Reliability and construct validity of the Instrument to Measure the Impact of Valve Heart Disease on the Patient's Daily Life

ABSTRACT Objective: evaluate the practicality, acceptability and the floor and ceiling effects, estimate the reliability and verify the convergent construct's validity with the instrument called the Heart Valve Disease Impact on daily life (IDCV) of the valve disease in patients with mitral and or aortic heart valve disease. Method: data was obtained from 86 heart valve disease patients through 3 phases: a face to face interview for a socio-demographic and clinic characterization and then other two done through phone calls of the interviewed patients for application of the instrument (test and repeat test). Results: as for the practicality and acceptability, the instrument was applied with an average time of 9,9 minutes and with 110% of responses, respectively. Ceiling and floor effects observed for all domains, especially floor effect. Reliability was tested using the test - repeating pattern to give evidence of temporal stability of the measurement. Significant negative correlations with moderate to strong magnitude were found between the score of the generic question about the impact of the disease and the scores of IDCV, which points to the validity of the instrument convergent construct. Conclusion: the instrument to measure the impact of valve heart disease on the patient's daily life showed evidence of reliability and validity when applied to patients with heart valve disease.


Introduction
Chronic disease may begin as an acute condition and extending through episodes of exacerbation and remission of symptoms. While it is possible to control the accumulation of events, the constraints imposed by the treatment can lead to a drastic change in the lifestyle of the subjects (1)(2) . Among the chronic diseases that evolve with these features, the cardiovascular disease (CVD), is an important cause of morbidity and mortality in the context of global health (3) . In Brazil, in 2013, cardiovascular diseases were the leading cause of death among all other conditions, corresponding to 28.0 % of the proportion of deaths with defined causes, wit acute myocardial infarction (AMI) being the cause of death of 85,939 people, and of these, 40,366 from the Southeast region. It is worth to highlight that in June 2015 alone, ischemic heart disease accounted for

2.3% of total admissions by the Brazilian Unified Health
System (4) .
Valve disease in Brazil, represents a significant portion of hospitalizations for CVD. Rheumatic fever is the main cause of valve disease in the national context, responsible for up to 70% of cases, unlike what happens in developed countries. However, national data on rheumatic fever, obtained through DATASUS, refer to the number of hospitalizations and valvular interventions, which may underestimate the actual number of cases, since it does not include heart valve disease patients diagnosed in the outpatients' clinic and that did not required hospitalization (4)(5) . The patient with valve disease may have different signs and symptoms (pain, fatigue, arrhythmia, palpitations, syncope, weariness and angina) whose frequency and intensity are associated with the valve apparatus affected, being the mitral or aortic valve , the type of injury (stenosis or insufficiency) and the stage of evolution of the valvular heart disease (5) . Due to the slow and progressive nature of many of these lesions, patients may not recognize the symptoms, since the limitation of their daily activities also occur gradually (6) .
The symptoms experienced by these patients result in changes in physical function, self-esteem, body image, social relations and a number of daily activities (7)(8) . Therefore, nurses should include in the care of these patients, not only biological aspects, but also those related to psychosocial variables, helping to overcome its limitations and the acquisition of coping mechanisms (9) .
In order to support nursing interventions that minimize the impact of valvular disease in the life of the subject, a specific instrument to measure the perception of valvular disease on the impact of the disease in his life, called "Heart Valve Disease Impact on daily life -IDCV", built and validated by the Brazilian cultural context (10)(11) .
This instrument showed reliable and valid psychometric properties when applied to valvular disease patients (11) . Although the instrument has been developed to be used with these patients, the refinement of its items resulted in the selection of issues that were pertinent to the impact assessment of valvular heart disease and also to assess the impact on other heart diseases with similar symptoms. In previous studies performed (12)(13)(14)(15) the reliability and validity of the instrument were shown, when applied in patients with coronary artery disease, heart failure and hypertension (AHT). A broader study was designed to assess the responsiveness of the instrument when applied to valvular disease patients and cardiac patients undergoing surgery (16) .
However, considering the psychometric evaluation of the performance of IDCV with patients with valvular disease, there was no estimation of the reliability of the instrument with regard to the stability of measurement, just as the occurrence of ceiling and floor effects.
Moreover, it was considered important to investigate the construct convergent validity through correlational evidence with a general question regarding the impact of the disease constructed by the authors of IDCV.
Thus, this study aimed to: assess the feasibility,

Type of study
This is a methodological instrument validation study to measure the impact of the disease -the IDCV (17) .

Study Location
The study was conducted in the cardiology

Subjects and Sample Size
This study included patients with mitral and / or aortic valve disease, of both sexes, aged over 18 years, subject to clinical and / or surgical treatment, in the aforementioned outpatient clinic. Patients who presented inability for effective verbal communication due to neurological or psychiatric changes were excluded.
The size of the sample followed the recommendations of validation studies, i.e., 100 subjects (18) . However, due to losses in the data collection stage, especially in the repeat test step, the final sample consisted of 86 patients.

