Quality Control Rules Design

Document Type: Rule Design (Tier 2) Domain: RULES-QC Domain Character: Algorithmic SRS References: rule-westgards.md, rule-minimum-fluorescence.md, rule-unexpected-fl.md, rule-baseline-check.md, rule-mincontrols.md, rule-extraction-controls.md Status: Draft Last Updated: 2026-01-25

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1. Overview

1.0 Rule Summary

Property	Value
Intent	Validate PCR run quality by detecting statistical anomalies in control samples (Westgard rules), fluorescence threshold violations, baseline configuration issues, and control well presence requirements.
Inputs	Control well observations (CT, quantity, fluorescence readings), Westgard limit configurations (mean, SD), target configurations (thresholds), run target settings, extraction details
Outputs	Error codes at well level and target level; Westgard event records for Levey-Jennings reporting
Precedence	After Runfile Import; Before Error Resolution

1.1 Purpose

The QC Rules domain implements quality control validation for PCR analysis runs. This encompasses:

• Westgard Rules: Statistical process control using industry-standard Westgard methodology to detect systematic and random errors in control samples
• Fluorescence Validation: Minimum and maximum fluorescence threshold checks to ensure signal quality
• Baseline Validation: Automatic baseline check configuration validation
• Control Presence: Validation that patient wells have required controls (PC/NC, PEC/NEC)

The rules operate independently but share common patterns for error assignment and resolution handling.

1.2 Requirements Covered

REQ ID	Title	Priority
REQ-RULES-WG-001	Exclude Resolved Controls from Calculations	Must
REQ-RULES-WG-002	Use Same-Run Controls as History	Must
REQ-RULES-WG-003	Scope WgInError to Affected Time Range	Must
REQ-RULES-WG-004	Set INVALID_SD Error for Invalid Standard Deviation	Must
REQ-RULES-WG-005	Set WESTGARDS_MISSED Error	Must
REQ-RULES-WG-006	Trigger 1:2s Rule	Must
REQ-RULES-WG-007	Trigger 1:3s Rule	Must
REQ-RULES-WG-008	Trigger 1:4s Rule	Must
REQ-RULES-WG-009	Trigger 2:2s Rule	Must
REQ-RULES-WG-010	Strict Boundary Enforcement	Should
REQ-RULES-WG-011	Trigger 7T Rule	Must
REQ-RULES-WG-012	Trigger WG13S22S Combined Rule	Must
REQ-RULES-WG-013	Trigger WG7T13S Combined Rule	Must
REQ-RULES-MINFL-001	Validate Well Fluorescence Against Minimum Thresholds	Must
REQ-RULES-MINFL-002	Propagate Control Well Fluorescence Failures to Target Level	Must
REQ-RULES-MINFL-003	Allow Users to Skip Minimum Fluorescence Rule via Resolution Code	Should
REQ-RULES-UNEXPFL-001	Validate Well Fluorescence Against Maximum Thresholds	Must
REQ-RULES-BASELINE-001	Apply Well-Level Manual Baseline Error	Must
REQ-RULES-BASELINE-002	Apply Target-Level Manual Baseline Error	Must
REQ-RULES-MINCTRL-001	Skip Rule for Non-Patient Wells	Must
REQ-RULES-MINCTRL-002	Skip Rule When MINCONTROL Resolution Exists	Must
REQ-RULES-MINCTRL-003	Set CONTROL_MISSING Error When Fallback Disabled	Must
REQ-RULES-MINCTRL-004	Check Backup Mix Controls When Fallback Enabled	Must
REQ-RULES-EXTCTRL-001	Validate Patient Well Extraction Controls	Must
REQ-RULES-EXTCTRL-002	Report Error When Fallback Disabled	Must
REQ-RULES-EXTCTRL-003	Check Backup Mix When Fallback Enabled	Must
REQ-RULES-EXTCTRL-004	Recognize Quantification and PC Role as Positive Control	Should
REQ-RULES-EXTCTRL-005	Exclude Label Error Wells from MINEXTRACT Control Association	Must
REQ-RULES-EXTCTRL-006	Exclude Label Error Wells from MINCONTROL Control Association	Must

