The Quality of Life In Depression Scale (QLDS), originally proposed by Sonja Hunt and Stephen McKenna, is a disease specific

patient-reported outcome A patient-reported outcome (PRO) is a health outcome directly reported by the patient who experienced it. It stands in contrast to an outcome reported by someone else, such as a physician-reported outcome, a nurse-reported outcome, and so on. PRO m ...

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 medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness, heada ...

therapy A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a medical diagnosis. As a rule, each therapy has indications and contraindications. There are many different ...

. It is a 34 item self-rated

questionnaire A questionnaire is a research Research is "creativity, creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, ...

which consists of

dichotomous A dichotomy is a 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: nothing can belong simultan ...

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 Beck ...

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 Subjectivity in a philosophical context has to do with a lack of objective reality. Subjectivity has been given various and ambiguous definitions by differing sources as it is not often the focal point of philosophical discourse.Bykova, Marina F ...

. Quality of life tends to be greatly influenced by factors such as depression,

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches rocks in two opposite directions * Voltage or el ...

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

. 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 nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...

sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

sex Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones (ova, oft ...

safety Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to risk management, the control of recognized hazards in order to achieve an acceptable level of risk. Meanings There are ...

love Love encompasses a range of strong and positive emotional and mental states, from the most sublime virtue or good habit, the deepest Interpersonal relationship, interpersonal affection, to the simplest pleasure. An example of this range of ...

enjoyment Happiness, in the context of mental or emotional states, is positive or pleasant emotions ranging from contentment to intense joy. Other forms include life satisfaction, well-being, subjective well-being, flourishing and eudaimonia. Sinc ...

self-esteem Self-esteem is confidence in one's own worth or abilities. 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 Mackie (2007) d ...

and

self-actualization Self-actualization, in Maslow's hierarchy of needs, is the highest level of psychological development, where personal potential is fully realized after basic bodily and ego needs have been fulfilled. Self-actualization was coined by the organism ...

. 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 Lilly may refer to: * an archaic spelling of lily, a flowering plant Arts and entertainment * ''Lilly'' (film), a 1958 Malayalam film * ''Lilly'' (album), by Antonello Venditti, 1975 * "Lilly", a song by Pink Martini from the 2004 album '' Ha ...

. 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 Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

in conjunction with the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

. 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. Sedi ...

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 administrative counties of Cheshire, Cumbria, Greater Manchester, Lancashire and Merseyside. The North West had a population of 7,052,000 in 2011. It is the th ...

and

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

. 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 * High availability * Reliability (computer networking), a ...

International development

The first two languages the QLDS was available in were UK English and

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

. These were shown to have good

validity Validity or Valid may refer to: Science/mathematics/statistics: * Validity (logic), a property of a logical argument * Scientific: ** Internal validity, the validity of causal inferences within scientific studies, usually based on experiments ** ...

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 dim ...

and the new measure's

. Across the majority of translations, no major difficulties arose excluding

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

. 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 in its broadest sense describes "particular ways of thinking about and doing reading and writing" with the purpose of understanding or expressing thoughts or ideas in written form in some specific context of use. In other words, huma ...

, 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 multiplicative factor in some term of a polynomial, a series, or an expression; it is usually a number, but may be any expression (including variables such as , and ). When the coefficients are themselves var ...

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 the name given in various nations, such as the United Kingdom, India, Australia, New Zealand and South Africa to the services provided by general practitioners. In some nations, such as the US, similar services may be describe ...

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 Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe *Norwegians, both a nation and an ethnic group native to Norway *Demographics of Norway *The Norwegian language, including the ...

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 Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Cana ...

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish ance ...

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...

and

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

. 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, panic di ...

duloxetine Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, fibromyalgia, neuropathic pain and central sensitization. It is taken by mouth. It is a serotoni ...

and

bupropion Bupropion, sold under the brand names Wellbutrin and Zyban among others, is an atypical antidepressant primarily used to treat major depressive disorder and to support smoking cessation. It is also popular as an add-on medication in the case ...

References

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