Section of Community Psychiatry (PRiSM), Institute of Psychiatry, London
Lewisham & Guy's NHS Trust, Ladywell Unit, Lewisham Hospital, London
Maudsley Centre for Behavioural Disorders, the Bethlem Royal Hospital Beckenham, Kent
The Green, Frant, Tunbridge, Wells, Kent
Ravensbourne Trust, Farnborough, Kent
Department of Psychological Medicine, Institute of Psychiatry, London
Declaration of interest K.X. was supported by the National Health Service Executive (South Thames).
The CANDID is available from the Section of Community Psychiatry (PRiSM), Institute of Psychiatry, De Crespigny Park, London SE5 8AF
Correspondence: K. Xenitidis, Section of Community Psychiatry (PRiSM), Institute of Psychiatry, De Crespigny Park, London SE5 8AF
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ABSTRACT |
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Aim To develop a standardised needs-assessment instrument for adults with learning disabilities and mental health problems.
Method The Camberwell Assessment of Need for Adults with Developmental and Intellectual Disabilities (CANDID) was developed by modifying the Camberwell Assessment of Need (CAN). Concurrent validity was tested using the Global Assessment of Functioning (GAF) and the Disability Assessment Schedule (DAS). Testretest and interrater reliability were investigated using 40 adults with learning disabilities and mental health problems.
Results CANDID scores were significantly correlated with both DAS (P < 0.05) and GAF scores (P < 0.01). Correlation coefficients for interrater reliability were 0.93 (user), 0.90 (carer), and 0.97 (staff ratings); for testretest reliability they were 0.71, 0.69 and 0.86 respectively. Mean interview duration was less than 30 minutes.
Conclusions The CANDID is a brief, valid and reliable needs assessment instrument for adults with learning disabilities and mental health problems.
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INTRODUCTION |
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METHOD |
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The questions in each of the 25 need areas of the CANDID are divided into four sections: Section 1 assesses the absence or presence of need, and, if present, whether it is met or unmet; Section 2 rates the help received from informal carers; Section 3 asks how much help by local services is provided (3a) and needed (3b); Section 4 inquires about the respondent's satisfaction with the type (4a) and amount (4b) of help received from local services.
First draft
Focus groups of service users, informal carers and staff identified areas
of needs relevant to people with learning disabilities and mental health
problems. The users group (n=8) consisted of adults with mild or
moderate learning disabilities who were attending a day centre or were living
in local residential facilities. The carers group (n=7) consisted of
informal carers of people using the above facilities. The staff group
(n=9) consisted of staff from a variety of disciplines working with
people with learning disabilities and mental health problems. The first draft
of the instrument was developed using findings from these focus groups.
Second draft
The first draft was commented on by health and social services
professionals (n=24) with expertise in working with adults with
learning disabilities and mental health problems. These consultations were
conducted on an individual basis and focused on the content and structure of
the instrument and its usefulness in research and clinical settings. Case
vignettes were used, taking into account the whole range of the target
population. As a result of these consultations the second draft was
developed.
Validity studies
Content validity
We designed a questionnaire that asked about the views of service users
(n=45) and their informal carers on the list of need areas identified
through the process described above. Users and carers were asked to score each
need area item according to its relevance, and to suggest any additional items
that should have been included. Adults with all levels of learning
disabilities were included in this sample. For those with a level of learning
disability severe enough to interfere significantly with the comprehension of
the questionnaire, it was completed by carers alone.
Consensual validity
Fifty-five experts in the field of mental health in people with learning
disabilities from a range of professional backgrounds and all parts of the UK
were surveyed. Their opinion was sought on the content, language and structure
of the CANDID by mailing them a copy of the second draft accompanied by a
questionnaire inviting them to rate, on a five-point Likert scale,
helpfulness of anchor points, ease of use and
appropriateness of language.
Criterion validity
No gold standard needs-assessment instrument currently exists
for people with learning disabilities and mental health problems. In order to
establish the concurrent validity of the CANDID, two instruments were used:
the Disability Assessment Schedule (DAS;
Holmes et al, 1982);
and the Global Assessment of Functioning (GAF;
American Psychiatric Association,
1994). The DAS was developed in order to assess level of
functioning in 12 life areas of people with learning disabilities; the GAF
measures global level of psychiatric symptom severity and disability.