1.3 Dependencies

Direction	Component	Purpose
Consumes	Well + Observations	Control sample data with CT/quantity values
	Westgard Limits	Mean, SD, lot per target/role/date
	Kit Configuration	Thresholds, role mappings, feature flags
	Historical PEC Wells	Previous controls for multi-control rules
Produces	Well Errors	Error codes at well level
	Target Errors	Error codes at run target level
	LJ Report Data	Westgard events for Levey-Jennings visualization

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2. Component Architecture

2.1 Component Diagram

2.2 Component Responsibilities

Component	File	Responsibility	REQ Trace
Wg12SRule	Analyzer/Rules/Wg12SRule.php	1:2s (2SD) threshold rule	REQ-RULES-WG-006
Wg13SRule	Analyzer/Rules/Wg13SRule.php	1:3s (3SD) threshold rule	REQ-RULES-WG-007
Wg14SRule	Analyzer/Rules/Wg14SRule.php	1:4s (4SD) threshold rule	REQ-RULES-WG-008
Wg22SRule	Analyzer/Rules/Wg22SRule.php	2:2s consecutive pattern rule	REQ-RULES-WG-009, REQ-RULES-WG-010
Wg7TRule	Analyzer/Rules/Wg7TRule.php	7T trend pattern rule	REQ-RULES-WG-011
Wg22S13SRule	Analyzer/Rules/Wg22S13SRule.php	Combined 2:2s + 1:3s rule	REQ-RULES-WG-012
Wg7T13SRule	Analyzer/Rules/Wg7T13SRule.php	Combined 7T + 1:3s rule	REQ-RULES-WG-013
WginerrorRule	Analyzer/Rules/WginerrorRule.php	Time-scoped error propagation	REQ-RULES-WG-003
MinFluorescenceRule	Analyzer/Rules/MinFluorescenceRule.php	Minimum fluorescence validation	REQ-RULES-MINFL-001, 002, 003
UnexpectedFlRule	Analyzer/Rules/UnexpectedFlRule.php	Maximum fluorescence validation	REQ-RULES-UNEXPFL-001
MinControlsRule	Analyzer/Rules/MinControlsRule.php	PC/NC presence validation	REQ-RULES-MINCTRL-001 to 004
MinextractRule	Analyzer/Rules/MinextractRule.php	PEC/NEC extraction control validation	REQ-RULES-EXTCTRL-001 to 006
ManualBaselineRule	Analyzer/Rules/ManualBaselineRule.php	Baseline check configuration	REQ-RULES-BASELINE-001, 002
SetErrorToWell	Analyzer/Rules/Concerns/SetErrorToWell.php	Shared error assignment	All
PecWellCollection	Analyzer/PecWellCollection.php	Historical PEC well queries	REQ-RULES-WG-001, 002, 009, 011

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3. Data Design

3.1 Entities

This domain reads from configuration and historical data, writes to well and run target records:

Entity	Owner	Read/Write	Fields Used
wells	RUNRPT	Read/Write	observations, error_code, lims_status, resolution_codes
observations	RUNRPT	Read/Write	final_cls, final_ct, final_quantity, sd_from_mean, lot
run_targets	RUNRPT	Read/Write	error_codes, automatic_baseline_check
westgard_limits	KITCFG	Read	mean, sd, lot, valid_from, valid_to
targets	KITCFG	Read	minimum_fluorescence, maximum_fl
role_to_target_mappings	KITCFG	Read	backup_mix
previous_pec_wells	RUNFILE	Read	Historical control data for trend/pattern detection

See Database Reference for full schema.

