In everyday clinical practice, patients attach greater and greater significance not only to treatment of organic lesions but also to the comfort of their life after this treatment. Despite the growth of interest in this subject, scientists are still debating the definition of quality of life and how to measure it. Thus, there is no one good working definition of quality of life. Nevertheless, all scientists accept the fact that the definition is very broad and it includes many aspects of life. Most often, quality of life is described as a total evaluation of psychical and emotional well-being, which is characterized by the use of various and widely understood living conditions, such as material status, the social environment in which a subject lives, the quality of the natural environment, and others [6].

Because of such a wide and inaccurate definition, medicine uses the term "health-related quality of life” [HRQL], which includes those aspects of living that are directly related to the patient´s health, but excludes such issues as, for example, income per family member, restriction or non-restriction of liberty, and quality of the natural environment [6]. The term "quality of life” as an element of health was first introduced by the World Health Organization in 1984. Health was defined not only as lack of disease but also as the presence of psychical, emotional and social well-being [2]. Division of health into physical and emotional helps us to understand better the influence of health state on the quality of life. Each of these areas affects the quality of life, where this quality includes the objective evaluation of functional condition and the subjective evaluation of mental state [7].

The objective evaluation of functional condition takes into account the physical capability to perform everyday activities as well as the ability to work or study. The objective evaluation of mental state includes the mental ability to deal both with everyday common tasks and with more complex objectives such as playing social roles. These areas may also reflect the estimated state of disability. Finally, the objective functional condition is complemented by the subjective evaluation made by a patient. It involves the evaluation of discomfort felt with disease symptoms – subjective physical state, which displays general satisfaction derived from the state of physical condition, and subjective mental state, which refers to patients´ emotional state and their level of social engagement. The state of physical and mental condition measured in a traditional way is only a part of HRQL and should not be considered equivalent to HRQL measurement 4.

Moreover, there is often no simple relation between the patient´s health and his/her frame of mind. Patients who suffer from severe disorders do not necessarily describe their quality of life as bad [4]. An explanation may be found in the way patients choose to evaluate this quality. People define it through their personal experience and expectations about their health state [4]. Persons with different expectations about their health state do not measure HQRL equally, even if their clinical state is indifferent. Furthermore, patients whose health state has improved may evaluate their quality of life at the same level as they did in the previous test. Thus, the HQRL evaluation varies for particular people and is changeable in time [4].

HQRL measurement can be used in clinical practice as well as in preparing norms of conduct or economic analysis. The HQRL evaluation gives us an opportunity to compare all possible methods of treatment so that we can choose the most suitable alternative for a patient. Yet it is possible only if both options provide equal survival rates and both forms of therapy pose a complication risk as well as a need of further diagnostic procedure and therapeutic management [4]. In addition, the measurement of quality of life helps us to evaluate how chronic illness influences the patients themselves. HQRL provides additional information which is very useful for medical treatment and immeasurable by traditional tests of physiologic parameters (e.g. the growth of stroke volume in the left ventricle in stagnant heart failure may not cause changes in patients´ everyday life) [4]. In the case of patients with chronic illness the HQRL measurement may let us distinguish those who need more advanced help (among patients and members of their families) [4]. Also, the HQRL measurement appears to be an independent factor helping to predict survival for patients suffering from cancer [4].

The HQRL measurement may consider one, two or three goals, which can be divided into: 1. discrimination, 2. prediction, 3. evaluation. The discrimination measurement serves to estimate the differences between particular persons or groups at a chosen moment of time. The evaluation measurement indicates differences among HQRL evaluations in time, whereas the prediction measurement helps us to predict future results [2, 6].

The HQRL analysis is based on 12 aspects of a child´s life, including physical, psychological and sociological well-being.

CHQ-PF 50 (Child Health Questionnaire – Parent Form 50) is a questionnaire of general use, which, according to psychometric rules, measures physical and socio-psychological well-being in children and youngsters aged five to eighteen. It was prepared in the USA, in 1994, by Jeanne M. Landgraf, John E. Ware and their partners. The questionnaire serves as an instrument to evaluate the quality of life for both healthy children and those who suffer from chronic illness. CHQ-P 50 is filled in by one parent or the child´s minder. The majority of questions focus on the preceding four-week period. In order to conduct measurements the original version of CHQ-P 50 has been professionally translated and its Polish equivalent has been adapted to our conditions. The Polish version was examined during tests on children with rheumatoid arthritis.

The measurement of well-being is conducted in 12 categories, which are:

1. physical functioning (PF)

2. limitations in social functioning caused by physical condition – role/social – physical (RP)

3. general health perception (GH)

4. bodily pain/ discomfort (BP)

5. limitations in parents´ free time caused by their child´s heath state – parental impact – time (PT)

6. child´s health state and its influence on parents´ emotions – parental impact – emotional (PE)

7. limitations in social functioning caused by emotional or behavioural problems – role/social emotional-behavioural (REB)

8. self-esteem (SE)

9. mental health (MH)

10. general behaviour (BE)

11. family – limitations in activities (FA)

12. family – cohesion (FC).

The results of measurement are presented as numbers from zero to 100, where a higher score defines a better state of well-being.

In literature devoted to our subject, we have found the HRQL test as a tool to measure quality of life in relation to health state in cancer, rheumatoid arthritis, asthma, diabetes, ADHD, cerebral palsy, epilepsy, chronic sinusitis, adenoidectomy, paediatric tonsil and adenoid disease, and otitis [1, 3, 4, 8].