title: Studying Hospitalizations and Mortality in the Netherlands: Feasible and Valid Using Two-Step Medical Record Linkage with Nationwide Registers.
abstract: In the Netherlands, the postal code is needed to study hospitalizations of individuals in the nationwide hospitalization register. Studying hospitalizations longitudinally becomes troublesome if individuals change address. We aimed to report on the feasibility and validity of a two-step medical record linkage approach to examine longitudinal trends in hospitalizations and mortality in a study cohort. First, we linked a study cohort of 1564 survivors of childhood cancer with the Municipal Personal Records Database (GBA) which has postal code history and mortality data available. Within GBA, we sampled a reference population matched on year of birth, gender and calendar year. Second, we extracted hospitalizations from the Hospital Discharge Register (LMR) with a date of discharge during unique follow-up (based on date of birth, gender and postal code in GBA). We calculated the agreement of death and being hospitalized in survivors according to the registers and to available cohort data. We retrieved 1477 (94%) survivors from GBA. Median percentages of unique/potential follow-up were 87% (survivors) and 83% (reference persons). Characteristics of survivors and reference persons contributing to unique follow-up were comparable. Agreement of hospitalization during unique follow-up was 94% and agreement of death was 98%. In absence of unique identifiers in the Dutch hospitalization register, it is feasible and valid to study hospitalizations and mortality of individuals longitudinally using a two-step medical record linkage approach. Cohort studies in the Netherlands have the opportunity to study mortality and hospitalization rates over time. These outcomes provide insight into the burden of clinical events and healthcare use in studies on patients at risk of long-term morbidities.
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital / Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Elske
authors.initials: E
authors.lastname: Sieswerda
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital / Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Anna
authors.initials: A
authors.lastname: Font-Gonzalez
authors.affiliation: Clinical Research Unit, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Marcel G W
authors.initials: MG
authors.lastname: Dijkgraaf
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Geskus
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital / Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Heinen
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital / Academic Medical Center, Amsterdam, the Netherlands; Department of Medical Oncology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Helena J
authors.initials: HJ
authors.lastname: van der Pal
authors.affiliation: Department of Epidemiology, Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Flora E
authors.initials: FE
authors.lastname: van Leeuwen
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital / Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Huib N
authors.initials: HN
authors.lastname: Caron
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital / Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Leontien C
authors.initials: LC
authors.lastname: Kremer
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Johannes B
authors.initials: JB
authors.lastname: Reitsma
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D018572:Disease-Free Survival; D005260:Female; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009369:Neoplasms / Q000401:mortality* / Q000628:therapy; D009426:Netherlands / Q000453:epidemiology; D012042:Registries; D012189:Retrospective Studies; D015996:Survival Rate