Validity of ICD-10 diagnoses of overweight and obesity in Danish hospitals

Sigrid Bjerge Gribsholt,1,2 Lars Pedersen,1 Bjørn Richelsen,3 Reimar Wernich Thomsen1 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 2Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark; 3The Steno Diabetes Centre Aarhus, Aarhus University Hospital, Aarhus, DenmarkCorrespondence: Sigrid Bjerge GribsholtDepartment of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, Aarhus N 8200, DenmarkTel +45 6 165 1148Email sigrgrib@rm.dkPurpose: Health care databases may be a valuable source for epidemiological research in obesity, if diagnoses are valid. We examined the validity and completeness of International Classification of Diseases, 10th revision [ICD-10] diagnosis coding for overweight/obesity in Danish hospitals.Patients and methods: We linked data from the Danish National Patient Registry on patients with a hospital diagnosis code of overweight/obesity (ICD-10 code E66) with computerized height and weight measurements made during hospital contacts in the Central Denmark Region Clinical Information System. We computed the positive predictive value (PPV) of the IDC-10 diagnosis of overweight/obesity, using a documented body mass index (BMI) ≥25 kg/m2 as gold standard. We also examined the completeness of obesity/overweight diagnosis coding among all patients recorded with BMI ≥25 kg/m2.Results: Of all 19,672 patients registered with a first diagnosis code of overweight/obesity in the National Patient Registry, 17,351 patients (88.2%) had any BMI measurement recorded in the Central Denmark Region Clinical Information System, and 17,240 patients (87.6%) had a BMI ≥25 kg/m2, yielding a PPV of 87.6% (95% CI: 87.2–88.1). The PPV was slightly higher for primary diagnosis codes of overweight/obesity: 94.1% (95% CI: 93.3–94.8) than for secondary diagnosis codes: 86.1% (95% CI: 85.6–86.6). The PPV increas