Health related quality of life (HRQoL) measures represent an important part of assessing the quality of routine care in general practice. They are useful in understanding the patient’s point of view about the disease and the treatment methods applied, and deserve important consideration when comparing different treatments methods and evaluating interventions [1].

Nurses are educated to provide a wide range of components of care and they are aware of the importance of the quality of patients’ lives because nursing is holistically concerned with the whole patient and is a caring practice aimed to health promotion and maintenance or restoration of function [2].

There is a growing evidence indicating that 'quality of life assessment' is particularly relevant to the scope of nursing practice [3] and can be considered as adjuvant to clinical and physiological assessments in many chronic conditions, particularly cancers [4] and cardiovascular diseases [5]. This approach is the 'gold standard' in the evaluation of nursing care, healthcare services and outcome assessment.

Health-related quality of life tools have the potential to identify specific and general health needs which is particularly important in nursing dealing with holistic care: components of HRQoL tools are likely to be associated with specific health care needs and measuring HRQoL may lead to improved quality of care and to improvement of patients’ QoL, but the administration of quality of life tools can also provide a rapid screening in order to identify patients’ health needs.

Nevertheless, one of the main barriers in using HRQoL as an outcome indicator in the comparison of different survey results is the so-called interpersonal incomparability [6]. The evaluation and decision-making process that leads a respondent to evaluate and choose among different response categories of survey questions is a quite complex phenomenon. This complexity is the result not only of the individuality, but also of socio-cultural factors: same question can be interpreted in different ways by people belonging to different cultural contexts, but this difference can be detected even among individuals belonging to the same cultural field.

These factors may hamper the comparability of survey research especially if they are related to heterogeneous study populations and if the phenomenon under investigation is somewhat abstract [7].

For these reasons, King and colleagues (2004) introduced the anchoring vignettes, a methodological tool that seeks to correct for the different interpretations that can be given to responses on ordinal scales.

The main research purpose in this article is the validation of a touch-screen format EQ-5D-5L questionnaire with anchoring vignettes, through comparison with SF-12 questionnaire in paper format without vignettes.

Furthermore, we investigated whether the questionnaire form (paper or touch screen format) and/or the presence of the vignettes in EQ-5D-5L affects the interpretation process of questions proposed to respondent.

Table 1 reports the correlation coefficients between the dimensions included in each questionnaire. These measures of convergent validity between EQ-5D (with vignettes) and SF-12 questionnaire, indicate that anxiety is related with all SF-12 dimensions excluding general mental health (MH), and that physical function (PF) is associated with all EQ-5D dimensions.

Five latent factors whose eigenvalues are greater than 1 are identified (Fig. 2).

Fig. (2). Scree plot of factorial and component analysis on polycoric correlation matrix.

Observing the loadings of variables on latent factors (Fig. 3) it is possible to assess that, on the first factor, the variables related to physical activity in EQ-5D and SF-12 questionnaire are coherently relevant. The variables with greater loadings on the second factor are related to emotional health and self-care status in both questionnaires. Mobility and selfcare variables are relevant for the third dimension, while on fourth factor are relevant activity and pain component, and the variable more contributing to last factor is the anxiety component. The identified dimensions are coherent with the different aspects of HRQoL, which the questionnaire aims to capture.

Fig. (3). Factor loadings on four latent components(Progressive code numbers at the end of the labels indicate items constituting each section of the questionnaire).

A comparison between EQ-5D questionnaire in paper and touch-screen format has been performed evaluating if the questionnaire form affects the subjective evaluation parameters modeled in a Chopit model. The Chopit model has been estimated on each questionnaire dimension.

The questionnaire form is not a significant factor affecting the subjective evaluation, as modeled by γ parameters (Tables 2-5).

For each computed model, the questionnaire form, in paper and touch screen format, does not affect the subjective interpretation of the ordinal scale proposed. This result comes from the lack of statistical significance of estimates on threshold defined on the latent variable; the subjective choice is modeled by a normal latent variable on which are defined covariates that may affect subjective evaluation process.

Moreover, the significant estimates (β) provided by a Chopit model, including vignettes, are also significant and coherent, in terms of estimated effect, compared to conventional proportional odds model (Tables 2-5), performed on EQ-5D questionnaire without vignettes.

Considering the Chopit model and ordinal Probit model, it seems that the main factor influencing each dimension of the subjective quality of life is represented by the educational attainment. As shown in Tables 2 and 3, it is statistically significant for mobility and activity dimension (P-value<0.05), indicating lower propensity in people with higher education level to perceive themselves as subjects with problems in mobility (OR=0.33) and activity (OR=0.44).

