Introduction

Healthcare research requires the use of cross-culturally validated instruments to measure implementation of healthcare interventions and their outcomes through quantitative comparisons over time and across organizations.1–4 The use of data obtained through culturally adapted evaluation instruments allows researchers, policymakers, managers and, health professionals to gain a more analytical view of the phenomena under study and to develop internationally accepted and recognized theories on the provision of patient care, based on the comparison of local data with broader data.5 This approach also facilitates the identification of factors contributing to the effectiveness of healthcare intervention programs,6 or other forms of Outcomes Research. This type of quantitative research, focused on the quality of healthcare provision, requires valid and reliable measuring instruments,7 obtained through cross-cultural validation studies. These studies aim to confirm the capacity of measurement instruments developed in one culture to produce meaningful results when applied in another culture.8 Measurement instruments can include questionnaires, tests, rating scales and self-reports,9 the latter being also known as Patient-Reported Outcomes Measures (PROMs).10

In recent years we have conducted several cross-cultural validation studies of different measuring instruments,11–19 which constitute a significant contribution to the development of experimental designs in the field of nursing and health services research. Several studies across different scientific areas are characterized by the use of specific terminology and by seeking to archive various equivalences across cultures. Additionally, cross-cultural validation studies involve a long and complex process that require researchers to have a wide-ranging technical knowledge of the translation, back translation, adaptation, and pre-test aspects, their purposes and options, the different psychometric properties, and the required evidence for their assessment and knowledge about quantitative data processing and analysis using statistical software. Furthermore, these studies involve specific risks of bias, which may affect the research process and results. To address these challenges, novice researchers must be well-informed about the most suitable methodological approaches.

Concepts and Specifics Terms

The adaptation and testing of measurement instruments across different international contexts over time, not only enhances their reliability and validity,20 but also facilitates comparisons between cultures and the identification of relevant factors for developing effective interventions.6 Cross-cultural adaptation is not limited to the translation of measurement instruments. It encompasses the adaptation and validation of these instruments in the cultural context in which they are intended to be used.21

Some specific terms are used in the process of cross-cultural adaptation. For example, the “target version” of a given measurement instrument is the version to be created through the process of cultural adaptation and the “target language” consists of the language into which the adaptation is intended. The “original version” is the version of the instrument that researchers intend to adapt and the “source language” is the language of the “original version”. Bilingual translators in the process of cross-cultural adaptation are individuals who have a full command of both the “target language” and the “original language”.22 Translation involves converting a document from the “source language” to the “target language”, considering the target audience, target culture, and the skopos (brief or communicative purpose).23 In the case of translating health instruments, this encompasses factors such as accuracy, fluency, and conceptual equivalence, but also, as argued by Montalt & Davies,24 the ethical priority of “cultural relevance”, while cross-cultural adaptation comprises the identification of differences between the “source culture” and the “target culture” to maintain the equivalence of concepts. Finally, cross-cultural validation aims to ensure that the “target instrument” works as intended and has the same properties as the “original instrument”.25 Within cross-cultural validation we can distinguish the psychometric validation performed after the field testing from the validation performed during pre-testing, which aims to validate the adapted version before its exploratory use.

Types of Equivalence

The purpose of cross-cultural adaptation consists of obtaining a measurement instrument in the “target language” that is conceptually equivalent to the original. Before researchers opt for a particular methodological approach for the translation, adaptation, and cross-cultural validation of measurement instruments, it is necessary to understand the different types of equivalence that can be achieved between the “target version” and the “original version”.

