Joost Peerbooms

87 2-year follow-up of PRP in lateral epicondylitis Figure 1. Flow diagram of a trial of injection therapy for chronic lateral epicondylitis. The dia- gram includes the number of patients actively followed up at different times during the trial. Statistical Analyses Frequencies were used to present the available sociodemographic and clinical data. Student t tests (continuous data) and x 2 tests (categorical data) were used to examine differences between (1) the protocol-compliant group and the reintervention patients, (2) the corticosteroid group and the PRP group, and (3) the successfully treated group and the nonsuccessfully treated group. The protocol-compliant group was defined as the group of patients who did not need a reintervention (i.e., reinjection, crossover, or surgery). Successful treatment was defined as more than 25% reduction on the VAS pain score and the DASH total scores without a reintervention after 2 years compared with the pre-injection scores. This 25% reduction closely resembles the MCID (minimum clinically important difference), which is 10.2 points for the DASH score. 21 To examine differences in VAS pain scores and DASH total scores between the PRP group and the corticosteroid group before and after the intervention, multivariate analyses of variance 6