Translation and psychometric assessment of the Persian version of the Rhodes Index of Nausea, Vomiting and Retching (INVR) scale for the assessment of chemotherapy-induced nausea and vomiting S. MORADIAN, PHD, MA, BNURS, RN, School of Nursing, Midwifery and Social Work, University of Manchester, Manchester, UK, S. SHAHIDSALES, MD, ASSISTANT PROFESSOR, Cancer Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran, M.R. GHAVAM NASIRI, MD, ASSOCIATE PROFESSOR, Cancer Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran, M. PILLING, PHD, RESEARCH STATISTICIAN, School of Nursing, Midwifery and Social Work, University of Manchester, Manchester, UK, A. MOLASSIOTIS, RN, PHD, CHAIR PROFESSOR OF NURSING AND HEAD OF SCHOOL OF NURSING, The Hong Kong Polytechnic University, Hong Kong, China, & C. WALSHE, PHD, MSC, BNURS (HONS), RGN, SENIOR LECTURER IN PALLIATIVE, Division of Health Research, Lancaster University, Lancaster, UK MORADIAN S., SHAHIDSALES S., GHAVAM NASIRI M.R., PILLING M., MOLASSIOTIS A. & WALSHE C. (2013) European Journal of Cancer Care Translation and psychometric assessment of the Persian version of the Rhodes Index of Nausea, Vomiting and Retching (INVR) scale for the assessment of chemotherapy-induced nausea and vomiting No tools are available to assess or measure the experience of chemotherapy-induced nausea and vomiting (CINV) for Persian/Farsi speakers. The purpose of this study is to translate the Rhodes Index of Nausea, Vomiting and Retching (INVR) scale for use with Persian-speaking cancer patients. A sample of 94 cancer patients were recruited from a cancer research centre in Mashhad-Iran. A standard two phase process of scale translation and validation was conducted. In phase I, standard ‘forward–backward’ translation procedure was used to translate the original version of the INVR questionnaire into Persian. The translated questionnaire was reviewed and revised and a Persian version of the scale was produced. In the second phase, a multiphase instrumentation study describing the internal consistency and test–retest reliability of the translated version was conducted. The inter-item correlation measured by Cronbach’s alpha was 0.88. Test/re-test reliability was measured by the weighted kappa and was between 0.63 and 0.79, indicating ‘substantial agreement’ and stability between the initial and subsequent administrations for each item. These results demonstrate that the Persian version of the INVR is acceptable for use among Iranian cancer patients. Researchers could use this study as a model for future translation and application of psychometric instrumentation.
Keywords: nausea, vomiting, psychometric testing, forward–backward translation, scale, Persian.
Correspondence address: Saeed Moradian, 61 Steeles Ave E, Toronto, ON M2M 3Y3, Canada (e-mail: [email protected]
Accepted 1 October 2013 DOI: 10.1111/ecc.12147 European Journal of Cancer Care, 2013
© 2013 John Wiley & Sons Ltd
INTRODUCTION Chemotherapy is an important part of cancer treatment, but is associated with debilitating nausea and vomiting (Cohen et al. 2007). Despite advances in antiemetic management, nausea and vomiting are still important
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problems in clinical practice, and approximately 50% of patients receiving chemotherapy experience nausea and/or vomiting. These symptoms can adversely affect patients overall health and well-being in different dimensions: physically, psychologically and emotionally (Fu et al. 2002; Wiser & Berger 2005; Schwartzberg 2007). Poor compliance with scheduled chemotherapy due to nausea and vomiting can result in treatment interruptions or discontinuation, leading to poor outcomes (Lindley et al. 1992; Lohr 2008). In order to improve management of nausea and vomiting, careful measurement of the experience of chemotherapyinduced nauseas and vomiting (CINV) is required so that the effect of interventions to manage these symptoms can be assessed. A variety of tools have been developed to measure the experience of nausea and vomiting and each instrument has its own characteristics, benefits and weaknesses (Wood et al. 2011). However, there is no assessment measure for nausea, vomiting and retching available for nurses and other healthcare providers in Iran. It is proposed that the Rhodes Index of Nausea, Vomiting and Retching (INVR) is the best choice of instrument to be translated, and it is known to be an accurate and effective researchbased instrument (Rhodes et al. 2000; Fu et al. 2002; Brearley et al. 2008). The aim of this study is to translate into Persian/Farsi (Farsi is the indigenous name of the Persian language speakers) and validate the Rhodes INVR by testing content validity, internal consistency and test–retest reliability.