The equivalence can be specified in different categories varying according to the authors. Herdman et al26 proposed a set of five categories: 1) conceptual equivalence; 2) item equivalence; 3) semantic equivalence; 4) operational equivalence and 5) equivalence of measurement. Conceptual equivalence verifies which domains and their inter-relations are important in the “target culture” for the concept of interest evaluated by the instrument. Item equivalence critically examines the items covered by the concept domains, while semantic equivalence ensures that translations of items semantically match the items in the “original version”. Operational equivalence seeks to guarantee that the measurement methods used are appropriate in the “target culture” and measurement equivalence corresponds to the verification of the process result with reference to instrument’s behavior related to its psychometric properties. Each one of these categories is important for judging the overall equivalence of the measurement instruments, ie their functional equivalence.26 Peña,27 described another equivalence categories, namely: 1) functional equivalence; 2) cultural equivalence; 3) metric equivalence and 4) linguistic equivalence. The latter corresponds to the semantic equivalence of Herdman et al.26 Functional equivalence assesses whether the instrument has the same behavior in both cultures. Cultural equivalence specifies how participants will answer to a given item covered by the same cultural meaning.28 Finally, metric equivalence concerns the difficulty of a given item being expressed in two different languages.29 According to Peña,27 the equivalences to be obtained in the cultural adaptation of measurement instruments depend on the objectives of the studies. To establish which equivalences obtain, researchers may choose one of these two categorizations. Understanding the different categories of equivalence enables researchers to design a methodological approach for cross-cultural adaptation procedures tailored to the types of equivalence sought. If researchers adopt a standardized methodological approach proposed by an author, it also allows them to supplement the process with other procedures better suited to the characteristics of their measurement instrument and target population. This is done with the purpose of achieving or strengthening a particular type of equivalence in the instrument.

Typologies of Biases

Another element that researchers need to understand before beginning the translation, adaptation and cross-cultural validation of measurement instruments is the risk of bias. Cultural biases pose the primary threat of this process. A measurement instrument is considered biased if two or more cultural versions are inadvertently affected by an undesirable source of variance, resulting from: 1) differences in concepts between the “source culture” and the “target culture”; 2) difference between the items used to represent the constructs in the instruments and 3) the method or form of administration used.30 Cultural biases are categorized into method bias, content bias, and construct bias based on their etiology.31 A challenge in cross-cultural adaptation of measurement instruments is managing different response styles across cultures, namely acquiescence, ceiling and floor effects, and the tendency toward neutral responses.32 These differences in response styles may be a source of method bias,33 and may be more expressive in certain cultures than others and related to the need to protect the identity and privacy,34 because of the presence of low levels of participants’ motivation and the valuing of social norms of politeness.35 Content bias can be introduced by items whose content is unfamiliar to the “target culture”,31 while construct bias occurs when there is only partial equivalence in the construct being measured between the cultures.36

To mitigate these cultural biases during cross-cultural adaptation, researchers can employ several strategies. One strategy is to pre-test the instrument with a sample of participants from the “target culture”. Another strategy comprises conducting interviews with participants after the pre-test to assess their attributes and functioning.30 Despite there is no robust evidence to prevent method bias, researchers may recourse to a) forced-choice response formats without middle neutral points and b) use Likert scales with an extended number of response options.32,37,38 For instance, using 5 to 7 point response formats is deemed suitable for measuring attitudes.39 To save time and resources, it is important that researchers identify the risk of any of these biases as early as possible, preferably before conducting pre-tests.

Methodological Approaches

The translation, adaptation and validation of instruments requires methodological guidelines developed and proposed by experienced researchers.40 Despite this, several validation studies do not mention whether they adopted an internationally accepted guideline for their work.41 Some authors have highlighted a lack of detailed information on the fundamentals of methodological approaches and the options available to researchers.42 Literature reviews have also reported a lack of consensus on the methodological approaches to be followed in the process of translation, adaptation and cross-cultural validation.25,42–44 Cha et al6 attributed this lack of consensus not only to the specificity of research questions but also to the research environment, namely the accessibility and availability of bilingual translators. Farina et al45 have recently shown that rigorous and pragmatic cross-cultural adaptation can be achieved with limited resources. Faced with a lack of consensus, Epstein et al25 recommended choosing methods that best suit the context in which the evaluation instrument will be used. Furukawa et al46 noted that this choice depends on research objectives, the availability of translators, budget, and time constraints. Additionally, Helmich et al47 advocated that in order to produce results that truly reflect the context, the choice of methods must align with the epistemological position of the researchers.

