The present study found that the overall rate of postmortem examination is low and falling. The incidence of 7.7% of all deaths is much lower than that in other published studies [3–7]. This finding probably represents the increasing reluctance of many clinicians in the UK to ask for permission to undertake a postmortem examination. This is further illustrated by the finding that a compulsory postmortem examination requested by the coroner represents 50% of all postmortem examinations undertaken in the study period, which is much higher than reported in other series [8]. There is an urgent need to reverse the decline in the rate of postmortem examinations. Despite concerns that relatives will be unwilling to give permission for a postmortem examination, a recent study has reported that if they are approached sensitively up to 46% of relatives may agree [9]. Additionally, recommendations to increase postmortem examination rates can be successfully implemented and such guidelines should be put in place [10].
This study has demonstrated poor agreement between the clinical diagnoses before death and postmortem findings in a group of patients who died while in the ICU. This finding is consistent with recent European and American studies that highlighted that even with modern diagnostic techniques discrepancies between clinical diagnoses and postmortem findings continue to occur [4, 6, 8, 11]. Although it has been proposed that the duration of stay in the ICU is associated with the number of unexpected findings at postmortem examination [6, 12], this was not confirmed by the present or previous studies [4, 5, 13].
Myocardial infarction represented the most frequent major missed diagnosis. It is notable that an electrocardiogram was performed in only 55% of patients undergoing postmortem examinations at any stage of the ICU stay. This suggests that the index of suspicion for ischaemic heart disease is inappropriately low and should be considered as a diagnostic possibility in the critically ill patient. The incidence of missed disseminated infection was lower in our patients than in previous studies [6, 8, 11, 14]. It is possible that the daily multidisciplinary microbiology review conducted in our unit may reduce the possibility of unrecognised occult infection. It may also reflect a difference in case mix; unrecognised infection is seen more commonly in immunocompromised patients [6, 11], who are not represented in our patient population. The finding of undiagnosed carcinoma and pulmonary embolism is consistent with previous studies emphasizing the importance of maintaining a high index of suspicion for these diagnoses in the critically ill [3, 5, 15]. These findings emphasize the need for adequate diagnostic algorithms for these frequently unrecognised conditions to be established in order to reduce the incidence of missed diagnoses.
Certain limitations of the present study should be recognised. It is retrospective, and the data for 11 patients were not available because of incomplete or missing charts. Given that this is a small study with a low postmortem examination rate, it is difficult to determine how representative the extent of the new findings at postmortem examination are of the overall population of patients dying in the ICU. Selection bias of patients for postmortem examination at the discretion of the intensive care physician might also have influenced the incidence of discrepancies in the patients studied. Given that a postmortem examination is more usually requested when diagnostic uncertainty exists, it may be more likely to identify unexpected findings, leading to a falsely high incidence of missed diagnoses. However, there is evidence that clinical diagnostic certainty does not predict postmortem findings, indicating that the incidence of missed diagnosis may in fact be accurate [3, 14, 15]. Finally, the diagnostic work-up of each individual was not critically reviewed, and it is possible that variability in investigation influenced the incidence of missed diagnosis.
The low incidence of postmortem examination in this study may explain, at least in part, the high incidence of major missed diagnoses. In a recent study with a high rate of postmortem examination [8] the incidence of major missed diagnoses was low whereas, consistent with our findings, in studies with a lower rate of postmortem examination [3, 6, 7] the incidence of major diagnostic error was higher.