OHIP-5 FOR SCHOOL-AGED CHILDREN

Abstract

Background

Different dental patient-reported outcome measures (dPROMs) exist for children and adults, leading to an incompatibility in outcome assessment in these 2 age groups. However, the dental patient-reported outcomes (dPROs) Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact are the same in the 2 groups, providing an opportunity for compatible dPRO assessment if dPROMs were identical. Therefore, we adapted the 5-item Oral Health Impact Profile (OHIP-5), a recommended dPROM for adults, to school-aged children to allow a standardized dPRO assessment in individuals aged 7 years and above.

Aim

It was the aim of this study to develop a 5-item OHIP for school-aged children (OHIP-5_School) and to investigate the instrument’s score reliability and validity.

Methods

German-speaking children (N = 95, mean age: 8.6 years +/− 1.3 years, 55% girls) from the Department of Pediatric Dentistry at the Medical University of Vienna, Austria and a private dental practice in Bergisch Gladbach, Germany participated. The original OHIP-5 was modified and adapted for school going children aged 7–13 years and this modified version was termed OHIP-5_School. It’s score reliability was studied by determining scores’ internal consistency and temporal stability by calculating Cronbach’s alpha and intraclass correlation coefficients, respectively. Construct validity was assessed comparing OHIP-5_School scores with OHIP-5 as well as Child Perceptions Questionnaire (CPQ-G_8–10) scores.

Results

Score reliability for the OHIP-5_School was “good” (Cronbach’s alpha: 0.81) or “excellent” (Intraclass correlation coefficient: 0.92). High correlations between OHIP-5_School, OHIP-5, and CPQ-G_8–10 scores were observed and hypotheses about a pattern of these correlations were confirmed, providing evidence for score validity.

Conclusion

The OHIP-5_School and the original OHIP-5 are short and psychometrically sound instruments to measure the oral health related quality of life in school-aged children, providing an opportunity for a standardized oral health impact assessment with the same metric in school-aged children, adolescents, and adults.

BACKGROUND

The orofacial system is affected by many diseases that frequently occur during childhood and then persist over a long time. The early identification and treatment of these diseases often changes the life course of these children, that is, the dental intervention often has an impact on the oral health related quality of life (OHRQoL) far beyond the childhood years.^1–3 Multi-item dental patient-reported outcome measures (dPROMs) in general and OHRQoL questionnaires specifically are well suited to measure this impact⁴; however, in order to assess the disease impact over the entire duration of the disease, these measures need to be compatible in both children and adults.

Several dPROMs exist for children and adults^5–7; nevertheless, none of these instruments were designed for both age groups. Two major reasons are (i) the view that children and adults suffer from different oral health impacts and (ii) both age groups have different cognitive abilities. For very young children, these abilities are not sufficiently developed to report the oral health impact validly and reliably; and therefore, their parents or caregivers need to report the oral disease impact they observe in their children. Nonetheless, at a certain age the cognitive situation has matured enough, enabling children to answer questions about the oral disease impact themselves. The literature demonstrates that even young children can respond to questions regarding pain^{8, 9} and nausea,¹⁰ and with age children’s understanding of health-related words and their ability to understand complex sentences increases.¹¹ When children attend school and they can read, they also seem to be able to answer dPROM questions similarly to adults. Consequently, the rationale to separate dPROMs of pediatric dental patients from adult dental patients only rests on the assumption that children and adults suffer from a different oral health impact and therefore need different questions to assess this impact. This rationale seems to be not well founded as the OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact are not only the major building blocks for the oral health experience of adults, but they are also the major things that matter greatly to children.^{12, 13} These dimensions offer an elegant approach for standardizing outcome measurement. Thus, the instrument that is currently recommended for oral health impact measurement in adults, the 5-item Oral Health Impact Profile (OHIP-5),^14–16 should also be applicable for school-aged and older children. Slight modifications to adapt OHIP-5’s adult verbiage to that of children might be necessary and then, to solidify such a statement, the psychometric properties of such a modified OHIP-5 (OHIP-5_School) need to be verified in the target population.

Therefore, we aimed to develop a 5-item OHIP for school-aged children (OHIP-5_School) and to investigate the instrument’s score reliability and validity.

