This summer as you rock your rotations, get your information uploaded to ERAS, and get your application for EM residency buffed and ready for prime time, one question comes up, are all EM letters better than a combination of SLOE and non-SLOE/EM letters.
SLOE are the Standard Letter of Evaluations, used by EM faculty to compare students to their fellow applicants, and predict their future potential success within an EM residency. These letters were designed by an EM task force, to minimize grade inflation, and focus on the student's characteristics and potential, when compared to their peers. Program faculty like to see two or more SLOE to consider an application complete, and consider for an interview.
Non SLOE letters of recommendation, within EM are usually used by non-residency EM faculty. They can be useful for community EM faculty to endorse a students attributes toward EM. While not ideal they are still within EM and are read and considered. Non EM letters, tend to be considered less useful, because they frequently do not reflect on the applicants attributes that apply to EM. Many students are intelligent, hard working, and enthusiastic, but not all can translate these attributes into the fast paced, chaotic EM environment.
Council of Residency Directors list serve recently had an active discussion on this topic and program leadership consistently expressed they want to see 2 EM SLOE from program faculty. All EM letters is generally preferable to non-EM letters. The one instance non EM/SLOE can be helpful is when it comes from a supervisor who has worked with the student closely over time. If a student did a longitudinal research, public health project, or graduate degree, the mentor of this project's endorsement is supportive for the application, adds another perspective of the student, and it's absence could be suspicious.
In the end the desire of program leadership is what matters, this is the audience you want to impress. Get SLOEs, as many as you can from different programs, and if you have been involved in a long term project, get your mentor's recommendation as well. Generally non-EM letters are unlikely to aid your application in EM.