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Medical certification of cause of death

The concept of underlying cause of death

A key concept in COD certification is the underlying cause of death (UCOD), which is defined as ‘(a) the disease or injury which initiated the train of morbid events leading directly to death', or '(b) the circumstances of the accident or violence which produced the fatal injury’.

Mortality statistics are based upon the UCOD, which is the disease or injury that initiated the sequence of events that led directly to death. It is extremely important that the underlying cause of each death is correctly determined and accurately recorded.

This initiating cause should not be confused with the ‘mode of dying’, such as heart failure, cardiac arrest, shock, brain failure, hepatic failure and renal failure. These conditions do not usually occur without a precipitating cause. If only the mode of dying is reported on the death certificates (eg ‘heart failure’), a potentially wide range of different underlying causes will be missed, which will result in significant proportions of deaths being classified as ‘ill defined’. This renders the resulting cause of death statistics of little value for health decision making. It is this UCOD that is amenable to preventative health interventions. Therefore, it is extremely important that the underlying cause is determined and accurately recorded. 


Volume 2 of the ICD-10 provides guidance and standards for mortality certification, and explains the rules and procedures for selecting the UCOD. It also sets out why the UCOD – rather than the immediate COD – should be used to certify deaths, and to produce statistics that are useful for health planning and disease prevention. 

The process of coding of COD is central to accurate identification of UCOD during the mortality coding process. 

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