Trial lecture title: Which psychometric properties of a test are important to know in order to assess whether and how it can be used clinically?
The ordinary opponents are:
- First opponent: Docent, Med Dr in Neuroscience, Physiotherapist, Maria Ekblom, The Swedish School of Sport and Health Sciences, GIH and Department of Neuroscience, Karolinska Institutet
- Second opponent: Associate Professor, Senior Researcher, Physiotherapist, PhD, Morten Tange Kristensen, Hvidovre Hospital, Copenhagen University
- Leader of the evaluation committee: Professor Sølvi Helseth, Vice-Dean for Research and Development, OsloMet
Leader of the public defense is Professor Unni Sveen, OsloMet.
The main supervisor is Associate Professor Terje Gjøvaag, OsloMet. The co-supervisors are Harald Steen, Oslo University Hospital Rikshospitalet, and Professor Peyman Mirtaheri, OsloMet.
Thesis abstract
Lower limb amputation (LLA) is a traumatic life-changing event that might have an impact on physical as well as psychological health and often leads to limitations in mobility. Many prosthetic users struggle with mobility and have reported the need to pay extra attention while walking (increased attentional demands).
Mobility in daily life often requires the ability to navigate in different environments and perform two activities simultaneously (i.e. dual-tasking) and this may challenge the available but limited attentional resources. Hence, mobility is closely linked to cognition and particularly attentional demands.
Dual-task tests have commonly been used to indirectly assess the interaction between attention and mobility, however, this interaction is not fully understood, and there is a need to assess the interaction between attention and mobility under walking conditions that reflect situations frequently faced in daily lives.
In addition, dual-task assessment does not examine the underlying cortical activity of attention. By using portable neuroimaging techniques such as functional near-infrared spectroscopy (fNIRS), it is possible to examine the underlying activity taking place in the prefrontal cortex (PFC) during mobility.
The PFC is a brain area that is particularly involved in cognitive processes and measurements of PFC activity will increase our knowledge on the interaction between mobility and cognition, which can be valuable for the field of rehabilitation science and can contribute to better rehabilitation strategies for lower limb prosthetic users.
Aim
The overall aim was to develop new evidence-based knowledge regarding mobility and cognition, particularly in terms of attentional demands, in persons with LLA exposed to different challenging walking conditions.
The main aims were three-fold:
- to examine the psychometric properties of the Figure-of-Eight Walk Test (F8W) in usual walking (UW) and with two novel conditions reflecting situations faced in daily lives (WCT: walking and carrying a tray, and WUT: walking on uneven and soft terrain)
- to examine walking performance and PFC activity in persons with and without LLA under F8W conditions (UW, WCT, and WUT)
- to examine variables that might potentially have an impact on PFC activity.
Materials and methods
This thesis includes three papers, all of which have a cross-sectional design. Paper I included 50 persons with LLA.
Papers II and III included 39 persons with LLA (with a non-vascular aetiology of LLA) and 33 able-bodied controls.
We used different types of outcome measures including performance-based and self-reported measures of mobility. Cognitive performance was assessed using different tools, which included fNIRS.
Results
The results from Paper I showed that F8W and the two novel conditions demonstrated excellent internal consistency, good convergent construct validity and evidence of known-groups construct validity.
The two novel conditions posed different challenges compared to the original F8W in persons with LLA.
In Paper II, the results showed that persons with LLA had increased PFC activity compared with the able-bodied controls during the walking conditions, except for the walking condition WCT. The persons with LLA showed reduced walking performance during the walking conditions of WCT and WUT, but not during UW when compared with the able-bodied persons.
In addition, the results revealed that higher mobility scores were associated with lower PFC activity during WUT in persons with LLA.
Paper III showed that the univariable associations between PFC activity and the independent variables were little to fair in strength.
However, functional capacity (measured by Six Minute Walk Test) was the only significant variable and showed the strongest association in the multivariable analysis, although the adjusted explained variance (R2) of the models was rather low.
Conclusions
This thesis provides evidence of reliability and validity for the F8W and two novel conditions as performance-based outcome measures of mobility.
The novel conditions (WCT and WUT) posed different challenges to persons with LLA compared to the original walking condition (UW), which might support the use of these additional outcome measures in providing meaningful information about walking ability in daily lives of persons with LLA.
However, attentional demands might not always be reflected in performance-based outcome measures, and the results support the need to use both performance-based and self-reported outcomes of mobility in persons with LLA.
By using fNIRS, this present thesis show that the attentional demands required during mobility are greater for persons with LLA, however this depends on the nature and complexity of the task.
The thesis demonstrates the importance of addressing mobility limitations in the context of environmental challenges that persons with LLA face in their daily lives.
The thesis also suggests that higher levels of mobility and functional capacity might be important factors for reducing attentional demands during mobility. This needs, however, to be further investigated in future randomized controlled trials.
