WC Rule (Cross Talk)
This rule has been deprecated as of 2026-02-02.
The WC (Cross-Talk) rule was never implemented in the application codebase (no WCRule.php exists). This documentation is retained for historical reference only. No test coverage is required.
Version: v3.0.0 Status:
NormativeDEPRECATED Scope: Cross-talk detection in wells where multiple non-IC targets test positive Domain: RULES-WC Precedence: N/A - Rule not implemented
Statement
The system shall detect cross-talk conditions in PCR wells where biological coinfection is unlikely and mark affected samples for re-extraction.
When more than one non-IC (non-Internal Control) target tests positive in a patient sample well during first-time extraction on HSV or HTLV assays, the system marks the LIMS export result as "RXT" and generates a warning message. This prevents potentially erroneous results from being released while creating an audit trail for quality control.
Quick Reference
| ID | Core Behavior | Priority | Status |
|---|---|---|---|
| REQ-RULES-WC-001 | Detect cross-talk and mark for re-extraction when multiple non-IC targets positive | HIGH | Draft |
Key Integration Points: Analytics Engine, LIMS Export, Kit Configuration, Sample Management
Rule Summary
| Property | Value |
|---|---|
| Name | WC (Cross Talk) |
| Triggers | Multiple non-IC targets positive in same well |
| Output | Sets LIMS result to "RXT", generates well warning |
Rule Flowchart (Illustrative)
This diagram illustrates the cross-talk detection logic. IC targets are always excluded from the positive count.
Definitions
| Term | Definition |
|---|---|
| Cross-talk | Detection of multiple positive targets in a single well where biological coinfection is unlikely, potentially indicating contamination or signal bleed |
| Non-IC Target | A target that is not an Internal Control; subject targets being tested for the pathogen of interest |
| IC (Internal Control) | A control target used to validate assay performance, excluded from cross-talk evaluation |
| RXT | LIMS export result code indicating a sample requires re-extraction due to cross-talk detection |
| First Time Extraction | Initial sample processing, as opposed to re-extractions which are already quality control measures |
Assumptions
- The rule executes during the analytics processing phase after target classification
- Target positivity has already been determined by upstream rules
- Assay type (HSV/HTLV) is known from kit configuration
- Sample type (patient/control) is determinable from sample metadata
- First extraction vs. re-extraction status is available in sample metadata
Requirements
Cross-Talk Detection (REQ-RULES-WC-001)
FR-WC-001: Detect Cross-Talk in Wells
The system shall mark the LIMS export result as "RXT" when more than one non-IC target in a well tests positive, indicating a cross-talk condition that requires sample re-extraction.
Inputs/Outputs
| Direction | Data | Source/Target |
|---|---|---|
| Input | Well observations (targets, positivity status) | PCR analysis |
| Input | Sample metadata (type, extraction status) | Sample management |
| Input | Assay type | Kit configuration |
| Output | LIMS result code (RXT) | Well record |
| Output | Well warning message | Well record |
Acceptance Criteria
Triggering Conditions:
- Given a well with more than one non-IC target that is positive, when the WC rule analyzes the well, then the system shall mark the LIMS export result as "RXT"
- The rule shall only apply to HSV assay or HTLV assay runs
- The rule shall only apply during first time extraction (re-extractions excluded)
- The rule shall only apply to patient samples (control samples excluded)
- The rule shall evaluate non-IC targets only (IC/Internal Control targets excluded from cross-talk evaluation)
Non-Triggering Conditions:
- A well with exactly one positive non-IC target shall NOT trigger this rule
- A well with zero positive non-IC targets shall NOT trigger this rule
Warning Generation:
- When cross-talk is detected, the system shall generate a well warning indicating which targets are positive
- The warning message shall follow the format: "{target A} and {target B} are both positive. Re-extract sample"
Error Handling
- Unable to determine sample type: Skip cross-talk evaluation and log the condition for investigation
- Unable to determine extraction status: Skip cross-talk evaluation and log the condition for investigation
- Assay type not determinable: Skip cross-talk evaluation for the well
Trace: Source: 3.0.0-WC Rule / Objective (Lines 23-25), Application (Lines 33-37), Requirements Table (Row 1) | Jira: BT-674 (Epic: Rules) | Tests: See scenarios
Configuration Options
[REVIEW REQUIRED: No explicit configuration options identified in source material. Verify if assay type list should be configurable.]
