Sensitivity Statistics Guidelines

Sensitivity Statistics

The module reports two sensitivity estimates and a sensitivity status classification:

First Abnormal Dilution

Highest actual dilution (%) where mean clotting time ≥ ULNR

A non-parametric estimate based directly on the observed data. Identifies the highest factor activity percentage at which the measured mean clotting time is already at or above the ULNR threshold — meaning the reagent is definitively detecting a deficiency at that level. Because it relies on the discrete observed data points, the First Abnormal Dilution is limited in resolution to the tested dilution levels.

Calculated Sensitivity

Actual dilution (%) where regression curve intersects ULNR

A continuous, regression-derived estimate of the factor activity percentage at which the clotting time exactly equals the ULNR. Computed by solving the regression equation for X when Y = ULNR. Provides finer resolution than the First Abnormal Dilution, but its accuracy depends on the quality of the regression fit (R² and SEE) and is only meaningful when the ULNR falls within the tested dilution range.

Upper Limit of Normal Range (ULNR)

Geometric Mean + 2 SD (from normal range study)

The threshold clotting time above which a result is considered abnormal. The ULNR must be established for each reagent lot before performing factor sensitivity calculations. The recommended approach is to measure at least 120 normal specimens and calculate the geometric mean plus 2 standard deviations. The ULNR is configured directly in the experiment setup and is specific to the reagent lot being tested.

Sensitivity Status

Status	Condition	Clinical Interpretation
Normal	ULNR falls within the tested dilution range	The reagent detects factor deficiency within the tested range. Calculated Sensitivity can be determined.
Insensitive	ULNR is above all data points — no dilution produces an abnormal clotting time	The reagent fails to detect deficiency within the tested range. Patients with severely reduced factor activity may not be flagged as abnormal.
Hypersensitive	ULNR is below all data points — all dilutions produce abnormal clotting times	The reagent responds to even the highest factor activity tested. May produce false-positive prolonged times in patients with borderline levels.