Diagnostic accuracy in the Swedish National Patient Register
The Swedish National Patient Register (NPR) has long been a cornerstone for epidemiological research. Researchers at Karolinska Institutet have published a new review examining the validity of the register and found that it is good for most diagnoses and very good for surgical procedures.
A previous review was conducted in 2010 but only included inpatient care. The new review also includes specialized outpatient care, providing a more complete picture of the validity of the NPR.
The researchers conducted systematic searches in medical databases and collected reports from members of the Swedish Epidemiological Association to identify all studies validating diagnoses and procedure codes in inpatient care since 2010 and all studies validating specialized outpatient care. Additionally, results from register validation work carried out by the National Board of Health and Welfare are summarized.
"Our review shows that the Swedish National Patient Register has good diagnostic accuracy for most diagnoses and very good accuracy for surgical procedures, but with significant variability in PPV and sensitivity depending on diagnosis, coding definitions, reference standards, and data sources" says Åsa Everhov, docent at the Department of Medicine Solna and the first author of the article.
The register has become more complete over time. The degree of underreporting is currently low, although it is higher among private healthcare providers and for specific variables such as drug administration.
"Longitudinal comparisons of incidence or prevalence are affected by changes in completeness. It is important that researchers are aware of these limitations when using the NPR for their studies," says Ola Olén, the last author of the study and professor at the Department of Medicine Solna.
The review emphasizes the value of the NPR while highlighting limitations to ensure it remains an important resource for epidemiological research both in Sweden and internationally.
Publication
Diagnostic accuracy in the Swedish national patient register: a review including diagnoses in the outpatient register.
Everhov ÅH, Frisell T, Osooli M, Brooke HL, Carlsen HK, Modig K, Mårild K, Lindström J, Sköldin K, Heurgren M, Ludvigsson JF, Olén O. European Journal of Epidemiology, online 27 March 2025, doi: 10.1007/s10654-025-01221-0.