Fichas técnicas aplicadas a la infraestructura

Prevalence surveys can be a useful tool to provide a snap-shot of the burden of disease (Coello et al., 2011), providing a picture of existing and new occurrences of healthcare-associated infection (Farmer and Miller, 1991). Gathering data on the epidemiology of infections through surveillance is considered an essential and important part of the overall management of healthcare infections (Gould and McDonald, 2008). Prevalence surveys differ from incident reporting, in that the latter method provides information on the number of new cases only that occur during a specified period in a defined population (Farmer and Miller, 1991). Prevalence surveys are easier, less expensive and less time consuming to perform than incident reporting, can be undertaken on a large scale (Humphreys and

Smyth, 2006) and can supplement other surveillance methods (The RAISIN Working Group, 2009).

Within Europe, the estimated incidence of healthcare-associated infection ranges from 4% to 10% of hospital admissions (Pratt et al., 2003) and within developing countries the rate has been estimated to exceed 25% (Pittet et al., 2008). In the United States in 2002 an estimated 1.7 million patients developed a healthcare- associated infection (Klevens et al., 2007) and reported mortality rates increased from 5.7 per million in 1999 to 23.7 per million in 2004 (Karas et al., 2010). In Canada an estimated 22,000 healthcare infections occur each year (Gould et al., 2010), contributing to the fourth leading cause of death within the country (Baker et al., 2004). Within the UK in 2004, the Department of Health estimated that there were 300,000 healthcare-associated infections each year (House of Commons Committee of Public Accounts, 2005), costing over a billion pounds annually (National Audit Office, 2009). In 2007, approximately 9,000 deaths were recorded in the UK with methicillin-resistant Staphylococcus aureus blood stream infections or Clostridium difficile infections as the underlying cause or contributory factor (Office for National Statistics, 2008).

Within the epidemiology literature the strengths of using prevalence surveys have been highlighted. Gastmeier et al. (2000) reported that repeated surveys can provide a baseline from which improvements with infection control programmes can be measured and priorities identified to focus resources (Humphreys and

Smyth, 2006). France reported improvements in their five yearly prevalence survey rate, from 6.7% in 1996 to 4.9% in 2006 (Carletet al., 2009). Muhlemann et al.(2004) reported that repeated surveys are a simple, cost effective method of benchmarking rates between hospitals and this is important to encourage learning. Various studies have reported that the prevalence of infection varies by speciality (Fitzpatrick et al., 2008; Klavs et al., 2003) suggesting the importance of implementing hospital wide infection control policies and standard precautions (Reillyet al.,2008).

Despite the strengths of using a prevalence survey as a surveillance tool, there are various limitations that need to be considered. Firstly, the rate determined is a crude estimation of infection which can vary depending on the type of establishment and the case mix. For example, a seven day survey in Switzerland in 1998 reported an overall prevalence of 11.3%, with 8.4% in acute wards and 16.4% in chronic wards (Sax et al., 2001). Secondly, as national prevalence surveys are expensive and time consuming, point prevalence surveys are more likely to be undertaken (Coelloet al., 2011), which may only include a sample of settings (type of hospital or unit) and sample of infections and the results may not be generalisable. Thirdly, although the definitions of infection used may be agreed within a country, for example the 1994 survey undertaken within the UK was agreed within a steering group (Emmerson et al.,1996), the definitions used may not be comparable with other internationally agreed definitions. Wilson et al. (2004) reported that the mean percentage of wounds infected varied depending on the definition of surgical wound used. Therefore, the differences in the data

collected, the definitions used to identify infection and the period over which data is collected may to some extent explain why rates of infection vary between countries. For example, Germany reported a prevalence rate of 3.5% and 4% respectively (Gastmeier, 1998, 2000), yet only confirmed cases of infection were included, which may partly explain their low rate compared with other countries (Humphreys and Smyth, 2006). A national prevalence survey undertaken in Spain (Rossello-Urgell et al., 2004), using data from surveys carried out from 1990- 2002, reported that the results varied depending on the day of the week in which the survey was undertaken. Rossello-Urgell et al. (2004) reported a rise in prevalence of healthcare infection as the week progressed, with the highest prevalence being Saturday – Monday. The authors suggest that patients who contract healthcare infection become progressively worse as the week progresses, and discharge on a Friday may therefore be postponed. They use this to explain why a higher rate of infection may be detected over the weekend, and advise that surveys are carried out Tuesday-Friday, preferably on the same day, to avoid changes in admission/discharge rates that can occur throughout the week. Results may also differ depending on the use of antibiotics (Jodra et al., 2006), or the implementation of infection control measures such as hand hygiene(Struweet al., 2006). These examples highlight the caution that needs to be taken when comparing prevalence rates between countries due to differences in the surveillance approach used (Prattet al., 2003).