METHODS In this study the original language (English) version of the Rhodes INVR was translated into Persian (Iranian languages) and adapted it both linguistically and culturally. The results of an initial psychometric testing with Iranian cancer patients were also documented.
The Rhodes INVR The Rhodes INVR is recognised as self-explanatory, easy to complete, and requires little or no training or time to explain to patients. The INVR was designed to measure the frequency, distress and duration of nausea and amount of vomiting (Rhodes & McDaniel 1999). It is an eight-item instrument that uses a five point Likert scale and consists of three subscales: nausea (range, 0–12), vomiting (range, 0–12) and retching (range, 0–8), giving a total range of 0–32. It focuses on all three domains of the experience (nausea, vomiting and retching) and the aspects of occur2
rence, amount and duration (Rhodes et al. 2000). It is designed to be administered every 12 h (morning and evening) and can address the anticipatory, acute and delayed phases of CINV (Brearley et al. 2008). The INVR was developed from the INV-1 and INV-2 (Chou et al. 2005), both of which have good evidence of reliability and validity (Belluomini et al. 1994; Zhou et al. 1999). The INV-1and INV-2 have demonstrated a strong reliability (Cronbach’s α = 0.89–0.97 and 0.98 respectively) and good concurrent validity, with a correlation coefficient of 0.87 (Rhodes & McDaniel 2001; Chou et al. 2005). The INV-2 has been translated into several languages (Japanese, Spanish, Swedish and Thai). It has been used in a variety of populations, including oncology, obstetrics, post anaesthesia, medical and surgical patients (Fu et al. 2002; Chou et al. 2005) the INVR, a new format of the INV-2, is reliable, more consistent and more user friendly than the INV-2 (Rhodes & McDaniel 1999). The INVR has been used in several clinical trials (Farley et al. 1997; Martin et al. 2000; Dibble et al. 2003) and also translated into other languages such as Chinese and Korean languages (Kobayashi et al. 1999; Glaus et al. 2004).
Study design This is a translation and multiphase instrumentation study to determine internal consistency, test–retest reliability and content validity in the translated Persian version of the Rhodes INVR. The study design incorporates two phases. Phase I is the iterative forward–backward translation/ linguistic process between Persian and English, and phase II is the results of the initial psychometric testing of the INVR in Iranian cancer patients. The design of the study is outlined in Figure 1.
Participants Participants were recruited from the cancer research centre affiliated to Mashhad University of Medical Sciences (MUMS) in Mashhad, Iran. Permission and approval for this study was received from MUMS. Permission from the author of the Rhodes INVR was also obtained. Both study phases were conducted in the same setting, with the same approach to sampling and recruitment. The patients were recruited if they met the following inclusion criteria: aged 18 years or over, having a confirmed diagnosis of cancer, having received adjuvant chemotherapy that might make them nauseous, able to read and write Persian, and willing to participate. As the level of nausea and vomiting in patients who are actively receiving emetogenic chemotherapy may change between the © 2013 John Wiley & Sons Ltd
Translation of the Persian version of the Rhodes INVR
Phase 2 Psychometric assessment phase
Provisional forward translation to Persian/Farsi
Recruiting 84 cancer patients
English backward translation
Good approximation to original?
Filling out the translated INVR questionnaire in clinic and at home tomorrow morning
Yes Final forward translation and modification
Analysing data (content validity and internal consistency)
Piloting to 10 patients
Figure 1. Flow chart of the process of translation and validation of the Persian version of the Index of Nausea, Vomiting and Retching (INVR).
