求教OG17 RC 两句话含义

可乐可乐

OG17 RC中的第503题目，下面两句为解析中的两句话 (page 482), 求教怎么理解这两句的含义？ 属于单词认识，句子读不顺的类型。

Frazier’s proposalinvolves enrolling more patients in clinical trials than is the case with thecategory of patients referred to.

(the case with, referredto 怎么理解)

By limiting the patientsused to those having the ailment under study, the passage suggests that…

(used to those having 什么意思)

谢谢~~！