Despite the lack of consensus, guidelines share some common elements. In a literature review carried out by Acquadro et al,44 it was found that in order to cross-culturally adapt the PROMs, the guidelines have in common a multi-step and centralized process, at least one translation and some kind of pre-test. Regarding the questionnaires in general, Epstein et al25 observed that most guidelines recommend an Expert Committee, Focus Groups, and back translation of the instrument.

Guidelines should cover not only translation and cross-cultural adaptation but also psychometric validation. Some reviews have reported a lack of knowledge about the psychometric properties of adapted measurement instruments,48–50 and incomplete information on all the psychometric validation domains.51 For example, Danielsen et al52 found that the psychometric properties of adapted versions validated with different tests, recommended the inclusion of a quantitative validation phase that includes one or more tests focused on content validity, criterion validity, reliability and construct validity. Additionally, in a scoping review of Øygarden et al53 on measurement instruments for parental stress during the postpartum period, it was reported that none of the 15 instruments contained information on measurement error, responsiveness, and interpretability. Echevarría-Guanilo et al54 argue that researchers should have a comprehensive knowledge of psychometric properties to tailor the research design to the most appropriate psychometric properties of the instrument of interest.

Regarding methodological approaches, Machado et al43 identified the most widely used cross-cultural adaptation methods in nursing, and found studies where researchers added methodological approaches to the method they followed and studies where researchers did not comply with all the established methodological steps. Cruchinho et al55 in a study that evaluated the methodological approaches used in the process of translation and cross-cultural adaptation of the Bedside Handover Attitudes and Behaviours (BHAB) questionnaire56 reported the suplemental use of Dual-Focus to increase conceptual equivalence between the “source version” and the “target version”. A methodological approach is defined as the way in which a phenomenon is studied systematically, shaped by the researchers’ ontological and epistemological frameworks.57 Applied to cross-cultural validation studies, it can be defined as a way of studying the equivalences intended to be achieved through the translation, adaptation, and validation of measurement instruments.

In the cross-cultural adaptation of instruments, different methodological approaches can be used for translation, such as: 1) one-away translation; 2) Dual-Panel approach, and 3) forward and back translation.58 The one-away translation is the fastest and cheapest method, since it only includes bilingual individuals who translate the instrument into the “target language”.59 The forward and back translation is the most recommended method in translation guidelines.21,60–62 It requires at least two independent translators: one translates the instrument into the “target language”, and the other translates this version back into the “source language”.58 The Dual-Panel approach is a kind of Committee Approach involving a consensus translation by a panel of native bilinguals for the “target language”, along with a member of the research team adapting the measurement instrument. This consensus version is then reviewed by a second panel of monolingual target population members.63 It can also include a third panel to translate the translated version back into the “source language”.58 Lee et al64 found that both the forward-backward and Dual-Panel methods enable the production of semantically equivalent translations and highlight that translation alone cannot eliminate cultural discrepancies.

Papadakis et al’s65 study comparing translations by translators with different characteristics, emphasized the importance of translators preferably being bicultural and having some content knowledge of the instruments, ideally selected from the target population. In-depth knowledge of everyday contexts (beliefs, values, habits, symbols, expressions) enables culture be reduced to a set of core variables for a given construct and facilitates cross-cultural research.66 Members of the target population could be patients with literacy skills to enhance cross-cultural adaptation.67 In addition, Papadakis et al65 concluded that Principal Component Analysis of the measurement instruments is a methodology that can be used to compare translations carried out by translators with different profiles.

