By Chuck Mikolajczak
NEW YORK (Reuters) - U.S. stock index futures edged higher on Friday, putting the S&P 500 on track to extend gains after the benchmark index scored its best two-day run in three years.
* The S&P has climbed 4.5 percent over the past two sessions, spurred by the U.S. Federal Reserve's commitment on Wednesday to take a "patient" approach toward raising interest rates while signaling it was on track to raise rates in 2015. That provided clarity and relief to investors over the policy outlook, analysts said.
* Brent crude
* Stocks may experience volatility on Friday as a result of "quadruple witching," the expiration of stock options, index options, index futures and single-stock futures.
* U.S.-listed shares of Blackberry
* Cerus Corp
* European stocks edged lower on Friday, reversing an early rise, as Italian banks came under pressure from a downgrade by S&P and Swiss drugmaker Roche saw two major drugs fail tests.[.EU]
* Asian shares enjoyed their best day in 15 months on Friday, tracking Wall Street's rally.
Futures snapshot at 7:20 a.m. (1220 GMT):
* S&P 500 e-minis
* Nasdaq 100 e-minis
* Dow e-minis <1YMc2> were up 48 points, or 0.27 percent, with 30,802 contracts changing hands.
(Editing by Bernadette Baum)