McKinsey hires less than 1% of the 225,000 applications they receive each year and recruit heavily from prestigious universities. I realize this doesn't answer your question, but I wouldn't imagine you'll find a Caribbean MD among them unless he/she is a truly exceptional doctor, in which case they probably wouldn't want to work for McKinsey & Co. in the first place.
source:
Deconstructing the Elusive Allure of McKinsey & Co.