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Table 1 Trial schedule for assessments

From: Selenium supplementation for patients with Graves’ hyperthyroidism (the GRASS trial): study protocol for a randomized controlled trial

   Follow up
Variable Inclusion (baseline) 6 weeks 12 weeks 6 months 12 months 18 months 24 months 12 (± 1) months after ATD treatment withdrawal
Visit x      x   x
ATD treatment       x x x
Thyroid function x1      x1   x1
TSH-Receptor Antibodies x1      xs   xs
Serum selenium x      (xs)   (xs)
Creatinine/iodine ratio in spot urine x        
Storage samples (blood and urine) x      x   x
ThyPRO xr xr xr xr xr xr xr xr
Tablet count   xr xr xr xr xr xr xr
Consumption of additional selenium     xr xr xr xr  
Adverse events*   xr xr xr xr xr xr xr
Serious adverse events         x
Referral to ablative therapy       x   x
  1. All assessments must be made at the time points specified above. If the assessment is not possible at the specified time, the assessment shall still be conducted, and the time shall be noted in the electronic case report form (eCRF). Following this, deviations from the protocol can be assessed. 1As part of usual clinical practice (f = free (non-protein bound)), that is, all measured analyses are collected continuously from medical systems; xs, analysed on stored plasma/serum samples after trial completion; xr, self-reported data by participant; participants for whom ATD treatment withdrawal has not been attempted, or has been unsuccessful, will be followed up at 36 months after randomisation (± 1 month). ATD, anti-thyroid drugs; TSH, thyroid stimulating hormone; ThyPRO, thyroid patient-reported outcome.