Time-dependent characteristics of analytical measurands

Area of Science:

• Clinical chemistry
• Laboratory medicine
• Biomedical science

Background:

• Biological variation, including diurnal rhythms, is a key factor in diagnostic uncertainty.
• Preanalytical variations contribute to overall biological variability, affecting lab test interpretation.

Purpose of the Study:

• To introduce and define four time-dependent characteristics (TDC) for assessing diurnal variations in measurands.
• To evaluate the impact of time dependence on laboratory result interpretation.

Main Methods:

• Development of four novel time-dependent characteristics (TDC) to quantify diurnal variations.
• Calculation of TDCs for common measurands (e.g., AST, CK, glucose, TSH, bilirubin) across different blood collection time slots.

Main Results:

• TDC quantify thresholds for diurnality, expected changes per time unit, permissible time intervals, and rhythm-expanded reference change values.
• Diurnal variation's amplitude and acrophase significantly influence diagnostic uncertainty, particularly for morning blood collections (07:00-09:00).

Conclusions:

• Recommend assessing measurands for diurnal variations.
• Propose the implementation of time-dependent characteristics (TDC) for a more accurate interpretation of laboratory results.