Positive Predictive Value of Diagnostic Codes for Inflammatory Bowel Disease in the Danish National Patient Registry Among Individuals 50+ Years, Using Patient Records as Reference Standard

Abstract

Purpose: Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic diseases. The aim was to validate diagnoses of IBD among patients aged 50+ years in the Danish National Patient Registry (NPR) by comparison with patient medical records. Patients and Methods: Men and women in the Diet, Cancer and Health (DCH) cohort were linked to NPR, and cases with a diagnosis of IBD and their respective hospital records were identified. Validation was performed by comparing patient medical records with information on discharge diagnoses of IBD from the NPR. Results: Of 57,053 individuals in the DCH-cohort, 339 were registered with an IBD diagnosis in NPR, with 277 (82%) records available for review. Among 277 patients, the positive predictive values (PPVs) of one CD or UC registration in NPR were 78% for IBD overall, 51% for CD and 54% for UC. One hundred fifty-seven patients had at least two CD and/or UC registrations with PPVs of 90% for IBD overall, 65% for CD and 73% for UC. One hundred and two patients had at least three registrations with PPVs of 97% for IBD overall, 75% for CD and 88% for UC. 96% were diagnosed at a specialized department. Other diagnoses coded as IBD mostly included microscopic colitis, irritable bowel syndrome and cancer. Conclusion: Validity of IBD diagnoses in the registry of individuals aged 50+ years increased with the number of registrations. It is recommended that these results are taken into consideration in future studies, especially in epidemiology research using NPR as a data source for patients diagnosed with IBD.

Identification of Childhood-Onset Inflammatory Bowel Disease in Swedish Healthcare Registers: A Validation Study

“…Our findings in the studied pediatric population are almost identical to earlier Swedish and Danish studies, assessing PPVs of the same register-based IBD definition in mostly or exclusively adult populations. 11 , 32 Two previous studies from Sweden and Denmark found markedly higher PPVs for IBD subtypes in adult patients (PPV = 89–97%), but these studies only included patients with confirmed IBD. 33 , 34 …”

“…The need for much more complex algorithms to identify IBD in Canada and Israel 35 , 36 compared to the corresponding Danish and Swedish algorithms 11 , 32 , 34 is likely due to several differences between the healthcare systems and databases used. The Canadian algorithms were created based on billing claims in systems where diagnostic codes for IBD seem to have been used also before a definitive diagnosis had been confirmed.…”

Risk of dementia in patients with inflammatory bowel disease: a Danish population‐based study

“…Validation of IBD diagnosis codes in the DNPR has reported a high completeness (94%) and a positive predictive value (PPV) of 90% and 98% for UC and CD, respectively, 51 yet lower in IBD patients aged above 50 52 . Potential misclassification would likely be non‐differential with bias towards the null.…”

Clinical procedures used to diagnose inflammatory bowel disease: real-world evidence from a Danish nationwide population-based study

“…Recent studies have used different diagnostic criteria, and no single ‘gold standard’ exists. 22 23 34–36 The length of the hospital admission was used to decrease the risk of misclassification (false positives) of patients with only one diagnosis. Among those patients with only one diagnosis registered but with a hospital admission lasting at least 7 days, 618 (13.8%) were diagnosed in the last year of the inclusion period (2018).…”