Department of General Psychiatry, St George's Hospital Medical School
MRC Biostatistics Unit, Institute of Public Health, Cambridge
Centre for the Economics of Mental Health, Institute of Psychiatry, London
Department of General Psychiatry, St George's Hospital Medical School, London
School of Psychiatry and Behavioural Sciences, Manchester Royal Infirmary
Institute of Psychiatry, King's College, London, UK
Correspondence: Professor Tom Burns, Department of General Psychiatry, St George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK. Tel: 020 8725 5547; fax: 020 8725 3538
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ABSTRACT |
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Aims To test whether patients successfully exposed to a minimum of 12 months' intensive case management over the 2-year follow-up period achieved reduced hospitalisation.
Method Of 679 participants with hospitalisation data, 84 were identified as having < 12 months' exposure owing to prolonged hospitalisation, imprisonment or a combination of the two. These patients were excluded and outcomes tested for the remaining 595 patients.
Results Overall reduced case-load size did not reduce hospitalisation or treatment costs over 2 years despite elimination of outliers. Age, previous hospitalisation and source of recruitment to the study all correlated with outcome.
Conclusions Case-load reduction is not in itself enough to reduce the need for hospital care in psychosis. Baseline patient characteristics (in particular length of previous hospitalisation and recruitment from in-patient care) have a significant influence and should be allowed for in power calculations. Identifying the optimal clinical profile for patients likely to benefit from intensive case management remains a pressing need for further studies.
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INTRODUCTION |
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METHOD |
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Information on the use of all hospital and community services was collected for each patient over the 2-year follow-up period. A number of sources were used, including event records of community mental health team activities, clinical records, patient interview at 1- and 2-year follow-up, local authority social services departments, and questionnaires completed by case managers. Where possible, unit costs were calculated on the basis of information provided by the relevant local service providers. Unit costs of services that could not be determined locally and those of relatively small service components were taken from national publications. All unit costs were calculated for the financial year 1997/8 and future costs were discounted at an annual rate of 6% (UK700 Group, 2000).
Identification of non-exposure
Patients could fail to receive their allocated form of case management
(whether intensive or standard case management) for any one or a combination
of three reasons: prolonged in-patient stay, prison, or loss of contact
through refusal, changing address or in a few cases where
major changes in their clinical condition required transfer to another service
(e.g. transfer to secure services after a violent offence, or transfer to a
rehabilitation team when schizophrenia had become complicated by a stroke
requiring residential care). The actual dates when patients dropped out of
contact and (where applicable) resumed contact were recorded by case managers.
Duration of in-patient and prison stays, however, were obtained directly from
the modified World Health Organization life chart
(World Health Organization,
1992) at the 24-month follow-up. Although the duration of these
stays was accurately recorded, their dates were not. To deal consistently with
these two types of data we developed a convention for computing days
unexposed in the community. We assumed that:
Total days unexposed to case management were the sum of days in hospital, days in prison and days unexposed in the community.
Associations with baseline variables
In testing for identifiable patient characteristics associated with shorter
exposure to case management, we considered the baseline variables used in the
original outcome study: age, gender, centre, ethnic group, father's occupation
at birth; months since onset, point of entry (in-patient or out-patient), days
in hospital over the previous 2 years; scores on the Comprehensive
Psychopathological Rating Scale (Asberg
et al, 1978), Disability Assessment Scale
(Jablensky et al,
1980), Lancashire Quality of Life Profile
(Oliver et al, 1997)
and Camberwell Assessment of Need (Phelan
et al, 1995) (unmet needs) scores; and user satisfaction
(UK700 Group, 1999). These
variables were entered into multiple regression analyses in which the outcomes
were the numbers of days unexposed overall and in each category (in-patient,
in jail, unexposed in the community). Any variable that was significant at the
10% level for any one outcome was included in the models for all four
outcomes. Randomised allocation was not significant at this level for any
outcome.
Estimated intervention effect
We estimated the effects of intensive case management compared with
standard case management in patients who were exposed for at least 50% of the
follow-up period. This is not a comparison between randomised groups, and thus
there is potential for selection bias if the groups differ in terms of
baseline factors that might influence the outcome of the evaluation. To reduce
selection bias we adjusted for the baseline variables that predicted days
exposed, singly and jointly. Dummy variables for missing baseline variables
were used to keep the sample size the same in all these analyses. Costs were
highly skewed so bootstrap methods were used to check the validity of the
confidence intervals (Efron &
Tibshirani, 1993); these gave similar results to standard methods,
so the latter are reported.
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RESULTS |
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Figure 2 displays the rates of unexposure by site, type of case management and cause. It can be seen that there are marked variations in the proportions of patients unexposed in the community across the sites. St Mary's had almost no patients unexposed in the community in either intensive or standard case management, while at the other extreme nearly 20% of King's College intensive case management patients were unexposed in the community. In the regression analyses (Table 1), these differences between centres are statistically significant both for all days unexposed and for days unexposed in the community, after adjusting for other predictors of exposure.
