Tobacco smoking is now a global epidemic of public health concern. Current reports conclude that cigarette smoking is the largest avoidable cause of premature death and disability worldwide [1, 2]. Tobacco now kills about 5 million people worldwide and if current trend continues, 10 million smokers per year are projected to die by 2025 [2, 3]. In Malaysia, the prevalence of smoking is moderately high and the Third National Health and Morbidity Survey has reported an overall smoking rate of 21.5%, and rates of 46.4% and 1.6% among male and female above 18 years of age, respectively [4]. The mortality rate from smoking-related respiratory diseases in Malaysia was 1017 per 100,000 population [5]. The Malaysian government has initiated smoking cessation clinics as part of its National Tobacco Control Program (NTCP).

Cigarette and other forms of tobacco are addictive in nature due to the nicotine contained in them. Nicotine dependence causes physical withdrawal as well as lifelong addiction. When tobacco use is stopped, nicotine withdrawal syndrome emerges, because the body has developed a homoeostatic response [2, 6, 7]. The withdrawal syndrome is characterized by symptoms such as irritability, frustration or anger, restlessness, insomnia, anxiety, depression, problems getting along with friends and family, poor concentration, increased appetite, and craving for tobacco [2, 7, 8]. Unfortunately, this syndrome is an important impediment to successful quitting and may lead to smoking relapse. Therefore, an effective counselling for smoking cessation should emphasize coping skills with stress and withdrawal symptoms as well as provision of social support as part of the treatment [9].

Consequently, assessment of withdrawal symptoms form an integral part of assessing health and quality of life in smokers during the process of quitting smoking as well as an important determinant of success. Accurate and efficient measurement of withdrawal symptoms is important theoretically and clinically in helping to understand nicotine dependence and in developing better treatment methods [8, 10]. A number of questionnaires with varying coverage of symptoms, quantitative indices of withdrawal and psychometric properties have been developed for this purpose [10, 11]. The Wisconsin Smoking Withdrawal Scale (WSWS), originally developed in U.S. English [8], is one of such instruments used to measure tobacco withdrawal symptoms experienced during the process of quitting smoking. This patient-reported outcome measure combines the strength of sensitivity to smoking withdrawal and is predictive of smoking cessation outcomes. Furthermore, WSWS is sufficiently brief to be used in routine clinical practice and research context [8, 10, 12]. Prior to use in international trials, the measure underwent linguistic validation in 18 languages [13].

Despite high smoking prevalence, several ongoing clinical studies related to smoking cessation in Malaysia and the obvious advantages of using WSWS as an indicator of nicotine withdrawal symptoms, there were no translated versions of any type of scale for the assessment of nicotine withdrawal in Malay for use in clinical research and routine clinical practice in Malaysia or other Malay-speaking populations. We therefore subjected this WSWS scale to linguistic validation and cultural adaptation processes in Malaysia for future use by clinicians and researchers.

The development of patient-reported outcomes measures such as WSWS for cross-cultural comparisons requires achieving "conceptual equivalence" between the original instrument and the target translation instrument [14–16]. Conceptual equivalence in the context of the current study is the absence of differences in meaning and content between the WSWS source language (U.S. English) and the translated version (Malay) [16]. This is achieved through a process called linguistic validation and cultural adaptation [14, 15, 17], as described henceforth. The cultural adaptation encompasses two essential and complementary stages: a translation stage to achieve linguistic validity of the questionnaire in the target language and psychometric evaluation. This paper aims to describe the linguistic validation of WSWS to produce a translated version in Malay language that was conceptually equivalent to the original version, as well as clear and easy to understand. Approval for the conduct of the study was obtained from the Human Research Ethics Committee of the Universiti Sains Malaysia.

The linguistic validation processes

The linguistic validation of the WSWS consists of three major steps: forward translation, backward translation for quality control, and pilot testing. Each stage helps to improve the quality of the translation in terms of conceptual equivalence and ease of understanding of potential users. A schematic presentation of the entire process used in this study is illustrated in Figure 1.

Forward translation

We obtained permission for the cultural adaptation and linguistic validation of the WSWS in Malay from the original questionnaire developers and the copyright owner at the University of Wisconsin Center for Tobacco Research and Intervention. All the concepts in the original questionnaire were clearly defined. The aim of the forward translation step was to produce a version in the target language (Malay) that is conceptually equivalent and close to the original WSWS in meaning. Two professional translators, who are native Malay speakers, bilingual and proficient in English, undertook independent forward translations of the original English questionnaire into Malay [14, 15, 17]. Comparison and reconciliation of the translations was done in a series of meetings between the investigators and the translators. Linguistic issues that arose were resolved by way of further consultations and consensus. The first reconciled version was developed in Malay based on the two forward translations and reconciliation.

