Deaths from active tuberculosis: can we rely on notification and mortality figures?

SETTING

Notification rates and mortality are the main indicators in the epidemiology of tuberculosis. While errors in case notification are known to be considerable, the quality of the data on deaths is largely unknown.

OBJECTIVE

To validate the quality of data on deaths from active tuberculosis.

DESIGN

We compared deaths from active tuberculosis in Statistics Norway with the National Tuberculosis Register (NTR) and cases found by autopsy in two Norwegian counties in 1977-1989. We also assessed the diagnostic classification and inclusion criteria for tuberculosis.

RESULTS

110 patients were entered into the study. We excluded 30 of 106 patients in Statistics Norway, primarily because of inactive tuberculosis (16) or minimal lesions (7). We found an additional 20 patients in the NTR and 14 more from autopsy reports. These missing cases were registered in Statistics Norway with a different diagnosis (28), inactive tuberculosis (4) or not found (2). Nineteen of them were diagnosed with tuberculosis by autopsy and five by cultures reported after death. We altered the diagnostic classification of underlying cause in 14% and found tuberculosis to be the underlying cause in 65 patients.

CONCLUSION

The mortality rate from active tuberculosis in Statistics Norway was fairly correct, but one-third were under-reported and one-third over-reported. The mortality rate includes only half of all the deaths from active tuberculosis. All the cases in which active tuberculosis is mentioned on the death certificate are a clearer indication of tuberculosis deaths.