6 PAF-study: results of a randomized controlled trial 161 PFPT group also benefited from PFPT. Although patients from the early PFPT group improved quickly, it is still worthwhile initiating PFPT at any time during treatment. The main strengths of this study are the prospective randomized control trial design, sufficiently powered intent-to treat analyses and the design of the study in which all patients received PFPT. In addition, the use of a PFPT- protocol performed by large group of collaborating pelvic floor physical therapist in the Netherlands makes this treatment suitable in all clinical settings. All pelvic floor physical therapists involved in the study were highly trained and had access to equipment for EMG-biofeedback. The use of a validated EMG electrode27 to measure pelvic floor muscle tone, the use of a standardised measurement protocol by the same investigator in the same environment diminished information bias.52 The willingness to participate and adherence of the patients to the trial procedures and the intervention was high, evidenced by the low rate of loss of follow-up. The use of this clinical trial set up with a postponed PFPT- group may have also positively influenced the adherence rate. Patients knew they would start with PFPT, albeit 8 weeks later. Our population was real world; we enrolled patients of all ages and both sexes with duration of complaints varying from 2 months to more than 3 years and living in different parts of the Netherlands. Thus, the results may be generalizable to the CAF population at large. There were several limitations in our study. The first concerns the risk of detection bias; we were unable to mask group allocation from patients, collaborating pelvic floor physical therapist and principal investigator, because of the trial design and the nature of the intervention. Second, the pelvic floor physical therapist was also the principal investigator and consequently investigator’s bias could not be ruled out. The balloon expulsion test, to identify patients with pelvic floor dyssynergia was only performed in 69 patients at inclusion with a high rate of loss to follow-up at 20 weeks. The main reason was a logistic one. It was not always possible to combine an appointment in the clinic with the nurse and principal investigator, especially during the COVID-19 pandemic. In addition, in a large percentage the balloon expulsion test failed. This could be a result of fear of patients with CAF in expelling a balloon. COVID-19 did have some influence on our study. During the first pandemic in 2020 we were not able to include patients in the study for 4 months and a small number of patients were lost to follow-up because they were diagnosed with COVID-19 at the follow-up appointment.
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