BackgroundThe Swedish National Inpatient Register (IPR), also called the Hospital Discharge Register, is a principal source of data for numerous research projects. The IPR is part of the National Patient Register. The Swedish IPR was launched in 1964 (psychiatric diagnoses from 1973) but complete coverage did not begin until 1987. Currently, more than 99% of all somatic (including surgery) and psychiatric hospital discharges are registered in the IPR. A previous validation of the IPR by the National Board of Health and Welfare showed that 85-95% of all diagnoses in the IPR are valid. The current paper describes the history, structure, coverage and quality of the Swedish IPR.Methods and resultsIn January 2010, we searched the medical databases, Medline and HighWire, using the search algorithm "validat* (inpatient or hospital discharge) Sweden". We also contacted 218 members of the Swedish Society of Epidemiology and an additional 201 medical researchers to identify papers that had validated the IPR. In total, 132 papers were reviewed. The positive predictive value (PPV) was found to differ between diagnoses in the IPR, but is generally 85-95%.ConclusionsIn conclusion, the validity of the Swedish IPR is high for many but not all diagnoses. The long follow-up makes the register particularly suitable for large-scale population-based research, but for certain research areas the use of other health registers, such as the Swedish Cancer Register, may be more suitable.

The weight, insulin-like growth factor, neonatal retinopathy of prematurity algorithm detected early 100% of infants who developed retinopathy of prematurity requiring treatment and correctly predicted the majority who did not require treatment. With this simple postnatal evaluation, costly stressful eye examinations can be markedly reduced (approximately 75% of infants). In addition, early identification of children at risk may lead to the initiation of interventions and possibly prevent sight-threatening retinopathy of prematurity.

To validate in a prospective study the surveillance algorithm WINROP for detecting infants at risk for proliferative retinopathy of prematurity (ROP).Methods: Fifty preterm infants with a mean gestational age of 26 weeks were included. In the first step of WINROP, weekly measures of body weight and serum insulinlike growth factor I (IGF-I) level from birth until postmenstrual age 36 weeks are entered and compared with expected development. If any of the variables show a negative deviation to a certain degree, an alarm is given. In the second step, gestational age, birth weight, and IGF binding protein 3 level are entered. Results:The WINROP algorithm identified all children (100% sensitivity) who were diagnosed with proliferative ROP 1.1 to 21.6 weeks later. No infants with no alarm or with alarm at low risk developed proliferative ROP. Alarm at high risk before postmenstrual age 32 weeks was given for 22 of 50 infants (44%); 9 of these infants developed proliferative ROP (54% specificity), of whom 8 were treated. Conclusion:The WINROP algorithm may be a useful tool for modification of ROP screening.