The original ECOHIS aimed to assess the impact of both oral health problems and related treatment experiences on the quality of life of preschool children and their families . This study is the first attempt to deploy a valid cross-cultural instrument that has been used effectively in many countries worldwide to measure OHRQoL of preschool children in Thailand. ECOHIS focuses on the impact of ECC, which has been a major health problem in Thai preschoolers. The most recent NOHS in Thailand in 2017 revealed that the prevalence of ECC was 52.9% in 3-year-olds and 75.6% in 5-year-olds . An assessment of the impact of these oral health problems on children’s quality of life has never been conducted. The ECOHIS has been adapted for use in some Asian populations with a similar ECC situation as in Thailand [22, 25]. The Thai version of ECOHIS was developed from the original version following the standard cross-cultural adaption process [36, 37]. All 13 items of the original ECOHIS were retained, and thus the Th-ECOHIS could be employed in cross-national comparisons. However, some minor revisions were made to be more applicable for the Thai context.
The original version of the ECOHIS was developed as a self-completed questionnaire by proxy . Although the Th-ECOHIS kept the original context, it was interviewer-administered in this study. The interview approach was considered suitable for the studied population because it is a personal approach, ensures full return rates, lessens the possibility of missing data, and is non-literacy dependent. Although the literacy rate of working-age adults in Thailand is about 82%, the literacy rates of females and older persons are lower, at 78 and 52%, respectively . One third of Thai adults aged 25 to 50 years are not fond of reading . This was confirmed during the face validation process, when the mode of administration was discussed; the participants preferred the interviewing mode because they felt it would help them focus on the questions and process them better. Both self- and interviewer-administered Brazilian versions of ECOHIS were shown to have similar levels of reliability and validity and psychometric findings . Studies using other OHRQoL instruments have demonstrated that the mode of administration does not affect the performance of the measure [43, 44]. However, self-administration has more advantages in terms of lower cost, the preservation of participants’ anonymity and autonomy, avoidance of interviewer bias, and availability for a large number of samples. The Th-ECOHIS questionnaire in self-completed mode should be tested in future studies.
Most of the caregivers who participated in this study were able to rate their children’s and family’s experience as asked in the Th-ECOHIS. The fact that there were only four responses of “Don’t Know” (1%) implies that only few caregivers had underestimated the effects of ECC. There were no blank responses in our study because the interview-administration mode encouraged respondents to answer each question. Approximately one half of caregivers reported at least one impact on either their children or families, or both (Th-ECOHIS score > 0). The ceiling Th-ECOHIS score of each section was not detected, and this was consistent with other validation studies [8, 21, 22, 24, 29]. Regarding the floor effect, our study showed a higher rate in the child impact section than did the original study ; it is possibly contributed from the lower percentage of affected children in this study. The participants recruited in this study were limited to 3-year-olds, whereas the original study included samples of 5-year-olds . The younger age group could have been less affected by ECC, with a lower level of severity causing fewer symptoms and less impairment than the older age group could have. However, the three most common problems reported in the child impact section, pain, irritation and frustration, and eating difficulty, were similar to those reported in the original version  and in other countries with different cultures [22, 26, 30]. Apparently, children’s physical complaints, psychological effects and limited routine function were more easily detected by parents than were children’s social effects. In the family impact section, as in some other studies [8, 22, 26, 30], the most frequent feelings of caregivers were guilt and being upset. Although dental insurance is not available in Thailand, most simple dental services are provided free of charge for children younger than 12 years; only 10% of caregivers reported experiencing a financial impact on their family.
The reliability assessment of the Th-ECOHIS demonstrated an excellent result similar to the original version and previous studies. The test–retest analysis that was conducted over a period of 2 weeks revealed good agreement (0.87), indicating that the Th-ECOHIS questionnaire was able to yield stability of the scores when administered at two different times. The ICC value was similar to that reported for the original English, German, and Farsi versions of the ECOHIS (0.84, 0.81, and 0.82, respectively) [8, 19, 21].
Regarding the consistency of results across items within questionnaire, the overall Cronbach’s alpha value was 0.85, demonstrating good internal reliability of the Th-ECOHIS. This value was slightly lower than that reported for the original English  and German versions  but was within the same range reported for the Arabic, Brazilian, Lithuanian, and Malay versions [21, 22, 24, 30]. Comparing the internal consistency of the child impact section and the family impact section, the Cronbach’s alpha coefficient in the family impact section (0.71) was lower than that in the child impact section (0.84). This was similar to previous studies in which the internal consistency in the child impact section and the family impact section ranging from 0.74 to 0.92 and 0.59 to 0.85, respectively [8, 19,20,21,22,23,24,25,26,27,28,29,30,31]. The smaller number of items in the family impact section in Th-ECOHIS might have been one of the factors influencing this lower consistency.