3.2 Westgard Limit Structure

interface WestgardLimit {
  id: string;
  role_id: string;
  target_id: string;
  lot: string;
  mean: number;
  sd: number;                    // Standard deviation
  valid_from: Date;
  valid_to: Date | null;
  extraction_instrument: string;
}

3.3 Control Matching Context

interface ControlMatchContext {
  well: Well;
  mix_id: string;
  extraction_date: Date;
  extraction_instrument: string;
  batch_number: string | null;

  // Computed during matching
  has_pc: boolean;
  has_nc: boolean;
  has_pec: boolean;
  has_nec: boolean;
  fallback_enabled: boolean;
  backup_mix_id: string | null;
}

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4. Interface Design

4.1 Rule Interface

All QC rules implement the standard AnalyzerRuleContract:

interface AnalyzerRuleContract {
    public function handle(
        ConfigurationRepository $config,
        AnalyzableObservation $observation,
        RunMix $runMix,
        RunTarget $runTarget,
        AnalyzableWell $well,
        WellCollection $wells,
        PatientWellCollection $previousPatientWells,
        PecWellCollection $previousPecWells,
        RunTargetsCollection $runTargets
    ): void;
}

4.2 Key Internal APIs

Method	Class	Purpose
getWestgardLimitForObservation()	ConfigurationRepository	Retrieve Westgard limit by observation
hasValidSd()	WestgardLimit	Validate SD > 0
setSdFromMeanFromWestgardLimit()	Observation	Calculate SD deviation from mean
isSdFromMeanGreaterThanTwo/Three/Four()	Observation	Check threshold violations
sdFromMeanIsPositive()	Observation	Determine direction (high/low)
hasSdFromMeanGreaterThanTwoInLatestTwoWellsForWell()	PecWellCollection	2:2s pattern check
hasTrendInLatestSevenWellsForWell()	PecWellCollection	7T pattern check
hasAssociatePositiveControl()	WellCollection	PC presence check
hasAssociateNegativeControl()	WellCollection	NC presence check
hasAssociatePositiveExtractionControl()	WellCollection	PEC presence check
hasAssociateNegativeExtractionControl()	WellCollection	NEC presence check

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5. Behavioral Design

5.1 Westgard Rules Family

5.1.1 Processing Order

WG14S (1st) -> WG13S (2nd) -> WG12S (3rd) -> WG22S -> WG7T -> Combined Rules

Higher SD thresholds are checked first. A 4SD violation takes precedence over 3SD.

5.1.2 Single-Control Rules (1:2s, 1:3s, 1:4s)

Algorithm: Evaluate Single-Control Westgard Rule

Inputs:
- well: Well - The control well being evaluated
- observation: Observation - Well's observation with CT/quantity
- westgard_limit: WestgardLimit - Configured mean and SD
- threshold_multiplier: number - 2, 3, or 4 (for respective rules)

Outputs:
- void (modifies well.error_code, run_target.errors)

Assumptions:
- Well is a control well (PEC)
- Westgard limit exists and has valid SD

Steps:
1. Resolution check:
   IF well.resolution_codes contains rule code:
     Apply LIMS status from resolution
     RETURN

2. Westgard limit validation:
   IF no westgard_limit found:
     Set WESTGARDS_MISSED error
     RETURN
   IF westgard_limit.sd <= 0 OR not numeric:
     Set INVALID_SD error
     RETURN

3. Calculate deviation:
   delta = ABS(observation.ct_or_quant - westgard_limit.mean)
   sd_from_mean = delta / westgard_limit.sd
   observation.setSdFromMean(sd_from_mean)

4. Skip conditions:
   IF observation.final_cls is negative: RETURN
   IF observation.final_ct is null: RETURN

5. Threshold check:
   IF sd_from_mean > threshold_multiplier:
     IF observation.value > westgard_limit.mean:
       Set WGxxS_HIGH_WELL error on well
       Set WGxxS_HIGH_TARGET error on run_target
     ELSE:
       Set WGxxS_LOW_WELL error on well
       Set WGxxS_LOW_TARGET error on run_target
     Create duplicate Westgard limit record for LJ

5.1.3 Westgard 1:2s/1:3s/1:4s Truth Table

SD from Mean	WG14S Result	WG13S Result	WG12S Result
> 4	ERROR	-	-
> 3, <= 4	-	ERROR	-
> 2, <= 3	-	-	WARNING*
<= 2	No error	No error	No error

*WG12S severity is client-configurable (default: WARNING, Viracor: ERROR)

Precedence: WG14S before WG13S before WG12S. First match wins for the same observation.