Create the Persian version of INVR
initial and second time of completion the questionnaire and this can negatively affect the scores for nausea, vomiting and retching, only patients who had previously received chemotherapy were recruited. All potentially eligible interested participants were referred to the researcher by oncologists after their visit at oncology clinic. Patients were given detailed information about the study and the research process. A convenience sampling method was used to recruit consecutive eligible patients. This technique was used because it includes all available subjects, making it a better representation of the entire population.
Phase I: Translation procedure and pilot testing of the INVR
foreign language education (English as a second language). The first translator was knowledgeable about healthcare terminology. The second translator was familiar with colloquial phrases, healthcare slang and jargon, idiomatic expressions, and common emotional terms used in Persian. The second translator did not have any special knowledge about medical terminology and/or the construct of the instrument. This approach led to generating two translated versions that contained words that covered both the medical and Persian spoken language, with its cultural nuances. The two independent translators and the translation co-ordinator (the principal researcher) compared the translated versions and selected the most appropriate wording both linguistically and culturally; the result became the preliminary translated version of the Persian INVR.
Forward translation Guidelines for the translation, adaptation and validation of instruments or scales for use in cross-cultural healthcare research were followed during the translation (Sousa & Rojjanasrirat 2011). First, the original (English) version of the instrument was translated to Persian. Translators 1 and 2 were bilingual (Persian and English), and were native Persian speakers. Translator 1 was a consultant oncologist, and had lived and studied in the UK, while the other was an academic translator, majoring in © 2013 John Wiley & Sons Ltd
Backward translation Second, the preliminary translated version of the Persian INVR was translated back into English by two additional independent translators (translators 3 and 4). Both translators were blind to the original version of the instrument. Translator 3 was a consultant oncologist and translator 4 was an academic translator majoring in foreign language education (English as a second language). The equivalence of the original and back-translated versions was evaluated 3
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by a committee including one experienced chemotherapy nurse, all four translators and the co-ordinator. The English back-translations were compared against the original English version by the committee to ensure that the meanings of the original questions were preserved. The committee checked the scales for any discrepancies. Slight discrepancies were solved by consensus with the committee members. The result was a pre-final version of the INVR.
Pilot testing of the pre-final INVR As suggested by Koller et al. (2007), 10 patients took part in this phase of the study. Participants, who had previously received chemotherapy, were asked to complete the pre-final version of the questionnaire. The aim was to know whether the questions in translated version are easy to read and understandable; therefore, recall bias that may result in loss of assay sensitivity was not an issue. All patients voluntarily agreed to participate in the pilot testing of the pre-final version of the INVR, following a detailed explanation by the translation co-ordinator. Written informed consent was obtained from all participants. After completing the questionnaire, the participants were asked, in a short, semi-structured interview, whether the translated questionnaire items were difficult to answer, confusing or difficult to understand. The patients were also asked whether they would have worded the questions in a different way (Koller et al. 2007; Sousa & Rojjanasrirat 2011). Most of the patients were male (7 out of 10) and older (ranging from 53 to 67 years). Persian was the only language used by the participants. Their educational levels ranged from junior high school to university degree. The time since their chemotherapy ranged from 3 weeks to 1 year. The results of the pilot testing revealed that the questionnaire could be completed in 3–5 min, and most patients (9 out of 10) confirmed that the questionnaire was easy to read and understand.