METHODS

Study Participants

We recruited a total of 95 children from the Department of Pediatric Dentistry at the Medical University of Vienna, Vienna, Austria and a private dental practice in Bergisch Gladbach, Germany. To be included in the study, the children had to be 7–13 years of age and German-speaking. Mentally impaired children or children with reading disabilities were excluded. Recruitment started in December 2020 and ended in September 2021. The study participants attended the dental clinics mainly for the purpose of first dental visits, periodic check-up visits and recommended follow-up appointments. At the time of enrolment in the study, parents/guardians of the children were informed about the study verbally and signed an informed consent form before a child’s verbal assent was sought. A child’s dissent superseded the parental consent. When a child’s verbal assent was obtained, the assent was documented. The study protocol was reviewed and approved by the Institutional Review Board of the Medical University of Vienna (Reg. Nr.: #2015–2025).

Study Design

Study participants received 3 dPROMs – the original OHIP-5,¹⁴ OHIP-5_School, and the German version of Child Perceptions Questionnaire, CPQ-G_8–10.¹⁷ During the first dental appointment, the children were asked to fill out 1 version (original or modified) of the OHIP-5 along with the CPQ-G_8–10 questionnaire (baseline CPQ-G_8–10). At the time of the second dental appointment around 1 week after the first, the other version of the OHIP-5 and another CPQ-G_8–10 questionnaire (follow-up CPQ-G_8–10) were administered. All questionnaires were answered by the study participants without their parents’ input.

The children were also clinically examined on both occasions by 1 examiner per site, and the number of missing primary and/or permanent teeth due to caries were recorded in accordance with the WHO Oral Health Surveys: Basic Methods criteria for the assessment of the dentition status.¹⁸

OHRQoL Measurement

Development of an OHIP-5 for school-aged patients

The 5-item OHIP questionnaire¹⁴ for adults is an ultra-short version of the original 49-item OHIP.¹⁹ It was first proposed in Germany and was developed using best subset regression. The questionnaire contains only 10% of the items but captures about 90% of the score information compared with the 49-item version.¹⁴ The instrument has excellent content validity because it contains at least 1 indicator for each of the 4 OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact, and therefore it captures the 4-dimensional oral health impact internationally²⁰ whilst simultaneously minimizing burden. For each of the 5 OHIP questions subjects are asked how frequently they have experienced the impact in the last week.²¹ Responses are made on an ordinal scale (0 = never, 1 = hardly ever, 2 = occasionally, 3 = often, and 4 = very often). Summing all responses results in a score ranging from a minimum of 0 to a maximum of 20. Higher scores imply poorer OHRQoL as the OHIP-5 measures the frequency of oral health problems.

Three modifications were made to create an OHIP-5_School from the OHIP-5:

1. To address children properly, the German OHIP-5 was slightly modified by changing the formal form of “you” (in German: “Sie”) to the informal “you” form (in German: “Du”).

2. To make the content for children more appropriate, for the modified version of the OHIP-5, we deleted the word “dentures” and added the word “braces.”

3. Furthermore, the question “Have you had difficulty doing your usual jobs … ?” was changed to: “Have you had difficulty doing your usual activities (eg, with your family, at school, with your friends) … ?” (Table 1).

Table 1.

Items included and domain distribution in the original and OHIP-5_School.

