The causal sequence on death certificates: errors affecting the reliability of mortality statistics for rheumatoid arthritis.

Physicians' amount of diagnostic information and the adequacy of the causal sequence(s) on death certificates involving rheumatoid arthritis (RA) were investigated. Physicians' reporting was compared with the Swedish National Central Bureau of Statistics' (NCBS) registration of the causal conditions, particularly the underlying cause of death. All Swedish RA death certificates for the years 1971 and 1975 were studied. A total of 1224 such certificates were identified. The causal sequences were inadequate in 35% of the certificates, 37% in 1971 and 33% in 1975. Ten types of inadequate sequences were identified. The NCBS rejected the underlying cause of death in 56% of the inadequate sequences and in 52% of the adequate sequences. When the whole sequence leading directly to death was described by only a single diagnosis, 374 (31%) of the cases, this diagnosis was rejected by the NCBS in 54% of the certificates from 1971 and 75% from 1975. More than one diagnosis on each line of the causal-sequence-description appeared on 28% of the certificates. The total number of diagnoses on each certificate did not, however, exceed the NCBS' registration capacity (up to seven diagnoses) in more than 1.6% of the 1224 cases. Thus, the major problem in the NCBS' data collecting process was not how to sort out excessive diagnostic information, but to record properly the causal classification of the conditions, and to interpret the physicians' account of the underlying cause of death.