Background
Musculoskeletal conditions are a major contributor to the burden of disease worldwide [
1]. These disorders were responsible for 6.8% of the global disability-adjusted life years worldwide [
2], with osteoarthritis representing the single most important condition [
3]. Due to its high incidence and low case-fatality, osteoarthritis affects a substantial part of the population [
4]. Even though the impact of osteoarthritis on individuals (impairment of daily activities and professional life) and society is undeniable [
5]-[
9], doubt persists about the usefulness of early diagnosis in modifying prognosis and patient general well-being, since most non-invasive management approaches show low efficacy or poor adherence [
10],[
11].
Current guidelines emphasize health-related quality of life as a priority in healthcare services, particularly as part of chronic disease management [
12]. Quality of life is a personal and autonomous concept that is influenced by social and emotional contexts and not simply explained by the absence of physical symptoms or disease [
13],[
14]. Accordingly, it is plausible that the impact of knowing the name and the expected consequences of a disease may contribute to modify the well-being and welfare judgments and, consequently, the overall perceived health-related quality of life.
Previous research on health-related quality of life suggested that diagnostic labelling affects the self-perception of physical and mental health status regardless of objective pathophysiological changes or previous knowledge about the presence of a certain condition without symptom history [
15]-[
18]. The medical labelling of a long-standing chronic disease with suboptimal management effectiveness, as it is expected for osteoarthritis, might impair health-related quality of life without providing the additional benefit to offset it [
19]. However, up to the present, the effect of osteoarthritis medical labelling on health-related quality of life remains unknown.
Therefore, using data from a community-based sample of adults, we compared the physical and mental health-related quality of life between previously diagnosed (labelled) and undiagnosed (not labelled) osteoarthritis patients, also using subjects without joint disease as reference.
Discussion
Our findings suggest that, compared to individuals with no evidence of significant chronic joint pain, osteoarthritis significantly reduces physical health-related quality of life regardless of its medical labelling. However, among individuals with clinically confirmed disease, the labelling of knee, hip or hand osteoarthritis did not play a major role in physical or mental health-related quality of life scores.
Previous research has shown that osteoarthritis patients frequently score lower in health-related quality of life when compared to those without this condition [
26]-[
28]. Beyond the negative emotional impact of living with a chronic joint disease, osteoarthritis affects joints that are crucial to the performance of daily activities [
29],[
30], which was underlined by our findings showing that a worse physical health-related quality of life occurs when osteoarthritis is present (compared to those with no evidence of osteoarthritis), independently of the joint considered.
Regarding the physical dimension of well-being, evidence has been consistent in showing that disease labelling negatively influences quality of life [
17],[
18],[
31]. Cancer labelling has been particularly investigated, showing that the awareness of disease presence and severity significantly worsened the perception of health-related quality of life [
32]-[
35]. Nevertheless, among individuals with clinical confirmed osteoarthritis, disease labelling did not significantly interfere with health-related quality of life. Diagnosis establishment is expected to positively change the natural history of the condition, since it is expected to guide clinical practice into a better treatment and management of the disease. Osteoarthritis is a particular case because the available conservative treatments have insufficient effectiveness, and its surgical alternative (joint replacement surgery) is usually restricted to more severe cases of disease and has low acceptability in some settings [
36]. Comparatively to other chronic diseases, osteoarthritis labelling may have lower potential to modify physical health-related quality of life particularly because without an obvious compensatory treatment benefit, the role of diagnosis may exclusively contribute to the amplification of the vigilance and concern about the joint disease-related symptoms [
37]. The fact that osteoarthritis has virtually null case-fatality when compared to other conditions such as cancer may also account for the negligible effect we have found in this study.
In relation to mental health-related quality of life, we did not observe a consistent effect of osteoarthritis labelling on this dimension of well-being, whether the reference group was composed by subjects without joint disease or by osteoarthritis patients not previously aware of the diagnosis. On the one hand, osteoarthritis labelling might trigger negative cognitions and emotions due to the awareness of living with a chronic disease whose effectiveness of treatments is doubtful [
38],[
39]. On the other hand, osteoarthritis labelling might have a positive interpretation, i.e., better chronicity than fatality. The balance between these two opposite meanings of osteoarthritis labelling is a probable explanation to the absence of significant results regarding mental-health related quality of life, even when the comparison group was composed by subjects without clinically confirmed joint disease.
Active case-finding of osteoarthritis, unlike clinical examination of unspecific complaints, implies the systematic search for one disease by taking advantage of the contacts of previously unaware individuals with the health care services. In clinical practice there is little advantage in searching for the presence of osteoarthritis in the absence of joint pain [
40], which is reasonable given that doubt persists about the usefulness of early diagnosis and treatment in modifying prognosis [
11],[
19]. If an effective medical intervention and management of the disease occurred after osteoarthritis diagnosis, the presence of a previous medical labelling should be associated to a significant improvement of health-related quality of life, especially in its physical dimension. However, as suggested by our findings, the labelling of osteoarthritis seems not to provide any specific additional benefit regarding health-related quality of life of patients.
