Concurrent validity of the Afrikaans versions of the Neck Disability Index Questionnaire and the Quadruple Visual Analogue Scale

Abstract

Background: Neck pain is a condition that is becoming more common throughout the world and most people can expect to experience some degree of neck pain sometime during their life. There is a need for early diagnosis and follow-up of neck pain to assess a patient’s level of self-rated disability due to the escalating disability burden and compensation costs associated with neck pain. For this reason, disability questionnaires are increasingly used for clinical assessment and as an outcome measurement for the treatment of neck pain. Translation and cross-cultural adaptation of disability questionnaires have thus become increasingly necessary when dealing with different cultural groups.

Methods: This is a quantitative validity and reliability assessment study comparing the English versions of the Neck Disability Index (NDI) and the Quadruple Visual Analogue Scale (QVAS) to their translated Afrikaans counterparts. The first step was to translate the questionnaires into Afrikaans. The translated questionnaires were then scrutinised and critiqued by an Expert group, who are fluent in both the Afrikaans and English languages, and back translated to English in order or establish their face validity. A small pilot study was conducted with the original and translated versions of the questionnaires to establish their content validity.

The translated and original versions of the NDI and QVAS were given to a study group to complete with a suitable time delay between the completions of the questionnaires. The results from the study group were statistically analysed to establish concurrent validity and reliability.

Results: There were 50 participants each completing one English NDI and QVAS and one Afrikaans NDI and QVAS. The results indicate high reliability for both the Afrikaans NDI (α = 0.900) and QVAS (α = 0.883). The Afrikaans NDI and QVAS are deemed reliable compared to their English counterparts.

The results indicated a significant level of concurrent validity for both the NDI and the QVAS.

Both the Afrikaans versions of the NDI and QVAS were deemed reliable and concurrent validity was established. The NDI and QVAS were successfully translated and the Afrikaans versions can now be used in the Afrikaans population as viable alternatives to the English NDI and QVAS.