Deaths involving Clostridium difficile, Wales: 2014

• In 2014 there were 111 death certificates mentioning Clostridium difficile (C. difficile) in Wales, 66 fewer than in 2013 (177 deaths)

• C. difficile was recorded as the underlying cause of death on 42 of the 111 (38%) death certificates mentioning it

• The age-standardised rate for deaths involving C. difficile increased, from 22.6 to 164.8 deaths per million population, between 1999 and 2008. The rate has since fallen significantly by 78% to 35.8 per million in 2014

• Deaths involving C. difficile increased with age. In the period 2012 to 2014, the age-specific death rate for those aged 85 years and over was 995.3 per million population, compared with 1.0 per million population for those aged under 55 years

• In 2014, over 95% of deaths involving C. difficile deaths occurred in hospitals

This bulletin presents the latest figures for deaths in Wales where C. difficile was mentioned, or identified as the underlying cause of death on death certificates. Figures are broken down by sex, age group and place of death. Comparisons are made between the 2014 data and previously published data from 1999 onwards. Information is given about the context and uses of these statistics, as well as the methods used to produce them.

Figures are based on deaths registered in each year, rather than occurring in each year, but since the majority of C. difficile deaths registered in 2014 also occurred that year, registration delays are unlikely to affect our findings. Please see the section on registration delays for more information.

Background

C. difficile is a type of bacteria which is naturally present in the intestine of 2 in 3 children and 3 in 100 adults, but causes no harm to healthy people. This is because its growth is controlled by other bacteria in the body. However, certain antibiotics can interfere with the natural balance of the intestine by destroying the bacteria that usually prevent C.difficile from multiplying (Bupa, 2015). If this happens, C.difficile bacteria can grow to unusually high levels and produce toxins which attack the intestines. Some people affected by C. difficile show no symptoms; while others go on to have diarrhoea, high temperature and abdominal cramping. In extreme cases, it may cause potentially life-threatening inflammation of the bowel (NHS, 2014).

C. difficile bacteria produce spores which leave the body through the stools of the infected individual. These spores are resistant to conditions outside the body, and can contaminate toilets, bedding, skin and clothes. They are easily spread through the air or by the hands of people coming into contact with infected patients or contaminated surfaces, and can only be removed through very thorough cleaning. This means that the bacteria can easily spread (NHS, 2014).

Since January 2005, all Health Boards in Wales have been required to undertake surveillance of the number of cases of C. difficile infections in their hospitals. This surveillance is managed by the Welsh Healthcare Associated Infection Programme (WHAIP), which is part of public health Wales. The latest figures for April 2014 to May 2015 showed that there were 847 cases of C. difficile infections reported in hospital inpatients. This represents a 22% decrease on the 1,089 cases recorded April 2013 to May 2014.

In 2014, there were 111 deaths involving C. difficile recorded in Wales, a decrease of 37% on the number recorded in 2013 (177) and the lowest since 2005. It also represents a 76% decrease on the highest number of deaths (461) which was registered in 2008.

The number of male deaths fell from 69 in 2013 to 52 in 2014, while female deaths fell from 108 to 59 deaths over the same period.

While C. difficile may contribute to a death, sometimes it is also directly responsible for causing it. In 2014, of the 111 death certificates mentioning C. difficile, 42 (38%) also identified it as the underlying cause of death. Deaths where C. difficile was the underlying cause fell by 54% from 91 to 42 between 2013 and 2014.

Of the 52 male death certificates where C. difficile was mentioned, 18 recorded it as the underlying cause of death. For females, 24 of the 59 deaths where C.difficile was mentioned also recorded it as the underlying cause.

The age-standardised rates for deaths involving C. difficile tend to fluctuate annually. For all persons, rates increased from 22.6 deaths per million population in 1999 to 164.8 deaths per million in 2008. Rates steadily decreased to 35.8 deaths per million population in 2014, the lowest since 2005.

Both male and female death rates followed this pattern. For males, rates increased from 18.8 per million males in 1999 to a peak of 177.2 deaths in 2008. After this, rates decreased to 41.7 deaths per million population in 2014. The increase in rates between 2006 and 2008 was much sharper than between 1999 and 2005.

A similar trend was observed for females, with rates increasing from 24.4 per million females in 1999 to 157.9 per million in 2008, before falling to 31.2 per million in 2014. As with males, the increase in rates between 2006 and 2008 was much sharper than in previous years. In 2014 the difference between the male and female death rate was not statistically significant (see Figure 1).

The majority of deaths where C. difficile is mentioned on the death certificate occur in elderly people. As people get older, they are more likely to be exposed to factors which increase their risk of contracting a C. difficile infection, such as suffering underlying health problems including cancers or chronic renal disease, exposure to longer periods of hospitalisation, and antibiotic use (NICE, 2013).

