Table 10 Process model of cross-cultural adaptation of an instrument, adapted from Herdman et al. [26] and Reichenheim and Moraes [52]

Conceptual equivalence

When the domains that represent the construct under study (e.g. engulfment, rejection, acceptance and enrichment domains within the IIQ) not only have the same relationship in both the original and target context but the weight placed on each domain is also the same

Review of literature on the concept under study and or its domain, published in both the original and target context

Domains are relevant to the target context and weight placed on each is the same, thus the construct may be deemed valid in the target context

Through conceptual equivalence, researchers can determine whether adapting the questionnaire is warranted or not

Exploration of how the domains under study are interpreted by the target population

Domains are relevant to the target context. However, weight placed on each is different

Discussion with experts and specialists in the field

Some of the domains are irrelevant in the target context, therefore only limited adaptation will be possible

All domains are irrelevant and as such adaptation cannot be justified

Item equivalence

When items that measure a latent trait (e.g. acceptance as one of the domains of illness identity in the current study) mean the same thing in both the original and the target context. Relevance and acceptability of items must also be the same in both target and original contexts

Review of available relevant literature

Item amendment not required and can be used as is in the target context

Exploration of how the items that measure the latent trait are interpreted by the target population

Although minor item adjustment required, items can still be used to a large degree in target context as was in the original context

Psychometric testing (e.g. Rasch item analysis)

There is a need to substitute some of the items

Both original and replaced items do not measure the latent trait, are unacceptable and irrelevant

Semantic equivalence

The same meaning of items in the original language (English in the current study) could be established in the target languages (IsiXhosa and Afrikaans) and in so doing, simultaneously attaining the same effect on respondents in the target context

First determining meaning of key words or phrases used within the instrument in the source language

Items are easy, difficult or impossible to translate

Actual translation and where necessary, adjusting the level of language to that of the target population

Translator being aware of the target population and as such adjusting the language of the instrument to the dialect of the target population

Operational equivalence

When mode of administration, format, instructions and measurement of the instrument can be applied in the same manner in the target context as was in the original context

Assessment of literacy levels of the target population will guide and inform operationalization of the instrument

Mode of administration, format, instructions and measurement of the instrument can be applied in the same way in the target population as was in the original context

Review of cultural norms of the target population

Only after adjusting some aspects of operationalisation (e.g. mode of administration) can the instrument be used in the target context

Actual testing of suggested methods within a sample of target population

Operational equivalence cannot be achieved

Measurement Equivalence

Assesses whether the psychometric properties (reliability, responsiveness and construct validity) of the translated version of the instrument are at an appropriate level

Cronbach’s α

Properties are the same, different or systematically different

Intra-class correlation coefficient

Paired t-statistic

Effect size statistic

Responsiveness statistic

Factor analysis