Many factors can play their part in driving a project, and a PEST analysis is a useful tool to understand the environment or culture you are working within.
It helps to prepare for [stakeholder mapping], an absolutely key part of preparing the business case and therefore of preparing the benefits analysis.
Politicalto do with policy rather than necessarily local need, for example national policy which may or may not be directly relevant to the needs of the local health and care economy, but which is a legal requirement (you will lose credibility, or funds, or both if you don't comply)
can include Legal, and Ethical
Economicthere are always more things that could be done, than there are resources to do them
Socialor Socio-cultural, can include Environmental
Technical in the purest sense, Technical can mean any specific technology including the IM&T, but also the buildings, knowledge, legal constraints, contractual, medical, etc
PEST is often used by marketing groups to understand a market, but it is just as relevant here.
Some useful links