| Option | Default | Description | Affects |
|---|---|---|---|
| - | - | - | - |
UI Notes (Illustrative)
FR-WC-001 UI Specifications
Flow Diagram:
- Rule decision flow visualized in media/image171.png
- Entry point: "Start crosstalk rule"
- Sequential evaluation of Target A and Target B positivity
- Decision diamonds for each target evaluation
- Warning generation highlighted in yellow when both targets positive
- Exit path to continue other rules when conditions not met
Warning Display:
- Well warning displays both positive target names
- Warning recommends re-extraction action
Implementation (Illustrative)
| Component | Location |
|---|---|
| Westgard Rules | Analyzer/Rules/Wg7TRule, Wg12SRule, Wg13SRule, Wg14SRule, Wg22SRule, Wg22S13SRule, Wg7T13SRule, WginerrorRule |
Traceability Matrix
| Requirement | Title | Verification | Implementation | Test Cases | Status |
|---|---|---|---|---|---|
| REQ-RULES-WC-001 | Detect Cross-Talk in Wells | Test | Westgard Rules | [Pending] | Draft |
Notes
- Cross-talk in PCR-based assays can occur when:
- Fluorescent signals from one target channel "bleed" into another
- Contamination between wells or reagents occurs
- Amplification products from different targets interact
- For HSV and HTLV assays, coinfection of multiple strains (e.g., HSV-1 and HSV-2) is biologically unlikely, making multiple positive targets suggestive of technical issues
- The "RXT" result code creates an audit trail for quality control purposes and prevents release of potentially erroneous results
- The first extraction restriction prevents infinite re-extraction loops when cross-talk persists
Open Questions
| ID | Question | Source | Owner | Date Raised |
|---|---|---|---|---|
| OQ-001 | No explicit configuration options identified in source material. Verify if assay type list should be configurable. | Configuration | @tbd | 2026-01-23 |
Acceptance Tests
Test: REQ-RULES-WC-001
Test: Multiple positive non-IC targets trigger RXT result
Given: A patient sample well in an HSV assay during first time extraction
And: Target A (non-IC) is positive
And: Target B (non-IC) is positive
When: The WC rule analyzes the well
Then: The system shall mark the LIMS export result as "RXT"
And: The system shall generate a warning message indicating both positive targets
Test: Single positive non-IC target does not trigger rule
Given: A patient sample well in an HSV assay during first time extraction
And: Target A (non-IC) is positive
And: Target B (non-IC) is negative
When: The WC rule analyzes the well
Then: The system shall NOT mark the LIMS export result as "RXT"
And: The system shall NOT generate a cross-talk warning
Test: Zero positive non-IC targets does not trigger rule
Given: A patient sample well in an HTLV assay during first time extraction
And: All non-IC targets are negative
When: The WC rule analyzes the well
Then: The system shall NOT mark the LIMS export result as "RXT"
Test: IC targets excluded from cross-talk evaluation
Given: A patient sample well in an HSV assay during first time extraction
And: One non-IC target is positive
And: The IC (Internal Control) target is positive
When: The WC rule analyzes the well
Then: The system shall NOT mark the LIMS export result as "RXT"
And: The IC target positivity shall be excluded from cross-talk count
Test: Control samples excluded from rule
Given: A control sample well in an HSV assay
And: Multiple non-IC targets are positive
When: The WC rule analyzes the well
Then: The system shall NOT apply the cross-talk rule
And: The system shall NOT mark the result as "RXT"
Test: Re-extractions excluded from rule
Given: A patient sample well in an HSV assay during re-extraction
And: Multiple non-IC targets are positive
When: The WC rule analyzes the well
Then: The system shall NOT apply the cross-talk rule
And: The system shall NOT mark the result as "RXT"
Test: Non-applicable assay type excluded from rule
Given: A patient sample well in an assay that is NOT HSV or HTLV
And: Multiple non-IC targets are positive
When: The analytics engine processes the well
Then: The WC rule shall NOT be applied
And: The system shall NOT mark the result as "RXT" based on cross-talk
Related Design Documents
| Design Document | Relevant Sections |
|---|---|
| SDD Algorithms | Rule Processing |
Appendix: Process Artifacts
Completion Checklist
- All requirements are capability-level (describe behavior, not UI)
- Requirement variants consolidated (no requirement explosion - single requirement in source)
- UI details are fully demoted to Illustrative section
- Configuration options are not encoded as requirements
- Acceptance criteria describe behavior, not UI mechanics
- Every requirement has acceptance criteria and source traceability
- Error handling addressed for I/O, validation, and external system requirements
- Open questions documented with owners assigned
- Consolidations documented in Reviewer Notes with reversibility info
- Module can survive a full UI redesign unchanged
- Refinements do not introduce new capabilities
- Traceability matrix is complete
Reviewer Notes
No Consolidation Required
This domain contains a single requirement (REQ-RULES-WC-001) representing the core cross-talk detection capability. No consolidation was performed as there was no requirement explosion in the source material.
Source Structure:
| Original Item | Source Reference | Disposition |
|---|---|---|
| REQ-RULES-WC-001 | 3.0.0-WC Rule (Lines 23-25, 33-37, Row 1) | Retained as REQ-RULES-WC-001 |
Notes:
- All acceptance criteria from source preserved as detailed ACs per RULES domain guidance
- Given/When/Then scenario retained as primary AC
- Application constraints retained as explicit ACs (triggering and non-triggering conditions)
- Warning generation added as explicit AC based on SDD flow diagram details
Reversibility: To reference original structure:
- Source:
output/pilot/rules/rule-wc/rule-wc-restructured.md - SDD:
output/pilot/rules/rule-wc/sdd/rule-wc-design.md - Confluence: 3.0.0-WC Rule