Development and psychometric evaluation of a new patient -reported outcome measure for stroke self -management: The Southampton Stroke Self

Mokken scale analysis revealed that the SSSMQ forms an acceptable unidimensional scale
consisting of 28 items. Each item concerns a stroke self-management attitude, skill
or behaviour. Collectively, based on the preliminary evidence of validity reported
here, and subject to further validation work, the SSSMQ measures stroke self-management
competency, the features an individual requires to be competent and capable of managing
health and wellbeing following stroke.

Self-efficacy is the most commonly purported theoretical basis underpinning stroke
self-management interventions 21], 41], whereby individuals with higher self-efficacy are thought better able to self-manage
42]. Self-efficacy is thought to mediate desirable health behaviours, such as, following
a healthy lifestyle, taking prescription medication, that lead to improved motivation,
treatment adherence, function and better clinical outcomes 43], 44]. Lower levels of self-efficacy are associated with lower mood and coping skills after
stroke 45]. Consistent with this literature, SSSMQ scores correlated moderately with stroke
self-efficacy, as measured by the SSEQ (Table 2) 46]. Higher self-efficacy scores were associated with increased SSSMQ scores and thus
more successful self-management behaviours, attitudes and skills.

Physical function is likely to affect individual’s ability to perform tasks or strategies
important to self-management 47], 48] along with social, emotional and cognitive factors. Total scores from the SSSMQ moderately
correlated with the Strength; Hand function; ADL/IADL and Mobility domains of the
SIS, although correlations with the Hand function and Strength domains were weak and
not significant (Table 2). Further investigation of the relationship between self-management competency and
physical function is therefore required.

Better self-management is thought to lead to improved well-being and mood 47], significant to recovery following stroke 48]. Low mood has been identified as a barrier to self-management 49], 50]. Scores from the SSSMQ correlated positively with scores on the emotion domain of
the SIS, suggesting that, individuals with lower mood, exhibit fewer desirable self-management
behaviours and attitudes. Improved mood may augment self-management competency, or
potentially vice versa. Positive correlations were also observed with the communication, memory and participation
domains of the SIS, suggesting that these elements are important to self-management
competency. Effective communication, which in stroke may be hindered by the presence
of aphasia, is likely to enabled successful self-management 51] as navigating services and negotiating treatment strategies with professionals is
key to self-management after stroke 52]. Improvement in the communication and participation domains of the SIS have been
reported following a stroke self-management intervention 53], suggesting that effective self-management may have the potential to impact upon
these domains.

Correlations with the SSSMQ and the SIS subscales provide preliminary evidence that
successful self-management is associated with improved quality of life. Conceptually,
quality of life may be important to self-management; gaining more control over health
and well-being can feasibly be considered to improve quality of life as people develop
the coping skills to adjust to and manage their life post-stroke 47], 54]. Alternatively, those who possess a greater quality of life may be more likely to
exhibit the skills necessary to self-manage competently.

A difference between gender and total SSSMQ scores was found. It is not surprising
that gender might impact upon self-management attitudes, behaviours and skills, as
women typically perform better in self-management interventions 55]–57]. Total SSSMQ scores were not statistically associated with age or living circumstances
as might have been expected given that previous research indicates that older adults
and people who live alone, often find self-management more difficult 50], 58], 59]. Further development of the SSSMQ with additional psychometric testing is warranted
to provide continuing evidence of discriminant validity.

Investigation of reliability demonstrates that the SSSMQ is an adequately stable measurement
of stroke self-management competency. Internal consistency and test-retest reliability
were excellent, but must be considered in light of the limitations of sample size.

The findings provide preliminary evidence of the reliability and validity of the SSSMQ.
The predicted hypotheses made with regard to the relationship of scores from the SSSMQ
and additional measures were borne out, suggesting that self-management competency
is consistent with previously validated measures of stroke self-management.

The optimal content, target outcomes, and mechanisms for change in stroke self-management
interventions remain unclear 21], 60]. Measurement of an individuals’ self-management competency, their attitudes towards
self-management and relevant behaviours relies upon patient report. The SSSMQ potentially
represents an instrument, grounded in the views of patients who have had experienced
stroke, with which to evaluate the impact of interventions on stroke self-management
competency following stroke.

There are several limitations of the study which are acknowledged. There are no definitive
answers regarding sample size requirements for IRT, however sample sizes of 100 are
often adequate 61]. Therefore, the inferences drawn from the results must be considered in light of
the relatively small sample size, and the possibility for type II errors in analysis.
The average age of the UK stroke population is 75 years 62]. The sample in this UK based research was considerably younger at just over 58 years,
which may in part explain the larger proportion of people who chose to take part on-line.
Moreover, it is not possible to say if those taking part on-line had differing competency
at using computers or different access to computers compared to a typical stroke population.
The SSSMQ and study information were only available in English, which may have prevented
or dissuaded those who do not have English as a first language from participating.
Over 60 % of the sample had a moderate communication impairment, according to scores
from the communication domain (60) of the Stroke Impact Scale. This is a strength
of this study since people with communication impairment are often excluded from stroke
research.

It is also acknowledged that a tension potentially exists between the items, which
were inductively generated and considered important to potential users, and the criteria
for discarding items that do not function well in a scale 63]. Nonetheless, Mokken scaling represents a measurement model with the least criteria
in this respect and is the method most likely to resolve this tension in favour of
retaining items 64], 65].

Further investigation of validity, including cross-cultural applications, is necessary
to provide further evidence of the psychometric properties of the SSSMQ with a larger,
more diverse sample. Future studies should also include clinician/researcher obtained
data regarding participants’ level of impairment. This would aid judgements about
the relationship between impairment and self-management competency. In this research,
selection of outcome measures with which to investigate theoretical relationships
with the SSSMQ focused on the prevailing theory of self-efficacy. Further exploration
of construct validity with additional measures of concepts associated with self-management,
such as health literacy, decision-making and the burden of self-management may further
enhance the strength of the construct of self-management competency.