Publishing and events group Informa PLC reiterated its full year guidance after a positive trading performance in the first quarter of 2015.The company said that excluding one-off non-annual events and the scheduled movement of events between quarters, revenue fell 0.5% but underlying growth in the three months to the end of March remained steady.The FTSE 250 group added that the underlying trends in its academic publishing business were positive and that the integration of the Medical Journals business was on track, while trading in the Knowledge & Networking arm was on track, but ongoing weakness in the Russian market offset strong performances in the UK and the US.Informa said that it expected a slight decline in revenue for the division, while headline revenue was down approximately 10% because of the planned re-scheduling of two events to the second quarter.The US businesses the group acquired in 2014 performed well within the Global Exhibitions arm, though the company added headline growth in the business had been boosted by the movement of certain events from the second to the first quarter.However, first quarter organic growth in the business suffered a 15.6% as a result."We have started the year in line with our growth acceleration plan objectives for 2015 and remain confident of meeting expectations for the full-year," said group chief executive Stephen Carter, who added the company was on track to meet its annual expectations.Informa shares were up 2.87% to 591.00p at 08:37 on Tuesday.