Interpreting Your Results
Sensitivity Chart
The primary visualization plots actual dilution (%) on the x-axis against mean clotting time (seconds) on the y-axis. The following elements appear on the chart:
| Chart Element | Color | What It Represents |
|---|---|---|
| Data points | Blue | Mean clotting time at each dilution level (within the regression range). |
| Data points (outside range) | Gray | Data points excluded from the regression because they fall outside the Regression Lower/Upper Limits. |
| Regression line | Red | Best-fit curve (polynomial or logarithmic) through the included data points. |
| ULNR threshold | Green (horizontal) | The Upper Limit of Normal Range — the clotting time above which a result is considered abnormal. |
| Calculated Sensitivity | Orange (vertical) | Vertical line at the factor activity % where the regression curve crosses the ULNR. |
The regression equation, SEE, and R² are displayed on the chart. Visually inspect whether the regression curve passes smoothly through the data points near the ULNR crossover — this is the region that most directly determines the Calculated Sensitivity value.
Results Summary
The results panel displays:
- First Abnormal Dilution — The highest actual dilution (%) at which the measured mean clotting time equals or exceeds the ULNR. This is a directly observed value. If no dilution produces an abnormal time, the status is Insensitive.
- Calculated Sensitivity — The regression-derived factor activity percentage at the ULNR crossover. Reported to the nearest percent due to uncertainty in the normal range limits and measurement variability. Not reported if status is Insensitive or Hypersensitive.
- ULNR — The configured threshold, shown for reference.
- Sensitivity Status — Normal, Insensitive, or Hypersensitive, as determined by where the ULNR falls relative to the data range.
- Regression fit statistics — SEE and R² quantify how well the curve represents the data. R² > 0.95 is generally considered acceptable for clinical use.
Comparing First Abnormal Dilution vs. Calculated Sensitivity
These two estimates will not always agree precisely, and both are clinically meaningful:
- The First Abnormal Dilution is a conservative, directly observed estimate. Because it depends on the discrete tested dilution levels, it may overestimate the true sensitivity (i.e., it is limited to the resolution of the tested levels). It requires no regression model assumptions.
- The Calculated Sensitivity provides a continuous, interpolated estimate that can fall between tested levels. It is more precise but depends on the quality of the regression fit. If R² is low or the curve does not fit well near the ULNR, the Calculated Sensitivity may be unreliable.
- If the two estimates differ substantially (e.g., by more than one dilution step), review the regression fit near the ULNR crossover and consider whether the tested dilution levels have adequate resolution in the clinically important range.