Reply to Moons

We thank Moons for his interest in our recent article on the quality of life in the GUCH patients [1]. This letter is in response to his valuable comments regarding our study.

In his letter, Moons emphasises that the SF 36 is most often used as a health-related quality of life instrument, whereas it says more about the perceived health status of the respondents. We agree with Mr Moons on this issue. However, the SF 36 questionnaire is a well-established tool for attempting to evaluate quality of life, and due to this ‘limitation’ it was applied in addition to two further questionnaires, one of the two especially created to evaluate the specific problems and also the functional status of the GUCH patients studied. Thus, not only the perceived health status was analysed, but it was also attempted to evaluate the functional status of the GUCH patients.

Regarding the concerns on some contradictions with respect to the normalising of the quality-of-life scores, we are happy to describe our methodology here in more detail. We followed the methodology applied in several previous studies and publications by our group [2,3]. First, the raw score of each of the eight dimensions of the SF 36 was transferred onto a scale from 0 to 100, as a step (technically not a necessary one) towards another transformation. This converts the scores so that the mean for each dimension is 100, giving a normal range from 85 to 115. The population mean found in the 1998 National Survey of Functional Health Status [4] serves as the reference for transformation factor in each dimension, the so-called norm-based scoring. The advantage of this process is the immediate comparability with ‘normality’: for each dimension’s value, one can see whether or not it falls into the normal range or to what extent it deviates. This methodology is also supported by Bullinger and Kirchberger [5] and is performed by the standard software used for collecting and evaluating the SF 36 data. As the aim of our study was the comparison of our GUCH patients with the ‘standard’ population, we felt this method was appropriate. We disagree with Mr Moons in that such a transformation of the data could possibly lead to other findings or results. Furthermore, Moons believes that the computing of an overall SF 36 score is not appropriate, because constructs that are conceptually different are mixed. He points out that one should use the two overall scores, physical and psychological, only. We agree that calculating a mean out of different constructs should be performed carefully. This is the reason why we showed the overall SF 36 score as additional information. Our conclusions were drawn from the results of all three different questionnaires, covering complementary aspects of daily life in GUCH patients – the SF 36 test, the HADS test and the additional GUCH-specific questionnaire. In using all three, we wanted to present a larger picture.

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