Functional assessment in chronic or advanced diseases is critical (Mehta et al., 2011). Acute illness and hospitalization often lead to disability, especially in older adults (Covinsky et al., 2003), increasing the odds of disability 60 times and accounting for almost half of all new cases of disability (Gill et al., 2004). The development of disability among older adults is often complex and multifactorial (Nagi, 1979; Grimby et al., 1988; Verbrugge and Jette, 1994). Considering the pathway to disability, it seems that there is a relationship between chronic diseases and disability (Nagi, 1979; Verbrugge and Jette, 1994). For example, a patient with chronic arthritis may develop mobility impairment or may not be able to carry out tasks that are essential for independent living (Hung et al., 2011).
Disability is defined as a physical or a mental impairment that has a marked and long-term adverse effect on an individual’s ability to carry out normal day-to-day activities. It is a recent transition from independence to dependence on another individual to perform basic activities of daily living (ADLs), such as bathing, dressing, transferring from a chair, or using a toilet. In addition, ADLs are an essential part of patients’ functional status, as is also stated in the International Classification of Functioning from the WHO (World Health Organization, 2001), which emphasizes functional status over diagnoses. With the new system, disabilities would be considered as activity limitations and participation restrictions.
Many tools have been developed over the past few decades to assess patients’ abilities to perform ADLs that should form part of a systematic approach to assessment and which have been able to bring order to the planning process (Katz et al., 1963; Lawton and Brody, 1969). The instrumental activities of daily living (IADL) scale was originally introduced in 1969 by Lawton and Brody. It explores the basic ability of individuals to care for themselves and refers to higher levels of performance (Lawton and Brody, 1969). It is a useful tool in assessing an individual’s IADL over time, especially in the elderly, and it seems to be a valid and reliable tool for the assessment of functional disabilities in patients with dementia (Ahn et al., 2009). In acute and disabling conditions such as stroke or hip fracture, obvious and drastic effects on IADL are present, whereas chronic conditions have a more complex and less easily predictable effect (Wu et al., 2003). Cancer patients also had poorer IADL related to healthy individuals (Zustovich et al., 2009), appearing to be deficient in one or more IADLs (Zustovich et al., 2009; Goodwin and Coleman, 2011).
The ability to perform IADL is a crucial factor for independent functioning and living at home; however, evidence on its reliability and validity is limited, especially in cancer patients. In older cancer patients, IADL problems related to household activities, managing finances, shopping, and administration of medication and somatic comorbidity further increased the prevalence of IADL problems (Grov et al., 2010). Therefore, the aims of the present study were to translate the IADL instrument and test IADL’s psychometric properties in terms of internal consistency reliability, test–retest reliability, and validity among Greek patients with advanced cancer.
Materials and methods
To develop the IADL-Greek (IADL-Gr), the forward and backward translation method was used (Brislin et al., 1973; Temple, 1997; Tamanin et al., 2002). The questionnaire was first translated into Greek by two independent translators whose native language was Greek. The translators were healthcare professionals and familiar with the terminology of the area. The instrument was then back translated into English by another two independent translators whose native language was English and who had not seen the original English version. Emphasis was on conceptual and cultural equivalence in both forward and backward translation. The new back-translated version was then compared with the original version to check the validity of the translated version. The next step was comparison of the original and back translation questionnaire by the palliative care research team. Finally, a meeting of translators and the palliative care research team was held to make a decision about the final version.
The study was carried out at the outpatient clinic of a pain relief and palliative care unit in Athens, Greece, from January 2009 to May 2010, where patients were treated for their symptoms of cancer. Inclusion criteria were age older than 65 years and ability to communicate with the study personnel. A sample of 160 patients was considered eligible to participate in the study. Of these, 24 patients declined to participate. The final sample thus included 136 cancer patients. The hospital’s ethics committee approved the study, and the patients signed an informed consent. The questionnaires were administered to an initial validation sample (n=136) and a subgroup of patients (n=45) served to assess test–retest stability 3 days later. To assess the effect of treatment, 75 patients from the original sample were studied.
All patients were interviewed by a member of the palliative care unit to obtain information on background medical history (demographic data, previous mental health, and current condition). The evaluations were completed in a simple interview. Data were recorded on disease status, cancer diagnosis, treatment regimen, and patient’s performance status as defined by the Eastern Cooperative Oncology Group (ECOG) (Oken et al., 1982). Patients with a performance status score of 0 or 1 were characterized as having good performance status whereas those with a score of 2 or 3 were characterized as having moderate to poor performance status.
The patient self-report scales included the following:
The Lawton IADL, which is an appropriate instrument to assess independent living skills (Lawton and Brody, 1969). It is most useful for identifying how an individual is functioning at the present time and to identify improvement or deterioration over time. There are eight domains of function measured with the IADL scale: using the telephone, shopping, preparing food/cooking, housekeeping, laundry, mode of transportation, responsibility for own medications, and ability to handle finances. Women are scored on all eight areas of function whereas for men the areas of food preparation, housekeeping, and laundering (items 6, 7, and 8) are excluded (Lawton and Brody, 1969). Patients are scored according to their highest level of functioning in that category. A summary score ranges from 0 to 8 for women and from 0 to 5 for men. Respondents were characterized as having a disability in a task if they reported difficulty, or received help for the task, or could not perform the task secondary to health reasons.
