Although cross-cultural validation studies are very difficult to be carried out, their results might be considered worthwhile. Firstly, they provide standard health measures that make health status comparisons between different populations possible. Secondly, they provide validated instrument to monitor population health, estimate burden of disease and investigate outcomes in clinical practice and evaluate treatment effects. This was the first study on psychometric properties of the Iranian version of EHP-5 among an Iranian population. The results showed that the instrument was a reliable and valid measure that can be used in monitoring and measuring health-related quality of life of women with endometriosis.
Similarly the validity of the EHP-5 in different cultures was well documented. For instance, the finding from an English study showed that the instrument had good validity and could be applied among women with endometriosis . Furthermore, a French version of the EHP-5 questionnaire has been developed and its acceptability and feasibility was desirable although validity was not reported .
Iranian version of the EHP-5 was extracted from its English version. The translation of the EHP-5 in Iran went through a rigorous method and was approved by the questionnaire's developers. Thus we did not encounter any difficulties in data collection.
The EHP-5 was basically designed to be a self-administrated questionnaire but it can be completed through an interview in person or by telephone . However, face-to-face administration of questionnaire allowed the interviewers to collect data without any missing data. Although method of completing the EHP-5 has not been mentioned in its manual, the designers administered it by mail (self-administrated) and the rate of returning the questionnaire was reported to be 37.1% .
Reliability was assessed by internal consistency and validity was examined by known groups comparison. Cronbach's alpha coefficient showed a satisfactory result . Known groups comparison indicated that the EHP-5 score were able to distinguish very well between subgroups of the respondents who differed in reproductive health status. The study showed that women with infertility and PMS had poorer health compared to women without infertility and PMS. These findings are consistent with results from other studies carried out in different countries [12–15]. However, there were no significant differences in social support between fertile and infertile or women with and without PMS. This might be explained by the fact that endometriosis by itself is a chronic disease and thus as it relates to social support, both fertile and infertile women or those with and without PMS showed a relatively similar scores and therefore one might not expect to find significant differences between women in this domain.
Tools assessing quality of life are being used in research and clinical trials rarely. For instance, only 17% of randomized trials assessed in a systematic review on the measurement of HRQoL in women had used standardized instruments . In addition, often the instruments have been used in research just measured one dimension of illness e.g. psychological health status without identifying other areas of well being affected by disease . Reasons for the limited use of health statues instruments in clinical setting are that they are too long and complicated for clinicians to understand and interpret the data gained by long health statues instruments, and also they are too burdensome for respondent to complete them [17, 18]. The short form EHP-5 provides the chance of using a very brief instrument that measures health outcome for women with endometriosis where the long form version would not be appropriate. The results obtained by the EHP-5 from the analyses suggest this instrument provides the same picture of health-related quality of life as the longer version .
Although this study did not provide evidence for test-retest reliability, responsiveness to change or other tests; overall the findings showed that the Iranian version of EHP-5 is a reliable measure for measuring health quality of life in endometriosis patients. It will be especially useful in clinical settings where a short and economical endometriosis health status measure is needed. The future studies could focus on other psychometric properties of the EHP-5 questionnaire and also on different applications of the questionnaire as a recent study has suggested even it is a useful index in order to evaluate cost-effectiveness of healthcare interventions .