* Blackberry posts quarterly results
* Brent edges above $60 a barrel
* Futures up: Dow 48 pts, S&P 5.25 pts, Nasdaq 16.75 pts
By Chuck Mikolajczak
NEW YORK, Dec 19 (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 oil rose above $60 a barrel on Friday, recovering from near a 5-1/2-year low while WTI crude advanced 1.7 percent to $55.02.
* 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 were halted, and were last up 2.8 percent to $10.35 in premarket after the company posted quarterly results.
* Cerus Corp shares jumped 13.6 percent to $7 before the opening bell after the company said the U.S. Food and Drug Administration approved its blood transfusion device for platelets.
* 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.
* 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 were up 5.25 points, or 0.25 percent, with 208,309 contracts changing hands.
* Nasdaq 100 e-minis were up 16.75 points, or 0.4 percent, in volume of 32,591 contracts.
* Dow e-minis were up 48 points, or 0.27 percent, with 30,802 contracts changing hands. (Editing by Bernadette Baum)