Concurrent validity was calculated in two ways: first CANDID summary scores
(total number of needs) rated by staff were compared with total DAS and GAF
scores; second, a comparison was made between DAS scores in individual areas
of need (behaviour, communication, mobility, social interaction and self-care)
and corresponding areas of the CANDID. These areas were selected because they
were the overlapping areas in the two instruments that could be meaningfully
compared.
Predictive validity is relative to a needs-assessment instrument because of its capacity to predict future service utilisation and therefore assist with needs-led service planning. However, no attempt was made to establish the predictive validity of the CANDID because this would require a longitudinal study design, which was beyond the scope of this study.
Reliability studies
Sample acquisition
Two sampling frames were used: first, all adults (n=210) using a
community-based specialist learning disabilities mental health service in an
outer London borough (Bromley); second, all in-patients (n=12) of a
national unit for adults with mild or moderate learning disabilities at a
psychiatric hospital (Bethlem Royal Hospital). The community subsample
(n=31), although not randomly selected, included people with a range
of levels of intellectual ability and a variety of mental health and
behavioural problems characteristic of users of specialist learning disability
mental health services. The in-patient subsample comprised nine people, after
three patients were judged by their consultant psychiatrist to be too
disturbed to participate. Thus, 40 people in total were recruited for the
reliability study. Only one of those approached refused to participate. An
estimate based on the original CAN data had indicated that for interrater
reliability a sample of this size would be adequate to estimate an intraclass
correlation of 0.88 to within ±0.1 with approximately 95%
confidence.
Reliability study design
Five interviewer/raters were used: a psychiatrist, an occupational
therapist, a social worker and two nurses. A brief explanation of the scope of
the instrument and the rating procedure, but no formal training, was
given.
Forty subject trios, each consisting of a service user, their informal carer and a member of staff, were enrolled in the reliability study. Of these, nine users could not be interviewed owing to the severity of their learning disabilities, and 13 carers were unavailable. Hence for the investigation of interrater reliability, 31 users, 27 carers and 40 staff were interviewed at a given point of time (T1). All interviews performed at T1 were timed. With 29 of the 40 triplets the interviews were conducted live by an interviewer in the presence of a silent second rater (all five raters rotated in their role as interviewer or second rater). The remaining 11 trios were interviewed by one interviewer alone (the same interviewer conducting all interviews), and the interviews were audio-taped. All four second raters rated the taped material at a later stage.
For the testretest reliability exercise, the same interviewer who performed interviews at T1 re-interviewed the respondents at a second point in time (T2), this time alone. The interval between T1 and T2 was on average 11 days, and 77.5% of the subjects were re-interviewed at T2. For the taped interviews (where all four second raters rated the same material), reliability was estimated separately for each second rater, and the overall reliability was calculated.
Statistical analysis
For testing criterion validity, non-parametric correlation (Spearman's
) and Student's t-test were used. Interrater and test-retest
reliability were examined for the total number of needs and for each need item
individually. For the reliability of individual items, two measures of
agreement were calculated: complete percentage agreement and unweighted
coefficient. For the reliability of the total number of needs,
variance component estimation was performed using the MINQUE (minimum norm
quadratic unbiased estimation) method in the Statistical Package for the
Social Sciences (SPSS) version 7.5 for Windows
(SPSS, 1996). Variance
components estimation is a flexible method of obtaining reliability
coefficients if there are several sources of variation, and the MINQUE method
is robust concerning moderate departure from normality
(Dunn, 1992). For interrater
estimates, both patient variation and rater variation were estimated as random
effects. For testretest estimates, time was included as a fixed effect.
Each interclass correlation coefficient was estimated as the ratio of
variation between subjects to total variation. Relative bias in
T2 estimates compared with T1
estimates was tested by using a paired t-test. Fixed effects between
raters were tested by using a fixed effect analysis of variance. Also, a
Student's t-test was used to compare the mean differences in the
ratings of users, carers and staff for the comparison of the individual DAS
scores in the two CANDID groups.