In 2006 a prevalence study was undertaken in the UK and the Republic of Ireland for the first time using internationally agreed definitions from the Centres for

Disease Control. The rate was found to be 7.6% (Humphreyset al., 2008; Smyth et al., 2008) compared with a reported rate of 19.1% in 1980 (Meers et al., 1981) and 9% in 1994 (Emmerson et al., 1996). Scotland was excluded as it used a different methodology (Reilly et al., 2008). Argentina carried out a prevalence survey in 2008 using an identical methodology employed by the UK (Smythet al., 2008) yet differences in their sampling strategy and case mix make comparisons difficult (Durlachet al., 2012). The overall prevalence rate of healthcare infection within Argentina was found to be 11.30% (Durlach et al., 2012), which is much higher than the level found within the UK (7.6%). These differences could be due to environmental factors, standard of hygiene, difference in infrastructure and equipment, relationship between staff and patients, differences in knowledge and implementation of infection control measures (Durlach et al., 2012). For example, Struwe et al. (2006) compared a point-prevalence survey undertaken in Sweden (Huddinge), Latvia (Riga) and Lithuania (Vilnius). The rate of healthcare infection was higher in Huddinge (15%) despite easier access to hand disinfectants. Whereas, staff in Riga (3%) and Vilnius (4%) were encouraged to use pocket containers of alcohol hand rub because of lack of hand wash basins. This suggests that even though the comparison of crude infection rates may not seem meaningful (because of the reasons already explained), comparisons between countries can contribute to valuable discussions about the quality of care.

There has been pressure for the standardisation of methods with agreed definitions of infection to facilitate direct comparisons between countries, within countries or institutions over time (European Centre for Disease Prevention and Control,

2008). In May/June 2011 - May/June 2012, the European Centre for Disease Prevention and Control led a point prevalence survey of healthcare infection within acute hospitals. All participating EU countries for the first time used standardised methodology to enable comparisons to be made from the results. All European countries were encouraged to participate however taking part was voluntary. The survey will be repeated every five years and the results of the first survey are due to be released shortly (European Centre for Disease Prevention and Control, 2012).

Data on levels of MRSA infections as a proportion of all Staphylococcus aureus bloodstream infections indicate that the UK has one of the highest levels in Europe (European Antimicrobial Resistance Surveillance System, 2007) (See Table 1). In comparison, the Netherlands and Denmark have the lowest levels of

methicillin-resistant Staphylococcus aureus. This has been attributed to their strict ‘search and destroy’ policy, whereby carriers and infected persons are identified by screening and treated in isolation using barrier precautions (Wagenvoort, 2000).

Denmark 0.8% France 28.5%

Netherlands 1.4% Portugal 48.4%

Austria 9.2% Italy 38%

Germany 16.3% Greece 48%

Spain 25.5% United Kingdom 35.6%

Source:European Antimicrobial Resistance Surveillance System data for 2007

Epidemiological data forClostridium difficileis sparse within Europe. To provide a more complete overview Bauer et al. (2011) carried out a prospective study within 34 European countries to test for C.difficile. In November 2008 a web based questionnaire was used to gather additional information about the infection after diagnosis and 3 months post diagnosis. This was undertaken with a maximum of ten of the first patients to be diagnosed per hospital. A high follow up rate (90% was achieved). Because only the first ten patients per hospital were included in the survey and hospitals were selected in relation to size rather than chosen randomly, the results may not be representative of each country. Some hospitals may have been selected because of outbreaks and no attempt was made to differentiate between relapses and re-infection (Bauer et al., 2011), therefore bias may have been introduced. The authors reported that the incidence of C.difficile infection and the causative organism varied greatly between hospitals across Europe. They reported an overall figure of 4.1 per 10,000 patient days which is higher than the overall figure of 2.45 per 10,000 patient days reported by

Table 1: Proportion of

Staphylococcus aureusblood isolates