Setting Up the Experiment
Prerequisites
Before creating a factor sensitivity experiment, complete the following setup steps:
- Establish the normal range (ULNR) — The ULNR must be determined before starting the factor sensitivity study. Measure at least 120 normal specimens on the same reagent lot that will be used for the factor sensitivity study. Calculate the geometric mean and add 2 standard deviations to obtain the ULNR. This value is entered directly into the experiment configuration.
- Obtain the Reference Factor Activity (RAF) — This value is published in the reference plasma package insert. The RAF accounts for the actual factor activity level of the specific lot of reference plasma being used, which may differ from exactly 100%. RAF is typically expressed as a percentage (e.g., 108% indicates the lot has 108% activity of the specific factor relative to the standard). Valid values are 50%–150% (up to 500% allowed).
- Add a lab area and analyzer — As with all statistical modules, the analyzer and lab area must be configured in Lab Settings before creating the experiment.
Configuration Fields
When creating the experiment, you will configure the following fields:
- Assay Type (PT / aPTT) — Specifies which coagulation pathway is being tested, which determines the coagulation factors evaluated.
- Upper Limit of Normal Range (ULNR) — The clotting time threshold (in seconds) above which a result is considered abnormal. Specific to the reagent lot being tested.
- Reference Factor Activity (%) (RAF) — From the reference plasma package insert. Used to convert theoretical dilutions to actual dilutions.
- Number of Dilutions — 3 to 15 dilutions supported; default is 8 (25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%). Custom dilution values can be entered if the default levels do not meet your study requirements.
- Regression Type — Polynomial (1st, 2nd, or 3rd degree) or Logarithmic. Second-degree polynomial is the default and works well for most coagulation reagents. Logarithmic may provide a better fit when the response flattens at higher factor activity.
- Regression Lower / Upper Limits (%) — Optional. Restricts the regression calculation to the specified actual dilution range. Recommended limits are 20%–75%. Dilutions outside this range are still displayed on the graph in gray.
Data Entry
For each dilution level, enter the following per data point:
| Field | Description |
|---|---|
| Theoretical Dilution (%) | The intended mixing percentage — e.g., 25%, 30%, 35%. These are the standard reference levels for the study. |
| Actual Dilution (%) | Calculated automatically as: Theoretical × RAF / 100. Can be manually overridden if needed. Used for all calculations. |
| Sample ID | A unique identifier for the dilution level (e.g., sequential numbering). |
| Rep 1 – Rep 4 | Individual replicate clotting times in seconds. The mean of available replicates is used for regression and sensitivity calculations. |
Data can be entered manually or uploaded via CSV. See the data upload guide within the module for the expected CSV format.