Quality Of Life In Depression Scale
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The Quality of Life In Depression Scale (QLDS), originally proposed by Sonja Hunt and Stephen McKenna, is a disease specific patient-reported outcome which assesses the impact that depression has on a patient's
quality of life Quality of life (QOL) is defined by the World Health Organization as "an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards ...
. It is the most commonly used measure of quality of life in clinical trials and studies of depression. The QLDS was developed as a measure to be used in future clinical trials of
anti-depressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include dry mouth, weight gain, dizziness, headaches, akathisia, sexua ...
therapy A therapy or medical treatment is the attempted remediation of a health problem, usually following a medical diagnosis. Both words, ''treatment'' and ''therapy'', are often abbreviated tx, Tx, or Tx. As a rule, each therapy has indications a ...
. It is a 34 item self-rated
questionnaire A questionnaire is a research instrument that consists of a set of questions (or other types of prompts) for the purpose of gathering information from respondents through survey or statistical study. A research questionnaire is typically a mix of ...
which consists of
dichotomous A dichotomy () is a partition of a set, partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be * jointly exhaustive: everything must belong to one part or the other, and * mutually exclusive: nothi ...
response questions, with the response being either True/Not True. It is scored binomially (0-1) with higher scores on the QLDS indicating a lower quality of life. Several tests of
construct validity Construct validity concerns how well a set of indicators represent or reflect a concept that is not directly measurable. ''Construct validation'' is the accumulation of evidence to support the interpretation of what a measure reflects.Polit DF Bec ...
and
internal consistency In statistics and research, internal consistency is typically a measure based on the correlations between different items on the same test (or the same subscale on a larger test). It measures whether several items that propose to measure the same g ...
have found the QLDS to be a good measure of quality of life. __TOC__


Needs-based model

The QLDS is built around the generally accepted assumption that one's quality of life can only be assessed
subjectively The distinction between subjectivity and objectivity is a basic idea of philosophy, particularly epistemology and metaphysics. Various understandings of this distinction have evolved through the work of countless philosophers over centuries. One b ...
. Quality of life tends to be greatly influenced by factors such as depression,
anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...
, tension or
fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...
. The QLDS is based around the needs-based model of quality of life. This is derived from the assumption that quality of life is dependent on a person's ability to fulfil particular human needs. The QLDS questions centre around a number of needs that were considered crucial in order to suffice a high quality of life. These include but are not limited to;
food Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...
,
sleep Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain Sensory nervous system, sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with th ...
,
sex Sex is the biological trait that determines whether a sexually reproducing organism produces male or female gametes. During sexual reproduction, a male and a female gamete fuse to form a zygote, which develops into an offspring that inheri ...
,
safety Safety is the state of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. Meanings The word 'safety' entered the English language in the 1 ...
,
love Love is a feeling of strong attraction and emotional attachment (psychology), attachment to a person, animal, or thing. It is expressed in many forms, encompassing a range of strong and positive emotional and mental states, from the most su ...
,
enjoyment Joy is the state of being that allows one to experience feelings of intense, long-lasting happiness and contentment of life. It is closely related to, and often evoked by, well-being, success, or good fortune. Happiness, pleasure, and gratit ...
,
self-esteem Self-esteem is confidence in one's own worth, abilities, or morals. Self-esteem encompasses beliefs about oneself (for example, "I am loved", "I am worthy") as well as emotional states, such as triumph, despair, pride, and shame. Smith and Macki ...
and
self-actualization Self-actualization, in Maslow's hierarchy of needs, is the highest personal aspirational human need in the hierarchy. It represents where one's potential is fully realized after more basic needs, such as for the body and the ego, have been fulfill ...
. The QLDS uses a two-point response system with either True or Not True. The high number of items in the questionnaire allows the detection of moderately minor changes in quality of life. Items on the QLDS are given a score of 1 when the question is applicable to the respondent and 0 when it is not applicable. The items are totalled to give a score ranging from 0–34. Low scores act as an indicator towards a high quality of life.


Development

The QLDS was developed by Galen Research in 1992 and was funded by Lilly Industries. It was developed in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
in conjunction with the
Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...
. The QLDS was the first quality of life instrument to be developed in 2 languages simultaneously. The development of the QLDS coincided with a rising interest on the impact of illness and its treatment on the quality of life of the patient. McKenna and Hunt constructed the QLDS on the basis of providing a measure for this, as well as attempting to overcome contemporary studies concerning low correlations between patient
self-assessment In social psychology, self-assessment is the process of looking at oneself in order to assess aspects that are important to one's identity. It is one of the motives that drive self-evaluation, along with self-verification and self-enhancement. S ...
and nurse or therapist evaluations. The items in the UK English QLDS were derived from statements made in qualitative interviews by 30 depressed or recently recovered patients based in the
North West of England North West England is one of nine official regions of England and consists of the ceremonial counties of England, ceremonial counties of Cheshire, Cumbria, Greater Manchester, Lancashire and Merseyside. The North West had a population of 7,4 ...
and
Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
. Interviews took a conversational approach and lasted between 30 minutes to 2 hours. Interviewees were between the age range of 19–64 years, with 22 females and 8 males. After a refinement process, based on categories of needs proposed by McKenna and Hunt, 426 relevant statements were derived from the interview transcripts. Upon further scrutinization they produced 41 statements for an initial questionnaire. A further 35 patients were asked to complete the draft questionnaire and review their experience with it. They were composed of 22 females and 13 males in the age range of 24–72 years. Interviewees expressed a great degree of approval with the questionnaire, although a few mentioned how the binomial system caused difficulty, as it required them to make complete choices. Following this, the questionnaire was revised to 34 items and field tested to determine construct validity and
reliability Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), a property of some disk arrays in computer storage * Reliability (computer networking), a category used to des ...
.