Methodological translation approaches can be symmetrical or asymmetrical. Symmetrical translations aim to make the instrument culturally relevant to the target population, while asymmetrical translations correspond to literal translations and maintain an one-to-one word correspondence.58 In a study that found some confusion among translators about which approach to take when performing back translations, whether more asymmetrical and literal or more symmetrical and understandable in the “target culture”, Bundgaard e Brøgger,68 stated that guidelines provide specific instructions on the translation process and strategy. This was to ensure clarity of item meaning and minimize threats to construct validity. In order to facilitate the negotiations of committees of translators in relation to the nuances of items and consequently minimize threats to construct validity, other authors have suggested providing a description of intentions for each of the items.69

Cha et al6 argues that the Committee Approach contributes to acceptable internal consistency coefficients. Concurrently, Epstein et al70 found that carrying out a multidisciplinary expert committee contributes to obtaining rigorous items in the adaptation of a multidimensional instrument.70 Other authors have reinforced the relevance of different types of Committee Approach. For instance, Teig et al71 reported that using the Delphi method in an Expert Committee with the criteria of anonymity, controlled feedback and statistical responses, provides a more accurate measure of the degree of consensus of all the elements than if a meeting had been held without any formal voting system.71 Tsai-T-I72 described a process of cross-cultural adaptation that involved a panel of experts to determine the content validity of the original instrument before translating it into the target language. Also, Jayawickreme et al73 stated the importance of using a Focus Group series to promote the evaluation of translated items by a panel of experts.73

Montenegro et al74 highlighted the importance of using Dual-Focus as a decentering strategy in the context of the Committee Approach. After forward-backward translation, items or parts of items that are not appropriate for the “target culture” may be identified. In these situations, decentering and Dual Focus can be used.75 Decentering is a translation procedure that does not require a literal translation, which is used to achieve idiomatic, grammatical-syntactical, experiential and conceptual equivalence between the two cultures.6 Dual-Focus involves replacing items or parts of items with more appropriate ones in the “target language” in order to mitigate the difficulty of adapting certain content from the “source culture”.22 It allows us to scrutinize what each of the items in the “original version” of the instrument seeks to assess in the light of the operational definition of the construct we want to measure, and thus, ensure that we are concerned with content validity.76 Several studies have reported the substitution of words and items as a result of using Dual-Focus.77–83

The specific relevance of different methodological approaches has been justified in scientific literature. Toma et al84 highlighted the effect of combining the back translations with Cognitive Testing (also called Cognitive Interviewing and Cognitive Debriefing) in modifying five items of an instrument with each of these approaches.84 Comparing the results of the Cognitive Debriefing with the original instrument is essential to ensure cultural relevance, since it can reveal problems with wording, phrasing and resonance with individual’s world views.85 Hasani et al86 recommended the inclusion of Cognitive Debriefing in the research design together with the Expert Committee approach to ensure the validity and reliability of the measurement model.86 However, in an integrative literature review which analyzed how back translators were described in 105 empirical studies, Bundgaard e Brøgger87 found limited information on translators’ qualifications in empirical studies.

Back translation is the methodological approach whose importance has been justified in various ways. It was first advocated to limit the substitution of item content for cultural reasons.88 Subsequently, other researchers defended its use not as a method of equivalence, but rather as a way of checking the content of the items and the purpose of the instrument.89 More recently, the use of back translation has been argued as a documentation tool to show “what the translation says” and thus support researchers’ decision-making when adapting the instrument.90 Epstein et al70 concluded that back translation has little effect on the content and psychometric properties of a multidimensional instrument. Despite this, the same authors warned that back translation is an essential methodological approach for the authors of measurement instruments when they are not proficient in the “target language”.70,87

