Population based mortality and quality of death certification in progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome)

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Abstract
Objective: To estimate the mortality of progressive supranuclear palsy (PSP) and to assess the quality of death certification in patients with PSP who died in England and Wales. Methods: An analysis was conducted of ICD-9 (International Classification of Diseases, version 9) coded deaths obtained through the Office of National Statistics over an eight year period. Results: The crude annual mortality rate was 1.77 (95% confidence interval, 1.64 to 1.90) cases per million, using the mid-1996 population estimate for England and Wales. Annual mortality increased over time, possibly as a result of increased incidence or increased awareness of the disorder. Forty nine death certificates from deceased patients previously diagnosed clinically showed that the commonest proximate cause of death was pneumonia, occurring in 45% of cases (22/49). The underlying cause of death was cited as pneumonia in 14% of cases (7/49). PSP was mentioned in only 65% of death certificates (32/49). Eight of the 49 cases (16%) underwent necropsy and results were available for five of these cases. PSP was confirmed pathologically in four; the remaining case was diagnosed as Parkinson’s disease. Conclusions: Further research is needed to establish the reasons for the observed increase in mortality. Determining the population mortality rate for PSP using the ICD-9 coding system is problematic but is likely to improve following the introduction of ICD-10 updated codes and coding rules.