In what sense is rheumatoid arthritis the principal cause of death? A study of the National Statistics Office's way of reasoning based on 1224 death certificates.

Physicians' inadequacies in making out death certificates involving rheumatoid arthritis (RA) and the coders' reasons for not registering physicians' stated underlying cause as the underlying cause of death were investigated. The starting point of the study was a disagreement between physicians' reporting of RA on death certificates and the Swedish National Central Bureau of Statistics' (NCBS) registration of this condition, to the effect that the NCBS registered a 3.0-fold increase in mortality for women and a 2.7-fold increase for men attributed to RA between 1971 and 1975, whereas the physicians had reported practically no change at all for women and a slight decrease for men between the years. All Swedish RA death certificates for the years 1971 and 1975 were studied. A total of 1224 such certificates were identified. Four major qualifications for the coders to reject physicians' non-RA underlying cause, and for giving preference to RA in the registration of the underlying cause of death were discerned: RA appeared to have been favoured to the greatest extent by the NCBS (i) when RA was likely to have caused the reported underlying condition; (ii) when there is only one, non-RA, diagnosis reported in Part I of the certificate, and this diagnosis does not completely describe the train of events leading to death; (iii) when the diagnosis for the non-RA underlying condition provides less precise information about the site or nature of the underlying condition, compared with another diagnosis for another condition, RA, stated on the certificate; or (iv) when the reported non-RA underlying condition was unlikely itself to cause death, and was not reported as a cause of a more serious condition. The NCBS' increased registration of RA as the underlying cause of death between 1971 and 1975 could be explained neither by physicians' inadequacies in making out death certificates nor by a strict application of the international coding rules for registration of the underlying cause of death.