OHIP-5 English	Original OHIP-5	OHRQoL dimension
In the past 7 days, have you had difficulty chewing any foods because of problems with your teeth, mouth, jaws, or dentures?	Hattest Du in den letzten 7 Tagen aufgrund von Problemen mit Deinen Zähnen, im Mundbereich oder Deinem Zahnersatz Schwierigkeiten beim Kauen von Nahrungsmittel?	Oral Function
In the past 7 days, have you felt that there has been less flavor in your food because of problems with your teeth, mouth, jaws, or dentures?	Hattest Du in den letzten 7 Tagen aufgrund von Problemen mit Deinen Zähnen, im Mundbereich oder Deinem Zahnersatz den Eindruck, Dein Essen war geschmacklich weniger gut?	Oral Function
In the past 7 days, have you had difficulty doing your usual jobs because of problems with your teeth, mouth, jaws, or dentures?	Ist es Dir in der letzten Woche aufgrund von Problemen mit Deinen Zähnen, im Mundbereich, Deiner Zahnprothese oder Deiner Zahnspange schwergefallen, Deinen alltäglichen Beschäftigungen nachzugehen?	Psychosocial Impact
In the past 7 days, have you had painful aching in your mouth?	Hattest Du in den letzten 7 Tagen Schmerzen im Mundbereich?	Orofacial Pain
In the past 7 days, have you felt uncomfortable about the appearance of your teeth or dentures?	Hattest Du Dich in den letzten 7 Tagen wegen des Aussehens Deiner Zähne oder Deinem Zahnersatz unwohl/unbehaglich gefühlt?	Orofacial Appearance
OHIP-5School Englisha	OHIP-5School German	OHRQoL dimension
In the past 7 days, have you had difficulty chewing any foods because of problems with your teeth, mouth, jaws, or braces?	Hattest Du in der letzten Woche aufgrund von Problemen mit Deinen Zähnen, im Mundbereich, Deiner Zahnprothese oder Deiner Zahnspange Schwierigkeiten beim Kauen von Nahrungsmitteln?	Oral Function
In the past 7 days, have you felt that there has been less flavor in your food because of problems with your teeth, mouth, jaws, or braces?	Hattest Du in der letzten Woche aufgrund von Problemen mit Deinen Zähnen, im Mundbereich, Deiner Zahnprothese oder Deiner Zahnspange den Eindruck, Dein Essen war geschmacklich weniger gut?	Oral Function
In the past 7 days, have you had difficulty doing your usual activities (eg, with your family, at school, with your friends) because of problems with your teeth, mouth, jaws, or braces?	Ist es Dir in der letzten Woche aufgrund von Problemen mit Deinen Zähnen, im Mundbereich, Deiner Zahnprothese oder Deiner Zahnspange schwergefallen, deinen alltäglichen Beschäftigungen (z.B. in der Familie, in der Schule, mit Deinen Freunden) nachzugehen?	Psychosocial Impact
In the past 7 days, have you had painful aching in your mouth?	Hattest Du in der letzten Woche Schmerzen im Mundbereich?	Orofacial Pain
In the past 7 days, have you felt uncomfortable about the appearance of your teeth or braces?	Hattest Du Dich in der letzten Woche wegen des Aussehens Deiner Zähne, Deiner Zahnprothese oder Deiner Zahnspange unwohl/unbehaglich gefühlt?	Orofacial Appearance

^aThe English translation of the OHIP-5_School was created in collaboration with colleagues from AppleTree Dental (https://www.appletreedental.org/) and Ready, Set, Smile (https://www.readysetsmile.org/).

These modifications were proposed, reviewed, and approved by a group of experts in the field of oral health-related quality of life and pediatric dentistry.

Child perceptions questionnaire (CPQ- G_8–10)

The self-complete Child Perceptions Questionnaire (CPQ) was originally developed in Canada to determine the frequency of various oral health-related impacts in 8–10-year-olds (CPQ_8–10).²² A German version (CPQ-G_8–10)¹⁷ was recently developed and cross-culturally adapted to assess the OHRQoL in German-speaking children of the same age group. This questionnaire contains a total of 25 items subdivided into 4 domains: Oral Symptoms, Functional Limitations, Emotional Well-being, and Social Well-being. Questions ask about the frequency of events, for example, symptoms such as pain or bad breath experienced by the child in the last 4 weeks. Responses are made on an ordinal scale 0- never, 1- once/twice, 2- sometimes, 3- often, 4- every day/almost every day. Summing all responses resulted in a score ranging from a minimum of 0 to a maximum of 100. A higher score reflected a more impaired OHRQoL status. Additionally, it includes 2 questions asking the child for a global rating of his/her oral health and their overall well-being. These global ratings had a 5-point response format (excellent, very good, good, moderate, poor).

Data Analysis

Reliability

To assess reliability of the OHIP-5_School, an internal consistency analysis was performed by computing the Cronbach’s alpha statistic.²³ Estimated values were interpreted according to Kline: acceptable (0.60–0.69); good (0.70–0.89); excellent (>0.90).²⁴ In addition, average interitem correlations were reported. Average inter-item correlations should fall between 0.15 and 0.50.²⁵

Additionally, we investigated the temporal stability of OHIP-5 scores using original and OHIP-5_School as test and retest. Test-retest reliability for OHIP-5 and CPQ-G_8–10 scores was assessed with an interval of 1 week, when patients did not receive any treatment between the 2 questionnaire administrations. Intra-class correlation coefficients (ICC) were calculated using a 2-way mixed-effects model.²⁶ ICC values of 0.5 indicate poor reliability, values between 0.5 and 0.75 indicate moderate reliability, values between 0.75 and 0.9 indicate good reliability, and values greater than 0.90 indicate excellent reliability.²⁷

Before computing correlation coefficients, to provide a visual impression about possibly nonlinear relationships between scores, we plotted the data and used LOWESS (LOcally WEighted Scatterplot Smoothing) to smooth a line through the scatterplot points.

