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A review in 2010 described the validity of recorded diagnoses for inpatient care, but did not include specialised outpatient care.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Method<\/jats:title>\n                    <jats:p>Using systematic searches of medical literature databases (Embase, Medline), and reports from members of the Swedish Epidemiological Association, we aimed to identify all studies validating diagnoses and procedure codes in inpatient care since 2010 and all studies validating specialised outpatient care. In addition, we summarize findings from register validation work performed by the National Board of Health and Welfare.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>The literature search and personal reports generated 3990 non-duplicate original studies, of which 89 were deemed relevant. Compared to data in patient charts (reference), the median positive predictive value (PPV) for diagnostic codes in the NPR was 84% (interquartile range 72\u201393%), but with clear differences between types of diagnoses. The median PPV for surgical procedures was 97% (86\u201399%). The median sensitivity of diagnoses and procedures compared to other registers and cohorts was 73% (45\u201380%). The completeness of the register has improved over time. Missingness originates mainly from underreporting of procedures performed by private healthcare providers, and for certain variables, e.g. medication codes.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>The NPR has good diagnostic accuracy for most diagnoses and very good for surgical procedures. The sensitivity is lower. Longitudinal comparisons of incidence or prevalence are affected by changes in completeness. Missingness is low, although it is higher among private healthcare providers and for specific variables such as drug administration.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1007\/s10654-025-01221-0","type":"journal-article","created":{"date-parts":[[2025,3,29]],"date-time":"2025-03-29T21:47:34Z","timestamp":1743284854000},"page":"359-369","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":143,"title":["Diagnostic accuracy in the Swedish national patient register: a review including diagnoses in the outpatient register"],"prefix":"10.1007","volume":"40","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0311-8894","authenticated-orcid":false,"given":"\u00c5sa H.","family":"Everhov","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas","family":"Frisell","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mehdi","family":"Osooli","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hannah L.","family":"Brooke","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hanne K.","family":"Carlsen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karin","family":"Modig","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karl","family":"M\u00e5rild","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan","family":"Lindstr\u00f6m","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karin","family":"Sk\u00f6ldin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mona","family":"Heurgren","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonas F.","family":"Ludvigsson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ola","family":"Ol\u00e9n","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2025,3,27]]},"reference":[{"key":"1221_CR1","unstructured":"The National Patient Register: Socialstyrelsen; [Available from: https:\/\/www.socialstyrelsen.se\/en\/statistics-and-data\/registers\/national-patient-register\/). ."},{"key":"1221_CR2","doi-asserted-by":"publisher","first-page":"450","DOI":"10.1186\/1471-2458-11-450","volume":"11","author":"JF Ludvigsson","year":"2011","unstructured":"Ludvigsson JF, Andersson E, Ekbom A, Feychting M, Kim JL, Reuterwall C, et al. 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That study received funding from Janssen corporation. Dr Ludvigsson has also received financial support from MSD developing a paper reviewing national healthcare registers in China. Dr Ludvigsson has an ongoing research collaboration on celiac disease with Takeda. Dr Ol\u00e9n has been PI for academic projects about inflammatory bowel disease at Karolinska Institutet, financed by grants from Janssen, Pfizer, AbbVie, Takeda, Ferring, and Bristol Myers Squibb. Karolinska Institutet has also received fees for lectures and participation by dr Ol\u00e9n on advisory boards from Janssen, Ferring, Galapagos, Bristol Myer Squibb, Takeda, and Pfizer. 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