Previously published guidelines and recommendations present a set of methodological approaches in a prescriptive way,21,60,62,91,92 that does not promote the researcher’s decision-making on the best options for the characteristics of their validation studies. To facilitate the decision-making process several authors have been proposed glossaries,93 decision trees,94 and checklists,95–98 which enable researchers to avoid gaps in the process that affect the quality of the final instrument,52,99 and promote the active role of researchers in conducting the processes. The scarcity studies comparing methodological approaches prevents the recommendation of a specific method,25,44 meaning the processes of translation, adaptation and cross-cultural validation dependent on skills, knowledge and time,100 something that young researchers may not always have. Peña27 and Arafat101 recommended developing guidelines to support researchers’ decisions throughout the process. Similary, Cruchinho et al55 called for comprehensive guidelines on methodological approaches for novice researchers decision-making. Comprehensive knowledge of methodological approaches is a prerequisite for cross-cultural validation studies of measurement instruments.

Research Rationale and Aims

The first guidelines produced for the healthcare field emerged from extensive literature reviews, including literature from the health, psychology, and sociology.21,42,102 In Brazil, an integrative review of nursing literature revealed an overemphasis on evaluating psychometric properties at the expense of exploring methodological approaches for translation and cross-cultural adaptation.41 To date, no study has identified the differences and similarities between existing guidelines in healthcare to support young researchers in the development of validation studies. Based on this, we formulated the following review question: - What similarities and differences exist in the methodological approaches recommended by existing guidelines on the process of translation, adaptation, and cross-cultural validation of measurement instruments in healthcare sciences? Therefore, this study aims to: 1) identify all guidelines and recommendations for translation, cross-cultural adaptation, and validation within the healthcare sciences; 2) describe the methodological approaches established in these guidelines, and 3) provide a practical guideline featuring various methodological options for novice researchers involved in translating, adapting, and validating measurement instruments. If you are planning to translate or adapt an measurement instrument, this article will assist you in critically choosing a methodological approach to obtain a valid, reliable, and unbiased instrument.

Materials and Methods Identification of Existing Guidelines

A methodological review was undertaken for this study. Methodological review is a type of literature review focused on summarizing the state-of-the-art in methodological practices within a particular domain.103 In this methodological review, the focus was on the methodological approaches used for the translation, adaptation, and cross-cultural validation of measurement instruments recommended by guidelines in the field of healthcare sciences. For this methodological review, we used a three-stage search strategy.104 The initial search was limited to the “CINAHL with Full Text” (via EBSCO) and “MEDLINE with Full Text” databases and included an analysis of the text words in the titles, abstracts and indexed terms used to describe the manuscripts in each of these databases. The second search involved the Boolean expression (((MM “Instrument Adaptation”) OR “cross-cultural translation” OR “cross-cultural validation”) AND (“recommendations” OR “best practice”)) in the “CINAHL with Full Text” (via EBSCO), and “cross-cultural adaptation”[Title] OR “cross-cultural translation”[Title] OR “cross-cultural validation”[Title]) AND (“recommendation*”[Title/abstract] OR “best practice*”[Title/abstract] OR “methodological approach*”[Title/abstract])) in the “MEDLINE with Full Text”. Finally, we reviewed the reference lists of the manuscripts obtained to identify any guideline(s) that were not retrieved in the initial literature search in the databases. We used this search strategy because it allowed us to identify additional guidelines. The database search was carried out between September and October 2023 and it was repeated in February 2024 to capture any guidelines that had been subsequently published. To select the articles, our criteria were based on the concept that a guideline summarizes evidence and expert opinions, considering existing resources and the feasibility of procedures.105 The inclusion criteria for selecting the manuscripts were: 1) a scientific article focused on the process of translation, adaptation, or cross-cultural validation of measurement instruments; 2) describing a guideline to be followed in one of these processes; 3) written in English, Spanish, or Portuguese; and 4) published in a scientific journal in the field of healthcare sciences. To define the areas of healthcare, we used the Classification of Health Care Providers (ICHA-HP) framework,106 which describes the actors who provide health care (eg general and specialized physicians, nurses and midwives, physiotherapists and physical therapists, occupational and speech therapists, audiologists, dental hygienists, mental health specialists, etc.). The exclusion criteria for manuscripts were: 1) editorial articles, literature reviews, thesis, dissertations, or book chapters, or scientific articles not focused on the process of translation, adaptation or cross-cultural validation of measurement instruments; 2) articles that do not describe any guidelines to be followed in one of these processes; 3) guidelines that have already been included for eligibility; 4) articles written in a language other than those specified; and 5) articles published in a field other than healthcare sciences (eg economics and management, education science and sociology). Figure 1 shows the results of the search and the selection of studies.