Validity

We investigated different aspects of validity. Convergent validity, that is, a construct’s measure should be closely related to other measures of the same construct, was studied by correlating OHIP-5 scores with CPQ-G_8–10 scores using a Pearson correlation coefficient. Assuming that the original and the OHIP-5_School are almost identical instruments, we expected that their correlation should be similar in magnitude compared to the correlation between CPQ-G_8–10 scores, 2 identical measures of the same construct. These correlations are expected to be “large” according to Cohen. Furthermore, we expected that the correlations between OHIP-5 and CPQ-G_8–10 scores, 2 different measures of the same construct, are also “large” (according to Cohen) in their absolute magnitude. We also expected that these 4 correlations are similar and lower than the correlation between (almost) identical instruments. Pearson correlation coefficients were computed.

We also studied known-groups validity, that is, questionnaires scores should discriminate between 2 or more groups of individuals known to differ on the questionnaires scores. Consequently, OHIP-5_School’s scores should differentiate groups of patients with different oral health status. Hence, we compared groups that differed in the following 2 major indicators of physical oral health: missing teeth vs no missing teeth.

We hypothesized that patients with missing teeth have higher modified OHIP-5 scores. In contrast, we also calculated an OHIP-5_School difference between girls and boys. Here, we hypothesized that an OHIP-5_School difference should be absent.

We calculated Cohen’s d, a standardized effect size for the magnitude of the difference between groups, and its 95% confidence interval (CI) for known-groups validity assessment. To interpret the magnitude of the group difference, effect sizes were interpreted according to Cohen.²⁸ Effect sizes (Cohen’s d) of 0.2, 0.5, and 0.8 represent “small,” “moderate,” and “large effects,” respectively. We considered effect sizes of less than 0.2 as “trivial.” The size of correlations was also interpreted according to Cohen. Cohen’s r of 0.1, 0.3, and 0.5 represent “small,” “moderate,” and “large effects,” respectively.

RESULTS

Study Participants Characteristics

Study participants were from Germany (63%) and from Austria (37%). The majority of the study participants were female (55%), and their mean age was 8.6+/−1.3 years (Table 2). Only 12% of the patients had 1 or more missing teeth.

Table 2.

Descriptive statistics for patients’ sociodemographic characteristics and measures of oral health impact.

Characteristic	Mean (SD) or %
Age (years)	8.6 (1.3)
Female	55
One or more missing teeth	12
Original OHIP-G at baseline	2.1 (3.0)
OHIP-5School at baseline	1.7 (2.7)
Global rating of oral health
Excellent	21
Very good	31
Good	34
Moderate	13
Poor	2
Global rating of overall well-being
Excellent	50
Very good	23
Good	24
Moderate	1
Poor	1

At baseline patients had an original and OHIP-5_School mean value of 2.1 and 1.7 points, respectively. More than half of the participants reported “very good” (31%) or “excellent” (21%) oral health. Half of the patients reported “excellent” overall well-being.

OHIP-5_School Item Characteristics

Mean OHIP-5_School item values and the OHIP-5_School sum score are shown in Table 3. The item values were highest for “painful aching,” closely followed by “difficulty chewing.” These items represented the OHRQoL dimensions Orofacial Pain and Oral Function, respectively. The majority of study participants (64%) reported that they did not experience painful aching in the last week. The lowest frequency was observed for “flavor in food” - another indicator for the dimension Oral Function.

Table 3.

Descriptive statistics of the OHIP-5_School items.

OHIP-5School items	Mean (SD)	Median (interquartile range)	Minimum-maximum (range)	Percentage of participants reporting
				“Never”	“Very often”
Difficulty chewing	0.5 (0.8)	0 (1)	0–4	71	1
Less flavor in food	0.1 (0.2)	0 (0)	0–2	96	0
Difficulty doing daily activities	0.2 (0.6)	0 (0)	0–2	93	0
Painful aching	0.6 (1.0)	0 (1)	0–4	64	3
Uncomfortable with appearance	0.3 (0.8)	0 (0)	0–3	80	0
OHIP-5School sum score	1.7 (2.7)	0 (2)	0–14

Score Reliability

Internal consistency

Cronbach’s alpha for the entire scale was “good” for both OHIP-5s (Table 4). Cronbach’s alpha for the remaining items when a particular item is deleted demonstrated that no item had an undue influence on the instruments’ internal consistency from a particular item. Average inter-item correlations for each item and the scale fell into the recommended range. When internal consistency characteristics were compared between the modified and original OHIP-5, they were found to be very similar, sometimes even identical.

