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Caroline Sanders Department of Social Medicine,
University of Bristol, Canynge Hall, Bristol BS8 2PR
Correspondence to: Ms Sanders
Caroline.Sanders{at}bristol.ac.uk
Objectives:
To examine the frequency and quality of
reporting on quality of life in randomised controlled
trials.
Quality of life has become an accepted end point in clinical
research trials in recent years, as interest in patients' experiences and preferences has grown.1 Quality of life is of
particular importance in trials comparing treatments with similar or no
impact on disease progression and survival. However, the term quality of life is often used vaguely and without clear
definition.2-4 This is not surprising, considering the
broad nature of a concept that includes physical functioning (ability
to carry out activities of daily living such as self care and walking
around), psychological functioning (emotional and mental wellbeing),
social functioning (relationships with others and participation in
social activities), and perception of health status, pain, and overall
satisfaction with life.5
The lack of a clear definition of quality of life is reflected in the
many instruments that have been proposed to measure it. Generic
measures (such as the sickness impact profile6 or the
short form health survey SF-367) broadly assess physical, mental, and social health and can be used to compare conditions and
treatments. Measures specific to illnesses can supplement generic
measures or can be used independently.8 Other methods include measures focusing on a single aspect such as pain or anxiety and individualised measures, in which patients themselves define and
rate the most important aspects of their quality of life.9
Inadequate reporting of randomised controlled trials is common
and hampers the appraisal of the validity and generalisability of
results.10-13 In an attempt to remedy this, consolidated
standards of reporting trials (CONSORT) have been
developed.14 To our knowledge, however, the quality of
reporting on quality of life outcomes in trials has not been
systematically assessed so far. In addition, it is unclear as to what
extent the growth in attention to quality of life is reflected in an
increasing number of reports from clinical trials. We addressed these
questions in a bibliographic study based on the Cochrane Controlled
Trials Register.
Prevalence of reporting on quality of life
Assessment of abstracts
Assessment of full reports
Prevalence of reporting on quality of life
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Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Design:
Search of the Cochrane Controlled Trials
Register 1980 to 1997 to identify trials from all disciplines, from
oncology, and from cardiovascular medicine that reported on quality of
life. Assessment of abstracts from articles published from 1993 to
1996. Assessment of a sample of full reports with a standardised
instrument.
Main outcome measures:
Prevalence of reporting on
quality of life. Conditions and interventions studied in trials
reporting on quality of life. Quality of reporting on quality of life.
Results:
During 1980-97 reporting on quality of life increased from 0.63% to 4.2% for trials from all disciplines, from
1.5% to 8.2% for cancer trials, and from 0.34% to 3.6% for cardiovascular trials. Of 364 abstracts, 65% reported on drug interventions. Of a sample of 67 full reports, authors of 48 (72%) used 62 established quality of life instruments. In 15 reports (22%)
authors developed their own measures, and in 2 (3%) methods were
unclear. Response rates were given in 38 (57%), and complete reporting
on all items and scales occurred in 31 (46%).
Conclusions:
Less than 5% of all randomised
controlled trials reported on quality of life, and this proportion was
below 10% even for cancer trials. A plethora of instruments was used in different studies, and the reporting of methods and results was
often inadequate. Standards for the measurement and reporting of
quality of life in clinical trials research need to be developed.
Key messages
![]()
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
![]()
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
We searched the Cochrane Controlled Trials Register on
The Cochrane Library (issue 3, 1998)15 to
identify randomised controlled trials published in any language between 1980 and 1997 that reported on quality of life. We entered the keyword
"random*" to identify randomised controlled trials, the wild card
(*) ensuring that all abstracts containing words with the stem
"random" (such as randomly, randomised, randomisation) were
included. We identified trials that reported on quality of life by
combining MeSH and free text terms "quality of life." For each
year, we calculated the proportion of reports mentioning quality of
life. We repeated the analysis for cancer trials, using the search
strategy of the Cochrane Cancer Network for this purpose. We also
examined cardiovascular trials: we exploded all subheadings of the MeSH
term "cardiovascular-diseases" and combined the results with free
text searches using a total of 28 key words (details of the search
strategy are available on the BMJ website).