To assess validity of the Th-ECOHIS, convergent and discriminant analyses were conducted. Both analyses showed that the Th-ECOHIS had good validity. Our study used the global measure of oral health to assess the convergent validity of the Th-ECOHIS. This measure is commonly used as a subjective indicator and has been shown to highly correlate with the clinical oral health status . The Th-ECOHIS showed a moderate correlation with the global measure of oral health. The correlation of our finding was higher than in the original version  and was comparable to the Turkish and Brazilian versions [29, 30]. This finding showed that parents who perceived their children’s oral health as poor tended to have a higher ECOHIS score.
In the discriminant validity analysis, our study compared the Th-ECOHIS scores among children with different caries status and treatment needs. The results clearly suggested the Th-ECOHIS score could be a valid indicator of compromised quality of life of children for different severity of caries and treatment needs. Children with a more severe caries category and treatment need had higher scores in both total and sub-sections. Other studies found that the treatment needs showing an effect on children’s quality of life were those related to pulpal involvement and pain [31, 46]; however, in our study, even non-pulpal-involved treatment need showed an effect on children’s OHRQoL. This also implied that parental responses are reliable for assessment of their child’s quality of life based on the child’s oral health. It was also noted that the ECOHIS scores were reported for the child and family impact sections even in caries-free children. ECOHIS might be able to detect other oral problems not limited to dental caries.
Most studies of translated versions of the ECOHIS focused on a mixed-age group of preschoolers [19,20,21,22,23,24,25,26,27,28,29,30,31], while the original focused on only 5-year-olds . Our study concentrated on 3-year-olds, the youngest group included in the NOHS and also targeted for early intervention in health policy. Two recent consecutive Thai NOHSs have shown high ECC prevalence in this age group [25, 26], approximately 53% with mean dmft of 2.8 in the country and 49.5% with dmft of 2.6 in Bangkok. Assessment of OHRQoL in this age group was scarce and deserves more attention. The ECOHIS score could be a simple subjective indicator of their quality of life. However, validation in the younger age group with relatively lower oral problems might raise some concerns regarding possible less relevant question items or poor responses by the proxies. In our study, full response from caregivers was achieved through the design of the interview-administered questionnaire; thus, the age group of the children should not have affected the validity and reliability of the instrument. On the other hand, it might affect the magnitude of the impact of oral health problems. The ECOHIS was proved valid for this particular age group.
It should be noted that the study was carried out in a specific group of children in the capital city from homogeneous socioeconomic status, middle-income families. In addition, we limited the socio-demographic characteristics of caregivers with respect to their relationship to the child and monthly income per household; age and level of education of caregivers were not collected. Further studies in different age groups and with a diversity of background would help strengthen our results. Future studies would also find it noteworthy to include more general health parameters such as perceived general health, general health behaviors, children’s weight, and height for convergent validity testing of this scale. However, those parameters at this young age with limited ECC severity might not show a correlation with or an impact on OHRQoL as in this study, all child samples were healthy with normal weight and height, and no any growth alteration was detected.
It could also be a limitation in this study that classical test theory (CTT) was used for psychometric testing of the scale, similar to what has been used in many previous studies [19,20,21,22,23,24,25,26,27,28,29,30,31]. All versions have kept all items as in the original. This would be useful in across-countries comparison of children’s OHRQoL measured by different versions of the ECOHIS. The CTT treats all questions equally, which contributes to simplicity in analysis and familiarity in dentistry. However, it would be useful to further analyze the translated version using item response theory (IRT) such as Rasch analysis [47, 48]. This would help detect any misfit items considered for modification or shortening the scale to customize it specifically for the Thai population.
This patient-based outcome measure will be a very useful parameter in demonstrating compromised quality of life in variety groups of preschool children. It could be incorporated into the National Oral Health Survey. Illustrating the deleterious effects of ECC would raise awareness in parents and families of the need for caries prevention. It could help improve communication among dentists, patients and policy makers. Future studies on responsiveness of the Th-ECOHIS would be necessary prior to applying the tool as a metric parameter to evaluate various intervention programs for ECC-affected children.