Table 4.

Internal consistency measured by Cronbach’s alpha and item-rest for the modified and the original OHIP-5.

	Modified OHIP-5		Original OHIP-5
	Alpha when item is deleted (lower limit of 95% confidence interval)	Average interitem correlation	Alpha when item is deleted (lower limit of 95% confidence interval)	Average interitem correlation
Difficulty chewing	0.77	0.45	0.76	0.44
Painful aching	0.81	0.51	0.81	0.51
Uncomfortable about appearance	0.73	0.40	0.79	0.49
Less flavor in food	0.72	0.40	0.75	0.43
Difficulty doing daily jobs	0.83	0.55	0.80	0.51
Scale	0.81 (0.76)	0.46	0.82 (0.77)	0.48

Test-retest reliability assessed with CPQ_8–10

Test and retest CPQ-G_8–10 scores showed a linear relationship when Locally Weighted Scatterplot Smoothing was applied (Figure 1, Panel A). One patient, having high impairment at the first time and low impairment at the second, was different compared to the rest of the data with the 2 impairments closer together. The ICCs including and excluding this patient were r = 0.74 and 0.92, respectively. We considered this level of reliability as “good.” This patient was excluded from further analyses.

Figure 1.

Summary score relationships between 2 assessments of the Child Perceptions Questionnaire (Panel A, baseline 1 and 2) and the Oral Health Impact Profile (Panel B, original and modified version), characterized using Locally Weighted Scatterplot Smoothing (LOWESS).

Test-retest reliability with OHIP-5

The modified and original OHIP-5 summary scores also correlated linearly (Figure 1, Panel B). The ICC summarizing this relationship was r = 0.91, a level considered “excellent.”

Score Validity

Convergent validity

Inspection of the graphical relationships between OHIP-5_School, OHIP-5, and CPQ-G_8–10 (Figure 2) revealed that the shapes of the LOWESS curves across the 3 instruments were similar.

Figure 2.

Correlations between OHIP-5 and CPQ-G_8–10 scores, characterized using Locally Weighted Scatterplot Smoothing (LOWESS) curves.

Interpretation of the numerical relationship across the 3 instruments (Table 5) as well as the test-retest correlations of OHIP-5 (considering original and the modified OHIP-5 are exchangeable) and CPQ-G_8–10 revealed the following pattern:

1. The correlation between the original and the modified OHIP-5, 2 almost identical measure was very similar to the correlation between CPQ-G_8–10, 2 identical measures of the same construct.

2. The correlations between different measures of the same construct (OHIP-5 original vs CPQ-G_8–10, OHIP-5 modified vs CPQ-G_8–10) was similar but slightly lower than correlations between (almost) identical measures.

Table 5.

Matrix of correlations coefficients (95% confidence intervals) between OHIP-5 and CPQ-G_8–10 scores – higher correlations expected for the shaded cells than for the nonshaded cells.

	Original OHIP-5	Modified OHIP-5	CPQ-G8–10 baseline
Original OHIP-5
Modified OHIP-5	0.90 (0.85–0.93)
CPQ-G8–10 baseline 1	0.77 (0.67–0.84)	0.76 (0.66–0.83)
CPQ-G8–10 baseline 2	0.82 (0.74–0.87)	0.85 (0.79–0.90)	0.91 (0.87–0.94)

Overall, the observed pattern confirmed our hypotheses about the varying magnitudes between different and (almost) identical measures of the OHRQoL construct.

Known-groups validity

As expected, patients with missing teeth had higher modified OHIP-5 scores than patients without these conditions (Table 6). According to Cohen, effect sizes were “large” or “moderate.” Boys had slightly higher modified OHIP-5 scores than girls. However, as expected, the size of the effect was considered “trivial.” Overall, the pattern of hypothesized effects could be confirmed, providing evidence for known-groups validity.

Table 6.

Known-groups validity: modified OHIP-5 score differences for patients with missing teeth and of both genders.

