Page 36 - The value of total hip and knee arthroplasties for patients

Chapter 2
to return postal questionnaires were included, maintaining a high postoperative response-rate. In order to stimulate patients to continue participation we also have patient-partners within our LOAS governing board and we mail patients several times a year (e.g. LOAS Happy New year cards and newsletters).
Besides, we observed considerable differences between the inclusion rates of the hospitals. A possible explanation would be that some hospitals informed all patients about the study and sent them all to the coordinating researcher, whereas others informed only those probably participating in the study.A direct link with the registered patients in the Dutch Ar throplasty Register is necessar y to get insight into these numbers.Another possible explanation would be discrepancies in the content and manner of the provided information to patients.
Concerning the mode of administration of the PROMs, the LOAS study only used pen-and-paper questionnaires during the inclusion period of the present analysis. Previous authors suggested that electronical questionnaires cannot replace pen-on- paper questionnaires,28;29 but, like other registers8 we are developing an Internet- based structure to collect the PROMs next to the traditional pen-and-paper questionnaires, to improve efficiency.
The selection of PROMs, to include in patient cohort studies necessitates the use of appropriate methodological techniques and the inclusion of both generic and condition-specific PROMs. Furthermore, the number of questions in the survey must be reasonable to provide a high patient-response rate.8;30 Moreover, PROMs should cover the domains of functioning that are relevant for osteoarthritis patients as described in ICF core sets for osteoarthritis.31 Recently the International Consortium for Health Outcomes Measurements (ICHOM) published a data collection reference guide with specific PROMs that should be included in joint arthroplasty registers.32 The ICHOM Standard Set for Hip & Knee OA outcomes comprises the hip or knee functional status (HOOS-PS or KOOS-PS), pain (numeric or VAS scales), Quality of life (either the EQ-5D-3L, VR-12 or SF-12), work status (no specific questionnaire) and satisfaction with results (no specific questionnaire). The set of PROMs used in the present study is in line with this standard set.
This study has a number of limitations. First, from the registered patients in the Dutch Ar throplasty Register from the par ticipating hospitals, we estimated that only
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