Syneos Health (SYNH) 8-K Changes in Registrant's Certifying Accountant

EXHIBIT 16.1

February 29, 2016

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Ladies and Gentlemen:

We have read Item 4.01 of Form 8-K dated February 28, 2016, of INC Research Holdings, Inc. and are in agreement with the statements contained in the second, third, fourth and fifth paragraphs on page 2 therein. We have no basis to agree or disagree with other statements of the registrant contained therein.

/s/ Ernst & Young LLP

Raleigh, North Carolina