From the core rules
"If a character has help, such as good tools, competent aids or other
beneficial circumstances, he receives a +1 DM to his skill check."
For me it is mostly situational role playing and the following is the general rule of thumb.
A standard med kit is required to do certain medical tasks
Trying to do certain tasks with a low tech med kit can result in a -1 DM
Working with a high tech med kit to do certain tasks can result in a +1 DM
And some medical tasks require proper facilities because a full medical lab does not fit into a medkit let alone a whole hospital.