1. Na‑heparin, Li‑heparin, K2‑EDTA and K3‑EDTA plasma. Li‑heparin plasma tubes containing separating gel can be used.2. Criterion: Slope 0.9‑1.1 + intercept within < ± 2x Limit of Blank + coefficient of correlation ≥ 0.95.3. Stable for 2 hours at 15‑25 °C, 48 hours at 2‑8 °C, 56 days at ‑20 °C (± 5 °C). Freeze once only.4. Stability of serum obtained with separating tubes: 24 hours at 2‑8 °C (note the data provided by the tube manufacturer).5. The sample types listed were tested with a selection of sample collection tubes that were commercially available at the time of testing, i.e. not all available tubes of all manufacturers were tested. Sample collection systems from various manufacturers may contain differing materials which could affect the test results in some cases. When processing samples in primary tubes (sample collection systems), follow the instructions of the tubemanufacturer.6. Centrifuge samples containing precipitates before performing the assay.7. Do not use heat‑inactivated samples.8. Avoid hemolysis.9. Do not use samples and controls stabilized with azide10. Due to possible evaporation effects, samples, calibrators and controls on the analyzers should be analyzed/measured within 2 hours.