[Citation analysis of research articles from Norwegian health enterprises, 2005-2011].

Background: The citation frequency of a publication is often interpreted as an expression of its scientific impact. Previous citation analyses of Norwegian medical research have either focused on universities and university hospitals or on subject areas at the national level. Such analyses have paid little attention to other health enterprises, despite a strong increase in their research activity during the last decade.

Material And Method: For all health enterprises with more than 25 publications in the Web of Science during the period 2005-2011 we have calculated field normalized citation indexes at the institution and subject levels.

Results: On the whole, research undertaken by the health enterprises is frequently cited, and some medium-sized health enterprises stand out in terms of their high average citation indexes: Helse Stavanger Health Enterprise, Diakonhjemmet Hospital and Helse Nord-Trøndelag Health Enterprise, although Oslo University Hospital Health Enterprise and Helse Bergen Health Enterprise account for more than half of the most cited articles.

Interpretation: In citation analyses at the aggregated level, highly and infrequently cited research groups/departments may balance each other. This appears to be the case in the largest health enterprises. Some medium-sized health enterprises that have a more concentrated research portfolio will thus accumulate higher average citation indexes than the largest university hospitals.