Variable	Frequency (N)	Modified OHIP-5 mean (SD)	Effect size Cohen’s d (95% CI)
(m + M) missing teeth
No	83	1.4 (2.4)	−0.81 (−1.44 to −0.17)
Yes	11	3.5 (4.0)
Gender
Boys	42	2.0 (3.1)	0.19 (−0.21 to 0.61)
Girls	52	1.4 (2.5)

DISCUSSION

This study introduces a modified OHIP-5 for school children to make the original OHIP-5 more suitable for these children. Both OHIP-5s have similar psychometric properties. Score reliability was “good” to “excellent” according to guidelines to interpret the magnitude of reliability coefficients. A priori formulated hypotheses about the pattern of correlation coefficients of OHIP-5_School’s correlation with the original OHIP-5 and the CPQ-G_8–10 could be confirmed in our sample of pediatric patients and, therefore, provided evidence for OHIP-5_School’s convergent validity. Additionally, finding an effect of patient characteristics on OHIP-5_School was observed when it was hypothesized to exist and was absent when none was hypothesized to exist provided evidence for known-groups validity.

Comparison With the Literature

OHIP-5_School is new and, therefore, we are only able to compare this instrument with literature findings for the original OHIP-5. The original OHIP-5 was for the first time used in children aged 7–13 and, therefore, we are only able to compare this instrument with literature results in older children or adults.

While OHIP-5 has been used in larger studies that contained adults and children (eg, in a national survey in Germany²⁹ or in clinical patient populations in Austria³⁰) which can be interpreted as evidence for OHIP-5’s content validity in both adults and children, psychometric properties of the OHIP-5 in children were not investigated. However, our results for OHIP-5_School’s reliability, which was “good” (Cronbach’s alpha, α = 0.81) according to Kline,²⁴ was consistent with results obtained in the German adult general population (α = 0.76),¹⁴ the Swedish adult general population (α = 0.77),³¹ the English adult general population in the USA (α = 0.75),³² the Persian adult general population (α = 0.80),³³ the Brazilian adult general population (α = 0.83),³⁴ and in Japanese adult prosthodontic patients (α = 0.81).³⁵ However, in specific adult populations like German patients with temporomandibular disorders (TMDs) only an “acceptable” level of reliability (α = 0.65) was reached.¹⁴ As was the case with Dutch patients with TMD (α = 0.67).³⁶ Sampling variability is certainly a very plausible explanation for the variation of results. True differences across population may exist, but they are certainly small in magnitude.

We also assessed the test-retest reliability by administering both versions of the OHIP-5 and the CPQ-G_8–10 within an interval of 1 week, during which the patients received no treatment. We observed high test-retest reliability coefficients of 0.90 and 0.91 for the 2 OHIP-5 and CPQ-G_8–10 versions, respectively. These results are in line with international OHIP-5 versions referenced above. When these studies investigated test-retest reliability, reported results were similar to ours.

Our validity assessment was different from a methodological point of view compared to previous international OHIP-5 studies. By applying also an original OHIP-5 as well as a CPQ-G_8–10 to our patients on 2 occasions, we were able to hypothesize a pattern of correlation sizes across instruments. For example, a correlation between identical instruments (CPQ-G_8–10 test vs retest) should be higher than a correlation between similar instruments (CPQ-G_8–10 vs OHIP-5_School).

This pattern could be confirmed in our patients. In addition, OHIP-5_School and the original OHIP-5, as 2 almost identical instruments, should correlate similarly with CPQ-G_8–10 – a finding that we also observed in our study.

When we compared our results that are directly comparable with literature results, for example, our known-groups validity results, our results were similar to what was reported before. Overall, the validity of OHIP-5 is well established.

Other studies have not investigated such a correlation pattern, but they compared OHIP-5 versions to other OHRQoL instruments. While we obtained correlation coefficients of 0.76 and 0.85 between the OHIP-5_School and the baseline and follow-up CPQ- G_8–10, respectively, correlation coefficients similar in magnitude to ours have been reported between the Spanish versions of the OHIP-5 and the Oral Impacts of Daily Performances (r = 0.73).³⁴ In Swedish adult dental patients, a higher correlation (r = 0.92) was observed between the Swedish versions of the OHIP-49 and OHIP-5.³¹

Importance of 4-Dimensional Oral Health Impact Assessment in School Children for a Standardized Assessment Over the Entire Life Span

