Positive predictive value of International Classification of Diseases, 10th revision, diagnosis codes for cardiogenic, hypovolemic, and septic shock in the Danish National Patient Registry

BACKGROUND Large registries are important data sources in epidemiological studies of shock, if these registries are valid. Therefore, we examined the positive predictive value (PPV) of diagnosis codes for shock, the procedure codes for inotropic/vasopressor therapy among patients with a diagnosis of shock, and the combination of a shock diagnosis and a code for inotropic/vasopressor therapy in the Danish National Patient Registry (DNPR). METHODS We randomly selected 190 inpatients with an International Classification of Diseases, 10th revision (ICD-10) diagnosis of shock at Aarhus University Hospital from 2005-2012 using the DNPR; 50 patients were diagnosed with cardiogenic shock, 40 patients with hypovolemic shock, and 100 patients with septic shock. We used medical charts as the reference standard and calculated the PPV with 95% confidence intervals (CI) for overall shock and for each type of shock separately. We also examined the PPV for inotropic/vasopressor therapy and the PPV for shock when a concurrent code for inotropic/vasopressor therapy was also registered. RESULTS The PPV was 86.1% (95% CI: 79.7-91.1) for shock overall, 93.5% (95% CI: 82.1-98.6) for cardiogenic shock, 70.6% (95% CI: 52.5-84.9) for hypovolemic shock, and 69.2% (95% CI: 57.7-79.2) for septic shock. The PPV of use of inotropes/vasopressors among shock patients was 88.9% (95% CI: 79.3-95.1). When both a shock code and a procedure code for inotropic/vasopressor therapy were used, the PPV for shock overall was 93.1% (95% CI: 84.5-97.7). ICD-10 codes for subtypes of shock and simultaneously registered use of inotropes/vasopressors provided PPVs of 96.0% (95% CI: 79.6-99.9) for cardiogenic shock, 69.2% (95% CI: 38.6-90.9) for hypovolemic shock, and 82.4% (95% CI: 65.5-93.2) for septic shock. CONCLUSIONS Overall, we found a moderately high PPV for shock in the DNPR. The PPV was highest for cardiogenic shock but lower for hypovolemic and septic shock. Combination diagnoses of shock with codes for inotropic/vasopressor therapy further increased the PPV of shock overall, and for cardiogenic and septic shock diagnoses.