Content validity According to Streiner and Norman (2008), 3–10 experts are appropriate for a panel to estimate the content validity of an instrument. Therefore, to further determine the conceptual and content equivalence of the items of the prefinal version of the INVR, an expert panel including one nurse and one general practitioner who were working in supportive cancer care, including control and management of nausea and vomiting in patients receiving chemotherapy; in addition, one language expert was chosen by the translation co-ordinator. None of the panel of experts 4
was involved in prior steps of scale development. The expert panel was asked to systematically examine the content of the Persian versions of the INVR, review the items and determine whether the items covered a representative sample of the behaviour domain to be measured (Polit & Hungler 1997). They independently rated the Persian versions of the INVR in terms of the instrument’s applicability to cancer patients in Iran, including its content and cultural relevance, and language equivalence to the original instrument. The expert panel was asked to indicate whether each item on a scale was congruent with (or relevant to) the construct; the percentage of items deemed to be relevant for each expert was then computed, and an average taken for the percentages across all of the experts. They were also asked to evaluate each item of the instrument for content equivalence [content-related validity (relevance)] using the following scale: 1 = not relevant, 2 = somewhat relevant, 3 = quite relevant, 4 = highly relevant (Sousa & Rojjanasrirat 2011). Comparing the definitions of nausea, vomiting and retching in the Persian and those provided by Rhodes et al. (1995), reveals that there are no essential differences. Based on the comments from the expert panel and the participants in the study, the sixth item, which uses ‘a cup’ to describe the amount of vomiting, can cause confusion. Therefore, it was clarified with a number (‘a cup is equal to 250 ml’) after the statement. The final Persian version of the INVR was created, and phase II of the study (initial psychometric testing) began. Phase II: Psychometric assessment of the instrument Sample size The sample size required for an intra-class correlation coefficient (ICC) estimate of 0.75, with at least a 95% margin of error of ±0.1; was calculated as 75 using Sample Size Tables for Clinical Studies software (Machin et al. 2009). The internal consistency or reliability of the scale was estimated using Cronbach’s alpha. The sample size required an alpha value of equal to 0.75 for an eight-item scale with a 95% confidence interval with a margin-oferror of ±0.1; was estimated to be 61, using a formula for variance from Bonett (2002). Conservatively allowing for a 10% drop-out between testing and re-testing, the required sample size was set to 84, which would allow a good estimation of both an ICC and Cronbach’s alpha. Procedure A self-report method was used to collect the data. After obtaining informed consent, the participants were given © 2013 John Wiley & Sons Ltd
Translation of the Persian version of the Rhodes INVR
the demographic questionnaire and the INVR scale to fill out. When the participants had completed these at the clinic, a second INVR questionnaire was given to them (with a pre-paid envelope) to take home and fill out in the next morning. Participants did not receive any antiemetics between the initial and second measurements. All participants were asked to provide suggestions about the wording of the instruments, in order to determine face validity. These steps were continued until 84 participants were obtained. A 1-week time limit was given before contacting the patient, as a reminder, to send back their questionnaire, as participants might have forgotten to post it.
Statistical analysis An instrument’s reliability can be examined using tests of internal consistency, replication with different samples, and test–retest using the same sample (Hendrickson et al. 1993). The most common approach in the assessment of reliability is to measure the same type of participants on two occasions, separated by hours or days (Lexell & Downham 2005). It has been also indicated that the ICC is the preferred retest correlation coefficient (Lexell & Downham 2005). Therefore, ICC was used to assess reliability of the instrument. Cronbach’s α was used to calculate internal consistency. Test–retest was analysed using paired t-tests or non-parametric equivalents (Hendrickson et al. 1993). It is stated that test–retest reliability may be measured by the ICC when the data are continuous and normally distributed (Baumgarter 1989; Bruton et al. 2000). In addition, correlations are not an ideal statistical method to measure test–retest reliability for ordinal data (which is the case here) and the weighted kappa should be used (Table 2) (Baumgarter 1989). Analysis of the individual questions using the weighted kappa was performed in SAS v9.3.
