In the 1960's the National Board of Health and Welfare started to collect information regarding in-patients at public hospitals, the National Patient Register (NPR). Initially it contained information about all patients treated in psychiatric care and approximately 16 percent of patients in somatic care. The register at that time covered 6 of the 26 county councils in Sweden.

In 1984 the Ministry of Health and Welfare together with the Federation of County Councils decided a mandatory participation for all county councils. From 1987 NPR includes all in-patient care in Sweden. Since 2001 the register also covers outpatient doctor visits including day surgery and psychiatric care from both private and public caregivers. Primary care is not yet covered in NPR.

The information in NPR can be divided into four different groups. These groups consist of several variables. You can find more information about them here:

• Information available in the National Patient Register (NPR)
• For a complete list of all variables see the variable list (xls)

Information to the register is delivered to the National Board of Health and Welfare once a month from each of the 21 county councils in Sweden and from private caregivers.

The underreporting for inpatient data is low. The underreporting for the outpatient data is higher and at the start of the data collection in 2001, many cases had missing main diagnoses. The quality of data for the outpatient visits have improved a lot since 2001. Rapid changes of hospital organization in Sweden make it difficult to precisely estimate the drop-out rate, particularly in the areas concerning psychiatric and geriatric care.

Time point variables reported for emergency visits have fair quality from 2016. All county councils, the primary emergency health care providers, have been able to report time points for emergency visits but data for some county councils still need to be improved before they can be used for analysis and research.

The quality in the data about involuntary psychiatric care and forensic psychiatric care has been improving every year from the start of reporting in 2009. The numbers, especially the ones about involuntary measures in the psychiatric care, have increased due to a better reporting each year. There still is an assessment that the quality of the data is not good enough for using the data for general analysis and research.

Quality controls of the register are performed on the submitted data. The control checks for quality and validity of, for instance, personal registration number, hospital and main diagnosis. If too much of the data are suspected to contain erroneous or invalid data points new data are requested from the caregivers.