Abstract In a previous paper, we presented a pro-posed expansion of the National Guideline Clearing-house (NGC) classification 1. We performed a pre-liminary evaluation of the classification based on 100 guidelines randomly selected from the NGC collec-tion. We found that 89 of the 100 guidelines could be assigned to a single guideline category. To test inter-observer agreement, twenty guidelines were also categorized by a second investigator. Agreement was found to be 40-90% depending on the axis, which compares favorably with agreement among MeSH indexers (30-60%)2. We conclude that categorization is feasible. Further research is needed to clarify axes with poor inter-observer agreement.