We examined the abstracts of reports published from 1993 to 1996. We had identified these in a search of an earlier issue of the Cochrane
Controlled Trials Register (issue 4, 1997) using the same keywords.
Abstracts from articles that reported the results of randomised
controlled trials and included at least one outcome that we considered
to be related to quality of life were assessed by CS and checked by JD.
The following information was recorded: language of article, condition
studied, and type of intervention.
A sample of reports from the database of abstracts was
assessed in more detail. Using a random number generator, we selected
20% of the trials reported in English. CS and DT independently examined the full reports of these using a standardised data sheet. The
data sheet covered the following items: conditions and interventions studied, primary and secondary end points, sample sizes, type and
documentation of the quality of life measures used, response rates, and
the presentation and direction of quality of life results. If not
explicitly stated by the authors, the primary end point was defined as
the one that was given prominence in the report. The results relating
to quality of life and other end points were also extracted. Finally,
CS and DT rated trial quality using the score described by Jadad et
al.16 The rate of agreement between the two observers was
generally high (median 80%, range 58-100%). Discrepancies were
resolved in discussions with ME.
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Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
The keyword "random*" identified 92 364 records, which shrank
to 1939 (2.1%) when "quality of life" was added. There were
10 896 cancer trials, of which 443 (4.1%) reported on quality of
life, and 18 398 cardiovascular trials, of which 393 (2.1%) reported
on quality of life. The proportion of trials reporting on quality of
life increased over time, from 0.63% in 1980 to 4.2% in 1997 for all
trials, from 1.5% to 8.2% for cancer trials, and from 0.34% to 3.6%
for cardiovascular trials (figure).

View larger version (20K):
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Prevalence of reporting on quality of life in randomised
controlled trials identified from Cochrane Controlled Trials Register
during 1980-97
Assessment of abstracts
We found 492 reports that were published during 1993-6, of which
we excluded 128 (26%) for not being a randomised controlled trial
(n=59), not reporting on quality of life (n=12), duplicate entry
(n=27), and not being a journal publication (n=30). We examined the
abstracts of the remaining 364 reports: the most commonly studied
conditions were cancer (29%) and cardiovascular disease (26%), with
other diseases occurring in less than 10% of studies (table 1). The
most common interventions were drugs (65%) and models of care (11%)
(table 2). Most of the reports (93%) were published in English
language journals.
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Assessment of full reports
We selected 67 English language reports at random and
examined them in detail (references are available on the
BMJ's website). They were published in 52 journals. Ten
journals published more than one report, and three (Circulation,
Lancet, and New England Journal of Medicine)
published more than two reports. The distribution of conditions and
interventions studied was similar to that in the database of abstracts,
with 30% of reports describing cancer trials, 25% describing
cardiovascular conditions, and 64% reporting on drug interventions.
Forty eight of
the trials used at least one of the 62 established instruments shown in
the box, and most (54) quoted a reference that described the
methodology. In 15 trials the authors used instruments or indicators
that they had developed for their study. Most of these were
questionnaires, and many used visual analogue scales. In a few cases
authors constructed composite indices. One of these indices, for
example, was described as "the sum of asthenia + unaided dressing + visits to the shops, etc + outside activities + number of consecutive
days spent without leaving home + number of days with a body
temperature of 38.5°C or less."17 In two studies it
was unclear how quality of life was measured.
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Quality of life instruments used in 48 randomised controlled
trials reporting on quality of life
No of trials given in parentheses if instrument was used in more than one trial. |
Quality of life was the principal end
point in 23 reports. Other end points were symptoms (n=12), disease progression or survival (n=8), exercise capacity (n=5), blood pressure
(n=3), pulmonary function (n=2), and 14 other end points (one study
each).
Quality of reporting on quality of life
The response rate
for quality of life end points was given in 38 of the studies, with
response rates ranging from 51% to 100%. In 46 reports the authors
clearly stated that the patients provided information on quality of
life, whereas in the remaining articles it was unclear to what extent
the information originated from patients, carers, or relatives.