Linear analogue scale assessment was used to measure patients’ quality of life (QoL) (Priestman and Baum, 1976; Gough et al., 1983; Mc Millan, 2007), consisting of three visual analogue scales to assess the continuum of selected energy, daily function, and overall QoL, respectively, graded from 0 (as bad as it can be) to 10 (as good as it can be). In the present study, only the scale of the overall QoL was used.
The first step was to examine the normality of the distribution of the data (using the Kolmogorov–Smirnov test and P–P plots). At the same time, the mean scores and SDs were determined. Subsequently, confirmatory factor analysis (CFA) was used to confirm the factor structure of the questionnaire as suggested by Lawton (1971). The CFA was carried out using analysis of moment structure version 7.0 software (Amos 7.0. James L. Arbuckle Technical Data and Computer Software; SPSS Inc., Chicago, Illinois, USA), whereby χ2 d.f. ratio less than 2.0 (Byrne, 1989), RMSEA less than 0.08 (Browne and Cudeck, 1993), and CFA greater than 0.90 (Bentler, 1990) were considered to indicate an acceptable fit. Finally, reliability (internal consistency, test–retest reliability) and validity (construct, treatment effect) of the IADL-Gr were determined as detailed below.
The internal consistency of the IADL-Gr was assessed using Cronbach’s α coefficient of the IADL-Gr. A threshold value of 0.70 was chosen, which indicates sufficient reliability for research purposes (Cronbach, 1951; Nunnally, 1978).
Test–retest reliability was determined by calculating Pearson’s correlation coefficient between the total scores of the IADL-Gr and the total scores of the reassessment (45 patients). Relative reliability, the degree to which individuals maintain their opinion in a sample with repeated measurements, was evaluated using ICC (intraclass correlation, i.e. the estimated error in measurements as a proportion of the total variance). Because correlation coefficients do not correct for systematic differences and agreement by chance, the scores of the two assessments were tested for systematic differences using the paired t-test.
Construct validity of the IADL-Gr was evaluated by establishing its correlation with ECOG and QoL scores. Correlation of the IADL-Gr with the well-established ECOG and QoL scores would support the validity of the IADL-Gr questionnaire in measuring important aspects of health status. The authors hypothesized that IADL-Gr would have a moderate correlation with ECOG and QoL, and that this would be consistent with the levels of correlation found in validation studies of several outcomes tools used in QoL.
Treatment effect validity of the IADL-Gr was assessed by comparing the initial score with the follow-up score (obtained 1 month after treatment in 75 patients).
The IADL-Gr score was further analyzed for the classification of patients as either high risk or low risk by calculating the respective areas under the curve (AUC). The areas under the receiver operating characteristic curves with their SE and 95% confidence interval (CI) were calculated using the maximum likelihood estimation method, which has the advantage of being free of an assumption about the Gaussian distribution of underlying variables. Furthermore, the sensitivity and specificity of different cut-off points of the IADL-Gr score were estimated using the constant score as the gold standard.
All analyses were carried out using SPSS 16.0 software (SPSS Inc., Chicago, Illinois, USA). The critical level for significance was chosen at P less than 0.05.
There were 76 men (55.9%) and 60 women (44.1%) in the initial sample; the mean age was 66.7 (SD 10.5) for men and 66.1 (SD 11.9) for women. The patients had lung cancer (26.5%), followed by breast cancer (19.1%), gastrointestinal (16.9%), genital (10.3%), and other cancer types; the majority (63.2%) had metastatic cancer (Table 1).
Confirmatory factor analysis
CFA yielded a single-factor model. The resulting global fit indices for men were χ2 d.f. ratio=2.05, RMSEA=0.092, CFA=0.914, RMR=0.343, GFI=0.841, AGFI=0.746, IFI=0.919, and TLI=0.908, indicating that the one-factor solution should be retained. The resulting global fit indices for women were χ2 d.f. ratio=1.94, RMSEA=0.082, CFA=0.944, RMR=0.350, GFI=0.881, AGFI=0.785, IFI=0.945, and TLI=0.938, thus also indicating that the one-factor solution should be retained and thereby confirming the results of Lawton’s study (1971).
Psychometric properties of the instrumental activities of daily living-Greek
The analysis of internal consistency showed that the reliability coefficients for the IADL-Gr scale were moderate to high. Cronbach’s α was 0.88 and 0.83 in men and women, respectively. The item-scale correlations ranged between 0.55 and 0.85 for men and between 0.63 and 0.90 for women (all P<0.0005).