Backward translation

A backward translation of the reconciled language version was produced in the source language (U.S. English) by a professional translator, native English speaker and bilingual in the Malay language [14, 15, 17]. The backward translation was compared to the original WSWS, leading to the production of the second reconciled version in Malay. Similarly, during this process, translation discrepancies and linguistic issues arose, and modifications were made accordingly.

Pilot testing (clinician's review and cognitive debriefing)

Two clinicians with cognate experience in smoking cessation reviewed the second Malay reconciled version of WSWS. This step aimed to obtain feedback from experts in the relevant medical field. Relevant feedbacks were incorporated into the second reconciled Malay version. A cognitive debriefing using face-to-face interview was further conducted. The translated questionnaire (second reconciled version) was administered on a sample of seven smokers with low to high level of education who were at different stages of quitting smoking [15, 17]. The sample was conveniently selected based on a sampling frame available at a quit smoking clinic at Universiti Sains Malaysia. The interview was conducted by investigators from the translation team using both rephrasing and probing techniques. The aim of this step was to ensure that the translation (instructions, items and response choices) was acceptable, understood in the way it was intended to be, and the language used was simple and appropriate for the target future users of the scale. The third reconciled Malay version was produced based on the results of the clinicians' review and respondents' feedback. A summary report was compiled at each stage of the process.

Finalization

Finally, the third reconciled version was proofread by a native Malay speaker in order to ensure that the final version was devoid of typographical, spelling and grammatical errors. Consequently, the final version of WSWS questionnaire in Malay was produced for clinical use (see Additional File 1: Appendix).

Here we present a summary of the linguistic issues and problems encountered during the linguistic validation processes and the necessary measures taken to resolve them. Grammatical and spelling errors corrected during proofreading of the third reconciled version of the translated questionnaire are not presented here.

Smoking harms nearly every organ in the body, causing a wide range of diseases and reducing quality of life and life expectancy [1]. Moreover, withdrawal symptoms can be unpleasant and may cause smokers trying to quit to relapse. Therefore, measuring withdrawal symptoms and quality of life is a vital part of assessing health in smokers during the action or maintenance stage of quitting [8, 13]. Cultural adaptation of quality of life instruments using standard procedures is becoming increasingly important in different countries and across different cultures. This is to ensure the optimal transfer of the original message and measuring what is intended to be measured. In the present study, linguistic validation of WSWS in Malay was carried out within the confines of internationally accepted guidelines [13–16, 18]. Most importantly, the translated instrument should be understood by most respondents in the Malaysian population and should maintain a reading and comprehension level that will be accessible by most respondents, even of a low education level.

It should also be kept in mind that the questionnaire should always be considered as a whole (e.g., the wording of the response choices may influence the translation of the items, and vice-versa). During the translation process of WSWS in Malay, a considerable number of linguistic and semantic issues arose. Most notable were the title, instructions, and items 1, 14, 20, and 26 of the questionnaire. The forward and backward translation processes permitted changes to be made with respect to the U.S. English version where words or concepts were untranslatable or where words or terms have a specific meaning in English but a semantically different or secondary meaning in Malay. For instance, in Malay language, the term "withdrawal" literally translates to "penarikan" ("to pull something"). Using the term as such would be meaningless and not easily understandable in spoken Malay. The phrase 'gejala penarikan' instead of 'penarikan', which means 'withdrawal symptoms' had to be utilized. Moreover, in Malay language, there is no literal translation to the expression "trouble getting cigarettes off my mind" (see item 26) and this had to be rendered as "difficult for me to forget about cigarettes". The backward translator was actively involved in the production of the second reconciled version in order to detect any misunderstandings, mistranslations or inaccuracies in the intermediary forward version of the questionnaire. This might have reduced cultural and social bias that may result when only one or two translators are responsible for the translation. Overall, the actions taken in the resolution of the problems encountered during these processes involved consultations and collaborations with experts in linguistics and the original developers. This reinforces the credibility of a rigorous translation method to ensure conceptual equivalence [15, 16]. Further, the cognitive interviewing techniques used can minimize sources of measurement error introduced by the translation process by detecting question items, terms, or response options that were difficult to understand or that were misunderstood by the respondents.

The availability of Malay version of WSWS has a promising role in helping clinicians and researchers providing smoking cessation interventions to better understand the withdrawal symptoms experienced by their patients and to individualize the treatments for tobacco dependence. In the light of the negative consequences associated with nicotine withdrawal syndrome on achieving abstinence, the authors recommend that all clinicians should use this tool as part of routine clinical practice in Malaysia.

A rigorous translation method was applied to ensure conceptual equivalence and acceptability of WSWS in Malaysian Malay language prior to its utilization in smoking cessation studies or clinical practice. However, further psychometric testing should be conducted to ensure the validity and reliability of the translation and its appropriateness among the Malaysian population.