RESULTS The characteristics of the participants and the setting were the same as in phase I. Eighty-four cancer patients were recruited in this phase of the study. The participants’ socio-demographic characteristics are described in Table 1. As shown, the majority of participants were female, educated only up to primary school level, and married. In total, 71 participants returned the questionnaire, making an attrition rate of 15%. No differences were found between the participants who completed the study and participants who did not complete the study. As the © 2013 John Wiley & Sons Ltd
Table 1. Demographic data of patient participants in phase II (n = 84) Patient completed the study n (%) Gender Male Female Age (year) 70 Education Primary school Secondary school High school diploma University degree Employment Manual work Housekeeper Farmer Clerical/admin Unemployment Other Marriage Single Married Separated (divorced) Widow Diagnosis Lymphoma Sarcoma Head and neck cancers Gastrointestinal cancers Breast cancer Genito-urinary cancers Other
Patient did not complete the study Total n (%) n (%)
29 (34.5) 42 (50.0)
6 (7.1) 7 (8.3)
35 (41.6) 49 (58.3)
4 (4.8) 8 (9.5) 14 (16.7) 15 (17.8) 15 (17.8) 9 (10.7) 6 (7.1)
1 (1.2) 1 (1.2) 2 (2.4) 2 (2.4) 2 (2.4) 3 (3.6) 2 (2.4)
5 (6.0) 9 (10.7) 16 (19.1) 17 (20.2) 17 (20.2) 12 (14.3) 8 (9.5)
42 (50.0) 13 (15.5) 13 (15.5) 3 (3.6)
9 (10.7) 1 (1.2) 3 (3.6) 0 (0.0)
51 (60.7) 14 (16.7) 16 (19.1) 3 (3.6)
11 (13.1) 36 (42.9) 7 (8.3) 7 (8.3) 6 (7.1) 4 (4.8)
1 (1.2) 8 (9.5) 1 (1.2) 0 (0.0) 2 (2.4) 1 (1.2)
12 (14.3) 44 (52.4) 8 (9.5) 7 (8.3) 8 (9.5) 5 (6.0)
6 (7.1) 57 (67.9) 2 (2.4) 6 (7.1)
2 (2.4) 10 (11.9) 1 (1.2) 0 (0.0)
8 (9.5) 67 (79.8) 3 (3.6) 6 (7.1)
12 (14.3) 4 (4.8) 4 (4.8) 20 (23.8) 15 (17.8) 4 (4.8) 12 (14.3)
3 (3.6) 1 (1.2) 0 (0.0) 3 (3.6) 4 (4.8) 0 (0.0) 2 (2.4)
15 (17.9) 5 (6.0) 4 (4.8) 23 (27.4) 19 (22.6) 4 (4.8) 14 (16.7)
differences between the score of the first and second administration were not normally distributed, the nonparametric two-sample Wilcoxon signed rank test was used to analyse the difference in responses. The results of the participants’ mean responses and the weighted kappa between individual scales items are shown in Table 2. The mean total symptom experience from nausea and vomiting was calculated by summing the patient’s responses to each of the eight items on the INVR and was 10.34 for the initial and 11.07 for the second administrations. It should be noted that the potential range of scores is from a low of 0 to a maximum score of 32 and a high score represents a higher level of symptoms. The scores in the first administration were generally lower than they were the second time around. 5
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Table 2. Two-sample Wilcoxon test and correlation between initial and second administration for each item Item
Test T1 Mean (SD)
Test T2 Mean (SD)
T1–T2 Mean (SD)
Question 1 Question 2 Question 3 Question 4 Question 5 Question 6 Question 7 Question 8 Total score
1.24 (0.72) 1.29 (0.63) 1.24 (0.67) 1.38 (0.90) 1.36 (0.83) 1.23 (0.61) 1.31 (0.73) 1.31 (0.76) 10.34 (4.82)
1.25 (0.65) 1.37 (0.81) 1.38 (0.87) 1.55 (1.01) 1.54 (0.97) 1.21 (0.53) 1.42 (0.92) 1.35 (0.81) 11.07 (5.62)
0.03 (0.61) 0.04 (0.55) 0.04 (0.84) 0.11 (0.90) 0.14 (0.61) 0.06 (0.41) 0.56 (0.56) 0.01 (0.62) 0.99 (5.10)
0.94 0.46 0.25 0.28 0.46 0.23 0.42 0.85 0.32
0.68 0.68 0.63 0.65 0.74 0.73 0.74 0.79
As shown (Table 2), the weighted kappa, as a measure of test–retest reliability, was between 0.63 and 0.79, indicating ‘substantial agreement’ and stability between the initial and subsequent administrations for each item (Viera & Garrett 2005). To calculate the ICC (total score) based on two time points, a two-way mixed anova with single measures in SPSS was used. The participants are the random factor, and we consider the time points as fixed factors. The ICC for the total score was calculated (ICC = 0.79). Overall Cronbach’s alpha was 0.88; alpha was 0.92 for the initial and 0.94 for the second administration of the questionnaire. Therefore both the internal consistency and the stability coefficients (the correlation between initial and second administration) of the INVR scale were high and satisfactory.
