Measuring the impact of lymphatic filariasis: the development of a quality of life tool using mixed methods

Lymphatic filariasis (LF) is a neglected tropical disease and the leading cause of physical impairment in the world. Globally, it is estimated that 40 million people live with LF-disability.\ud \ud In its chronic stages, LF causes scrotal hydrocele and lymphoedema of the limbs and genitals. Approximately twenty five million men have LF-related scrotal hydrocele and 15 million people live with LF-related lymphoedema (World Health Organization [WHO], 2010). The disease is estimated to equate to 5.54 million disability adjusted life years (Fenwick, 2012). Impacts of LF-disability expand beyond physical impairment; social isolation, stigma, poverty and reduced workplace and school productivity are also common impacts of LF-disability.\ud \ud The Global Programme to Eliminate Lymphatic Filariasis (GPELF) has two pillars of focus (WHO, 2012). The first is to interrupt transmission of the disease through mass drug administration (MDA) programs. The second is to alleviate suffering due to LF-disability. The GPELF as a whole has focused efforts and funding on addressing the first pillar, whilst the second pillar remains poorly documented and addressed.\ud \ud Despite LF being a leading cause of disability globally, little research has been conducted on the lived experience of LF-disability. It remains unknown how LF-disability impacts quality of life (QOL) and what interventions improve the QOL for people with chronic manifestations of the disease.\ud \ud The GPELF has acknowledged the need for disability metrics to capture the impact of LF-disability and the outcomes of intervention programs (WHO, 2010). However, there remain no LF-specific disability measurement tools. This research developed and field tested an LFspecific QOL tool for use in Bangladesh.\ud \ud A literature review of the current studies of LF-disability found minimal research into the experiences of LF-disability. The majority of the qualitative research in the field was found to be lacking methodological rigour. However, there were 46 common findings across the studies indicating that some experiences may be common to LF-disability. These included negative impacts on daily activities, participation and psychological wellbeing. There were also a number of environmental barriers (such as attitudes and a lack of access to treatment) and personal factors (such as poverty) that compounded the impact of LF-disability for people across the studies. The review found no research on LF-disability in Bangladesh.\ud \ud A further review of the tools currently used in the field identified six tools that have been used or recommended for use to measure the impacts of LF-disability. These tools were generic disability or QOL tools and none were specific to LF. A review of the tools against known impacts of LF-disability found that the tools poorly measured the known impacts that were culturally and clinically relevant for people living with LF-disability. These findings confirmed the need for an LF-specific tool to be developed.\ud \ud Only one tool used in the field, the World Health Organization Quality of Life Brief (WHOQOL-Bref), had a Bangladeshi version. Cognitive interviewing was conducted (n=34) to test this tools language and cultural applicability for an LF-endemic population. The study found that 22 of the 26 items in the tool were problematic and that the WHOQOL-Bref Bangladesh was not culturally or linguistically valid for a Bangladeshi population with LF-disability. These findings further justified the development of a new Bangladeshi LF-specific tool.\ud \ud In order to develop a culturally and clinically effective QOL tool for LF in Bangladesh, research was undertaken to identify the constructs of QOL relevant to LF-disability in Bangladesh. Ten focus groups were conducted in Bangladesh with a purposefully selected sample of key informants (n=60). The focus groups identified an additional 43 new impacts of LF-disability relevant to a Bangladeshi context.\ud \ud The impacts found from the literature review (n=46) and in-country focus groups (n=43) were then combined into a tool with 122 items. Back translation occurred to translate the tool from English to Bangla before field testing was completed to test the linguistic and cultural validity of the tool.\ud \ud Cognitive interviews (n=16) were conducted to field test the initial 122 item tool. The interviews identified 41 items with wording, cultural and conceptual issues. The findings of the cognitive interviews informed revision, alteration and removal of many items, however 13 items still remained unresolved from the cognitive interview process.\ud \ud Focus groups were conducted with three patients groups (n=17) to explore if the constructs in the problem items were relevant to people living with LF-disability and if so, what language people used to describe the issues. The focus groups identified that the constructs of 11 problematic items were relevant, however they were described differently in the local language. The language used in the focus groups informed the revision of those 11 items. Two items were deemed to be not applicable and were removed from the tool. Cognitive interviewing (n=6) confirmed that the final 72 items on the tool were culturally and linguistically valid.\ud \ud Reliability testing of the final 72 item tool found the tool to have excellent overall internal consistency (0.917) and confirmed that the tool is reliable for use for community surveys in Bangladesh.\ud \ud The overall findings of this thesis have contributed to the field in the following ways:\ud \ud 1) Contribution to the understanding of LF-disability:\ud \ud - Demonstrated that the evidence into LF-disability is scarce and lacking methodological rigour. - Found that tools currently used in LF-disability measurement fail to capture the majority of the known impacts of the disease.\ud \ud - Identified an additional 43 impacts that relate to LF-disability in Bangladesh.\ud \ud 2) Contribution to cross-cultural QOL tool development methods:\ud \ud - Demonstrated that psychometric testing of international generic tools, such as the WHOQOL-Bref Bangladesh, were insufficient to confirm the linguistic or cultural validity of the tool in a new population.\ud \ud - Evidenced the importance of a mixed methods, iterative approach to cross-cultural tool development and field testing.\ud \ud - Evidenced the importance of cognitive interviewing to instrument testing and refinement.\ud \ud - Demonstrated the use of focus groups to assist with identifying and solving problem items when cognitive interviews fail to identify why an item is problematic.\ud \ud 3) Contribution to LF-disability measurement:\ud \ud - Developed the only QOL tool for LF-disability, the LF-QOL Bangladesh that has demonstrated validity and reliability in the field.\ud \ud Future research should utilise the LF-QOL Bangladesh in community surveys, to identify the impacts of LF-disability across presentation and stages of the disease and look at any potential demographic differences. A test-retest reliability study of the LF-QOL Bangladesh would identify if the tool is suitable for use as an outcome measurement and hence, whether the tool can capture changes in QOL status following intervention.\ud \ud The development of the LF-QOL Bangladesh is a significant contribution to the field and provides the first opportunity to reliably capture the impact of LF-disability in an LF-endemic community