The validity of revised death certificates (ICD-10) for ischemic heart disease in Oita City, Japan

PURPOSE: Mortality statistics have recorded an increased number of deaths from ischemic heart disease (IHD) since death certificates were revised to reflect the International Classification of Diseases, tenth revision (ICD-10) in Japan, in 1995. However, it remains unclear whether the validity of IHD diagnosis improved after this revision. METHODS: We conducted the Oita Cardiac Death Survey to validate IHD certified deaths that occurred among residents aged 25-74 in Oita City, Japan (mean population = 273,000). Of the eligible 342 fatalities, 328 cases (95.0%) were examined by a review of the medical records and/or interviews with physicians. The MONICA criteria were applied and provided a reference standard against which to assess the validity of certified fatal IHD. Sensitivity (Se), positive predictive value (PPV), specificity (Sp) and negative predictive value (NPV) for IHD as the cause of death were analyzed, assuming that all validated IHD deaths were true. Multivariate logistic models were used to determine associations of false positive and false negative cases with sex, age at time of death and place of death. RESULTS: Vital statistics revealed 273 fatalities to be due to cardiac disease, including 143 from acute myocardial infarctions (AMI), 27 from other IHD, 52 from heart failure and 51 from other heart diseases. After validation, 25 'definite fatal AMI' and 71 'possible fatal AMI or IHD death' were identified among all subjects according to the MONICA criteria. In all, Se, PPV, Sp and NPV for IHD certified as the cause of death were 86.5% (95% Cl: 77.6-92.3), 50.3% (42.5-58.1), 64.7% (58.1-70.7), and 92.0% (86.5-95.5), respectively. PPV among persons aged 25-54 years was remarkably decreased. PPV and Sp among out-of-hospital deaths were significantly lower than for in-hospital deaths. Multivariate logistic models revealed out-of-hospital deaths and being aged 25-54 years to be significant predictors of false positive cases (odds ratio (OR) = 2.03, P < 0.001 versus in-hospital deaths and OR = 2.79, P < 0.05 versus ages of 65-74 years, respectively). CONCLUSIONS: Because false positive cases increased among certified IHD deaths after the revision, PPV and Sp percentages decreased. Out-of-hospital deaths and being aged 25-54 years were associated with increased possibility of false positive. Given our findings, IHD deaths in vital statistics may increase due to the tendency of physicians to certify IHD as the cause of death in cases without clear sign suggestive of other causes.