Introduction

Quality of life is intertwined with an individual's perception within their cultural and value systems, aligned with their goals, expectations, standards, and perspectives [1, 2]. Based on this premise, measures of health-related quality of life have been developed, known as patient-reported outcome measures. These measures aim to gauge the impact of a health condition or treatment from the patient's psychosocial viewpoint, contrasting with the professional approach [3].

The evaluation of oral health based solely on clinical criteria falls short of measuring the genuine impact of oral issues on people's lives [4]. Consequently, to comprehensively understand the effects of changes in oral health assessment methods, the development of oral health-related quality of life (OHRQoL) questionnaires has been encouraged, and increasingly utilized in research [5]. Nonetheless, some of these instruments have limitations in their applicability, given that most are developed in English and countries with social and cultural realities distinct from Brazil [6]. Hence, these questionnaires must undergo cross-cultural adaptation and psychometric validation before implementation in Brazil [7].

Standardized guidelines for this validation and cross-cultural adaptation outline a process comprising stages aimed at ensuring equivalence and maintaining quality [6]. Moreover, these instruments must substantiate the accuracy of their results through psychometric properties, serving as benchmarks for measurement quality. These criteria encompass content validity, internal consistency, construct validity, responsiveness, reliability, reproducibility, convergent validity, discriminant validity, and interpretation [7, 8].

These cross-culturally adapted questionnaires, translated into Brazilian Portuguese and deemed suitable for use, have facilitated the assessment of how oral health impacts quality of life [9]. Notably, most of these questionnaires target adults, posing a significant challenge in evaluating oral health-related quality of life in children [10, 11]. Given the multitude of pediatric oral disorders with potential negative impacts on quality of life, there's a need for measures documenting oral health outcomes in these younger populations [12].

However, to circumvent reliability issues linked to cross-cultural adaptations, a critical evaluation of these translated versions is necessary to verify their adapted measures and preservation of psychometric properties.

This study aimed to review the reliability and validity of adapted OHRQoL questionnaires for children and adolescents, assessing their suitability for research and clinical practice in Brazil. Additionally, it critically evaluated and summarized the cross-cultural adaptation process of the revised questionnaires.

Methodology

The present systematic review is registered in PROSPERO (CRD42022300018) and was performed based on the COSMIN guideline for systematic reviews of patient-reported outcome measures (https://www.cosmin.nl/).

Focus question

The COSMIN manual was used to establish the study question and to conduct the search. According to the manual, the question should include the following four key elements: 1) the construct; 2) the population(s); 3) the type of instrument(s); and 4) the measurement properties of interest. Hence, the focus question became:

What is the reliability and validity of transculturally adapted and translated questionnaires used to assess OHRQoL in Brazilian children and adolescents?

Eligibility criteria

For this systematic review, studies were included based on the following criteria: validation studies and cross-cultural adaptation of OHRQoL instruments into Brazilian Portuguese, studies evaluating measurement properties of OHRQoL questionnaires in children/adolescents, and those reporting at least one of these measurement properties: reliability, internal consistency, measurement error, content validity, construct validity, criterion validity, discriminant validity, and/or convergent validity. Excluded from consideration were systematic reviews of OHRQoL measures, studies solely reporting OHRQoL assessment through instruments, the development and validation of new instruments, questionnaires consisting of a single item, and validations conducted specifically for Portuguese from Portugal.

Search strategy

The studies were acquired through electronic searches conducted in the PubMed/MEDLINE, Web of Science, Lilacs, VHL (BIREME), Scielo, and Embase databases. Keywords were utilized and searched within Health Sciences Descriptors (DeCs), Medical Subject Headings (MeSH), and published manuscripts focusing on oral health-related quality of life. The boolean operators AND and OR were employed alongside the following terms: quality of life, oral health quality of life, instrument, scale, questionnaire, measurement, measurement tool, psychometrics, reliability, validity, instrument validation, cross-cultural adaptation, instrument translation, Brazilian version, Brazil, Portuguese, Brazilian Portuguese. A generic search strategy was tailored to suit the specific attributes of each database, aiming to identify relevant studies for this review (Table 1). Articles and abstracts from databases were sought without language or time restrictions. Furthermore, an additional search was conducted for grey literature using Google Scholar. All included study references were reviewed to identify supplementary studies. Searches in these databases were conducted until March/2023.