DISCUSSION The lack of a specific tool to measure nausea, vomiting and retching in cancer patients in Iran led us to develop (translate, culturally adapt and pilot test) and validate the self-reported INVR scale. Therefore, the purpose was to produce and test the validity and reliability of the INVR in Persian-spoken cancer patients to use for this population. Previous translation studies on the INVR showed good reliability coefficient, as the Korean translation found Cronbach’s α = 0.84 (Kobayashi et al. 1999) and the Chinese translation had a Cronbach’s α = 0.94 (Chou et al. 2005). Similar to the findings from these studies, the Persian version of the INVR possessed high Cronbach’s α = 0.88 (0.92–0.94). The integrative translation approach is a systematic, methodical and valid method for translating an instrument from the source language to the target language (Fu et al. 2002). Forward and backward translations and professional review of the target language version provided a valid method for establishing the equivalence of the target language version. A few changes were made during the translation and validation process of the Persian version of 6
the INVR. As Fu et al. (2002) indicated, several assumptions might explain this phenomenon. First, nausea, vomiting and retching are universal symptoms; few differences were found when comparing the conceptual equivalence between the English and Persian languages. This universal conceptual equivalence led to less mix-up and uncertainty during the translation process. Second, short and simple English sentences are more easily translated into another language (Brislin et al. 1973; Fu et al. 2002). The sentences in INVR contain fewer than 20 words, with one introductory statement for each question, plus insertion of one of the five possible patient responses. The simple sentence structure in the INVR probably resulted in less confusion in the translation process. In spite of the fact that a number of instruments measuring nausea and vomiting and their impact on quality of life do exist (Morrow 1984; Rhodes & McDaniel 1999; Martin et al. 2003), this is the first time that an instrument for measuring nausea, vomiting and retching to health professionals in Iran has been introduced. Clinicians may use this in clinical practice to assess CINV more regularly and systematically. Also, patients can use it to document their CINV experience as a communication tool with their clinicians. The instrument should have utility in future clinical trials or other studies of outcome research. The outcomes of the study may improve patients’ self-care and quality of life by helping them to better control nausea and vomiting in clinical settings. The results of this study should be stated as preliminary; because this study has several limitations that we hope to address in future studies. Geographic limitation of the sample restricts generalisability of the study. In previous studies conducted in Iran (Babu et al. 2011; Samah & Ahmadian 2012), it is shown that low level of education is one of the major variables linked with seeking less healthcare services and might be associated with how a patient reports symptoms. Understanding the manner in which an assessing tool is influenced by socio-demographics characteristics, medication use or © 2013 John Wiley & Sons Ltd
Translation of the Persian version of the Rhodes INVR
clinical procedures is important to ensure its utility and accuracy (Pepe & Longton 2005). Iran is comprised of people with different socio-cultural contexts and social class (Samah & Ahmadian 2012); and this may account for a difference in symptoms reported. The study would have been improved by examining the performance of the Persian version of INVR scale among more heterogeneous patient samples in Iran. Another limitation was lack of a tested instrument for measuring nausea and vomiting in Iran that could serve as the gold standard for the criterion validity. In addition, there is no instrument in Iran with a comparable content or construct that would serve as a suitable reference for the definition of construct validity. Construct validity might also be examined with factor analysis; however, much larger sample size was needed
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