Positive predictive values of the International Classification of Disease, 10th edition diagnoses codes for diverticular disease in the Danish National Registry of Patients

OBJECTIVE: To investigate the accuracy of diagnostic coding for diverticular disease in the Danish National Registry of Patients (NRP). STUDY DESIGN AND SETTING: At Aalborg Hospital, Denmark, with a catchment area of 640,000 inhabitants, we identified 100 patients recorded in the NRP with a diagnosis of diverticular disease (International Classification of Disease codes, 10th revision [ICD-10] K572–K579) during the 1999–2008 period. We assessed the positive predictive value (PPV) as a measure of the accuracy of discharge codes for diverticular disease using information from discharge abstracts and outpatient notes as the reference standard. RESULTS: Of the 100 patients coded with diverticular disease, 49 had complicated diverticular disease, whereas 51 had uncomplicated diverticulosis. For the overall diagnosis of diverticular disease (K57), the PPV was 0.98 (95% confidence intervals [CIs]: 0.93, 0.99). For the more detailed subgroups of diagnosis indicating the presence or absence of complications (K573–K579) the PPVs ranged from 0.67 (95% CI: 0.09, 0.99) to 0.92 (95% CI: 0.52, 1.00). The diagnosis codes did not allow accurate identification of uncomplicated disease or any specific complication. However, the combined ICD-10 codes K572, K574, and K578 had a PPV of 0.91 (95% CI: 0.71, 0.99) for any complication. CONCLUSION: The diagnosis codes in the NRP can be used to identify patients with diverticular disease in general; however, they do not accurately discern patients with uncomplicated diverticulosis or with specific diverticular complications.