Table 1 Search strategy adapted for each database
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Studies selection

The Rayyan tool (https://rayyan.qcri.org/welcome) was used in the selection of studies, duplicates identification, management, and citation of references during the development of this review [13]. The study selection process was performed by three reviewers (DWDdeO, FSL, and YGG) in two phases. In the first phase, reviewers independently identified all relevant studies through electronic search methods based on inclusion criteria applied to titles and abstracts. The full text was pre-selected for studies that appeared to meet the inclusion criteria or for which insufficient data were found in the title and abstract to make a clear decision. In the second phase, the pre-selected studies were read in full by the same researchers to define whether the study met the inclusion criteria. When necessary, the authors of the studies were contacted by email to clarify questions related to the research. Studies excluded at this or subsequent stages were recorded, along with the reasons for rejection. Observational studies that met the eligibility criteria were included in the final analysis and submitted to data synthesis. Articles identified twice or more were considered only once. Disagreements were resolved by consensus among the three reviewers. This procedure was applied at all stages. The reviewers were trained for database use before the study.

Data extraction

The data were qualitatively recorded to allow comparisons of the selected studies. Each researcher qualitatively evaluated the studies. Data were collected on the following items: author, year of publication, country, study design, characteristics of the participants (gender and mean age), original language of the instrument, cross-cultural adaptation process, target population, main reported results, conclusion, name of the questionnaire, acronym, generality or specificity of the instrument, method of conclusion, domains, number of items, score, period of evaluation, time of completion, availability of the questionnaire in Brazilian Portuguese, Cronbach’s alpha, internal consistency, criterion validity, construct validity, reliability, discriminant validity, general ICC value, translation, back-translation, synthesis, committee approach, pre-test and psychometric evaluation.

Measurement properties assessment

The psychometric properties of oral health-related quality of life questionnaires identified were then evaluated according to nine criteria: content validity, internal consistency, criterion validity, construct validity, reproducibility, responsiveness, floor, ceiling effects, and interpretability. Each scale received a positive (+), undetermined (?), or negative (-) rating for each of these measures, or a rating of 0 if no information is available. The evaluation results were presented in a table, but not using an overall score, as this gives equal importance to each psychometric property, which is not necessarily appropriate [14].

The cross-cultural adaptation process of the instruments was evaluated according to the five steps [15], namely: (1) translation, (2) back-translation, (3) committee review, (4) pre-test, and (5) re-examination of score weighting. In the first step, at least two qualified translators translated the scale from the original language into the target language. In the second step, two independent translators must translate the translated version back into the original language to ensure that the translation reflects the content of the original. The third step ideally involves a committee review to develop the penultimate version for pre-testing, and the fourth step consists of applying this version among 30–40 individuals from the target population. The final step is to re-examine the weighting of scores considering the cultural context.

Risk of bias assessment

The risk of bias was evaluated using the COSMIN Risk of Bias Checklist [16]. This checklist includes three parts with 10 boxes. Boxes 1 and 7 to 10 were not applicable to this systematic review. Measurement properties related to content validity (box 2), internal structure (boxes 3 to 5), and cross-cultural validity (box 6) were assessed. Each included article was assessed using “very good,” “adequate,” “doubtful,” and “inadequate” to grade the above five domains. Two reviewers (DWDdeO and FSL) independently completed this assessment of the included study, with discrepancies solved through consensus.

Certainty assessment

The certainty of evidence was assessed according to the GRADE methodology using the GRADEpro program, depending on each analyzed outcome (psychometric properties and cross-cultural adaptation). It was classified as high, moderate, low, or very low. The starting point always assumes that the pooled or overall result is of high quality. The certainty of evidence was reduced by one or two levels when risks of bias, inconsistency, imprecision, and/or indirectness were identified.

Results

Search and selection

A total of 6556 articles were identified in the databases, and 1647 duplicates were removed. The manual search did not identify additional studies. In the first phase, 4879 publications were excluded. In the second phase, 11 studies were excluded (Supplement 1). Therefore, 19 articles were included in this review [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35] (Fig. 1).

Fig. 1
figure 1

Flowchart of the included studies

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Qualitative assessment

All studies [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35] have a cross-sectional design and were carried out in Brazil. The mean age of participants ranged from 2 [20] to 15.42 years [22], however, two studies did not report this information [21, 32]. The number of participants ranged from 20 [32, 35] to 342 [25]. Three studies did not go through the cross-cultural adaptation process [17, 28, 29] (Table 2).

