4.4. Sample Collection and Storage
After a 12 h fast, venous blood samples were collected from the antecubital vein in each individual. Plasma was separated (centrifuged at 4 °C on 3500 rpm for 10 min) and kept at −20 °C within 1–2 h of collection. Each sample was marked with the study number, the test session number, the date, and the time for each patient. Per patient, two urine samples (5–10 mL) and three plasma samples (1.5–2 mL) were sent directly to the lab for evaluation. All plasma and urine samples were tested in the same laboratory in accordance with proper laboratory practices, and analysts were unaware of the distribution of patients in the studied groups.