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RESULTS |
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The mean total number of needs per user identified at T1 by the users themselves (n=31) was 11.55 (s.d.=2.51, 95% CI 10.63-12.47), while informal carers (n=27) identified 14.10 needs (s.d.=2.34, 95% CI 13.11-14.96) and staff (n=40) identified 13.98 (s.d.=2.97, 95% CI 13.03-14.92). The ratings by carers and staff did not differ significantly, whereas the ratings by users and carers were significantly different, as were ratings by users and staff, (P < 0.01). Table 2 shows the staff ratings for the 25 areas of the CANDID. The mean duration of the interviews at T1 was 28.25 minutes (s.d.=7.84) for users, 39.56 (s.d.=6.52) for carers and 27.42 (s.d.=5.00) for staff.
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Validity
Face validity
A number of different perspectives were taken into account during the
development process, and comments were incorporated into the final version.
Professionals from a variety of disciplines expressed the view that the CANDID
is a comprehensive instrument covering a wide range of needs of people with
learning disabilities and mental health problems. The CANDID, therefore, has
acceptable face validity.
Content validity
All 45 users and carers approached responded to the questionnaire.
Following the survey a total score for each need item was calculated and all
items were ranked according to this score. The highest scoring items were
accommodation and self-care, while the lowest were autistic features and
telephone use. No additional items were suggested by more than two
respondents.
Consensual validity
Forty-five experts (81.8%) responded to the questionnaire. Regarding the
instrument's content, no item was rated as redundant and only
communication was suggested for inclusion by more than two
respondents. Only 5% of respondents rated the instrument's structure as low
for helpfulness of anchor points and ease of use.
The draft instrument's language was rated as inappropriate by
20% of respondents, and their comments were taken into account in developing
the final version. Thus, satisfactory consensus on the content and structure
of the instrument was ensured.
Criterion validity
The CANDID summary scores (total number of needs) were compared with the
total DAS and GAF scores. In both DAS and GAF, higher scores indicate higher
levels of functioning, whereas high CANDID scores indicate high need. The
Spearman's correlation coefficients were 33 (P <
0.05) and 47 (P < 0.01) respectively, implying high
concurrent validity.
In the individual areas examined (behaviour, communication, mobility, social interaction and self-care), the DAS scores were consistently lower for those assessed by the CANDID as having a need than for those assessed as not having a need, indicating an association between the DAS and CANDID in the expected direction. In the first three areas the differences were statistically significant and the respective mean difference values were 2.95 (P < 0.001, 95% CI 1.63-4.27), 0.79 (P < 0.05, 95% CI 0.60-1.51) and 1.2 (P < 0.001, 95% CI 0.78-1.62). In the remaining two areas, where statistical significance was not reached the DAS items inquired about much narrower areas of functioning than the corresponding CANDID items.
Reliability
Intraclass correlations between summary scores of the two raters (for
interrater reliability) and at the two points in time T1
and T2 (for testretest reliability) were calculated
using variance components analysis as described above. For interrater
reliability the intraclass coefficients were 0.93 for user, 0.90 for carer and
0.97 for staff ratings. For testretest reliability they were 0.71, 0.69
and 0.86 respectively. On the basis of paired t-tests there was no
evidence of relative bias between the two time points or between live and
taped interviews. In addition to total number of needs (section 1), the
interrater and testretest reliability of the summary scores for
Sections 2, 3 and 4a were calculated. There was a high degree of agreement
between raters and across time, and the correlations were generally higher for
interrater than for testretest reliability. The results are shown in
Table 3.
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Interrater and testretest reliability were also examined for each
need area item separately and two measures of agreement were calculated:
percentage of complete agreement and coefficients. Values of
in the range 0.81-1.00 indicate almost perfect agreement with
0.61-0.80 indicating substantial, 0.41-0.60
moderate and 0.00-0.40 indicating poor agreement
(Landis & Koch, 1977). Only
three
values were in the poor agreement range; all were
derived from user ratings and concerned testretest reliability in the
scores of self-care, information and welfare benefits. Values of the
in some instances were very low despite high complete agreement. Examination
of the raw data in such instances showed that this was due to highly skewed
distribution of scores. This difficulty with misleading
values is
discussed by Feinstein & Cicchetti
(1990).