International development

The first two languages the QLDS was available in were UK English and Dutch. These were shown to have good
reliability Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), a property of some disk arrays in computer storage * Reliability (computer networking), a category used to des ...
, validity and responsiveness. In 1999, McKenna in collaboration with a team of international researchers developed and tested the QLDS in 9 new languages. This involved translation, followed by field testing for
content validity In psychometrics, content validity (also known as logical validity) refers to the extent to which a measure represents all facets of a given construct. For example, a depression scale may lack content validity if it only assesses the affective di ...
and the new measure's
construct validity Construct validity concerns how well a set of indicators represent or reflect a concept that is not directly measurable. ''Construct validation'' is the accumulation of evidence to support the interpretation of what a measure reflects.Polit DF Bec ...
. Across the majority of translations, no major difficulties arose excluding
Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...
. Cultural differences between Morocco and the UK provided challenge, alongside a lack of literal equivalents between the two languages. An example of this is the absence of an equivalent for the verb 'to enjoy' in Arabic. Researchers also faced further difficulty due to the contemporarily high rate of
illiteracy Literacy is the ability to read and write, while illiteracy refers to an inability to read and write. Some researchers suggest that the study of "literacy" as a concept can be divided into two periods: the period before 1950, when literacy was ...
, as the test could not be self-administrative on as large a scale as anticipated. As a result, although the data demonstrated both reliability and construct validity, they were unable to place confidence in the Arabic adaptation's equivalence to the other developed versions.


Reliability, validity and responsiveness


Testing the Anglo-Dutch project

Following the collaborative Anglo-Dutch project, researchers had to compare the QLDS' success with established measures of the same concept. No measure of quality of life in depression was available so both versions had to be matched to related measures. In the UK this was the General Well-Being Index (GWBI) whilst in the Netherlands the Sickness Impact Profile (PS-SIP) acted as a comparison.


Reliability and internal consistency

For use in a clinical trial, an instrument like the QLDS should have a test-retest reliability
coefficient In mathematics, a coefficient is a Factor (arithmetic), multiplicative factor involved in some Summand, term of a polynomial, a series (mathematics), series, or any other type of expression (mathematics), expression. It may be a Dimensionless qu ...
of minimum 0.85. Internal consistency also requires a minimum of 0.85 and is assessed using Cronbach’s alpha-coefficient. In the UK, the test-retest correlation coefficient for patients with stable depression was 0.94 (n=37). The test-retest correlation coefficient in the Netherlands was 0.87 (n=33). For internal consistency the UK recorded a value of 0.95 and the Netherlands a value of 0.92. These results suggested the QLDS produced a low degree of measurement error and high internal consistency.


Content and construct validity

No missing items applicable to participants were recognised. The relevancy and ease of completion indicated by field-test interviews suggested the high content validity of the QLDS. The QLDS and GWBI had a correlation score of 0.79 in the UK (n=65). The Dutch adaptation had a correlation of 0.71 with the PS-SIP (n=77). These measurements were anticipated to be slightly lower due to the difference of purpose between measures.


Responsiveness

The QLDS’ responsiveness was analysed in a
general practice General practice is personal, family, and community-orientated comprehensive primary care that includes diagnosis, continues over time and is anticipatory as well as responsive. Definitions A general practitioner (GP) is a doctor who is a consu ...
population of 540 patients with major depression. Over a 6-month period, substantial progress in the level of depression was seen. 8 weeks into treatment the mean QLDS score rose by 68%, with patients who continued treatment for the full 6-months recording an increase of 78%. The QLDS was concluded by the researchers to be responsive to change in quality of life throughout successful pharmacological depression treatment.


International use

Since its development, the QLDS has been adapted and validated in 17 languages other than UK English, including Norwegian,
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...
, Danish, French,
German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...
and
Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...
. This has allowed the QLDS to be used in research and clinical studies worldwide. Studies utilizing the QLDS include investigations into
venlafaxine Venlafaxine, sold under the brand name Effexor among others, is an antidepressant medication of the serotonin–norepinephrine reuptake inhibitor (SNRI) class. It is used to treat major depressive disorder, generalized anxiety disorder, pani ...
,
duloxetine Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, obsessive–compulsive disorder, fibromyalgia, neuropathic pain, central sensitization, and ...
and
bupropion Bupropion, formerly called amfebutamone, and sold under the brand name Wellbutrin among others, is an atypical antidepressant that is indicated in the treatment of major depressive disorder, seasonal affective disorder, and to support smo ...
.


References

{{reflist, 32em Depression screening and assessment tools Patient reported outcome measures