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Baseline associations with non-exposure
The multivariate analysis identified several further independent predictors
of exposure (Table 1). Younger
patients had significantly more time unexposed because of being in hospital or
in prison. Men had greater exposure overall because they were less likely to
be lost to contact, despite spending more time in prison on average. Patients
with longer periods of hospitalisation in the 2 years before the randomisation
tended to have further prolonged hospitalisation, as did those recruited to
the study from hospital rather than from team community case-loads. Patients
recruited at discharge from in-patient care also had more loss to contact in
the community. Patients who were more symptomatic at recruitment spent more
time in hospital and less time in prison than those who were less symptomatic.
A higher reported baseline quality of life was associated with significantly
less time in prison.
Intervention effects
Table 2 lists the
differences between the mean hospital days in intensive case management and
standard case management for the 679 patients in the intention-to-treat
analysis and for the 595 patients who had been exposed to more than 12 months
in the community. In the intention-to-treat analysis, intensive case
management patients had a mean of 0.4 more days in hospital over the 2-year
follow-up. For those with more than 50% exposure, intensive case management
patients spent a mean of 11.3 days less in hospital during follow-up. Neither
of these differences was significant, although that for the exposed patients
did show a trend towards significance.
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Adjusting for previous hospitalisation in a regression analysis reduced this difference from 11.3 days to 8.6 days (Table 2). Adjusting for other baseline variables had little impact. After adjustment for all baseline variables simultaneously, patients in the intensive case management arm spent a mean of 9.4 days less in hospital, but with a 95% confidence interval extending from 22.1 days less to 3.2 days more. None of the adjustments was clinically significant. Costs were higher by an average of £173 in patients who had been exposed to more than 12 months in the community, and £720 after adjustment for baseline variables. None of these differences was statistically significant.
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DISCUSSION |
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Selection bias
Analyses other than intention-to-treat should always be viewed with
caution, since they are prone to selection bias. We attempted to reduce
selection bias by adjusting for baseline variables, but bias could still
remain owing to other unmeasured factors which differed between the exposed
groups in the two arms. However, our results agree closely with a comparison
of median hospitalisations. The primary analysis compared mean
hospitalisations, because the investigators believed that the most likely
effect of intensive case management would be to shorten the longer hospital
stays with less impact on shorter stays
(UK700 Group, 1999). It would
appear that the main effect of our analysis is to reduce the impact of the few
patients with very long hospitalisations on a comparison of mean
hospitalisation. There is a need for a simple form of analysis that is
appropriate for interventions expected to have their main impact on longer
hospital stays but not on the very longest stays.
Site variations
There were interesting differences in the causes of non-exposure in the 84
patients. Of these, 57 were unexposed in the community. This
usually means that the case managers were unable to maintain contact with them
because the patient either moved away or consistently refused contact. This
category of patients demonstrated marked variation across the four sites,
which is hard to explain. From examination of contact frequency data
(Burns et al, 2000),
it appears that at least three of the sites had different expectations of
contact frequency and therefore different thresholds for deciding that a
patient was lost to contact. In particular, the St Mary's team demonstrated
lower rates of contact than the King's College or St George's teams, possibly
explaining why they identified fewer patients lost to contact. The original
study protocol enjoined teams to keep patients in their treatment of
randomisation for the whole 2 years if possible. Days unexposed in the
community were also associated with being male and having been recruited from
hospital across the four sites.
Baseline characteristics
Younger patients were significantly more likely to remain in hospital for
longer periods or to be imprisoned. For each year of increasing age patients
spent a mean of 1.9 days less in hospital and 0.5 days less in prison over the
2 years. Duration of hospitalisation in the 2 years prior to randomisation,
not surprisingly, also predicted increased hospitalisation during follow-up
and indeed increased costs (Byford et
al, 2001). Days unexposed because of prison were,
predictably, highly associated with being male and also with being less ill at
baseline. They were also associated with a worse subjective quality of life at
intake.
Overall, this study sustains the conclusions of the main outcome paper (UK700 Group, 1999) that a reduced case-load size alone is not significantly associated with a reduced need for hospitalisation. It confirms that previous hospitalisation is a strong predictor of subsequent protracted hospitalisation, as is recruitment from in-patient care. Power calculations for future studies which may recruit such patients should allow for the likelihood that they will experience less benefit from any case management intervention. Identifying the optimal clinical profile for patients likely to benefit from intensive case management remains a pressing need for further studies.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Received for publication September 19, 2001. Revision received May 3, 2002. Accepted for publication May 8, 2002.
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