A German version of the Oral Impacts of Daily Performances—reliability and validity

According to the World Health Organization’s (WHO) definition health is not only seen as pure absence of diseases rather than absolute physical, mental, and social well-being [1‐4]. Measuring quality of life accounts for this postulation as subjective patient-reported outcomes (PROs) are evaluated [5]. Regarding medical issues, health-related quality of life (HQoL) is a subset of quality of life, and specific questionnaires are available; in turn, there are also dental patient-reported outcome measures (dPROM) to be used for dental patient-reported outcomes (dPRO) or oral health–related quality of life (OHRQoL) in particular. The construct of OHQRoL is based on patients’ impacts of oral problems, i.e., pain and functional impairment, but also includes social and psychological limitations. In addition, OHRQoL is modified by cultural surroundings and expectations with respect to dental care and care experiences [6‐10]. DPROMs can be used—amongst epidemiologic applications and evaluations—i.e., for the process control during dental treatments. The most frequently used dPROM is the Oral Health Impact Profile (OHIP-49) and its derivates including population-adapted (i.e., children) and shorter versions [9, 10]. Using OHRQoL is administered by determination of impacts during the past month on a 5-point Likert scale. As an alternative, the Geriatric Oral Health Assessment Index is widely used in elderly populations as it merged into less bottom effects and only includes 12 items [6, 7]. However, most OHRQoL inventories solely access the presence of impacts. Their frequencies and severities are not evaluated separately. An exception is the Oral Impacts on Daily Performances (OIDP) [11]. Here, both frequency and severity are administered to build a sum score based on a multiplication. In, addition, the response burden is quite low as it only includes ten items. As the division of problems’ frequencies and severities has been seen as valuable in the evaluation of OHRQoL, OIDP was translated and validated in several languages [12‐17]. However, to date, there is no German version of the OIDP. Thus, the aim of this study was to prove the reliability (construct stability and response to treatment) and validity (validated dPROM, objective dental findings) of a German version of OIDP in a cohort of German adults. The study hypothesis was that the German version of the OIDP is a reliable dPROM for the evaluation of OHRQoL.

The results of the study suggest that the German version of the OIDP is a predominately reliable and valid dPROM for the evaluation of the oral health–related quality of life of adults; thus, in an overall view, the study hypothesis had to be accepted.

When evaluating OIDP reliability which focused on the reproducibility of the values of items when the same subjects responded to the questionnaire twice, the correlation coefficients was acceptable. All the inter-item correlations were positive, thus demonstrating acceptable internal consistency and acceptable homogeneity of the items. This result is similar to the results of the Malaysian version of the OIDP [23]. With respect to reliability, the ICC higher than 0.60 found in this study was comparable to other international adaptions of the OIDP and indicative of acceptable construct stability of the German version of the OIDP [12‐17]. When testing validity, the German version of the OIDP was in acceptable agreement with other measures of self-perceived OHRQoL. However, the OIDP has similar mean scores and a higher standard deviation compared to the OHIP which is maybe indicative of partially minor bottom effects in a rather healthy study cohort. In addition, the OIDP might be more specific in a study population with more frequent and greater impairments. One could further speculate that the division of the OIDP in the query of severity and frequency might lead to an increased sensitivity of the questions due to the multiplication of the two sub-scores per item, i.e., seldom burden (1 point in OIDP-f) combined with very strong severity (5 points in OIDP-s) or vice versa. This could be another reason for the rather high standard deviation. This assumption is supported by the fact that OIDP-s and OIDP-f in separate view showed standard deviations comparable to that of OHIP whilst the mean score is even smaller. Nevertheless, the OIDP is the only screening assessment tool that evaluates severity and frequency and has therefore a justification and importance if a more dedicated OHRQoL is required (insight into frequency and severity). When interpreting the results, it should be kept in mind that the different dPROMs were validated in different study populations. For example, the GOHAI was developed for the elderly [6, 7]. It is not surprising, that this community usually has different impairments compared to young and healthy persons which were investigated in this study setting. The focus of the different dPROMs is therefore shifted. This could explain the weaker correlation between OHIP and GOHAI in this study population. Furthermore, it has to be kept in mind that Hassel et al. found similar correlations in their validation study (GOHAI vs. OHIP: − 0.721) [6]. It further should be kept in mind that the response to treatment reliability was rather low, presuming that the impact of treatment on the patients was very inhomogenous from less invasive to very extensive.

Another interesting result is that this study found no association between OIDP scores and gender, age group, or level of education. These results are in accordance with Ostberg et al., in Swedish, and Razanamihaja and Ranivoharilanto et al. in the Malaysian version [12, 17].

Although the sample size was not calculated prior to the study because it is explorative in nature, the sample size was much larger than recommended in the literature [23, 24] and therefore sufficient for testing reliability and validity. The responsiveness to treatment and construct stability, however, was tested in a small number of patients only, but this group was inhomogeneous as all patients received different treatment under comparable treatment conditions. However, the result suggests that the German OIDP responds to changes in clinical factors, as expected. In this context, it must be noted the prevalence of negative impact on oral health was low in this study population. This can be again explained by a young and healthy study population and a high number of natural teeth present (mean 26.1) as well as many fixed dental prostheses rather than removable dentures. Those factors are described to have a high impact on OHRQoL [25‐27] and 94.2% of the study population stated that they were happy with their oral function. For participants with natural teeth and fixed dental prosthesis, individual problems like tooth color or tooth position might be more relevant than the chewing function.

The OIDP is the only validated dPROM yet that evaluates both severity and frequency and is therefore of high interest. The German version of the OIDP seems to be predominately reliable and valid for the administration of OHRQoL. However, results may not unreservedly be extrapolated to other populations.