Development, Validation, Grading And Use Of The Vulval Disease Life Quality Index (VQLI)

Abstract

Objective – To develop a validated instrument to test Health related Quality of Life (H-QoL) in vulval disease. To propose severity banding for VQLI. Compare the VQLI with previously validated questionnaires in assessing vulval disease. Method –After a comprehensive literature review, consultation with specialist clinicians and focused patient interviews a 22-item questionnaire was generated. Content validity was established through field testing, patient interviews and pilot questionnaires. Validity and reliability was assessed against pre-existing questionnaires in vulval disease related areas and test retest administration of the VQLI on a cohort of women. The development of severity banding for the VQLI was developed by comparing the scores of 516 women contemporaneously completing the VQLI and DLQI. The scores of VQLI were correlated with the Dermatology Life Quality Index (DLQI) completed by women attending a vulval clinic. The VQLI was then applied to another cohort of 300 women for preliminary assessment of its application in clinical practice. Floor effect analysis and feasibility of VQLI were assessed. Preliminary analysis was also performed assessing differences between specific vulval diseases and changes in scores with treatment. Comparison was made between clinical outcomes of the VQLI and DLQI. Statistical Analysis – Reliability of the questionnaire was assessed in two ways; internal consistency was measured using Cronbach’s alpha and test-retest reliability was calculated using quadratic weighted kappa. Construct validity was assessed from correlations between the VQLI and previously validated questionnaires completed contemporaneously including; Dermatology Quality of life Index (DLQI), Hospital Anxiety and Depression Scale (HADS) and Female Sexual Dysfunction Scale (FSDS). Each question of the VQLI was correlated with the corrected total VQLI score and grouped VQLI themes were correlated with DLQI, HADS, FSDS and convergent validity assessed using Spearman correlations. For the development of severity banding a previously established DLQI global question (GQ) score was correlated with overall VQLI score. Spearman rank correlation coefficient was applied to assess correlation between the VQLI and GQ scores. The mean, mode and median of the GQ scores for each VQLI score were used to delineate bands VQLI scores and the kappa coefficient of agreement were calculated for each band. Results – The VQLI had excellent internal consistency (Cronbach’s alpha, 0.93). Test-rest reliability showed most questions had a substantial weighted kappa value of 0.5 or above and a good intraclass correlation coefficient (0.88; CI 0.8-0.93). Spearman correlations were consistently positive between VQLI and other previously validated scales and individual VQLI scores were all strongly correlated with overall corrected VQLI score. The proposed scoring bands of the VQLI includes: 0–5 = no effect on patient’s life (GQ 0, n = 110]), 6–13 = small effect on patient’s life (GQ 1, n =156), 14–23 = moderate effect on patient’s life (GQ 2, n =144), 24–37 = very large effect on patient’s life (GQ 3, n = 95), 38–45 = extremely large effect on patient’s life (GQ 4, n = 11). The kappa coefficient for the proposed banding system was 0.505. The advantages of the VQLI over other validated questionnaires such as the DLQI were demonstrated with its emphasis of impact of disease on relationships and the psychosocial impact of disease. Additionally, the VQLI demonstrated the significantly increased impact vulval diseases have on the younger population as compared to older (p = 0.034). This demonstrates the utility of the VQLI in trial and clinical settings. Limitations – The VQLI was limited geographically as the two centres are both located on lower North Shore of Sydney, Australia. There was an observed floor effect when the VQLI was applied to a mixed cohort of patients attending a vulval clinic. Conclusion – The VQLI is a validated and reliable tool for measurement of quality of life in vulval disease which assesses vulval disease in context of both the physical and psychosexual context. The questionnaire will be further tested to assess correspondence of impact on quality of life with level of clinician graded disease severity.