Practice and ethnic variations in avoidable hospital admission rates in Christchurch, New Zealand

Abstract

Using hospital admissions data for 2005–2007 this paper examines variations in avoidable hospital admission rates between general practitioner surgeries in Christchurch, New Zealand. There is a substantial variation in rates between surgeries which largely reflects the influence of material deprivation and also the independent effect of ethnicity. By contrast, other quantitative measures of primary care provision were insignificant. There was also a wide variation between practices in the uptake of Care Plus funding for patients with chronic conditions. Practice deprivation, ethnicity and age only explained a minor part of this variation. The findings suggest a need for possible strategies, in particular a greater targeting of funding to high risk patients in more deprived practices, to reduce hospitalisation. The wide variability in general practice use of hospital services needs further study to identify possible individual and contextual explanations.

Introduction

Reduction of hospital admissions through greater intensity of care in the primary care sector has been strongly emphasised in many countries including New Zealand. A considerable body of research has begun to emerge which demonstrates that hospital admissions can be halved through more effective use of primary health care (PHC) (Feachem et al., 2002; Basu et al., 2002; Lindström et al., 2003; Niti and Ng, 2003; Bermudez-Tamayo et al., 2004; Saha et al., 2007; Dias-da-Costa et al., 2008). A key factor in this strategy is the organisational integration of primary and secondary care which has become an important issue in many countries (Crooks and Andrews, 2009).

Despite the importance of reducing hospital admissions, there has been little research which has examined variations, especially ethnic ones, in hospital admission rates between general practices. While studies of medical practice variation are well documented in primary and secondary care, both in New Zealand (Davis et al. 1999, Davis et al. 2002; Love et al., 2004; Brown and Barnett, 1992) and elsewhere (Wilkin and Smith, 1987; Adams et al., 2003; Alberti et al., 2004; Sirovich et al., 2005; Verstappen et al., 2005), there have been few studies which have specifically examined links between the two. Those which have been conducted suggest that socio-demographic characteristics of general practitioner (GP) surgeries explain most of the variation in hospitalisation rates and that other practice characteristics add very little (Slack et al., 1997; Reid et al., 1999; Saxena et al., 2006). By contrast, Congdon (2006), after controlling for need factors, found significant variation in admission rates across areas and GP practices in London and suggested that the remaining differences could be due to staffing, resourcing and access issues. Other studies, such as Casanova and Starfield (1995), Majeed et al. (2002) and Bottle et al. (2008), also found that variations in different types of surgical procedures between primary care groups in England were poorly explained by differences in both population and practice characteristics and suggested that the underlying reasons for such variations needed to be better understood. If variation in admission rates cannot be accounted for by differences in patient morbidity then questions arise regarding equity of access to hospital care, appropriateness of hospital referrals and admissions and the effectiveness of primary care.

The emergence of chronic care management programmes has recently been an important part of PHC initiatives to limit hospitalisation rates in many countries. While there have been a number of studies which have examined the effects of such programmes on health outcomes and effects on hospitalisation rates (for example, Tiep et al., 1998; Lorig et al., 1999; Pushparaiah et al., 2006; Dennis et al., 2008), there has been little research which has explored equity issues associated with their implementation (Barnett et al., 2006). Those which have been undertaken suggest that GP interventions may be poorly targeted and often less developed in more deprived areas (Khunti et al., 2001; Williams et al., 2004; Sirovich et al., 2005). In view of such trends, Beaglehole et al. (2008) have argued that more evidence is needed about the cost effectiveness of prevention and treatment strategies in primary health care and the success of such interventions in limiting hospitalisation rates.

Hospitalisation for ambulatory care-sensitive conditions (ACSH or ASH), also called ‘potentially preventable’ or ‘avoidable’ hospitalisations, has been used extensively as an indicator of the accessibility and overall effectiveness of PHC (Ansari et al., 2006; Caminal et al., 2004). The indicator is commonly used by governments to provide an evidence-based foundation for targeted interventions designed to control costs and improve PHC effectiveness. The majority of potentially avoidable hospitalisations involve conditions that could have been identified and treated earlier by either primary health care or public health interventions and thus prevented, or at least limited, the necessity for hospital care. Not surprisingly, ASH admissions often tend to be higher among disadvantaged populations and ethnic groups with the worst access to primary care (Pappas et al., 1997; Laditka et al. 2003, Laditka et al. 2005; Roos et al., 2005; Gusmano et al., 2006). In the light of such trends, Chang et al. (2008) have argued that the variation in ASH admissions across racial categories and the extra risks on the part of such groups associated with chronic conditions deserve greater attention.

