This was a validation study of one of the most widely used instruments to measure anxiety and depression in cancer patients. The Iranian version of the HADS proved to be acceptable to patients and it is worth noting that the questionnaire was administered by a trained nurse in face-to-face interviews, although the original questionnaire is a self-rating instrument. This was due to the fact that there were a relatively considerable proportion of illiterate patients in the study. It is argued that face-to-face interviews may lead to social desirability bias particularly in sensitive areas such as assessment of mental health . We do not know mode of administration through interviews how much affected the results. However, patients indicated that some questions were difficult to answer, especially items 10 and 11. Perhaps this was the reason why a weaker correlation was found for these items with their corresponding subscale. It seems that weaker correlation of items 10 and 11 would also be due to some problems of translation that might not be reached cross-cultural comparability with the original version of the questionnaire.
Similar to most studies reliability of the Iranian version of the HADS as measured by the internal consistency of the anxiety and the depression subscales was found to be satisfactory. However, there was a strong correlation between anxiety and depression subscales. One may argue that this is evidence to suggest that the instrument is a general measure of distress rather than a measure of anxiety and depression. In other words it is possible to suggest that because of the high correlation between the two HADS subscales it can be used as an unidimensional scale with a global score for the whole instrument (Table 3). A recent study in breast cancer patients concluded that the total score of the HADS is a valid measure of emotional distress and it can be used as a screening questionnaire for psychiatric disorders. The same study indicated that the use of the two subscales as a 'case identifiers' or as an outcome measure should be considered with caution . In contrast, apart from findings from several studies that showed the HADS is a two-factor instrument , it has been suggested that inter-correlation between the anxiety and the depression subscales is not surprising since this is mainly due to a real coincidence of anxious and depressed symptoms and only to a lesser extent to inadequacies of the instrument .
The known groups comparison analysis indicated that the Iranian version of the HADS is a valid instrument for measuring anxiety and depression in breast cancer patients since the instrument was able to discriminate between patients who were clinically different. However, the striking finding from this preliminary validation study was that Iranian women with breast cancer showed a higher level of anxiety and a relatively lower level of depression. This may reflect the fact that the cut-off score would be different in Iranian cancer patients so further investigation might be necessary. Indeed the sensitivity analysis using an objective criteria or a gold standard test is needed to answer this question. Unfortunately the present study was limited in this respect.
As far as assessment of anxiety and depression in breast cancer patients is concerned studies have shown that the HADS may result in under estimation of psychiatric morbidity among women with early stage breast cancer and therefore its utility for screening purposes in early stage breast cancer patients is limited [11, 12]. In contrast, most of the exiting literature suggests that the HADS is a suitable instrument for measuring anxiety and depression in breast cancer patients [13, 14].
The HADS anxiety and depression scores showed a negative but significant correlation with emotional functioning and global quality of life as was expected. This means that those who were more anxious or depressed showed lower levels of emotional functioning and global quality of life. Thus this could be regarded as additional evidence to suggest the HADS is a valid questionnaire. In a few validation studies usually concurrent validity analysis was applied using the correlation between the HADS and the Beck's Depression Inventory (BDI), or the General Health Questionnaire (GHQ), or the State-Trait Anxiety Inventory (SATI) [15–17]. However, since there was no an Iranian version of these questionnaires we used two subscales from the validated Iranian version of the EORTC QLQ-C30.