The rationale for including children aged 7–13 in the present study was based on the literature available about children and their self-reported health experiences. A cognitive study interview was conducted by researchers from the Johns Hopkins Institute to assess the ability of children aged 5–11 years to respond to various pictorially illustrated questions about their health.¹¹ The study concluded that children as young as age 8 were able to report on all aspects of their health experiences. In contrast younger children aged 6–7 had some difficulty with health-related terms and tended to use extreme responses but were overall able to report on their health experiences. Most of the youngest participants of this study, aged 5 were unable to understand most of the terms related to health and unlike their older counterparts were unable to report on their health. This study also stated that children as young as 5 years old can describe mental states such as perceptions, emotions, cognitions, and physiological states, but there was concern that they are unable until about the age of 7 or 8 to distinguish between their inner experience and the external behavior that others see. The main difference to our study is that the study participants were verbally asked questions regarding their health whilst being shown visual analogue scales. In contrast we administered questionnaires that were to be read and answered by the participants. Hence the focus of our study was children who could exhibit sufficient reading skills. In most European countries the average child learns to read once in school at the age of 6. By contrast children in some of the English-speaking countries in Europe learn to read at a tender age of 4 to 5. We therefore restricted our lower age limit to 7-year olds. We are aware that the average age at which children commence reading differs globally. Factors like socio-economic status and parental literacy status amongst others influence the age at which children begin to read.³⁷ Hence future studies must take into consideration the age at which their target population can sufficiently read.

Our study focused on children aged 7–13 because it can be assumed that older children have even better cognitive abilities. We therefore used a sample with a reasonable number of children to investigate psychometric properties for OHIP-5_School and the original OHIP-5 at the lower end of the cognitive ability spectrum. In addition, children of this age group generally have a more limited concentration span as compared to older children³⁸ – a situation that challenges OHRQoL assessment. Having observed evidence for score reliability and validity in this age group, we do not see a problem to not generalize our findings to school-aged children in general. Therefore, we call this modified instrument OHIP-5_School.

Strengths and Limitations

Our study has several strengths and some limitations. One of the strengths of the current study is the target population. Our study sample consisted of regular pediatric dental patients and therefore our results should be widely generalizable. We studied children in 2 settings. The private dental practice represented the setting where most children would receive oral health care. The potential for substantial generalizability is further supported by our 100% response rate. All patients that were approached were willing to participate in the study, making the targeted sample identical to the eligible.

A strong methodological point was that we used several methods to investigate reliability and validity. They all agreed in their findings.

The sample size was a limiting factor in our study. The sample sizes of comparable adult population studies have ranged from 85 to 2050.^{14, 31–35} Our sample size is on the lower side of these numbers; however, the precision of our results as judged by the width of confidence results was reasonable.

Clinical and Public Health Relevance

This study extends the applicability of the OHIP-5 to school-aged children. While a modification of the original OHIP-5 to children makes intuitive sense, the modifications were small. In our study these modifications did not even seem necessary because the modified OHIP-5 and the original OHIP-5 seems to perform equally well regarding their psychometric properties. This situation, while it needs to be replicated, would indicate that users of OHIP-5 in children have a choice regarding which OHIP-5 version is more suitable in their situation.

Extending OHIP-5’s application range from adult dental patients to school-aged children has tremendous clinical and public health relevance. A psychometrically solid measurement system targeting the 4 OHRQoL dimensions can now be extended to school children. This allows compatible measurement over the age range from 7 years onwards. Oral health impact for almost two-thirds of the pediatric age range can now be compared with oral health impacts of adults and older adults.³⁹ Effects of behavioral⁴⁰ and dental interventions in this age group can now be compared with treatments effects for all adult groups. Oral health impact assessment starting in school-aged children and crossing over to adulthood becomes now easier and more informative. In this broad age range, over the entire spectrum of settings from low resource settings⁴¹ to randomized trials performed in tertiary care centers⁴² with treatments provided by the entire oral health care provider spectrum from dental hygienists and dental therapists⁴³ to general dentists and specialists⁴⁴ oral health impact can now be assessed in a standardized way.⁴⁵

CONCLUSION

We developed a new 5-item OHIP for school-aged children and we validated the original OHIP-5 in this age group. The OHIP-5_School and the original OHIP-5 are short and psychometrically sound instruments to measure oral health related quality of life in school-aged children, providing an opportunity for a standardized oral health impact assessment with the same metric in school-aged children, adolescents, and adults.