However, there has been some debate regarding the effects of PHC upon hospitalisation rates. While some studies have reported links between better primary care and reduced rates of hospital admission (Clark, 1990; Gottlieb et al., 1995; Nakanishi et al., 1996; Friedman and Basu, 2001; Niti and Ng, 2003; Frederico and Macinko, 2009), others have not (Parchman and Culler, 1994; Slack et al., 1997; Reid et al., 1999; Saxena et al., 2006). For example, in contrast to Cloutier-Fisher et al. (2006), both Ricketts et al. (2001) and Laditka et al. (2005) found that there was no strong relationship between rural ASH rates and the level of primary care resources. Others have also suggested that ASH admission rates may also depend, at least in part, on hospital admission policies and have emphasised the need for careful review of the choice of specific ASH indicators in different types of health care systems, especially when such indicators are intended as a measure of the performance of PHC. Thus variability in both ASH criteria and in factors associated with hospitalisation rates raises questions regarding the extent to which ASH hospitalisations are actually preventable by PHC.

Despite these caveats, the study of GP practice variations in hospitalisation rates is timely, especially in view of the need to evaluate the effect of organisational changes in general practice upon admission rates. In New Zealand two recent policy initiatives are important in this regard: the New Zealand Primary Health Care Strategy (King, 2001) and the implementation of chronic care management programmes designed to limit hospitalisation. With respect to the first initiative, of significance has been the growth of ‘third sector’ primary heath organisations (PHOs), which represent a movement beyond a narrow general practice model towards a broader conceptualisation of primary care. This has been an important development, aimed at reorienting patterns of service delivery to encompass greater community participation (Kearns and Neuwelt, 2009) and producing more equitable access to primary care, particularly for vulnerable populations (Barnett and Barnett, 2009).

The second important initiative of the Primary Health Care Strategy has been the development of the new nationally based chronic care management programme, Care Plus. First introduced in 2004, Care Plus seeks to provide additional funding for PHOs to give better care to people who have high health needs by creating improved teamwork and improving the management of patients with chronic conditions that need ‘intensive clinical management’ (Ministry of Health, 2004). Because Care Plus has a ‘health’ rather than a ‘disease’ focus, it should also have positive outcomes in terms of a reduction in health inequalities and in unnecessary hospital admissions. Care Plus differs from the longer established High Use Health Card (HUHC) in that it co-ordinates a comprehensive approach to improve outcomes for people with chronic conditions whereas the HUHC is an individual subsidy-based approach tied to the number of GP visits. Care Plus patients are also different from HUHC holders in that they are usually people who previously accessed care less frequently than was clinically desirable (Ministry of Health, 2006).

However, there has been little evaluation of both of these initiatives. Despite some recent research (Ministry of Health, 1999; Barnett and Lauer, 2003; Dharmalingham et al., 2004; Sheerin et al., 2006; Copeland, 2009) there have been no analyses of GP practice variations in avoidable hospitalisation rates nor of their links to patterns of ethnic disadvantage. The need for such research has become more important in view of the development of the PHO Performance Management Programme (Ministry of Health, 2007), which itself has only recently been evaluated (Martin Jenkins, 2008). An important criticism has been the absence of any indicator of avoidable hospitalisation in the initial Ministry of Health evaluation criteria. Similarly while there has been a recent evaluation of Care Plus (Ministry of Health, 2006) and that this showed that Care Plus is reaching Maori and Pacific patients than at greater rates than for other population groups, there was no assessment of the degree to which special access funding is related to practice need. This is highest in the most disadvantaged neighbourhoods, especially those with high proportions of Maori and Pacific Island persons who report the poorest self-rated health (Ministry of Health, 2008).

In view of such criticisms, this paper has three main objectives:

• To examine the level of variation in avoidable hospital admission rates between general practices.

• To determine the extent to which practice variations in hospitalisation rates can be explained by patient ‘need’ characteristics, in particular deprivation and ethnicity.

• To assess whether special access (Care Plus) funding is associated with practice need characteristics and reduced risks of hospitalisation.