Amgen Inc. on Tuesday reported that first-quarter earnings rose 17 percent on double-digit sales growth of its drugs to treat anemia and arthritis.

But sales at the world’s largest biotechnology company were just shy of Wall Street expectations and Amgen shares slipped about 1 percent $70.26 in after-hours trading after close up 2 percent in regular trading.

Total revenue for the first quarter rose 14 percent to $3.22 billion, just missing of Wall Street expectations of $3.32 billion. Net income climbed to $1 billion, or 82 cents a share, from $854 million, or 67 cents, a year earlier, when the company wasn’t required to account for the cost of employee stock options in its earnings.

“It was a solid in-line quarter,” Geoffrey Porges, analyst for Sanford Bernstein, told Reuters. “Expenses were a bit lighter than expected and that’s what gave them the beat.”

Amgen raised the lower end of its 2006 earnings forecast range by 5 cents and now expects $3.60 to $3.70 per share. The estimate includes expected costs from the acquisition of Fremont-based Abgenix Inc., which gives the company full control of the much-anticipated experimental colon cancer drug panitumumab.

Worldwide sales of Aranesp for anemia in cancer and kidney dialysis patients rose 24 percent to $893 million for the quarter. Epogen, an earlier version of Aranesp, saw sales rise 4 percent to $604 million. Enbrel for arthritis and the skin condition psoriasis had sales of $658 million, an 11 percent increase. Sales of Neulasta and Neupogen, used to boost white blood cells in chemotherapy patients, rose 13 percent to $896 million.