COMPARATIVE VALIDITY OF THE DIFFERENT COMPONENTS OF THE EUROQOL
SCALE TO DETERMINE THE QUALITY OF LIFE IN PATIENTS WITH BACK
PAIN
Title.
Determining the quality of life in patients
with acute and subacute low back pain; a study of the validity
of EuroQol's assessing the results.
Background.
To determine the treatment most appropriate
at each moment for a patient and to evaluate its effect, it
is necessary to measure the quality of life by means of reliable
and valid instruments. Currently, different scales exist for
this purpose. Among them, the EuroQol questionnaire presents
several advantages: it is relatively easy to fill out, so
that it can be answered directly by the patient without needing
assistance from the health care personnel, and without taking
time from the consultation with the doctor, and it has been
developed keeping in mind perspectives of cost analysis. Thus,
it is the scale which health economists tend to recommend
in order to compare the cost/usefulness of different treatments
(that is to say, the cost one treatment or another has in
improving the quality of life) or to determine the illness
it is most efficient to spend resources on in order to improve
the general quality of a population's life.
The EuroQol questionnaire is made up of two parts whose independent
results are combined into an overall score. The first part
consists of various questions referring to different settings
that make up the quality of life. Each question has multiple-choice
answers, arranged according to higher or lower level of quality
of life they reflect. The second part of the scale is a "thermometer"
(actually, it is a visual analog scale) numbered from 0 to
100 on which the patient must situate what he or she feels
his/her quality of life to be at that moment, with 0 as dead
and 100 as the best imaginable level of quality of life. The
level the patient indicates on this "thermometer"
is divided by 100 and adjusted according to the values that
the general population attributes to different situations.
Thus, for example, the range of global values possible on
the EuroQol scale for the Spanish population oscillates between
1 (maximum quality of life) and -0,1304. The scores between
0 and -0,1304 correspond to the quality of life in the situations
which the general Spanish population considers worse than
death. Since this score depends on the cultural environment
(different populations may perceive differently what is worse
than death), the scale's range must be adjusted for each specific
population in which it is going to be used.
Therefore, while the response to the questions in the first
part of the EuroQol produce a specific score that depends
exclusively on the perception of the specific patient whose
quality of life is being appraised, the scoring from the "thermometer"
is affected by the general population's opinion on how different
situations or illnesses lower the quality of life. As it is
impossible for a normal individual to determine at a glance
the severity of back pain another subject may suffer, or the
limitation of his/her daily activities when observed in a
situation that pain does not prevent, it is possible that
the "thermometer" on the EuroQol scale is not really
valid to measure the reduction in the quality of life in patients
with back pain.
This is important, since as the scoring of the two parts
of the EuroQol are combined into a final score, if one of
its components is not really valid for low back pain, it is
possible that the final appraisal is less valid than it should
be. Furthermore, if the EuroQol actually undervalues the decline
in the quality of life of low back pain patients, the application
of innovations in this field could suffer since the health-policy-makers
would have the mistaken perception that the resources given
to that field improve the quality of life of the population
less than they really do.
Therefore, if it is proven that one of the two components
of the EuroQol scale is penalizing the validity of the scale's
overall score in determining the level of quality of life
in patients with back disorders, this situation should be
brought to the attention of the health care authorities so
that they bear it in mind when making decisions and to the
attention of doctors and researchers specialized in this field
so that they adapt the use of the EuroQol scale to patients
with back problems. For this reason it is important to prove
the validity of the questionnaire's scoring method and develop
a better one as needed.
Objective.
To study the validity of the scoring method
currently recommended in order to correct the result of the
EuroQol questionnaire.
Design
Prospective, cohort study.
Methodology.
The study was made with a convenience sample
of 366 patients who visited their Primary Care physician for
acute or subacute low back pain (that is, of less than 90
days' duration), with or without referred or radiated pain.
The patients were evaluated on three occasions: the first
day they solicited attention, and 15 and 60 days later. On
each occasion, they filled out two scales to measure the intensity
of their pain (one for low back pain and another for referred
or radiated pain), a Roland-Morris scale to determine their
degree of disability and a complete EuroQol scale.
In the analysis phase, the correlations among the different
scales were calculated, analyzing separately the correlation
of the overall EuroQol scale, with the score from the questionnaire
part and with the score from the "thermometer".
Participants, along with the Foundation's
Science Department.
106 researchers from 40 Primary Care centers
and Primary Care Research Units in Badajoz, Baleares, Bilbao,
Burgos, Cáceres, Cuenca, Guadalajara, Huesca, Madrid,
Murcia, Palencia, Valencia, as well as the Unit of Clinical
Biostatistics at the Hospital Ramón y Cajal, Madrid;
all of them part of the Spanish Network of Researchers in
Back Disorders.
The study was funded by the Kovacs Foundation.
Status.
Data collection has
concluded and data is currently being analyzed.
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