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Inès Ben Ghezala, Johan Frederik Berg Arendt, Rune Erichsen, Jihen Zalfani, Henrik Gammelager, Trine Frøslev, Morten OlsenDepartment of Clinical Epidemiology, Aarhus University Hospital, Aarhus, DenmarkPurpose: The aim of this validation study was to assess the positive predictive value (PPV) of the International Classification of Diseases, 10th revision (ICD-10) diagnosis of vitamin B12 (cobalamin [Cbl]) deficiency anemia in the Danish National Patient Register (DNPR).Patients and methods: We identified all patients above 18 years of age recorded in the DNPR with a diagnosis of Cbl deficiency anemia (ICD-10 code: D51) admitted to two Danish university hospitals and one Danish regional hospital from 2000 through 2009. We assessed the PPV using biochemical parameters on Cbl deficiency with or without anemia as reference standards. These data were obtained from the Laboratory Information Systems Database. Data on prescriptions with Cbl supplementation drugs were obtained from the Aarhus University Prescription Database.Results: We identified 1089 patients coded with a Cbl deficiency anemia diagnosis in the DNPR. The PPV was 31.5% (95% confidence interval [CI]: 28.8%–34.3%) and 36.8% (95% CI: 34.0%–39.7%) depending on definitions of Cbl deficiency with anemia. When using Cbl deficiency without anemia as a reference standard, the PPV was 51.3% (95% CI: 48.4%–54.3%). The PPV for Cbl supplemented patients was 22.2% (95% CI: 18.0%–26.9%) and for non-Cbl supplemented patients 63.9% (95% CI: 60.5%–67.3%).Conclusion: The PPVs of the ICD-10 diagnosis coding for Cbl deficiency anemia were generally low in the DNPR. Therefore, this register should be used with caution to study patients with Cbl deficiency anemia.Keywords: vitamin B12 deficiency anemia, Danish National Patient Register, Laboratory Information Systems Database, International Classification of Diseases, positive predictive value, validation study

Jihen Zalfani, Trine Frøslev, Morten Olsen, Inès Ben Ghezala, Henrik Gammelager, Johan FB Arendt, Rune ErichsenDepartment of Clinical Epidemiology, Aarhus University Hospital, Aarhus, DenmarkObjective: Valid data on anemia caused by bleeding are needed for epidemiological research and monitoring health care. The Danish National Registry of Patients (DNRP) is a nationwide medical database with information on all Danish residents' hospital history. We aimed to assess the positive predictive value (PPV) of the diagnostic coding of anemia caused by bleeding in the DNRP.Methods: In the DNRP, we identified all patients with International Classification of Disease, 10th edition codes for anemia caused by bleeding (acute: D50.0; chronic: D62.6) at three Danish hospitals from 2000 through 2009. For these patients we computed the PPV using hemoglobin level data, from Aarhus University laboratory database, as reference standard. Anemia was defined by a hemoglobin level less than 7.0 mmol/L for women and less than 8.0 mmol/L for men.Results: We identified 3391 patients in the DNRP with a diagnosis of anemia caused by bleeding. The overall PPV was 95.4% (95% confidence interval [CI]: 94.6%–96.0%). The PPV was 97.6% (95% CI: 96.6%–98.3%) for men and 94.0% (95% CI: 92.9%–94.9%) for women, and the PPV increased with age at diagnosis. The PPV varied according to type of discharging departments, from 89.2% (95% CI: 83.4%–93.4%) in gynecology to 96.8% (95% CI: 94.9%–98.2%) in surgery, and was lower for outpatients compared with inpatients.Conclusion: We found a high PPV of the coding for anemia caused by bleeding in the DNRP. The registry is a valid source of data on anemia caused by bleeding for various purposes including research and monitoring health care.Keywords: anemia, Danish National Registry of Patients, International Classification of Diseases, predictive value, laboratory database, validation