Dr.Huerta says many Latin and South American communities do not have mammography machines, and there is a general lack of knowledge about the disease.

VOA: standard.2010.02.02

to express a lack of complete knowledge about the multitude of subjects.

它可以用来表达你对一些话题并不完全了解。

I don't know 课堂 - SpeakingMax英语口语达人

but also very non-affrontively, express a lack of complete knowledge

又不冒犯地表达对某事不完全清楚，

I don't know 课堂 - SpeakingMax英语口语达人