Table 9. Number and concentration levels.

Recommended practice	Use an IQC with level close to clinical decision limits practice (e.g., infectious serology, troponin, D-Dimers, haemoglobin A1c, glucose). Cover the physiological and pathological range (if IQCs are available). Use multiple levels of IQC and at least 2 levels after calibration (12).
Acceptable practice	Other uses of IQC (excluding calibration verification).
Unacceptable practice	Use only one level of IQC after calibration practice (unless recommended by the supplier). No appropriate verification over the entire measuring range. Absence of a well thought-out strategy leading to a risk of not detecting drift of clinical decision limits in the measurement ranges.
IQC – internal quality control.