Hypothesis / aims of study
The purpose of our study is to cover this need and assess the psychometric properties of the OAB-q in Greek patients with overactive bladder. To our knowledge, there is no validated questionnaire for quality of life concerning patients with overactive bladder in the Greek language. OAB-q has been already translated officially to the Greek language, but not validated for Greek patients yet.
Study design, materials and methods
Sample
Data were collected from consecutive patients with overactive bladder who visited the Outpatients Clinic of our Department in a period of three months. Patients were of both sexes and over 18 years old. The diagnosis was made according to the definition of overactive bladder acquired by the International Continence Society [1]. Urodynamic studies were also performed whenever there was doubt in diagnosis. Urinanalysis and urine culture were negative in all patients. Mixed type incontinence was not an exclusion criterion, as long as the urgency compound was the main type of incontinence. Patients not fluent in Greek were excluded.
Procedure
The linguistic and cultural adaptation to Greek had already been carried out before the beginning of our study. The patients filled the OAB-q and SF-36 questionnaires in their first and second visit (three months apart). In the meantime, lifestyle measures and drug therapy were initiated. The present study was approved by the Committee of our Hospital and all the patients signed an informed consent.
Reliability, Validity and Statistical Analysis
The reliability was evaluated by the evaluation of internal consistency. The Cronbach’s α factor was used as an indicator of internal consistency. Concerning the validity, the criterion validity was used comparing OAB-Q with another already validated questionnaire (SF-36). The validity was assessed by comparing OAB-q with SF-36. SF-36 has been officially translated in Greek and already validated in Greek patients [2]. Furthermore, SF-36 has shown good psychometric properties for symptoms of lower urinary tract [3]. The present study was approved by the Committee of our Hospital and all the patients signed an informed consent. The statistical analysis was performed by the 21st edition of the SPSS software.
Results
Patients had a mean age of 62.1 years and 74.8 % of them were women.
Reliability
In Table 1, we show Cronbach’s α at the beginning and at the end of the study. Cronbach’s α is over 0.70 in all the categories of OAB-Q and SF-36. In most categories, it is over 0.85. Therefore, OAB-Q has internal consistency and is evaluated as reliable.
Validity
In Table 2, we show the correlation among most categories of OAB-q and SF-36. The categories’ distributions were normal and therefore, the Pearson product-moment correlation coefficient (Pearson’s r) was used for the evaluation of their correlation. In the beginning of the study, symptom bother, concern/worry and health-related quality of life showed strong correlation with almost all the categories of SF-36. Sleep is correlated with all the categories of SF-36, while coping behaviors with only 6 categories. At the end of the study, every category of OAB-q is correlated with every category of SF-36 (p<0,001). Symptom bother and sleep showed the highest correlation (r>0.5).
Interpretation of results
In our study, OAB-q has shown good psychometric properties in Greek patients. Reliability is shown by its internal consistency, as Cronbach’s α is over 0.70 in all categories; both at the beginning and at the end of the study. In most categories, it is about 0.90. In addition, its values are similar to the values found in the original study for the questionnaire. On the other hand, validity is shown by the clear correlation of the OAB-q categories with almost all categories of SF-36. Pearson’s r is over 0.3 in almost all cases and even more than 0.5 in some cases. This is similar to the correlation found in the original validation study for the OAB-q, where the same comparison had been made. Besides, in our study, the internal consistency of SF-36 is similar to that of the SF-36 Greek validation study. This leads to the conclusion that the comparison made is valid.