Figure 1 PRISMA Flow Chart of literature review. Adapted from Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021:n71. Creative Commons.107

Figure 2 Distribution of guidelines by years.

Figure 3 Distribution of guidelines by countries.

Figure 4 Flowchart of the translation, adaptation and cross-cultural validation process.

Content Analysis of Existing Guidelines

A content analysis was conducted,108 which included a total of 42 guidelines retrieved from the literature search. Based on this, we established two objectives: 1) to provide an overview of the range of methodological approaches included in the guidelines and 2) to identify the similarities and differences that exist in terms of the methodological approaches recommended. In a first step, all relevant excerpts from the guidelines focusing on methodological approaches were paraphrased, summarized, and structured. Based on these excerpts, paraphrases were formed, and categories were inductively generated. Subsequently, the categories generated were reviewed and grouped by similarities and differences into broader thematic categories. Finally, the paraphrases and categories derived from the guidelines were described narratively.

Proposal for a Practical Guideline

The development of guidelines is a multidisciplinary process that should include all relevant areas of expertise and perspectives.109 Based on the synthesis of the methodological approaches from existing guidelines, we have drawn up a practical guideline based from an universalist perspective,26 enriched by contributions from experts in the fields of nursing management, statistics, and linguistics with experience in the translation and cross-cultural adaptation of health measurement instruments and in the supervision of novice researchers. Our recommendations are grounded in the common elements identified among the guidelines retrieved from the methodological review, and are supplemented by our own professional expertise.

Results

We reviewed 42 guidelines on the processes of translation, adaptation, and cross-cultural validation of measurement instruments. The guidelines included were published between 1993–2021, and most were published during the first two decades of the 21st century (Figure 2). The main countries of publication were UK (7), Netherlands (7), USA (4), Canada (4), Spain (4), and Brazil (2) (Figure 3). The findings will be presented using the four thematic categories developed because of the analysis: general information, cross cultural translation, cross-cultural adaptation, and cross-cultural validation. Here, in keeping with the aims of this methodological review, we provide an overview of the similarities and differences of methodological approaches recommended by the guidelines about each thematic category.

General Information

Some guidelines recommend a preliminary stage before the translation of the instrument called preparation.60,92,98 This stage includes obtaining permission to use the instrument,60,92,96 without clarifying whether this permission is given by the authors of the instrument or by the publisher who holds the copyright to the articles. Other authors suggest that permission should be requested from the instrument’s publisher,98 the affiliation institution,98 or the authors.60,92,98,110 In addition, other authors indicate that permission should be obtained from the owner of the instrument’s intellectual property rights.91,99,111

The initial phase also involves deciding which instrument to adapt cross-culturally. Some guidelines recommend that this decision should be based on checking that no version of the instrument exists for the target population,98,112 understanding their context,112 its purpose,91,98,112 features,112 the dimensions of the construct,98 the conceptual equivalence of the construct for the target population,91,98 its suitability for the intended clinical context,91,112,113 adequacy of psychometric properties,91,98,112 the existence of other cross-culturally adapted versions,114 and feasibility.98 Regarding feasibility, some authors specify factors such as completion time, cost and duration of the instrument, and the type and ease of administration.115 Other guidelines recommend only identifying the evidence on the quality of the selected instrument.92,116

