Hi Ahmed,

I m not sure about the availability of the particular data, it will take extra effort to collect this such data.

The contribution point may be: This can be a feedback/review for the doctor or hospital, especially about their services. 

I find it difficult to understand how you would do this given the fact that most health systems do not collect text messages on opinions regarding physician care.  That is mostly done through surveys.  I think you have the wrong method, sentiment analysis, survey is the may method for collecting information to address patient perceptions of physician care.  Sentiment analysis is used to get at perception questions regarding larger issues such as public perception of industry or government.

I ran into this resource at the Robert Wood Johnson Foundation.  Take a look and see if this is a better answer to your question.

http://www.rwjf.org/en/library/research/2013/12/using-social-network-analysis-in-evaluation.html