Default: No error if SD from mean <= 2.

5.1.4 Multi-Control Rules (2:2s, 7T)

Westgard 2:2s Algorithm

Algorithm: Evaluate 2:2s Westgard Rule

Inputs:
- well: Well - Current control well
- observation: Observation - Current observation
- previous_pec_wells: PecWellCollection - Historical PEC wells

Steps:
1-4. Same validation as single-control rules

5. Pattern check:
   IF previousPecWells.hasSdFromMeanGreaterThanTwoInLatestTwoWellsForWell(well):
     - Check both current and previous control are >2SD
     - Check both are on same side of mean (same direction)
     - Check strict_boundary_enforcement config for >3SD exclusion

     IF pattern matches:
       Set WG22S_HIGH/LOW_WELL and WG22S_HIGH/LOW_TARGET errors

Westgard 2:2s Decision Logic

Current Control	Previous Control	Same Direction	Strict Boundary	Result
> 2SD	> 2SD	Yes	N/A	WG22S ERROR
> 2SD	> 2SD	No	N/A	No error
> 2SD	> 3SD	Yes	Enabled	No error (excluded)
> 2SD	> 3SD	Yes	Disabled	WG22S ERROR
> 2SD	< 2SD	*	*	No error
< 2SD	*	*	*	No error

Precedence: Evaluated after single-control rules.

Default: No error if pattern not matched.

Westgard 7T Algorithm

Algorithm: Evaluate 7T Westgard Rule

Steps:
1-4. Same validation as single-control rules

5. Trend check:
   IF previousPecWells.hasTrendInLatestSevenWellsForWell(well):
     - Retrieve last 7 control values including current
     - Check all 7 trend in same direction (all increasing OR all decreasing)

     IF trend detected:
       Set WG7T_HIGH/LOW_WELL and WG7T_HIGH/LOW_TARGET errors

5.1.5 Combined Rules (WG13S22S, WG7T13S)

Algorithm: Evaluate WG13S22S Combined Rule

Steps:
1. Check for 1:3s violation (>3SD)
2. Check for 2:2s pattern (>2SD same direction)
3. IF both conditions met:
     IF high direction: Set WG13S22S_HIGH_WELL, WG13S22S_HIGH_TARGET
     ELSE: Set WG13S22S_LOW_WELL, WG13S22S_LOW_TARGET

Algorithm: Evaluate WG7T13S Combined Rule

Steps:
1. Check for 1:3s violation (>3SD)
2. Check for 7T trend pattern
3. IF both conditions met:
     IF increasing trend: Set WG7T13S_HIGH_WELL, WG7T13S_HIGH_TARGET
     ELSE: Set WG7T13S_LOW_WELL, WG7T13S_LOW_TARGET

5.1.6 Westgard Resolution and History Handling

Resolved Control Exclusion (REQ-RULES-WG-001):

When checking history for 2:2s or 7T patterns:
  - Exclude wells with resolution codes (RPTNEG, RPTALL, RXTALL)
  - A resolved 1:3s control followed by 1:2s does NOT trigger 2:2s

Same-Run History (REQ-RULES-WG-002):

Controls within the same run are processed sequentially.
The second control in a run uses the first as history for 2:2s evaluation.

