4 71 Chronic Achilles Tendinopathy: Impact on Quality of Life and Costs to evaluate self-rated current overall health status. The EQ-VAS consists of a tape ruler from 0 -100 (with 0 points being the worst imaginable health status). Secondary outcome measures We assessed work performance with a questionnaire by asking the number of lost days of work and a decrease in work productivity (yes/no) since the onset of symptoms. We corrected this secondary outcome measure for symptom duration, thereby displaying work performance outcome measures on an annual basis. Healthcare utilization was expressed in the total annual number of healthcare visits, the type of healthcare provider, and type of treatment. Participants who reported visiting a healthcare provider, but could not specify the number of visits or treatments were recorded as missing data. Participants who reported visiting a sports medicine physician or orthopedic surgeon were assumed to have at least one consultation with a general practitioner (GP), as a referral from a GP to a medical specialist (e.g. sports physician or orthopedic surgeon) is required in the Netherlands. Participants who reported treatment with a certain number of injections, but did not specify the number of visits to a medical specialist were assumed to have an equal number of visits to a medical specialist as the number of injections. We divided costs into two categories: direct costs as a result of medical consumption and indirect costs as a result of lost working days or decreased work productivity. The direct medical costs were calculated with the following formula: total number of visits/treatments multiplied with estimated medical costs for those visits/treatments. In 2016 the Dutch Healthcare Authority published a guideline for economic evaluations in healthcare.22 Using this guideline we established medical costs per visit/treatment and estimated productivity costs per hour at €34.75 (US $38.57) per person.22,23 Costs used for the economic evaluation are specified in supplementary file 1. Costs in dollars were calculated using the average exchange rate of the respective study period. We did not register the profession of the patients and therefore did not adjust the costs for type of profession. Indirect costs were calculated by lost working days/work productivity multiplied by the costs per working day. Costs per working day were calculated using the productivity costs per hour. To calculate indirect costs due to a decrease in work productivity we estimated reduced productivity without sickness absence at 1.0 hour per month. This is based on previous research on self-reported productivity loss in patients with musculoskeletal disorders.24 The annual direct and indirect costs were adjusted for symptom duration, because we asked patients about these costs during their symptomatic period. Statistical analysis We assessed data for having a normal distribution using the Shapiro Wilk test. Normally distributed data are presented as mean with standard deviation (SD) and non-normally
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