Keywords: control survey, radioimmunoassay, α-fetoprotein, aldosterone, β₂-microglobulin, carcinoembryonic antigen, cortisol, C-peptide, digoxin, elastase 1, estradiol, ferritin, free thyroxin, follicle stimulating hormone, gastrin, growth hormone, glucagon, immunoglobulin E, insulin, luteinizing hormone, prostatic acid phosphatase, progesterone, prolactin, triiodothyronine, triiodothyronine uptake, testosterone, thyroxine, thyroid stimulating hormone, thyroxine binding globulin