5.2 Fluorescence Validation Rules

5.2.1 Minimum Fluorescence Algorithm

Algorithm: Validate Minimum Fluorescence

Inputs:
- well: Well
- observation: Observation with fluorescence readings
- minimum_fluorescence: number (from target config) or null

Steps:
1. Resolution check:
   IF well.resolution_codes contains 'MIN_FLUORESCENCE': RETURN

2. Configuration check:
   IF minimum_fluorescence is null:
     Set MINIMUM_FLUORESCENCE_MISSED error
     RETURN

3. Threshold comparison:
   min_reading = MIN(observation.readings)
   IF min_reading < minimum_fluorescence:
     Set LOW_FLUORESCENCE_WELL on well
     IF well.isControlWell():
       Set LOW_FLUORESCENCE_TARGET on run_target

Notes:
- Reading equal to threshold passes (no error)
- Only control wells (PC, NC, Quantification) propagate to target level

5.2.2 Minimum Fluorescence Decision Logic

Reading	Threshold	Well Type	Well Error	Target Error
< threshold	Configured	Control	LOW_FLUORESCENCE_WELL	LOW_FLUORESCENCE_TARGET
< threshold	Configured	Sample	LOW_FLUORESCENCE_WELL	None
>= threshold	Configured	*	None	None
*	null	*	MINIMUM_FLUORESCENCE_MISSED	None

Precedence: Standard rule pipeline position.

Default: No error if reading >= threshold.

5.2.3 Unexpected (Maximum) Fluorescence Algorithm

Algorithm: Validate Maximum Fluorescence

Inputs:
- observation: Observation with readings
- maximum_fl: number (from target config) or null

Steps:
1. Configuration check:
   IF maximum_fl is null:
     Set MAXIMUM_FLUORESCENCE_MISSED error
     RETURN

2. Rox normalization (if enabled):
   IF target.rox_normalization:
     Apply Rox divide to readings before calculating max

3. Threshold comparison:
   max_reading = MAX(observation.readings)
   IF max_reading > maximum_fl:
     Set UNEXPECTED_FL error on well

5.3 Manual Baseline Rule

Algorithm: Validate Manual Baseline Check

Inputs:
- run_target: RunTarget with automatic_baseline_check setting

Steps:
1. Configuration check:
   IF run_target.hasAutoBaseline() == true: RETURN

2. Apply errors:
   Set MANUAL_BASELINE_CHECK_WELL on well
   Set MANUAL_BASELINE_CHECK_TARGET on run_target

5.3.1 Manual Baseline Decision Logic

automatic_baseline_check	Well Error	Target Error
true	None	None
false	MANUAL_BASELINE_CHECK_WELL	MANUAL_BASELINE_CHECK_TARGET

5.4 Control Presence Rules

5.4.1 MIN_CONTROLS Algorithm

Algorithm: Validate Control Presence

Inputs:
- well: Well
- wells: WellCollection (all wells in run)
- config: ConfigurationRepository

Steps:
1. Resolution check:
   IF well.resolution_codes contains 'MINCONTROL': RETURN

2. Patient check:
   IF NOT well.isPatientWell(): RETURN

3. Control presence check:
   has_pc = wells.hasAssociatePositiveControl(config, well)
   has_nc = wells.hasAssociateNegativeControl(config, well)

   IF has_pc AND has_nc: RETURN (success)

   IF fallback_shared_control enabled:
     Check backup_mix for controls
     IF backup_mix has controls: RETURN (success)

4. Error assignment:
   Set CONTROL_MISSING error on well

5.4.2 MINEXTRACT Algorithm

Algorithm: Validate Extraction Controls

Inputs:
- well: Well (with extraction details)
- wells: WellCollection

Steps:
1-2. Same as MIN_CONTROLS (resolution, patient checks)

3. Extraction control matching:
   Match controls on:
   - Same mix (or backup_mix if fallback enabled)
   - Same extraction_date
   - Same extraction_instrument
   - Same batch_number (if present)

   Exclude wells with Label Error type errors

   Accept "Quantification & PC" role as valid PEC

4. Error assignment:
   IF NOT (has_pec AND has_nec):
     Set EXTRACTION_CONTROLS_MISSING error on well

5.4.3 Control Presence Decision Logic

Well Type	Resolution	PC Present	NC Present	Fallback	Backup Has Controls	Result
Control	*	*	*	*	*	Skip (no error)
Patient	MINCONTROL	*	*	*	*	Skip (no error)
Patient	None	Yes	Yes	*	*	No error
Patient	None	No	*	Disabled	*	CONTROL_MISSING
Patient	None	*	No	Disabled	*	CONTROL_MISSING
Patient	None	No	*	Enabled	Yes	No error
Patient	None	No	*	Enabled	No	CONTROL_MISSING

Precedence: After basic well validation.