In the period 2012 to 2014, the age-specific death rate for all persons aged 85 years and over was 995.3 per million population, compared with 1.0 per million population for those aged under 55 years. There was no statistically significant change in rates for people in age groups under the age of 65 years over time. For those in age groups over 64 years, there were statistically significant changes, with rates initially increasing before peaking in the late 2000s and then decreasing. The same is true for both male and females separately.

For males, the highest rate was in the period 2007 to 2009 for those aged 85 years and over (2,634.3 per million males). This was 3 times higher than the rate for those aged 75 to 84 years over the same period. The highest female rate was in the period 2008 to 2010 (2,777.1 per million population) this was almost 4 times higher than the rate of those aged 75 to 84 years over the same time period (see Figures 2 and 3).

Deaths involving C. difficile accounted for 0.5% of all deaths registered in Wales in the period 2012 to 2014.

A breakdown by place of death shows that 96% of deaths involving C. difficile in Wales occurred in NHS hospitals. These deaths represent 0.8% of deaths in NHS hospitals over the period. A similar pattern was observed in each period between 2001 to 2003 and 2012 to 2014. Most deaths occur in NHS hospitals, so it is expected that the proportions of C. difficile deaths would be higher in NHS hospitals than in other establishment types.

Although relatively small in comparison to NHS Hospitals, care homes consistently had the second highest proportion of deaths involving C. difficile over time (see Table 2).

The information used to produce mortality statistics is based on the details collected when deaths are certified and registered. In Wales, deaths should be registered within five days of the death occurring, but there are some situations where this isn’t possible. Deaths considered unexpected, accidental or suspicious will be referred to a coroner, who may order a post-mortem or carry out a full inquest to ascertain the reasons for the death.

Statistics on deaths involving C. difficile are presented based on the number of deaths registered in each calendar year, rather than deaths that occurred in each calendar year. This method is used because there is a requirement for consistent and timely data, despite a potential limitation in the data quality if registrations are delayed.

In 2014, the average (median) number of days between date of death and death registration for deaths mentioning C. difficile and where it was identified as the underlying cause of death was 3 days. The majority of deaths mentioning C. difficile and those identifying it as the underlying cause were registered in 5 days (84% and 76% respectively) while 94% and 90% were registered within 30 days.

Figures for deaths involving C. difficile from 1999 to 2014 can be found in the reference table on the ONS website. This Excel workbook contains the following results for Wales:

• number of death certificates with Clostridium difficile mentioned and as the underlying cause of death, Wales, deaths registered between 1999 and 2014

• age-standardised mortality rates (with 95% confidence intervals) for deaths where Clostridium difficile was mentioned on the death certificate, by sex, Wales, deaths registered between 1999 and 2014

• number of deaths where Clostridium difficile was mentioned on the death certificate by place of death, Wales, deaths registered between 2001 to 2003 and 2012 to 2014

• age-specific mortality rates (with 95% confidence limits) for deaths where Clostridium difficile was mentioned on the death certificate, by age and sex, Wales, deaths registered in 2001–03 and 2012–14

The information used in this bulletin is based on the details collected when deaths are certified and registered. All deaths are coded by ONS according to the International Classification of Diseases (ICD) produced by the World Health Organisation (WHO). In the Tenth Revision (ICD-10), there is a specific code (A04.7) for ‘Enterocolitis due to Clostridium difficile’. While this code identifies the vast majority of deaths involving C. difficile, a small number of C. difficile-related deaths are not captured by this code alone.

Since 1993, ONS has stored the text of death certificates on a database, along with all the ICD coding relating to causes identified on the death certificate. This means that it is possible to identify records where C. difficile is mentioned, but is not coded under the specific ICD-10 code. ICD-10 has been used to code deaths in Wales since 2001.

In addition to extracting all deaths related to the specific A04.7 ICD-10 code, deaths mentioning other codes to which diseases including C. difficile could be coded were also extracted. The text of these death certificates was searched manually for mentions of Clostridium difficile, C. difficile or pseudomembranous colitis. The ICD-10 codes used to select deaths in order to search manually are shown in Box 1.

Deaths registered in 1999 were coded to both ICD–9 and ICD–10 as part of a special study to compare the two ICD revisions.

Deaths with an underlying cause of C. difficile were identified by selecting those deaths with a mention of C. difficile that also had an underlying cause of one of the following ICD-10 codes: A04.7, A41.4 and A49.8. Death certificates that mention C. difficile and record the code A09 (diarrhoea and gastroenteritis of presumed infectious origin) as the underlying cause of death are also taken to indicate that C. difficile was the underlying cause of death.

Since 1986, ONS has used the internationally recommended death certificate for neonatal deaths (infants under 28 days). This certificate was only designed to record all conditions found at death. This means that neonates cannot be assigned an underlying cause of death. However, as the data were based on deaths where C. difficile or pseudomembranous colitis was mentioned on the death certificate, neonates have been included. Neonatal deaths were extracted in the same way as described for post-neonatal deaths.

C. difficile deaths in Scotland are published by National Records of Scotland and figures for Northern Ireland are published by the Northern Ireland Statistics and Research Agency.