Gender is related to the perceived quality of life (P-value<0.05), in particular for the anxiety dimension (Table 5), denoting a greater tendency for females to perceive a poorer quality of life (OR=2.79).

Considering pain dimension, in Table 4, gender and ICD implantation are associated with subjective pain perception; specifically, women perceive more pain and discomfort (OR=2.58). Moreover, ICD implantation is associated with a higher propensity to pain perception (OR=5.74).

The model has not been estimated for self-care dimension because the majority of individuals in the sample (33 subject) confirmed not to have any problems in washing or dressing themselves, indicating that almost all patients are autonomous in the management of their daily chores.

The aim of the study is the assessment of the coherence between EQ-5D with SF-12 paper questionnaire, a validated tool useful to measure HRQoL outcome. The assessment of convergent validity between EQ-5D and SF-12 indicates that comparable dimensions are more related (i.e. Activity versus Physical Function, or Pain versus Bodily Pain and Anxiety versus Vitality and Social Functioning). A similar correlation pattern has been reported in Pattanaphesaj et al. [20].

Considering the overall score on EQ-5D in vignettes and SF-12, it is possible to consider that there are five latent dimensions (Health and Physical activity, Emotional health, Selfcare, Pain and discomfort, and Anxiety) coherently with EQ-5D questionnaire structure. Also, other studies confirmed the convergent validity of both instruments to measure the HRQoL [21].

Once an overall coherence between different instruments used to measure the same HRQoL outcome has been established, another objective was to evaluate if the touch screen form of the vignettes questionnaire affect the item interpretation process.

EQ-5D vignettes questionnaire, in paper form, has been considered in literature as a validated instrument useful to take into account of heterogeneity in item interpretation process [11]. It has been shown that EQ-5D questionnaire may be subject to DIF [3] (Different Item Functioning), a different item evaluation process across heterogeneous subjects. If DIF is not considered, the conclusions about perceived HRQoL may be misleading especially when heterogeneous groups are analyzed [19].

Chopit model, performed on vignettes questionnaire, leads to consider covariates on Item evaluation process identifying variables that may affect the subjective question interpretation [7], for this reason, the questionnaire form, has been included in the model as explanatory covariate defined on variable’s interpretation performed by respondent.

Concerning the validation of EQ-5D questionnaire with vignettes in touch screen format, the questionnaire form does not affect the interpretation of questions among subjects, confirming that the electronic format is equivalent with correspondent validated paper tool.

Moreover, as the administration of the electronic questionnaire is a widespread practice, many patient reported outcome studies confirm that paper and computer administered questionnaires are equivalent [22].

Considering also the patient’s prospective, an important aspect in PCOR research, in some studies, patients preferred electronic surveys, especially when being assessed for psychological aspects [23, 24]. A further point under consideration is the evaluation of coherence, in terms of results estimation between a Chopit model performed including vignettes in the data, and the results obtained estimating a conventional Ordinal probit model.

The results are very similar in term of effects related to factors affecting the HRQoL in both estimated models. Consistently with existing literature [25], it is possible to confirm that subjects with higher education attainment level achieve lower scores on EQ-5D scale in mobility, activity and anxiety dimensions, thus indicating a better quality of life in these domains.

Considering pain dimension, the factors affecting the HRQoL seem to be ICD implantation and gender. Other studies confirmed that the disease severity is associated with the subjective pain perception: in fact, the presence of previous chronic disease was associated with higher pain and discomfort perception [26, 27]. As shown in other researches, there is a significant relation between gender and anxiety/depression dimension in the EQ-5D questionnaire [21].

However, we acknowledge that further research is needed to generalize the validity of EQ-5D vignettes questionnaire in electronic form, given that we have built our conclusions on the small study sample. In fact, 90% of articles reporting validation of patient centered outcomes had a sample size greater than or equal to 100 [28].

Moreover, when an abstract concept such as HRQoL is considered, it appears pretty obvious that it is necessary to make most of the vignettes, but in our case the questionnaire has been validated using a sample of fairly homogeneous patients. Vignettes questionnaire is useful to correct DIF especially in case of rising heterogeneity of individuals in terms of socio-cultural characteristics [29]. A further research development may be the validation of EQ-5D questionnaire using a larger sample of patients with more heterogeneous features in terms of health, social background and culture.

The EQ-5D in vignettes in electronic format is a tool to measure HRQoL, which seems as valid as other validated questionnaires used to measure the same concept as SF-12 questionnaire.

Moreover, the questionnaire electronic form, seems to be a factor not affecting the subjective item evaluation process.