Complete reporting of all items and scales occurred in 31 trials.
Probability values were presented in 52, but only 11 provided
confidence intervals. The mean Jadad quality score was 2.68, corresponding to 54% of the maximum score of 5.
Quality of reporting on quality of life was higher in the trials with
quality of life as the principal end point (table 3). These trials were
significantly more likely to have used an established instrument, to
state respondents, to give response rates, to report on all items and
scales, and to present absolute differences. Jadad scores tended to be
lower for these trials, although this did not reach significance
(P=0.15).
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Discussion |
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Quality of life is widely accepted as an important end point in clinical trials. 1 3 5 The prevalence and quality of reporting on quality of life in clinical research is unclear, however. We examined trends in the reporting of quality of life data in randomised controlled trials during 1980-97 and assessed the quality of such reporting in more detail for 1993-6. Based on the Cochrane Controlled Trials Register, the most comprehensive source of trials available, our results indicate that the prevalence of reporting on quality of life remains trivial. Overall, the proportion of trials reporting on quality of life increased from less than 1% in 1980 to about 4% in 1997. A higher proportion might be expected for cancer considering the nature of the disease and the fact that a number of key funding bodies recently introduced policies to promote the assessment of quality of life in randomised controlled trials.18 However, even among these the proportion reporting on quality of life was less than 10% in 1997. Furthermore, these low levels of reporting of quality of life may be an overestimate as almost a quarter of papers retrieved in our abstract search were considered to be irrelevant.
One reason why relatively few trialists embark on measuring quality of life may be because of methodological difficulties. Of the 67 studies sampled for detailed examination, 48 used 62 different pre-existing instruments and a further 15 studies reported new measures, with few following the methods proposed for the development and testing of instruments. 8 19 The need for both generic and condition specific instruments means that a range of measures is required, but it is implausible that some 40 different measures of generic or psychological wellbeing could be justified in 48 trials. Critical analysis of these instruments was beyond the scope of our study, but the dimensions of quality of life assessed as well as the levels of validity and reliability of the instruments varied considerably. Such variations will obstruct comparisons between studies.
Quality of reporting on quality of life
Gill and Feinstein examined 75 articles with "quality of life"
in their titles.2 Selection was independent of study
design, and most studies were published during 1987-91. They focused on
the investigators' definition of quality of life, their reasons for
choosing a given instrument, and the importance given to the patients'
own rating of quality of life. Gill and Feinstein showed that only 15%
of investigators defined quality of life, only 36% gave reasons for
their choice of instrument, and only 13% invited patients to
contribute personal assessments. We focused on reporting of quality of
life outcomes and found that similar problems apply in clinical trials.
For example, not only were patients generally not asked to
supplement the questionnaire based data with personal responses, in
about 30% of studies it remained unclear whether patients had
contributed any information at all. Clearly, some investigators
continue to believe that health professionals can make a valid
assessment of their patients' quality of life, in spite of evidence to
the contrary.20
Conclusions
Our comprehensive analysis of the literature shows that, although
it is increasing, the reporting on quality of life end points remains
uncommon in randomised controlled trials, and the quality of reporting
is often poor. An initiative similar to CONSORT14 that
involves trialists, specialists in the measurement of quality of life,
and journal editors is required to develop standards of assessing and
reporting quality of life in clinical trials. Decades after the
invention of the randomised controlled trial, such an initiative may
finally lead to trials assessing end points that really matter to
patients.
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Acknowledgments |
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The department of social medicine at University of Bristol is part of the MRC Health Services Research Collaboration.
Contributors: ME, SF, and JD designed the protocol for the study. CS performed the literature searches under the supervision of ME. Data were extracted by CS and DT. ME and CS analysed the data. All authors helped to write the paper. ME, JD, and SF are the guarantors for the study.
Funding: This work was partially funded by the University of Bristol.
Competing interests: None declared.
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References |
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(Accepted 29 September 1998)
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