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Troels Munch,1 Lotte B Christensen,1 Kasper Adelborg,1 Grethe S Tell,2 Ellen M Apalset,2,3 Anna Westerlund,3,4 Ylva T Lagerros,5,6 Johnny Kahlert,1 Fei Xue,7 Vera Ehrenstein1 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 2Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway; 3Department of Rheumatology, Bergen Group of Epidemiology and Biomarkers in Rheumatic Disease, Haukeland University Hospital, Bergen, Norway; 4Department of Medicine Solna, Centre for Pharmacoepidemiology, Karolinska Institutet, Stockholm, Sweden; 5Department of Medicine Solna, Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden; 6Department of Medicine, Clinic of Endocrinology, Metabolism and Diabetes, Karolinska University Hospital, Sweden; 7Center for Observational Research, Amgen Inc., Thousand Oaks, CA, USA Background: Validation of definitions used to identify conditions of interest is imperative to epidemiologic studies based on routinely collected data. The objective of the study was thus to estimate positive predictive values (PPVs) of International Classification of Diseases, 10th Revision (ICD-10) codes to identify cases of incident acute pancreatitis leading to hospitalization and incident primary malignancy in the Scandinavian (Denmark, Norway, and Sweden) national patient registries in women with postmenopausal osteoporosis (PMO). Methods: This validation study included postmenopausal (defined as 55 years or older) women with osteoporosis, identified between 2005–2014. Potential cases were sampled based on ICD-10 codes from the three national patient registries. Cases were adjudicated by physicians, using medical record review as gold standard. PPVs with corresponding 95% CIs were computed. Results: Medical records of 286 of 325 (retrieval rate 88%) women with PMO were available for adjudication. Acute pancreatitis leading to hospitalization had a PPV of 87.6% (95% CI: 80.8%–90.2%). Incident primary malignancy had a PPV of 88.1% (95% CI: 81.3%–92.7%). The PPVs did not vary substantially across the three countries. Conclusion: ICD-10 codes to identify acute pancreatitis leading to hospitalization, and incident primary malignancy in the Scandinavian national patient registries had high PPVs among women with PMO. This allows identification of cases of acute pancreatitis and incident primary malignancy with reasonable validity and to use these as outcomes in comparative analyses. Keywords: validation, primary malignancy, acute pancreatitis, positive predictive value, postmenopausal women

Kasper Adelborg,1 Lotte Brix Christensen,1 Troels Munch,1 Johnny Kahlert,1 Ylva Trolle Lagerros,2,3 Grethe S Tell,4 Ellen M Apalset,4,5 Fei Xue,6 Vera Ehrenstein1 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, Denmark; 2Department of Medicine, Clinical Epidemiology Unit, Karolinska Institutet, 3Department of Medicine, Clinic of Endocrinology, Metabolism and Diabetes, Karolinska University Hospital, Stockholm, Sweden; 4Department of Global Public Health and Primary Care, University of Bergen, 5Department of Rheumatology, Haukeland University Hospital, Bergen, Norway; 6Center for Observational Research, Amgen Inc. Thousand Oaks, CA, USA Background: Clinical epidemiology research studies, including pharmacoepidemiology and pharmacovigilance studies, use routinely collected health data, such as diagnoses recorded in national health and administrative registries, to assess clinical effectiveness and safety of treatments. We estimated positive predictive values (PPVs) of International Classification of Diseases, 10th revision (ICD-10) codes for primary diagnoses of dermatologic events and hypersensitivity recorded at hospitalization or emergency room visit in the national patient registries of Denmark and Sweden among women with postmenopausal osteoporosis (PMO). Methods: This validation study included women with PMO identified from the Danish and Swedish national patient registries (2005–2014). Medical charts of the potential cases served as the gold standard for the diagnosis confirmation and were reviewed and adjudicated by physicians. Results: We obtained and reviewed 189 of 221 sampled medical records (86%). The overall PPV was 92.4% (95% confidence interval [CI], 85.1%–96.3%) for dermatologic events, while the PPVs for bullous events and erythematous dermatologic events were 52.5% (95% CI, 37.5%–67.1%) and 12.5% (95% CI, 2.2%–47.1%), respectively. The PPV was 59.0% (95% CI, 48.3%–69.0%) for hypersensitivity; however, the PPV of hypersensitivity increased to 100.0% (95% CI, 67.6%–100.0%) when restricting to diagnostic codes for anaphylaxis. The overall results did not vary by country. Conclusion: Among women with PMO, the PPV for any dermatologic event recorded as the primary diagnosis at hospitalization or at an emergency room visit was high and acceptable for epidemiologic research in the Danish and Swedish national patient registries. The PPV was substantially lower for hypersensitivity leading to hospitalization or emergency room visit. Keywords: dermatology, positive predictive value, validation, pharmacoepidemiology