For interrater reliability the lowest percentages of complete agreement on
ratings of presence of need in a defined area were 71.0% for users, 85.1% for
carers and 77.5% for staff; only 0.7% of the percentages were below 75%. For
testretest reliability the lowest percentages were 58.3% for users,
66.6% carers and 71.0% for staff; only 4.7% of the percentages were below 75%.
Table 4 shows the
coefficients for each need area item for interrater and testretest
reliability.
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DISCUSSION |
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Second, there is a lack of consensus about who should assess need. Some argue that need can only be assessed by professionals (Mooney, 1986), whereas others (Bradshaw, 1972) claim that individuals' assessment of their own (felt and expressed) needs is valid. The combination of cognitive impairment, mental state abnormalities and behavioural disorders exhibited by adults with learning disabilities and mental health problems may significantly affect their mental capacity. However, it is important to take into account the views of the service users themselves, especially if they differ systematically from those of other assessors (Slade, 1994).
Validity
A balance had to be struck between the utility and the comprehensiveness of
the new instrument. The decision to retain or add items was taken on the basis
of the balanced views of those who participated in the validity study.
Accordingly, one item (communication) was added, whereas four (intimate
relationships, autistic features, telephone use and medication) were not
retained from the original list of items.
The lack of a gold standard instrument necessitated the use of instruments that only indirectly measure level of need. Furthermore, it was only possible to compare five out of the 12 DAS items with the corresponding areas in the CANDID. The remaining seven either did not correspond to any CANDID areas or had their scoring based on different criteria, thus not allowing meaningful comparison.
Reliability
A difficulty associated with testing the interrater reliability of
instruments administered via a semi-structured interview is that the second
rater may be influenced by the interviewer. The rating of Sections 2-4 is
dependent on the rating of the presence of a need in Section 1. Moreover, this
process reduces the sample sizes available for analysis and caution therefore
is required in interpreting the reliability of Sections 2-4.
Generalisability
The reliability study sample was nonrandom and our research was conducted
in only two sites, whereas there are large variations in the philosophy,
structure and aims of services providing care for adults with learning
disabilities and mental health problems in the UK. Nevertheless, an effort was
made to make the sample as representative as possible by including service
users from a variety of settings and with a range of levels of learning
disability and associated mental or behavioural disorders.
Assessing needs from multiple perspectives is one of the main characteristics of the CANDID. However, the views of the service users are skewed towards the high end of ability, as individuals with severe and profound disability were not able to rate their own needs. Although not investigated in this study, one approach for future work will be to assess the views of an advocate whenever it is not possible to obtain the views of the service user.
Implications for health and social services
A valid and reliable needs-assessment instrument for people with learning
disabilities and mental health problems will be a useful clinical and research
tool. The increasing costs of health care and lack of consensus about the most
effective way of organising and providing health and social care have led
government policy to be increasingly informed by evidence-based practice. The
CANDID will enable rational use and fair distribution of scarce resources by
encouraging needs-led service provision. However, the CANDID was not designed
as an outcome measure, so other appropriate instruments should be used when
measurement of change over time is required.
The CANDID will facilitate the fulfilment of the local authorities' statutory obligation for needs assessment. It can be used for planning services, both at an individual level (developing individualised care plans) and at a population level (designing a service in a geographical area). The CANDID can, through systematic inquiry, help to identify areas of need that may require further exploration. However, it is a screening instrument rather than a diagnostic one and as such it is not a substitute for health or social care interventions, such as regular health checks.
As with the CAN, the need for separate versions for research and clinical use emerged during the developmental process. The findings reported here were obtained using the research version of the CANDID. Two areas of concern about the draft clinical version have arisen: difficulty with its use in busy routine clinical settings, and the potential loss of useful clinical information caused by the structured nature of responses. The clinical version of the CANDID has adopted a combined approach: it uses the structured format of Section 1 to rate systematically the presence or absence of need, followed by semi-structured sections which allow the recording of relevant clinical information as part of the individual's care plan.
The findings of this study suggest that the CANDID has acceptable validity and reliability when used under the research conditions of this study. More data on its utility and feasibility are required; these characteristics will be established with its application in routine settings in the long term. A pilot study by the core research team aimed at investigating the feasibility of the instrument's use in routine community-based and in-patient settings is currently under way.
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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 May 17, 1999. Revision received August 13, 1999. Accepted for publication August 17, 1999.