Death certificates and autopsy reports serve as the basis for public mortality statistics, which are published annually by Statistics Norway. These statistics are used as the basis for assessment of public health, and it is therefore essential that the registry is of good quality.
Since medical autopsy findings produced a change in the underlying cause of death for a full 61 % of the deaths, as well as a cause of death from another ICD-10 chapter for 32 %, this study demonstrates that there is a large margin of uncertainty associated with determination of the cause of death. Even though a medical autopsy was performed on a relatively limited number of deaths (n = 1,773) when compared to the total number of deaths (n = 41,152) and the sample is highly selective, in our opinion the results would warrant a debate on the quality of mortality statistics.
One weakness of most autopsy studies, including our own, is that the patients are not representative of the population as a whole. In our material, the proportion of deaths caused by infections, mental disorders and diseases of the digestive system differs from what is found in the population as a whole. The higher occurrence of infections and diseases of the digestive system reflects the fact that patients suffering from such diseases more often die following admission to hospital, while the low proportion of mental disorders can mainly be explained by the fact that patients with unspecific dementia, which is coded as a mental disorder, more often die in nursing homes. In addition, autopsy studies tend to be biased with regard to gender and age, as they include a preponderance of men and people in younger age groups (11, 12). The lower frequency of autopsies performed on women can be explained by women’s higher age at death, and their concurrently higher likelihood of dying not in a hospital, but in a nursing home.
We are not familiar with any similar studies undertaken on the basis of the ACME system, but several previous comparisons of death certificates and autopsy results have yielded similar findings. A study undertaken in Connecticut in 1980 showed that the autopsy findings produced a change in the underlying cause of death with a transfer to another ICD chapter in 29 % of the cases (5). The autopsy frequency for the population of Connecticut was not reported. An East German study from 1987 with an autopsy frequency of approximately 100 % showed that the autopsy findings produced a change in the underlying cause of death and a change of ICD chapter in 30 % of the cases (6).
The fact that our findings from 2005 are similar to findings in older studies may indicate that the progress of diagnostic methodology in recent decades has not produced a better conformity between the clinician and the medical examiner with regard to the reporting of causes of death. There is a possibility that falling autopsy rates have caused autopsies to be reserved for especially complicated courses of illness, for which the cause of death is difficult to determine. Most of the patients in our material, however, have been examined in regional hospitals, and the doctors have had access to all medical records. The fact that the patients autopsied were on average close to ten years younger than the median age at death of the population as a whole also implies that age-related multi-morbidity has only to a lesser extent complicated the determination of the underlying causes of death in our material.
As in the previous studies, we found a marked increase in causes of death from diseases of the circulatory system (ICD-10 chapter IX) after having taken the autopsy results into account. During the last forty years, a consistent decrease in mortality rates from cardiovascular diseases has been reported (13). An overview study from 1998 on the role of autopsies for epidemiological studies of cardiovascular diseases concluded that the death certificate, the clinical records or an interview could replace autopsies (14). Most of the decrease in mortality from cardiovascular diseases is undoubtedly real, but a Finnish study on causes of death among middle-aged men has pointed out that a high autopsy rate is important (especially for those who die outside hospitals) to monitor the further development of mortality from cardiovascular diseases (15). In Norway, the declining rate of mortality from cardiovascular diseases has occurred simultaneously with a strong decrease in the number of autopsies undertaken after sudden and unexpected deaths (16).
The correspondence between the death certificate and the autopsy result was best for deaths caused by cancer. This notwithstanding, as a result of the autopsy findings approximately ten per cent of the cases for which the death certificate had given cancer as the cause of death were reclassified to other causes. However, the shift in the opposite direction was even greater, so that the proportion of deaths caused by cancer increased from 23.3 % to 25.4 %. One in ten of these cases of cancer was not referred to on the death certificate. These findings tally with a Swedish study from 1997, which reported that a decreasing autopsy rate may be the cause of the declining rate of several forms of cancer (11). The Swedish researchers therefore warned against drawing conclusions on the development of the incidence of cancer without taking differences in autopsy rates into account.
We cannot exclude the possibility that some of the death certificates have been completed following the availability of preliminary autopsy findings. If so, we may underestimate the importance of autopsies for the determination of the underlying cause of death.
The poor quality of death certificates and the validity of mortality statistics are frequently being discussed (1). Articles questioning the quality of autopsy results are published less frequently. It is appropriate to note that autopsy results may not always provide the ultimate answer. A study from 2006 on the quality of autopsy reports from the British system of coroners who investigate deaths showed that 25 % of the reports were of poor or unacceptable quality (17). In addition to recommending quality controls at regular intervals, including a second opinion, the study concluded that there was a need to define a national standard for identification of causes of death in the autopsy reports.
Even though the examinations undertaken by the British coroners are not directly comparable to Norwegian medical autopsies, there is reason to note that Norway has no standard for the performance of autopsies and assessment of their results either. For forensic post mortems in Norway, the Forensic Commission undertakes a systematic quality control (16). An introduction of a national standard and a systematic quality review could help strengthen the role of medical autopsies in the assessment of the cause of death.
The changes in recorded cause of death after autopsy may indicate that the clinician and the pathologist differ in their understanding of the listing of causes of death. The absence of deaths from epilepsy and a reduction in diabetes-related deaths by half indicate that pathologists to some extent fail to diagnose causes of death from certain groups of diseases. Insufficient use of clinical-chemical supplementary examinations may also cause some diseases without a morphological correlate to be left out of the autopsy diagnoses. Differences in understanding may also be caused by insufficient knowledge. Most likely, a major proportion of the autopsy reports are completed without any knowledge of the diagnosis given in the death certificate, which is often completed by other doctors than those who submit the autopsy request. If a discussion of the clinically provided cause of death on the death certificate were made into a regular procedure in the autopsy report, this would make the interpretation of the various diagnoses easier for the Cause of Death Registry.
A new, electronic death certificate is currently being planned. In this context it will be possible to introduce changes that could improve the quality of the registration of causes of death, including the registration of autopsy findings. For example, one should consider whether the coding personnel at the Cause of Death Registry should be charged with the assessment of the list of diagnoses in the autopsy report against the list of diagnoses on the death certificates. In Finland, this responsibility lies with the doctor who completes the death certificate and requests the autopsy (15).