Before entering values
- Confirm the same analyte and specimen.
- Confirm the same unit and preferably the same method.
- Record timing, fasting, posture, hydration, treatment changes, and acute illness.
- Use an assay-specific delta rule when required, especially for cardiac troponin.
Outputs
- Net direction and absolute change.
- Percentage change.
- Linear velocity and R-squared.
- Reference-interval crossings.
- Doubling or halving time for eligible positive values.
- Optional reference change value when validated CVa and CVi estimates are supplied.
Interpretation limits
R-squared describes how closely the values follow a straight line; it does not establish causality. A statistically significant reference change value does not automatically mean the change is clinically important.
When not to rely on the trend tool
Do not delay action for critical results, rapidly changing symptoms, suspected specimen error, or a result governed by a validated emergency pathway.