Introduction

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The important and necessary involvement of general practice in diabetes care is well recognised.^1-5 Since 1970, increasing numbers of family doctors in the United Kingdom have assumed responsibility for the routine review of their patients with diabetes, for a variety of underlying reasons, although it is sometimes difficult to assess whether care has been shared or simply shifted. ^{3 6}

Evaluation of diabetes care in the community has produced conflicting results. Satisfactory follow up in primary care has been far from universal and cannot be guaranteed,^7-9 but in certain circumstances general practitioners have achieved follow up and metabolic control at least as good as their hospital colleagues.^10-12

This study aimed to identify and evaluate all published randomised trials of hospital versus general practice care for people with diabetes, to compare the effectiveness of general practice and hospital care through the use of meta-analysis of the identified trials, and to explore variations in the findings of the individual trials.

	Methods

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Identification of relevant trials
Eight bibliographic and research databases were searched. The medical subject heading "diabetes" was combined with each of the terms in the box to identify all studies, in any language, indexed on Embase, CRIB, or Dissertation Abstracts. The search terms were then combined with the Cochrane Collaboration strategy for identifying randomised trials¹³ on Medline, National Research Register, CINAHL, PsychLit, and Healthstar. Finally, bibliographies of trials identified by computerised search were hand searched for further references to trials. Studies were included in which people with diabetes (insulin dependent or non-insulin dependent) were randomly allocated to hospital or to general practice or shared care for routine review and surveillance for complications, regardless of the quality of concealment of allocation or choice of outcome measures.

Data extraction
Descriptive data about each trial were extracted from the published reports; original authors were contacted for clarification when details about randomisation were not reported. Values for the following outcomes, where available, were extracted for hospital and general practice groups: means (and standard deviations) for glycated haemoglobin, final systolic and diastolic blood pressure, patient and health service costs, the number of diabetes reviews and glycated haemoglobin estimations per patient per year, and the numbers of patients dying, admitted to hospital, referred to dietitians and chiropodists, and lost to follow up. Losses to follow up were calculated as the mean number not attending each of the three stipulated interim appointments between annual reviews in one study¹⁴ and the number with no record of an annual review in the rest.

Statistical methods
Peto odds ratios, weighted difference in means, and ² tests of intertrial heterogeneity were calculated by using the fixed effects model of the Cochrane review manager software.¹⁵ The denominator used to calculate effect sizes for mortality, follow up, and hospital admissions was the number of subjects randomised. The denominator for the remaining effect sizes was the number of subjects in whom that outcome had been assessed.

Sensitivity analysis
To determine if the findings were robust to different analyses, a random effects model was used, and the numbers of subjects randomised and the numbers in whom the outcome was assessed were substituted into the denominator for each of the comparisons. A stratified analysis was performed according to whether the model of shared care was basic or computer assisted (with a central computer to prompt both family doctors and patients to undertake protocol driven diabetes reviews), after the taxonomy of Hickman et al.¹⁶ In addition, trials were stratified by publication year, the proportion of local practices taking part, and whether patients treated with insulin were included.

	Results

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The combined searches identified over 1200 studies, but only five met the inclusion criteria (table 1). All five trials used satisfactory randomisation of individual subjects, but they were of short duration, only one lasting more than 2 years.¹⁷ In aggregate, 1058 people seen in hospital diabetes clinics were eligible and agreeable to randomisation to continuing hospital outpatient review or follow up in the community, either by their family doctor alone or as part of a shared care scheme. The organisation of care for the hospital outpatient group was not clearly defined, although the descriptions seem broadly similar. All the general practitioners were provided with educational sessions or protocols before the trials. However, the support for care in general practice changed over time. Two studies published in the 1980s evaluated basic general practice care, ^{17 18} two more recent studies included computer prompting systems, ^{19 20} and one recent trial by Hoskins et al compared both basic and prompted general practice care with hospital care and is therefore included in the table as two separate studies.¹⁴

View larger version (24K): [in this window] [in a new window]   Fig 1.   Weighted difference in mean percentage of glycated haemoglobin between general practice and hospital care. Bars indicate 95% confidence intervals

View larger version (21K): [in this window] [in a new window]   Fig 2.   Odds ratios of mortality in general practice and hospital care. Bars indicate 95% confidence intervals

In the four studies that reported patients' age and sex, the overall mean age was 58.4 years, with no significant difference between groups (weighted difference in mean ages 0.26 years, 95% confidence interval 1.25 to 1.77, ² test of between trial heterogeneity 3.36, P>0.3); 44.2% of the subjects were female. ^{14 17 19 20} Patients were free of "significant diabetic complications or serious medical conditions," and only a minority of subjects (124, 12.2%) were treated with insulin. ^{14 19 20}

The report of Porter's study provided data only on mortality, although it was stated that "no statistically significant differences could be demonstrated between the two groups (hospital and general practice care) in any of the biochemical or clinical indicators selected for measurement."¹⁸

Meta-analysis

Metabolic control
Overall, there was no significant difference in metabolic control of patients receiving general practice and hospital care (fig 1; the weighted difference in mean glycated haemoglobin was 0.005% (0.26% to 0.25%). The mean glycated haemoglobin in the general practice group was equal to or less than that of the hospital group in all three studies that evaluated prompted care. ^{14 19 20} This heterogeneity between trials was confirmed by the ² value of 17.0 (P<0.001).