Default: Error if required controls not found.

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6. Error Handling

Condition	Detection	Response	Error Code
Westgard limit not found	Config lookup returns null	Set error, skip rule	WESTGARDS_MISSED
Invalid SD (0 or non-numeric)	SD validation	Set error, skip rule	INVALID_SD
Missing fluorescence config	Config null check	Set error	MINIMUM_FLUORESCENCE_MISSED, MAXIMUM_FLUORESCENCE_MISSED
Missing controls	Control lookup fails	Set error	CONTROL_MISSING, EXTRACTION_CONTROLS_MISSING
Control with label error	Error type check	Exclude from matching	N/A (continue search)

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7. Configuration

Setting	Path	Default	Effect	REQ
westgard_limit.mean	Kit Config	Required	Mean value for Westgard calculation	WG-006 to WG-013
westgard_limit.sd	Kit Config	Required	Standard deviation (must be > 0)	WG-004
wg12s_severity	Client Config	WARNING	Severity for 1:2s rule	WG-006
wg13s_severity	Client Config	ERROR	Severity for 1:3s rule	WG-007
strict_boundary_enforcement	Client Config	varies	Exclude >3SD from 2:2s pairing	WG-010
target.minimum_fluorescence	Kit Config	null	Minimum FL threshold	MINFL-001
target.maximum_fl	Kit Config	null	Maximum FL threshold	UNEXPFL-001
target.rox_normalization	Kit Config	false	Enable Rox divide before max FL	UNEXPFL-001
run_target.automatic_baseline_check	Run Config	true	Automatic baseline mode	BASELINE-001, 002
fallback_shared_control	Kit Config	false	Enable backup mix fallback	MINCTRL-003, 004, EXTCTRL-002, 003
role_to_target_mapping.backup_mix	Kit Config	null	Backup mix for fallback	MINCTRL-004, EXTCTRL-003

See Configuration Reference for full documentation.

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8. Implementation Mapping

8.1 Code Locations

Component	Path
Wg12SRule	app/Analyzer/Rules/Wg12SRule.php
Wg13SRule	app/Analyzer/Rules/Wg13SRule.php
Wg14SRule	app/Analyzer/Rules/Wg14SRule.php
Wg22SRule	app/Analyzer/Rules/Wg22SRule.php
Wg7TRule	app/Analyzer/Rules/Wg7TRule.php
Wg22S13SRule	app/Analyzer/Rules/Wg22S13SRule.php
Wg7T13SRule	app/Analyzer/Rules/Wg7T13SRule.php
WginerrorRule	app/Analyzer/Rules/WginerrorRule.php
MinFluorescenceRule	app/Analyzer/Rules/MinFluorescenceRule.php
UnexpectedFlRule	app/Analyzer/Rules/UnexpectedFlRule.php
MinControlsRule	app/Analyzer/Rules/MinControlsRule.php
MinextractRule	app/Analyzer/Rules/MinextractRule.php
ManualBaselineRule	app/Analyzer/Rules/ManualBaselineRule.php
SetErrorToWell	app/Analyzer/Rules/Concerns/SetErrorToWell.php
PecWellCollection	app/Analyzer/PecWellCollection.php

