On Assignment Inc. (NYSE: ASGN) reported revenue rose 13.6 percent on a pro forma basis to $389.2 million in the first quarter. Pro forma revenue treats On Assignment’s acquisition of Apex Systems, a provider of information technology staffing, in the second quarter of last year as if it occurred on Jan. 1, 2012. Apex marked a major acquisition for the firm. First-quarter revenue was up 148.3 percent when not looking at results on a pro forma basis.

Apex Systems’ first-quarter revenue rose 14.4 percent on a year-over-year basis to $212.7 million.

Revenue also rose across On Assignment’s other business lines, with the exception of its life sciences business where revenue fell 2.1 percent in the first quarter to $40.5 million.

First-quarter revenue for the other divisions include:

• Oxford, a provider of IT and engineering staffing, first-quarter revenue rose 21.0 percent to $95.3 million.
• Healthcare staffing revenue rose 14.9 percent to $14.4 million in the first quarter. The healthcare segment includes allied healthcare staffing.
• Physician staffing revenue rose to $26.3 million in the first quarter, up 9.2 percent from the first quarter of 2012.

In addition to the Apex acquisition, the company announced in February that it sold its nurse travel division.

On Assignment’s first-quarter gross margin narrowed to 29.1 percent from 33.6 percent in the year-ago quarter. The company reported gross margin fell mainly as a result of the inclusion of Apex, which has a lower gross margin than the company’s other businesses.

Net income rose to $24.6 million in the first quarter from $5.4 million in the year-ago quarter.

On Assignment Inc. (NYSE: ASGN)
 For the quarter ended March 31, 2013, compared with the year-ago quarter.
 Revenue: $389.2 million, +148.3 percent
 Net income: $24.6 million vs. net income of $5.4 million