To the best of our knowledge, this is the first study looking at the effect of osteoarthritis medical labelling on physical and mental health-related quality of life, using as reference a group of subjects from the general population without evidence of joint disease. This is a major strength since baseline health-related quality of life may depend on specific characteristics of the source population, particularly in middle-aged individuals. Another major strength of this study is that it provides an ample spectrum of the disease severity because it was based on data collected in a community-based sample. All participants were assessed using the same protocol and were evaluated by a single observer (rheumatologist) using the gold standard method for case ascertainment, which is also a relevant advantage of this research.
Nevertheless, some methodological issues need to be addressed. Recall bias may reduce the validity of the evocation of the information that was used to define preceding label of osteoarthritis. The number of years elapsed between knee, hip or hand osteoarthritis medical labelling and the moment of evaluation of the EPIPorto cohort was analysed as a potential marker of recall bias but its inclusion did not meaningfully change the magnitude of the estimates and was not considered in the multiple linear regression models as covariate. In addition, the validity of self-reported information on previous medical diagnoses was not optimal. Accurate reporting of osteoarthritis medical labelling is dependent on the characteristics of patients as well as on the medical workup used (clinical evaluation and/or radiography). Previous studies have shown that self-reported diagnosis of this type of condition is not commonly congruent with the medical one [
41]. In our study, we found that agreement between self-reported and clinical and radiographic osteoarthritis diagnosis in our sample was poor (data not shown). However, independently of the accuracy of self-reported osteoarthritis (our main exposure), our priority was to assess the beliefs of individuals regarding a potential presence of osteoarthritis, whether it was clinically valid or not.
The identification of subjects with osteoarthritis was based on a structured questionnaire where individuals were asked about joint pain: individuals that did not report joint pain were classified as not having osteoarthritis. We assumed that questions about joint pain presence had a negative predictive value of 100%. Although most osteoarthritis patients have joint pain [
42], we recognize the possibility of occurrence of false negatives. Additionally, alternative diagnoses of the most common inflammatory joint conditions were inquired (rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis and systemic lupus erythematosus). As expected, given their epidemiological pattern, the frequency of those diseases was much lower than that of osteoarthritis (below 2%). Thus, we do not expect that these contribute substantially to osteoarthritis misclassification in this community-based sample.
Data on potential confounders of the associations between osteoarthritis medical labelling and health-related quality of life were measured and included as covariates in the multiple linear regression models (sex and age, body mass index, clinical comorbidities – wide spectrum of chronic diseases – and intensity of pain). Since these variables returned significant changes in the magnitude of the estimates and were statistically significant, they remained in the models as confounders. Intensity of pain episodes in the preceding month was used as proxy of osteoarthritis severity. We understand that using diaries of pain in which participants should report the intensity of pain
in loco was probably the most adequate approach to measure the intensity of retrospective episodes of pain and consequent severity of the disease. However, since previous literature has shown that subjects are able to accurately recall and rate severity of pain or discomfort and that retrospective reports of intensity of pain are sufficiently reliable [
43], we believe that our methodological option did not substantially change our main findings.
In addition, both osteoarthritis labelling and health-related quality of life may be influenced by exposure to joint pain treatments [
11]. Nevertheless, we did not find any significant difference between exposed and not exposed individuals to osteoarthritis treatments (painkillers and anti-inflammatory drugs, physiotherapy or thermal spa) regarding the physical and mental health-related quality of life scores, independently of the joint in study.
Osteoarthritis presence was clinically evaluated in three different joints: knee, hip and hand. Concomitant osteoarthritis in the remaining sites may confound the associations between labelling in a specific site and quality of life: a subject may be included in the analysis as exposed to labelling regarding one joint and not exposed for the remaining joints. A sensitivity analysis was conducted, by stratifying the estimates according to the number of joints affected. Since changes in the magnitude or direction of associations were not observed, we believe that the number of joints diagnosed with osteoarthritis was not a major drawback to the interpretation of our results.
Finally, the small sample sizes used in the linear regression models may be a methodological limitation, especially when the models were computed using data only from individuals with clinically confirmed osteoarthritis. Sensitivity analyses were performed in order to test the impact in our estimates of the small sample size using the bootstrap method (replications = 100) [
44]. We observed a remarkable similarity between the 95% confidence intervals obtained in the original analyses and those computed by bootstrapping, which suggests that the small numbers of participants that were used in the linear regression models did not significantly impair our findings.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
SL drafted the first version of the manuscript, performed the statistical analysis and contributed to the interpretation of the results. RL, FA, MB and RAS provided significant advice and contributed to the interpretation and discussion of the results. HB coordinated the manuscript and contributed to the interpretation and discussion of the results. All authors critically reviewed the drafts of the manuscript and approved its final version.