8.2 Requirement Traceability

REQ ID	Design Section	Primary Code
REQ-RULES-WG-001	SS5.1.6	PecWellCollection.php
REQ-RULES-WG-002	SS5.1.6	PecWellCollection.php
REQ-RULES-WG-003	SS5.1	WginerrorRule.php
REQ-RULES-WG-004	SS5.1.2	Wg12SRule.php, Wg13SRule.php, Wg14SRule.php
REQ-RULES-WG-005	SS5.1.2	All Westgard rules
REQ-RULES-WG-006	SS5.1.2, SS5.1.3	Wg12SRule.php
REQ-RULES-WG-007	SS5.1.2, SS5.1.3	Wg13SRule.php
REQ-RULES-WG-008	SS5.1.2, SS5.1.3	Wg14SRule.php
REQ-RULES-WG-009	SS5.1.4	Wg22SRule.php
REQ-RULES-WG-010	SS5.1.4	Wg22SRule.php, Wg22S13SRule.php
REQ-RULES-WG-011	SS5.1.4	Wg7TRule.php
REQ-RULES-WG-012	SS5.1.5	Wg22S13SRule.php
REQ-RULES-WG-013	SS5.1.5	Wg7T13SRule.php
REQ-RULES-MINFL-001	SS5.2.1	MinFluorescenceRule.php
REQ-RULES-MINFL-002	SS5.2.1, SS5.2.2	MinFluorescenceRule.php
REQ-RULES-MINFL-003	SS5.2.1	MinFluorescenceRule.php
REQ-RULES-UNEXPFL-001	SS5.2.3	UnexpectedFlRule.php
REQ-RULES-BASELINE-001	SS5.3	ManualBaselineRule.php
REQ-RULES-BASELINE-002	SS5.3	ManualBaselineRule.php
REQ-RULES-MINCTRL-001	SS5.4.1	MinControlsRule.php
REQ-RULES-MINCTRL-002	SS5.4.1	MinControlsRule.php
REQ-RULES-MINCTRL-003	SS5.4.1, SS5.4.3	MinControlsRule.php
REQ-RULES-MINCTRL-004	SS5.4.1, SS5.4.3	MinControlsRule.php
REQ-RULES-EXTCTRL-001	SS5.4.2	MinextractRule.php
REQ-RULES-EXTCTRL-002	SS5.4.2, SS5.4.3	MinextractRule.php
REQ-RULES-EXTCTRL-003	SS5.4.2, SS5.4.3	MinextractRule.php
REQ-RULES-EXTCTRL-004	SS5.4.2	MinextractRule.php
REQ-RULES-EXTCTRL-005	SS5.4.2	MinextractRule.php, WellCollection.php
REQ-RULES-EXTCTRL-006	SS5.4.2	MinControlsRule.php, WellCollection.php

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9. Design Decisions

Decision	Rationale	Alternatives Considered
Separate classes per Westgard rule	Different thresholds and behaviors, easier testing	Single class with multiplier parameter (rejected: combined rules need different logic)
Westgard processing order (4S->3S->2S)	Higher threshold = more severe, should take precedence	Evaluate all and report highest (rejected: multiple errors confusing)
Resolved control exclusion	Industry standard - resolved issues shouldn't affect future controls	Include all (rejected: violates Westgard methodology)
Label error exclusion from control matching	Wells with uncertain identity shouldn't validate patient wells	Include all controls (rejected: could validate with wrong control)
Dual-level error (well + target)	Well-level for detail, target-level for Assay Summary reporting	Well-level only (rejected: loses aggregate view)
Fallback shared control as feature flag	Different lab workflows; some labs share controls across mixes	Always enabled (rejected: changes existing behavior)

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10. Performance Considerations

Scenario	Concern	Mitigation
Large control history (7T rule)	Query performance for 7 historical wells	Index on target/role/date; limit lookback period
Multiple Westgard rules per well	Repeated Westgard limit lookups	Single lookup, cached for rule duration
Control presence with fallback	Double-check (primary + backup mix)	Early return if primary satisfies

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11. Related Documents

Document	Relevant Sections
SRS: rule-westgards.md	Westgard requirements
SRS: rule-minimum-fluorescence.md	Min FL requirements
SRS: rule-unexpected-fl.md	Max FL requirements
SRS: rule-baseline-check.md	Baseline requirements
SRS: rule-mincontrols.md	MIN_CONTROLS requirements
SRS: rule-extraction-controls.md	MINEXTRACT requirements
SDS: Rules Engine	Framework overview
SDS: Outcome Rules	RQUAL fallback
SDS: Domain RUNRPT	Well/observation data