Table 2 Characteristics of the reviewed studies
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Table 3 presents the health conditions assessed by the instruments. The self-completion method [18, 23, 27,28,29,30,31,32,33, 35], interviews answered by the participants themselves [19, 22, 24,25,26], and interviews answered by parents [17, 20, 21, 26] were used to fill out the questionnaires. The domains/dimensions of the questionnaires were not reported in the two studies [22, 26]. The Brazilian version of the cross-culturally validated instrument was available in only six publications [18, 20, 21, 25, 32, 34].

Table 3 Characteristics of oral health-related quality of life questionnaires
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Measurement properties and risk of bias assessment

The psychometric evaluation process, internal consistency, criterion validity, construct validity, reliability, general discriminant validity, Cronbach's alpha value, and general ICC value are presented in Table 4. The stages of the cross-cultural adaptation process; translation, back-translation, committee approach, synthesis, and pre-test were absent in three studies [17, 21, 28] (Table 5).

Table 4 Evaluation of the psychometric properties
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Table 5 Evaluation of the cross-cultural adaptation process
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 The results of the risk of bias assessment are presented in Table 6. All studies were rated very good in the structural validity domain.

Table 6 COSMIN risk of bias assessment
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Certainty assessment

The certainty of the evidence was downgraded one level by risk of bias, and it was considered moderate for both psychometrics and adaptation outcomes (Table 7).

Table 7 Systematic review level assessment
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Discussion

The quality-of-life assessment is an important parameter in several areas of health, including oral health, which allows an analysis of the condition's impact on daily activities and the individual's personal life [36]. However, clinical evaluation alone cannot analyze the psychosocial effects of oral health status and general well-being [37]. In this sense, it is necessary to use OHRQoL questionnaires to correctly assess this individual, understanding their multidimensionality and recording subjectivity in a uniform and reproducible way [38]. Nineteen OHRQoL instruments have been cross-culturally adapted for Brazil and had the psychometrics validated, and all of them proved to be valid and ready for use in children and adolescents.

All instruments included in this review had English as the original language [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]. Cultural and linguistic sensitivity is a common issue associated with the use of these questionnaires in non-English-speaking and/or cross-cultural populations, as certain items may not be relevant to all population groups. Therefore, translation and cross-cultural adaptation of these instruments are necessary when using them in a new country, culture, and/or language [39]. The reviewed studies were carried out in Brazil. They were all designed following the literature recommendations, which propose the use of cross-sectional studies in which data are collected in a single moment, without longitudinal follow-up. Studies using a cross-sectional design are very useful in several areas of research, especially in assessing the prevalence of diseases, attitudes, and knowledge among patients and health professionals [40]. Furthermore, this design is also used in validation studies comparing different measurement instruments and in reliability research [41].

Global population growth and the demand for cross-cultural studies highlight the importance of having reliable and validated instruments or measures available to clinicians and researchers in diverse cultures and/or languages [42]. However, among the reviewed studies, a few one provided the instruments adapted for Brazil [18, 20, 21, 25, 32, 34]. This situation can restrict the use of these instruments, limit the reference to the original studies, and even encourage other authors to develop similar instruments.

The average age of the participants ranged from 2 [20] to 15.42 years old [22]. Age is an important factor to be considered when evaluating the results reported by patients in childhood, as it influences not only the sources of information available but also the way they perceive and experience the quality of life-related to oral health. For this reason, it is crucial to develop specific assessment instruments for each age group [11].

The reviewed instruments were developed to be answered by the children themselves [18, 19, 22,23,24,25,26, 28, 30, 31, 33,34,35] or by their guardians [17, 20, 21, 27, 32] which is confirmed by the face validation. Quality of life assessment instruments for children should be segmented by different age groups, such as 6 to 7, 8 to 10, and 11 to 12 years old, and should be self-administered by the children themselves, since they have the right to voice their opinions and have their perspectives considered [10]. However, some groups of children, such as the very young ones, may have difficulty providing accurate information about their quality of life. For this reason, it is common for questionnaires aimed at preschoolers to be answered by their guardians [43, 44]. Adults and children have different perceptions about how health problems affect the quality of life, especially since children and adolescents have different views of themselves and the world given their physical and emotional development stages. Therefore, the development of specific instruments for children allows for a more accurate measurement of the impact of oral problems on their quality of life [10].