Data Collection
Data was collected through personal interviews  (19) . It is noteworthy that the implementation of IDCV through telephone contact was chosen, because of the difficulties of the participants attending the second time of application of IDCV (repeat test). The literature recommendations for the use of the telephone contact in data collection were followed. In this sense, it was evidenced an invariance in performance scales used in different application groups -in person or by phone, suggesting that telephone contact is a reliable strategy to obtain data when compared to face-to-face interview, in addition to being effective, inexpensive and accessible (20) . Thus, in this study the IDCV applications in the test and repeat test were conducted by telephone contact in order to maintain the same method of data collection and avoid bias collection, thus ensuring the accuracy in obtaining these data. patients, it appears that the set of statements that compose it assesses the impact of chronicity imposed by different cardiovascular diseases (11) . The instrument obtained satisfactory psychometric performance when applied in CAD patients (12)(13) , those with heart failure (14) , just as in hypertensive patients (15) .

Data Analysis
The psychometric properties of IDCV were assessed according to the criteria recommended by international literature (22) . Data were entered into a spreadsheet Ceiling and floor effects were considered moderate up to 25% and substantial when higher than 25% (23) .
-Reliability with regards to the agreement between repeated measurements (Test-repeat test) through the use of the intra-class correlation coefficient (ICC).
The significance level for the statistical tests was 5%.

Ethical Aspects
The study was approved by the Ethics Committee

Socio-demographic and Clinical Characterization
Of the 86 participants, 58.1% were women, with a Regarding the analysis of the ceiling and floor effects (Table 1), it is pointed out that 32.6% of patients

Analysis of convergent construct validity
The results of the convergent construct validity assessed by the correlation between the total scores and the areas of IDCV and the scores of the general question on the assessment of the impact on subject's life are presented in Table 3.
Considering the assessment of the general question of the impact, the lower the score the higher the impact perceived by the subject and that the interpretation of the total score of IDCV the lower the score, the lower the impact perceived by the subject, statistically significant negative correlations were expected between variables analyzed. Negative significant correlations were found, moderate to strong magnitude between the measurement provided by the generic question about the impact of the disease and the total IDCV and most of its domains, except for the Adaptation to Disease that showed no correlation with the generic measure of impact. There was a significant correlation of strong magnitude between the scores of the general question of impact and the total IDCV (r = -0.5273), just as among the general measure and the field Social and Emotional Impact (r = -0, 5174) ( Table 3).

Discussion
This study aimed to evaluate the feasibility, acceptability and ceiling and floor effects; estimating the reliability as regards the stability of the measure and verify validity of the convergent construct IDCV, when applied to patients with valvular heart disease as outpatients.
The evaluation of practicability of the IDCV showed that it is a rapid implementation tool with an application average time of 9.9 minutes (SD = 3.3). This finding is consistent with those found in previous study (12) , in which the average application time was 09 minutes, according to another study (15) , the application of IDCV lasted 08 minutes. Regarding acceptability, all patients responded to all items, not being detected a score 3, which corresponds to the neutral response. Thus, the findings show that the IDCV proved easy to apply in the study group.
In the present study we evaluated the ceiling effects, which may indicate involvement in the instrument's ability to detect changes in health status with regard to the increase in perceived impact and thus, in situations of clinical worsening. Floor effect was detected suggesting impairment in the instrument's ability to detect changes in situations where there is an improvement in health condition due to the reduced impact of the disease (23) .
The analysis of data on ceiling and floor effects In other studies of IDCV, it was also observed floor effect in the areas of Physical Impact of the Disease -symptoms and in the field of Social and Emotional Impact (12,15) . In a study by Santos et al. (12) (15) . These findings can be explained in part by the constitution of their items: Item 1 "After I got heart troubles, did I start to pay more attention to my health? Another assessed property was the reliability of the instrument by the criteria of temporal stability by using the test-repeat test. We sought to assess whether in a given time interval, the participants' answers to IDCV showed little variation in the absence of external factors that could affect the perception of the subject on the concept studied (15) . In the present study the temporal stability was investigated in the interval of 7 to 22 days, by telephone contact, a strategy previously used (20) .
An appropriate level of agreement has been found between test / repeat test for total IDCV and for most areas, with the lowest value of ICC found in the field of disease impact on daily activities (ICC = 0.76).
These results coincide with those obtained in previous studies (14)(15) . In the study among patients with heart failure we observed an ICC> 0.96 for most IDCV fields except for the field Adaptation to the Disease (14) . In the study involving patients with AHT it has been found an ICC> 0.99 for the total IDCV, as well as their domains (15) .  (17,24). It seems there is no consensus on the number of hypotheses to be verified to ensure adequate validity (26). The convergent construct validity in turn, relates to the correlation between similar constructs measures (24) . According to Polit (27) in the absence of a gold standard, assumptions about the correlation between instrument scores and the scores of a measure with which is expected conceptual convergence, are tested. Therefore, the finding of a

Conclusion
This study concludes that the instrument to measure the Heart Valve Disease Impact on daily life -IDCV is an instrument with good acceptability and easy to apply, but it found the need to review the items that make up the domain of adaptation to the disease. The