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.