Qualitative / Semi-Quantitative Method Comparison
The Qualitative/Semi-Quantitative Method Comparison module evaluates agreement between two measurement procedures whose results are expressed as discrete categories — such as Positive/Negative, Reactive/Non-Reactive, or multi-level ordinal classifications. One method is designated the reference method — the established or gold-standard procedure — and the other is the test method — the candidate or new procedure being evaluated.
Unlike quantitative method comparison, this module does not analyze continuous bias across a measurement range. Instead, it assesses the proportion of specimens that receive the same categorical classification on both methods and characterizes the pattern of disagreement using positive percent agreement (PPA), negative percent agreement (NPA), and supplemental statistics such as Cohen's Kappa. For semi-quantitative methods — those that produce a numeric index that is then converted to a categorical result using a cutoff threshold — the module applies the configured cutoffs before computing agreement statistics.
Finding This Module
The Qualitative/Semi-Quantitative Method Comparison module is only available for experiments created with a qualitative assay. It will not appear on the standard experiment home page used for quantitative assays. If you don't see this module, the steps below explain how to configure your assay correctly so it becomes accessible.
Configure the assay as qualitative in Lab Settings
Navigate to Lab Settings and select the analyzer that runs the test. On the analyzer's analytes page, add the assay (or edit an existing one) and set its type to Qualitative. This is the step that unlocks qualitative-specific modules throughout Legion Diagnostics.
Create a new experiment and select the qualitative assay
When creating a new verification experiment, select the qualitative assay configured in step 1. Legion Diagnostics will automatically detect the assay type and route the experiment to the qualitative experiment home page.
Open the Qualitative Method Comparison module from the experiment home page
The qualitative experiment home page shows a focused set of modules appropriate for qualitative assays — including Precision and Qualitative Method Comparison. Select Qualitative Method Comparison to begin the study.
When to Use This Module
This module is appropriate when the test being evaluated produces categorical results rather than continuous numeric values:
- New qualitative test implementation — Before placing a new rapid, immunoassay, or molecular test into routine use, agreement with the established reference method must be documented to confirm equivalent patient classification.
- Platform or reagent change for a qualitative assay — Switching reagent systems, platforms, or manufacturers for an existing qualitative test requires a formal comparison to confirm that positive and negative specimen classifications are preserved.
- Semi-quantitative tests with a numeric index — When a test produces a numeric value that is interpreted against a cutoff threshold (e.g., an absorbance ratio or index value), this module applies the cutoff and evaluates whether the resulting categorical calls agree with the reference method.
- Multi-level result schemes — When results are reported at more than two levels (e.g., Negative / Indeterminate / Positive), the custom result coding feature allows you to define each level and evaluate agreement across all levels. Note that ordinal (multi-level) results are outside the formal scope of CLSI EP12, which covers binary output examinations only; no separate CLSI guideline currently governs ordinal method comparison for laboratory qualitative tests.
- Accreditation requirements — CAP, The Joint Commission, and CLIA require documented method comparison data for all non-waived qualitative tests placed into routine use.