The stability (test–retest reliability) of a patient’s response was evaluated by randomly selecting 45 patients who completed the questionnaire on two occasions (3 days apart). The paired samples t-test between the initial administration and reassessment indicated no statistically significant difference for either men or women. Pearson’s r and ICC coefficients between the initial administration and reassessment were 0.922 and 0.925, respectively, for men and 0.912 and 0.917, respectively, for women (all P<0.0005), indicating that the IADL-Gr total scores were highly consistent between the two occasions (Table 2).
In terms of construct validity, high Pearson’s correlation (P<0.0005) of IADL-Gr with ECOG was observed in men (r=−0.87) as well as in women (r=−0.85). A statistically significant correlation of IADL-Gr (P<0.0005) was also observed with QoL both in men (r=0.55) and in women (r=0.53).
In terms of treatment effect validity of the IADL-Gr (Table 3), there was a statistically significant difference between two time points among both sexes (P=0.035 for men and P=0.025 for women).
The sensitivity and specificity of different cut-off points of the IADL-Gr score were estimated using the maximum ECOG score as the gold standard. The AUC of IADL-Gr for men was 0.95 (95% CI 0.90–1.00, P<0.0005), with a cut-off point of 3.5, and the corresponding sensitivity and specificity were 84 and 95%, respectively (i.e. patients with an IADL-Gr score more than 3.5 have an estimated 84% probability to be correctly characterized as having a good status, and those with an IADL-Gr score less than 3.5 have an estimated 95% probability to be correctly characterized as having a moderate or a poor performance status). The AUC of IADL-Gr for women was 0.95 (95% CI 0.89–1.00, P<0.0005), with the estimated cut-off point of 6.5 and a corresponding sensitivity and specificity of 85 and 82%, respectively.
One of the main aspects of the healthcare of patients with chronic diseases is the attention paid to maintain functional ability (Hung et al., 2011). The aims of palliative therapy are to reduce symptoms, to stabilize or improve patients’ level of functioning, to reduce hospitalization, and to improve patients’ overall QoL (Mystakidou et al., 2001). Functional disability in cancer patients might be a consequence of the disease and its effects such as cachexia because of cancer (Zustovich et al., 2009). Little has been reported in the literature on IADL’s utility in cancer patients; thus, it is significant that the present work has resulted in the translation and validation of the Greek version of the IADL in cancer patients attending a palliative care unit.
The loss of self-care abilities results in serious short-term consequences for patients and families as patients found to be dependent as per the IADL scale cannot successfully live at home without the assistance of caregivers (Boyd et al., 2008). For women, the maintenance of earlier life levels of adequacy in tasks such as shopping, cooking, and performing laundry may be a means of assessing general competence. For men, the list of such representative activities is shorter. The sex-related content of these three items probably makes a difference (Lawton and Brody, 1969), and some authors have mentioned that the frequencies of the IADL items are different for women and men (Extermann et al., 2005). Similarly, in the current study, it was also found that there were sex disparities in disability as the prevalence of disability was higher in men than in women, which is in contrast with the result of Hung et al. (2011) study, where IADL scores were higher in women than in men.
The estimated validity and reliability of the Greek version of the IADL are similar to those obtained with other languages and confirm the unidimensionality of the IADL scale, hence suggesting that the instrument can be considered as measuring a single dimension of functioning as argued by Lawton and Brody (1969). In the present study, the reliability coefficients were moderate to high, thus supporting the robustness of the instrument, in agreement with other validation studies (Tong and Man, 2002). The construct validity analysis confirmed that the IADL-Gr scores for men and women were highly correlated with QoL as well as with the patients’ performance status as measured by the ECOG. This result encourages the use of IADL-Gr in clinical studies as a simple measure of patients’ functional impairment. Reasonably good cross-cultural validity was found among Chinese, Malays, and Indians, with the strongest validity for Indians (Ng et al., 2006).
The optimal balance between sensitivity and specificity for IADL-Gr was achieved at a cut-off score of 3.5 for men and 6.5 for women (which can be considered as equivalent), yielding an estimated sensitivity and specificity of 84 and 95%, respectively, for men and 85 and 82%, respectively, for women. In addition, IADL-Gr was found to be useful for detecting changes over time in declining health status in patients with advanced cancer.
Preventing disability by effective management of chronic diseases and impairments is of paramount importance to the care of older adults, especially of those with cancer, so that they can continue to live independently in the community for as long as possible. The major strengths of the IADL-Gr were that it showed satisfactory psychometric properties, that no cases were excluded from the analysis because of missing data, and the high degree of compliance, which indicated that the format and the content of the questionnaire were acceptable for patients with advanced cancer. However, the internal validity of the instrument in cancer patients remains to be verified in the future (using Rasch analysis).
In addition, further IADL-based investigations on the effect of chronic pain or other cancer symptoms on daily life activities should be carried out. It would also be worthwhile to examine whether IADL can be used to identify the stages and the special needs of cancer patients, as well as to develop predictive information on the functional outcomes related to cancer and its treatments in a palliative care setting.
Conflicts of interest
There are no conflicts of interest.
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