Table 1

Variables in the Swedish IPR

Variable

Description


Patient-related data

Personal Identity Number (PIN)

Combination of date of birth, three-digit birth number and a check digit [3]. Personal identity number shall be reported for all admissions/discharges, except for induced abortions where it is not registered for legal reasons

Sex

1 = male; 2 = female

Age

Age in years at discharge. In individuals with missing birth dates, the difference between year of discharge and birth year is used to calculate age.

County

The county where the patient has his/her permanent residence (this is not necessarily the county where the patient is admitted).

Municipality and parish

Usually consists of six digits, where positions 1-2 indicate county, 3-4 municipality and 5-6 parish. Individuals living outside Sweden are assigned the value "99". Missing data have been replaced by data from Statistics Sweden.

Data about caregiver (hospital/department)

Hospital

Each hospital in Sweden has a unique 5-digit code assigned by the National Board of Health and Welfare (NBHW)(e.g., Lund University Hospital has code 41001).

Type of department

Each type of department or health centre has a unique code assigned by the NBHW (e.g. ophthalmology departments have code 511)

Administrative data

Admission date

Year-month-day

Discharge date

Year-month-day

Duration of admission

Number of days at hospital. Patients discharged on the day of admission are assigned the value "1".

Elective health care

1 = Yes, 2 = No

Mode of admission

1 = from other hospital/department, 2 = from special living (e.g., home for disabled people, or geriatric care), 3 = other (i.e. from home)

Mode of discharge

1 = to other hospital/department, 2 = to special living (e.g., home for disabled people or geriatric care), 3 = other (i.e. discharged to home), 4 = deceased.

Medical data

Diagnoses

In 1964-1996, the IPR permitted up to 6 diagnoses per discharge. Between 1997-2009 8 diagnoses could be recorded (one of them being the primary diagnosis).

Primary and

additional diagnoses

The primary diagnosis or "main condition" should be the condition diagnosed at the end of the episode of health care responsible for the patient's need for treatment or investigation.

The additional (secondary or contributory diagnoses/conditions) may or may not contribute to the primary diagnosis. They may be co-morbidities and/or complications. Since 2010 the number of possible additional diagnoses per case is unlimited (however, the NBHW will generally only deliver the first 7 additional diagnoses to researchers who request data from the IPR).

External cause of injury or poisoning (E-code) - or "Chapter XX codes".

Until 1997, only one E-code could be recorded per discharge; from 1998, numerous "E-codes" may be recorded. With the introduction of ICD-10 in 1997, E-codes should be referred to as "Chapter XX-codes". (In ICD-10, E00-E99 codes represent metabolic conditions).

Procedures

In 1964 the Swedish NBHW introduced a national classification of procedures based on an American classification of surgical procedures. It had four digit-codes (e.g. appendectomy 4510). Since 1997, a Swedish version of the NOMESCO Classification of Surgical Procedures is in use. This classification is based on five-character alpha-numeric codes (e.g. JEA01 for appendectomy). Current procedures are listed in the Swedish Classification of surgical and medical procedures (Swedish: "KVÅ" - klassifikation av vårdåtgärder)(issued by the NBHW).

Between 1964 and 1996, up to 6 operations/surgical procedures could be listed per discharge. From 1997, up to 12 operations/surgical procedures could be listed per discharge. In the future it will be possible to record more than 12 diagnoses per discharge. Since 2007, all performed procedures are mandatory to record, including medical procedures. The surgeon may also (voluntarily) report date of operation and type of anaesthesia and drugs used according to the ATC list.

Psychiatric care

0 = voluntary care, 1-4: compulsory psychiatric inpatient care (under different conditions or according to certain laws). If a patient has been treated according to categories 1, 2, 3 or 4, the condition prevailing most of the time shall be reported. Compulsory care can be further divided into "forensic" and "civil", depending on the reasons for compulsory care.


IPR = Inpatient Register. NBHW = National Board of Health and Welfare.

Since January 2009, the NBHW collects additional data on compulsory psychiatric care (psychiatric care under certain laws) in addition to the IPR. The data are collected three times per year.

In older versions of the IPR, the variable "Billing forms (between counties)" was also included.

Ludvigsson et al. BMC Public Health 2011 11:450   doi:10.1186/1471-2458-11-450

Open Data