Relevance of Norm Values as Part of the Documentation of Quality of Life Instruments for Use in Upper Gastrointestinal Disease

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Abstract
This article presents the relevance of norm values to a battery of Quality of Life questionnaires for use in upper gastrointestinal disorders. The derivation of reference values offers an important contribution by confirming the ability of the questionnaires to differentiate patients from healthy controls. Two self-administered questionnaires, the Psychological General Well-being (PGWB) index and the Gastrointestinal Symptom Rating Scale (GSRS) were used. The norm values were derived in a randomly selected sample from a Swedish population consisting of 4624 individuals (reference group). The patients comprised more than 900 patients with gastroesophageal reflux disease (GORD) included in clinical trials. In the reference group, males reported significantly higher values on well-being as compared with women, whereas women reported more pronounced gastrointestinal symptoms than men. Generally, the younger persons and the group aged 60–70 years reported the highest well-being. Among gastrointestinal patients women scored lower and reported more symptoms than men. With increasing age, well-being improved and symptoms declined. Even though the well-being and symptoms scores differed between patient and the reference group similar patterns in terms of age and gender were observed. In summary, the results show that there are differences with respect to gender and age among normal controls as well as in GORD patients. These aspects have to be considered in clinical studies. The results also support the discriminative ability of the Quality of Life instruments.