Quality of life in South East Asian patients who consult for dyspepsia: validation of the short form Nepean Dyspepsia Index

BACKGROUND:
Treatment objectives for dyspepsia include improvements in both symptoms and health-related quality of life (HRQoL). There is a lack of disease-specific instruments measuring HRQoL in South East Asian dyspeptics.

OBJECTIVES:
To validate English and locally translated version of the Short-Form Nepean Dyspepsia Index (SF-NDI) in Malaysian patients who consult for dyspepsia.

METHODS:
The English version of the SF-NDI was culturally adapted locally and a Malay translation was developed using standard procedures. English and Malay versions of the SF-NDI were assessed against the SF-36 and the Leeds Dyspepsia Questionnaire (LDQ), examining internal consistency, test-retest reliability and construct validity.

RESULTS:
Pilot testing of the translated Malay and original English versions of the SF-NDI in twenty subjects did not identify any cross-cultural adaptation problems. 143 patients (86 English-speaking and 57 Malay speaking) with dyspepsia were interviewed and the overall response rate was 100% with nil missing data. The median total SF-NDI score for both languages were 72.5 and 60.0 respectively. Test-retest reliability was good with intraclass correlation coefficients of 0.90 (English) and 0.83 (Malay), while internal consistency of SF-NDI subscales revealed alpha values ranging from 0.83 - 0.88 (English) and 0.83 - 0.90 (Malay). In both languages, SF-NDI sub-scales and total score demonstrated lower values in patients with more severe symptoms and in patients with functional vs organic dyspepsia (known groups validity), although these were less marked in the Malay language version. There was moderate to good correlation (r = 0.3 - 0.6) between all SF-NDI sub-scales and various domains of the SF-36 (convergent validity).

CONCLUSION:
This study demonstrates that both English and Malay versions of the SF-NDI are reliable and probably valid instruments for measuring HRQoL in Malaysian patients with dyspepsia.