To support the decision on which instrument to adapt, some authors recommend studying the relevance of the construct in the target population,99 as well as its conceptual framework,116 or meaning,96,116 which can be carried out through a literature review,26,61,117,118 open interview or Focus Group,26,61 or observation of members of the target population.9,26 Other authors emphasize the importance of researchers identifying early on the cultural and linguistic differences between the “target culture” and the “source culture”.92,96,111 To facilitate the translation and adaptation process, some authors propose developing a definition of the instrument’s constructs.98,112,116 Some guidelines recommend providing translators with information about the instrument’s construct,26 that can help translators resolve cultural and linguistic differences between the “source culture” and the “target culture”,119 eg scientific articles.91

Also included in the preparation phase is the design of a protocol for the process of cross-cultural adaptation of the selected instrument.91,99 Some authors recommend researchers decide which method to use:1) the same language adaptation approach for instruments adapted in another country or population with the same language; 2) the universal approach for translations intended for multiple locations simultaneously; or 3) the country-specific approach for different translation versions developed for each subpopulation.120 The use of combined methodological approaches and procedures that maximize conceptual equivalence between the translated version and the “original version” is proposed by some authors,111 which may vary according to the particular characteristics of the studies and the resources available to the researchers.121 This includes setting up a multiprofessional team comprising translators and experts in the field of the instrument’s construct.96

Few guidelines specify the leadership role of researchers within the team of translators and experts, for example in reviewing decisions to reconcile translations and in producing a more literal or more conceptual translation.60,98 Some special roles can be assumed by researchers, such as qualified moderators of Expert Committees,116 translation coordinators,122 or reviewers6,98,112,120,123 of proofreading after forward translation,6,98,112,120 back translation,92,120,122,123 pre-tests,60 and the final version of the adapted instrument.98 Some authors also advocate including members of the target population in the team when reviewing the cultural differences of the assessment instrument,124 and its developers,26 in the translation and cross-cultural adaptation process,26,98 and the study of the instrument’s measurement properties.116

Many guidelines recommend documenting the translation process, cross-cultural adaptation, and validation in a report that describes all methodological approaches and procedures used, and their results, problems identified, proposed modifications,21,60,92,93,96,98,99,112,116,121–123,125–127 along with the names, roles and background of all those involved,125 the testing process, and the statistical analysis.128 Some authors recommend creating a template for continuous recording of the process.98,112 The information in this template can be used to prove the equivalence between the adapted and original versions of the instrument and as supplementary material in the publication of a scientific article reporting on the process of cross-cultural adaptation of the measurement instrument.121 McKenna,114 argues that the overall process should be reported.

Cross-Cultural Translation

Forward translation and subsequent back translation is recommended in some guidelines.6,9,21,27,42,60–62,91–93,98,110,116–120,122–127,129,130 Some authors propose forward translation without back translation,99,114,118,128,131 or suggest back translation as an option.112 The majority, also propose that forward translation and back translation be carried out independently.9,42,60–62,80,91–93,98,99,110,112,116–119,122,123,125–127,131 Despite this, some authors propose the use of collaborative approaches to translation, such as the Committee or Focus Group Approach,128 the Dual-Panel,114 the use of a Bilingual Committee,118 translation with teams of two translators,80,129 or two to four translators.91 Others authors recommend using the one way or expert´s translation by a committee when human or financial resources do not allow the back translation to be planned.128

Regarding the number of translators, most guidelines suggest using at least two translators to translate the instrument and the same number for the back translation,9,21,42,60–62,92,93,98,110,117,122 or two translators for each of these approaches.9,91,123,126 Others propose at least two translators for forward translation and at least one for back translation,60,92,98,129,130 and others, at least one different translator for forward translation and back translation.27,118,128 Other authors recommend three translators for forward translation and one for back translation.6 Some of the guidelines that do not recommend back translation recommend using one translator,118 and two translators for the forward translation.112,131 Other authors recommend multiple translations without specifying a minimum number.99,116

