inadequate results, scientists turned to a procedure developed years ago to evaluate new tuberculosis drugs: randomized screening trials. Such trials begin with the selection of women at risk of developing breast cancer, and randomly allocate them to be screened or not.
因为观察研究得不出有意义的结果，科学家们转而采用随机筛选试验，这是多年前发明的一种评估新的抗结核药的方法。上述试验开始时要挑选有可能患乳腺癌的女性，并把她们随机分入筛查组和对照组。