Mortality
Two patients in the Hoskins trial who died were excluded from analysis and their treatment group was not reported. A total of 84 patients died during the remaining studies, significantly more in the general practice group (odds ratio 1.75, 1.11 to 2.74) (fig 2). Mortality remained significantly higher in primary care even if the two patients from the Hoskins trial were assigned to the hospital care group. Mortality varied between studies (²=3.74, P>0.25), with most of the excess deaths in general practice care accounted for by the two earlier trials of care without prompting. ^{17 18}

Losses to follow up
Patients randomised to general practice care were more likely to be lost to follow up (odds ratio 3.05, 2.15 to 4.33). This finding was accounted for almost entirely by the early study by Hayes,¹⁷ in which no organised system for recall was set up in general practice (²=114.8, P<0.0001), supporting a stratified approach to analysis (see below).

Hospital admissions
Only two studies reported usable data for hospital admissions: the earlier study favoured hospital care and the later one favoured prompted general practice care. ^{17 19} In addition, the diabetes integrated care evaluation (DICE) study, without reporting raw data, found no significant differences between prompted general practice and hospital care in unscheduled diabetes consultations or diabetes related hospital admissions.²⁰

Blood pressure
Systolic and diastolic blood pressure did not differ between the prompted and hospital groups in two studies that included this variable (table 2). ^{14 20}

Reviews and referrals
Two of the recent studies showed that patients were reviewed more often in the prompted group than in hospital outpatient departments and were tested more frequently for glycated haemoglobin (table 2) but were less likely to be referred to the dietitian (table 3). More chiropody referrals were made in the prompted group (table 3); however, as the two trials produced conflicting results for this outcome, the pooled data are unreliable. ^{19 20}

Costs
Data on costs were not comparable between studies. Both studies that assessed costs borne by patients reported that they were lower in the community. ^{18 20} As regards the health service, basic general practice care cost about half as much as hospital care ^{14 18} ; prompted general practice care was found to be cheaper than hospital care by Hoskins¹⁴ but more expensive than hospital care in the DICE study.²⁰

Stratified analysis
The studies fell into two categories based on the presence or absence of central, computerised prompted recall for patients and professionals in general practice. This division was supported by the heterogeneity of glycated haemoglobin results (fig 1) and mortality (fig 2). The between trial heterogeneity identified for each outcome when all trials were included in the analysis almost disappeared when trials of prompted care were considered separately (for glycated haemoglobin ²=3.90, P>0.10; for mortality ²=0, P=1.0; and for losses to follow up ²=1.63, P>0.30).

	Discussion

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Meta-analysis based on a few small trials should be treated with caution, but this study suggests that prompted general practice care of people with diabetes, in certain circumstances, can be as good or better than hospital care. Furthermore, as losses to follow up were significantly higher from the hospital than from prompted general practice care and these defaulters tend to have poor outcomes, ^{21 22} the other comparisons may underestimate the achievements of prompted care in general practice.

Generalisability
The study populationpatients who were happy to attend hospital clinics, had no diabetic complications or serious medical conditions, and were prepared to be randomisedrepresented between 38%¹⁹ and 88%²⁰ of clinic attenders. Furthermore, the representativeness of the general practice participants was variable, from just three practices,²⁰ through half,¹⁸ to almost all local practices becoming involved. ^{14 17} Thus conclusions from the meta-analysis should be generalised with caution. There is certainly little evidence to support the existing degree of general practice responsibility for diabetes care. Stratification of trials by the proportion of local practices involved did not explain interstudy heterogeneity.

Selection bias
The five trials were published in two of the journals that have been extensively hand searched. ^{23 24} The search strategy identified the same randomised trials and most non-randomised studies cited in a comprehensive systematic review including personal communication with authors.³ Thus publication bias and selective identification of positive studies are unlikely to explain the heterogeneity.

Sources of heterogeneity
Although stratifying by prompted or routine care explained the statistical heterogeneity, there are potential alternative explanations. The prompted care trials all reported in the past 5 years, so any variation could be a function of time. Fortunately, one recent study included both a prompted group (Hoskins 1) with better outcomes and a routine general practice care group (Hoskins 2) with rather poorer outcomes.¹⁴ Although the delivery of diabetes care by family doctors has undoubtedly improved over the past 20 years, time does not explain the heterogeneity and central prompting seems to confer additional benefit.

Other limitations of meta-analysis
The relationship between a complex, multivariate intervention (for example, introducing prompted care) and mortality or glycaemic control is unlikely to be linear; hence meta-analysis may produce imprecise estimates of effect size.²⁶ In addition, data were extracted by just one author. However, it is reassuring that the findings are consistent with earlier reviews. ^{3 27} Perhaps the traditional literature review with meta-analysis for a few key outcomes provides a suitably balanced perspective. Furthermore, the heterogeneity between studies, and possible explanations for it, provide the main conclusion. Meta-analysis can magnify biases in original reports, and it attributes similar weight to findings from excellent and mediocre studies. This meta-analysis included all randomised studies to avoid subjective judgments of trial quality or arbitrary choices of an inclusion threshold based on explicit assessment criteria. ^{26 28}

Limitations of the trials
One concern is whether these outcomes can be maintained in the long term. Clearly, 14 years ago in Cardiff, patients lacking regular prompted recall were worse after 5 years.¹⁷ As no other studies lasted longer than 2 years and the Hayes trial was responsible for much of the heterogeneity, this needs further research, as does the cost effectiveness of prompted care. Research should consider the potential duplication of care in the hospital and community and the balance between extra expenditure early on, as unmet need is identified, and longer term savings as expensive complications are avoided. ^{11 29} The extent to which the differences in process measures identified in this review influence the inexorable progress of diabetes remains unclear.³⁰ Nevertheless, the variation in long term outcomes seen in these trials, and in other studies, ^{8 31} suggests that the organisation and delivery of care for this costly and increasingly common chronic disease are extremely important.³²