Page 127 - Bladder Dysfunction in the Context of the Bladder-Brain Connection - Ilse Groenendijk.pdf

agreement and the limits of agreement were calculated, demonstrating an adequate reliability and reproducibility. These results are in accordance with the original OAB-q SF study,9 and the Spanish validation study.18
Concerning the criterion validity, the present study used the UDI-6, the ICIQ-OAB and the EQ-5D-5L to correlate with the OAB-q SF because of the absence of a gold standard. As expected, the symptom bother subscale showed a strong correlation with the UDI-6 and the ICIQ-questionnaires for both test and retest. Moreover, the OAB-q SF HRQOL subscale showed a strong correlation with the ICIQ-bother scales, but the correlations with the EQ-5D-5L index value and EQ-VAS were moderate. The ICIQ-OAB bother scales are focused on OAB symptoms and the EQ5D5L is more in general, which might be a possible explanation for the moderate compared to strong correlation. The Spanish validation study also used the EQ-5D and -VAS and showed comparable, moderate cor- relations.18 All predefined hypotheses in the present study were confirmed demonstrat- ing that patients and references are well distinguishable, and therewith showing a good construct validity.
In the patient group, no floor and ceiling effects were detected, which implies that although many patients had severe OAB, the questionnaire is still discriminative enough to detect worsening or improvement of symptom bother or in HRQOL. In the reference group, as expected, a floor effect was found in the symptom bother scale (17.5%), in- dicating that in the reference group patients had no bother due to bladder problems. Moreover, a ceiling effect was seen in the HRQOL scale (29.4%), indicating that in the reference group, bladder problems were not severe enough or not present to create a decrease in HRQOL.
The strength of the current study is the use of standardized measurement properties as described by Terwee et al. to evaluate the reliability and validity of the OAB-q SF.15 The current study did not determine the responsiveness and interpretability due to short follow-up, and a lack of therapy changes over time in the study group. This is a limita- tion of the study, however previous literature on the English OAB-q SF demonstrates a good responsiveness and interpretability.9 There was a difference in the mean age between the patient and the reference group. The reference group is only used for one of the four hypotheses of the construct validity. All the other measurement properties are calculated without the use of the reference group, so without influence of this age difference. Another limitation of the study is the absence of a gold standard to assess the criterion validity. On the other hand, the absence of a gold standard in this highly prevalent disease demonstrates the need for a good PRO in OAB. The choice to imple- ment the OAB-q SF in the ICHOM OAB-set suggests that this questionnaire might be a valid PRO for OAB symptoms.
6
The validation of the Dutch OAB-q SF questionnaire 125