Purpose The purpose of this study was to determine the degree of overlap between the International Classification for Nursing Practice (ICNP®) and the Systematized Nomenclature of Medicine–Clinical Terms (SNOMED–CT), with a specific focus on nursing problems, as a first step towards harmonization of content between the two terminologies. Methods Work within this study was divided across two ICNP subsets. The first subset (n =238) was made up of ICNP diagnosis/outcome concepts that had been included in previous experimental mapping activities with Clinical Care Classification (CCC) and NANDA-International (NANDA-I). These ICNP concepts and their equivalent concepts within CCC and NANDA-I were used within the Unified Medical Language System (UMLS) framework to derive automatically candidate mappings to SNOMED–CT for validation by two reviewers. The second subset (n =565) included all other ICNP diagnosis/outcome concepts plus those concepts from the first subset where the candidate mappings were rejected. Mappings from the second subset to SNOMED–CT were manually identified independently by the same two reviewers. Differences between the reviewers were resolved through discussion. The observed agreement between the two reviewers was calculated along with the inter-rater reliability using Cohen’s Kappa (κ). Results For the first semi-automated mapping, according to the two reviewers the great majority of ICNP concepts (91.6%) correctly mapped to SNOMED–CT in UMLS. There was a good level of agreement between the reviewers in this part of the exercise (κ =0.7). For the second manual mapping, nearly two-thirds of ICNP concepts (61.4%) could not be mapped to any SNOMED–CT concept. There was only a moderate level of agreement between the reviewers (κ =0.45). While most of the mappings were one-to-one mappings, there were ambiguities in both terminologies which led to difficulties. The absence of mappings was due to a large extent to differences in content coverage, although lexical variations and semantic differences also played a part. Conclusions This study demonstrated a degree of overlap between ICNP and SNOMED–CT; it also identified significant differences in content coverage. The results from the semi-automated mapping were encouraging, particularly for ‘older’ ICNP content. The results from the manual mapping were less favorable suggesting a need for further enhancement of both terminologies, content development within SNOMED–CT and further research on mechanisms for harmonization. 
Inter-terminology mapping of nursing problems