Some guidelines recommend that researchers give translators instructions on which translation approach to follow (whether more literal or more cultural),119,125,131 explaining the concepts of the measurement instrument and how to use its definitions in each of the items,60,98 which may involve the prior supply of materials.91,98 Others only recommend providing information about the purpose of the instrument, the target population and the aim of the translation if the study involves professional translators.92 Most authors recommend using native translators,21,26,60,61,80,91,92,110–112,116,118,119,122,123,126,127 who are bilingual in both the source and target languages.6,21,26,62,91–93,98,110,111,117,123,125,128 Other authors suggest that the translation process should include at least one different professional translator in both forward and back translation approaches,92,98 others establish only the inclusion of professional translators in both approaches,96,127 and others only for back translation.93

In relation to the translators involved in forward translation, various characteristics are described, for example: 1) familiarity with the construct of the instrument;6,9,62,92,99,111,112,116,123,125 2) be a health professional familiar with the terminology used in the measurement instrument,91,112,119 or with experience in the clinical condition of interest;98 3) have translation experience;93,112 4) have previous experience of PROMs,60 and 5) be a representative member of the target population.98,128 Some authors require having a translator familiar with the instrument’s construct and an unfamiliar translator,21,62,110,116,123,128 while others require two translators familiar with the instrument and the context.6,9,42,91,92,125,126 It is, also, recommended that translators taking part in back translation: 1) not have access to the “original instrument”,21,62,92,98,110,123–125,127 2) are both naive about the construct to be measured,21,42,92,98,116,119 or one of them familiar with the construct area of the instrument and the other familiar with the linguistic and cultural nuances of the “source language”.62

Most guidelines establish a synthesis or reconciliation stage after forward translation to identify and resolve discrepancies in the translation.21,60,62,93,98,110,119,123,131 To do this, some authors recommended using a third translator to reconcile the two versions of the forward translation,61,62,98,117,131 or one reviewer,60,98 or two.6,126 To obtain more accurate translations, researchers, also can provide materials to reconciliation translators.119 Some guidelines stipulate that the reviewer should reconcile the two translations into a single version together with the translators involved,91 including elements of the target population.61 To discuss and reach consensus on the differences found between forward translation versions, can be used the Committee Approach,6,130 Focus Group,61 or Delphi Panel.92 If a consensus cannot be reached on some of the discrepancies, one of the developers of the “original instrument” may be involved,91 or the use of an independent translator, who decides on the translation alone with input from the developers of the measurement instrument or another forward translator.98,122 Others recommend using the Delphi Panel to evaluate and resolve discrepancies between the constructs with elements not involved in the previous translations but with extensive knowledge of the constructs to be measured.92 As an alternative to using a collaborative approach, some authors propose having the back translated version reviewed by an independent translator who decides on semantic equivalence by comparison with the “original version” of the measurement instrument.6,123,127 Other authors suggest that the forward and back translation versions be synthesized by the same independent translator.117

With regard to deciding on the differences found, some authors argue that the meaning of an original term can be modified during the translation process if only part of the meaning is present in the “target culture” or if the term in the “target culture” expands the meaning of the term in the “source culture”.125 Some authors establish criteria based on source and comprehensibility, cultural appropriateness, grammar and terminology to support the reconciliation process decision.122

Cross-Cultural Adaptation

To adapt instruments cross-culturally, several guidelines include the use of collaborative approaches in the form of Expert Committees.9,21,42,62,92,93,96,98,99,116,117,123 For some authors,117 the committee of experts aim to ensure only semantic equivalence, while for others additionally aim to ensure idiomatic, experiential equivalence,21 and conceptual equivalence.21,62 Authors with a narrower purpose call the committee the Bilingual Committee,118 and the authors with a broader purpose call the procedure carried out by the committee o