* Apple off as CEO takes medical leave; to post results
* Citigroup seen reporting 4th quarterly profit in row
* Futures: S&P up 0.9 pt, Dow up 26 pts, Nasdaq off 14 pts
By Angela Moon
NEW YORK, Jan 18 (Reuters) - S&P and Dow index futures were higher on Tuesday as investors were upbeat about corporate earnings, but Nasdaq futures were weighed by Apple after the iPad maker said its chief executive was taking another medical leave.
* Apple Inc shares fell nearly 5 percent to $331.37 in premarket trade after it said CEO Steve Jobs was taking his third medical leave since 2004, reviving concerns about the future of the maker of the iPhone. Apple is due to report results later Tuesday.
* Citigroup Inc, the bank that took $45 billion in U.S. bailout funds during the financial crisis, is widely expected to report its fourth consecutive quarterly profit on Tuesday, signaling its recovery is largely completed. Analysts estimated a quarterly profit of 8 cents per share, according to Thomson Reuters I/B/E/S.
* Investors also braced for results from International Business Machines Corp.
* S&P 500 futures rose 0.9 point and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 26 points, while Nasdaq 100 futures lost 14 points.
* Goldman Sachs Group Inc will limit its private placement of shares of Facebook, the social networking site, to investors outside the United States, citing "intense media coverage."
* Brewing giant SABMiller Plc beat forecasts with a 3 percent rise in quarterly beer volumes on growth in Africa and Asia.
* GlaxoSmithKline Plc will take a legal charge of $3.4 billion for the fourth quarter, effectively wiping out its profit, to settle claims related to its Avandia drug and sales practices.
* South African retailer Massmart's shareholders have accepted a takeover bid from U.S. group Wal-Mart Stores Inc.
* European stocks hit a 28-month high Tuesday, led by mining shares after Rio Tinto Plc's output figures pleased investors and as metal prices climbed.
* The S&P 500 ended a seventh straight week of gains with a banks-led rally amid healthy volume after encouraging financial results from JPMorgan.