In the present review, both specific [17, 18, 21,22,23, 28, 30, 31, 33,34,35] and generic [19,20,21, 24,25,26,27, 32] instruments were identified, offering a broad range of options for researchers to choose from based on the study’s objective. Generic instruments are developed to represent the impact of a health condition on an individual's life and can be used in different populations [43]. They allow for assessing overall health and measures that demonstrate the patient's preference for a particular health state, treatment, or intervention [45]. In addition, they play an important role in allowing comparisons of health-related quality of life between patients who have different chronic diseases or even to assess the ORQoL of a single population concerning a disease; however, they are not able to detect situations experienced by patients with specific diseases [46].

On the other hand, specific instruments can individually assess specific aspects of quality of life, allowing a greater ability to detect positive or negative aspects. The main advantage of these instruments is their sensitivity to measure changes resulting from the natural history of the disease or after a specific intervention [47]. Some authors suggest that OHRQoL instruments aimed at specific conditions tend to be more sensitive to changes when compared to generic instruments, which have the advantage of being comprehensive and meeting all conditions and interventions [43]. This view is based on a focus on health aspects that are relevant to a specific group of patients, as evidenced by the inclusion of several items in each domain. However, the application of these specific instruments to different populations may make it impossible to compare these experiences. Consequently, it is common for the researcher to seek a combination of generic and specific instruments to obtain the desired response capacity and enable comparison between different groups [48].

The availability of these instruments to the researcher offers an enhanced opportunity for expression, language understanding, and evaluation, which develop into a more effective investigation and, therefore, promote the humanization of care [49]. Three studies did not undergo the process of cross-cultural adaptation [17, 21, 28]. The importance of these instruments going through the process of cross-cultural adaptation lies in their equivalence in different cultures, ensuring the preservation of their content, psychometric properties, and validity in a different cultural context [50]. Therefore, a flawed translation and adaptation process can result in unreliability, generating an inconsistency between the translated and original versions, which can compromise its validity and psychometric properties, affecting the reliability of a specific item or scale level [38].

Assessing the reliability of the data provided by these research instruments is critical and requires high-quality testing. In this sense, researchers must estimate this quantity to improve the validity and accuracy of the interpretation of their data [51]. The Alpha test is an important concept in the assessments of these questionnaires, as it measures the reliability and correlation between answers reported by patients [52]. An Alpha value greater than 0.70 is considered adequate for comparison between groups, indicating satisfactory internal consistency and the presence of a high Alpha coefficient (> 0.90) may imply the existence of redundancies [51].

The methods used in the evaluated studies to record the reports of individuals were the self-completion method (self-report scale) and the interview (evaluation scale). A good way to assess the child's subjective experience is through self-reports, which are accessible and easy to administer. With proper guidance, children can adequately describe the characteristics and levels of discomfort they are experiencing [53].

Reporting the time taken to complete these questionnaires is highly relevant information since the researcher would have prior knowledge about the time required for data collection when using the instrument. In this review, this information was mentioned in the study by [34]. Another important piece of data that should be considered in these instruments so that there is no response bias and/or methodological bias compromising the results found is the indication of the period to be considered in the participant's response [54, 55], information that was absent in most of the studies [17, 21,22,23,24, 26,27,28, 31,32,33,34,35].

GRADE is a tool used to assess the certainty of evidence in systematic reviews [56]. Moderate certainty of evidence suggests that the available data from the psychometric validation studies are generally reliable and provide a reasonable level of confidence in the findings. In other words, the results are likely to be accurate, but some uncertainty or limitations may still exist [13, 56]. These limitations could be due to potential bias in the study design caused by the absence of a translation process and psychometric validation. Researchers and practitioners should consider the limitations and uncertainties associated with the evidence when making decisions or drawing conclusions based on these instruments.

This review has some limitations, such as the lack of complete reports on the information investigated in some studies, the lack of publication of transcultural adapted instruments, and the lack of analysis of the longitudinal validation of the reviewed studies. In this sense, cross-sectional studies are recommended to validate the oral health-related quality of life instruments adapted for the Brazilian context. It is suggested that researchers publish the OHRQoL instruments that have already been validated, in addition to using the guidelines proposed in the literature to ensure equivalence of content with the original scale.

Conclusion

It can be concluded that most studies provided information and evidence regarding validity, reliability, translation, and cultural adaptation. The quality of the evidence was moderate, and five papers failed to establish the reliability of PIDAQ, DDQ-B, ECOHIS, CPQ8-10, and CPQ11-14 Brazilian version instruments. Overall, the oral health-related quality of life questionnaires adapted for children and adolescents were considered valid for use in Brazil.