STD: WDCT Rule (CT Discrepancy Detection)

Version: v1.0.0 Status: Draft SRS Source: docusaurus/docs/srs/rules/rule-wdct.md Rule Name: WDCT Domain: RULES-WDCT

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Overview

This document specifies tests for the WDCT rule using decision tables and test vectors. The rule detects CT (Cycle Threshold) discrepancies between pcr.ai-calculated values and machine-reported CT values for Patient wells, flagging wells where the absolute difference exceeds the configured ct_discrepancy_delta threshold.

Rule Characteristics:

• Pure business logic (no UI)
• Sequential condition evaluation (fluorescence -> classification -> max CT threshold -> CT difference)
• Two configuration-based modifiers (suppression and skip)
• Patient wells only (Control wells delegated to WDCTC)

Test Method: TM-API (per Test Plan Section 3.3 - Rules use automated API tests)

Verification Approach: Rule verification is performed using data-driven test vectors. Each row in a decision table represents a complete verification scenario with defined inputs and expected outputs. This format enables exhaustive condition coverage while remaining concise and auditable.

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Coverage Summary

REQ ID	Title	Conditions	Test Vectors	Coverage	Gaps
REQ-RULES-WDCT-001	CT Discrepancy Detection	11	17	100%	None
REQ-RULES-WDCT-002	Max CT Threshold Suppression	4	5	100%	None
REQ-RULES-WDCT-003	Fluorescence-Based Skip	3	4	100%	None

Totals: 3 REQs, 18 Conditions, 26 Test Vectors, 100% Coverage

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Input Variables

Variable	Type	Valid Values	Description
well.type	string	Patient, Control	Well classification type
obs.classification	string	Positive, Negative, Ambiguous	Observation classification result
obs.pcrai_ct	float	numeric	CT value calculated by pcr.ai algorithm
obs.machine_ct	float	numeric	CT value reported by thermocycler instrument
obs.final_ct	float	numeric	Authoritative CT value for downstream analysis
obs.max_reading	float	numeric	max(observation.readings) - highest fluorescence reading
target.ct_discrepancy_delta	float?	null, numeric	Configurable threshold for CT difference detection; null disables rule for target
target.max_ct_for_ct_discrepancy	float?	null, numeric	Maximum CT value above which CT discrepancy checks are suppressed
target.minimum_fluorescence_to_positive	float	numeric	Minimum fluorescence threshold for rule evaluation

Output Variables

Variable	Type	Description
well.error_code	string?	CTDISC_WELL if discrepancy detected, null otherwise
rule_evaluated	bool	Whether the rule completed evaluation (false if skipped)
error_suppressed	bool	Whether an error was suppressed by threshold

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REQ-RULES-WDCT-001: CT Discrepancy Detection

Decision Table: Well Type Filter

TV	well.type	rule_applies	Covers
TV-001-001	Patient	true	AC: Apply rule to Patient wells
TV-001-002	Control	false	AC: Delegate control wells to WDCTC

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Decision Table: Classification Handling

TV	obs.classification	ct_diff	error_code	Covers
TV-001-003	Negative	5.0	null	AC: Skip discrepancy detection for negative classification
TV-001-004	Positive	5.0	CTDISC_WELL	AC: Compare CTs for non-negative classification
TV-001-005	Ambiguous	5.0	CTDISC_WELL	AC: Compare CTs for non-negative classification

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Decision Table: CT Difference Threshold (Default ct_discrepancy_delta=2)

Note: These test vectors assume ct_discrepancy_delta=2 (the default threshold). See "Configurable Threshold" table below for variable threshold tests.

TV	obs.pcrai_ct	obs.machine_ct	abs_diff	error_code	Covers
TV-001-006	25.0	28.5	3.5	CTDISC_WELL	AC: Flag when abs diff > threshold
TV-001-007	25.0	22.0	3.0	CTDISC_WELL	AC: Flag when abs diff > threshold (negative direction)
TV-001-008	25.0	26.5	1.5	null	AC: No error when abs diff <= threshold
TV-001-009	25.0	27.0	2.0	null	AC: No error when abs diff = threshold (boundary)
TV-001-010	25.0	27.01	2.01	CTDISC_WELL	AC: Flag when abs diff > threshold (boundary exceeded)

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Decision Table: Configurable Threshold (ct_discrepancy_delta)

TV	ct_discrepancy_delta	obs.pcrai_ct	obs.machine_ct	ct_diff	error_code	Covers
TV-001-011	null	25.0	35.0	10.0	null	AC: Null threshold disables rule for target
TV-001-012	3	25.0	27.5	2.5	null	AC: No error when diff within threshold=3
TV-001-013	3	25.0	28.5	3.5	CTDISC_WELL	AC: Flag when diff exceeds threshold=3
TV-001-014	5	25.0	29.9	4.9	null	AC: No error when diff within larger threshold=5
TV-001-015	5	25.0	30.1	5.1	CTDISC_WELL	AC: Flag when diff exceeds larger threshold=5
TV-001-016	2	25.0	27.0	2.0	null	AC: No error when diff equals threshold (boundary)
TV-001-017	2	25.0	27.01	2.01	CTDISC_WELL	AC: Flag when diff just exceeds threshold (boundary)

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REQ-RULES-WDCT-002: Max CT Threshold Suppression

Decision Table: Suppression Logic

TV	max_ct_for_ct_discrepancy	obs.final_ct	ct_diff	error_code	error_suppressed	Covers
TV-002-001	null	36.0	5.0	CTDISC_WELL	false	AC: Null threshold = no suppression
TV-002-002	35	36.0	5.0	null	true	AC: final_ct > threshold = suppressed
TV-002-003	36	36.0	5.0	null	true	AC: final_ct = threshold = suppressed (>=)
TV-002-004	37	36.0	5.0	CTDISC_WELL	false	AC: final_ct < threshold = not suppressed
TV-002-005	35	34.0	5.0	CTDISC_WELL	false	AC: final_ct below threshold = not suppressed

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REQ-RULES-WDCT-003: Fluorescence-Based Skip

Decision Table: Minimum Fluorescence Check

TV	minimum_fluorescence_to_positive	obs.max_reading	rule_evaluated	Covers
TV-003-001	100	99	false	AC: Skip rule when max reading < threshold
TV-003-002	100	100	true	AC: Evaluate rule when max reading = threshold
TV-003-003	100	150	true	AC: Evaluate rule when max reading > threshold
TV-003-004	100	50	false	AC: Skip to prevent false discrepancy errors on low fluorescence

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Combined Evaluation: End-to-End Scenarios

The following decision table tests the complete rule evaluation path, verifying the execution order: fluorescence check (003) -> classification -> max CT threshold (002) -> CT difference (001).

Decision Table: Full Evaluation Path

TV	max_reading	min_fluor	classification	final_ct	max_ct_thresh	pcrai_ct	machine_ct	rule_evaluated	error_suppressed	error_code	Covers
TV-E2E-001	50	100	Positive	25.0	null	25.0	30.0	false	false	null	AC: Fluorescence skip takes precedence
TV-E2E-002	150	100	Negative	25.0	null	25.0	30.0	true	false	null	AC: Negative classification ends without error
TV-E2E-003	150	100	Positive	36.0	35	25.0	30.0	true	true	null	AC: Max CT threshold suppresses error
TV-E2E-004	150	100	Positive	34.0	35	25.0	30.0	true	false	CTDISC_WELL	AC: All checks pass, error flagged
TV-E2E-005	150	100	Positive	34.0	null	25.0	26.0	true	false	null	AC: All checks pass, within tolerance

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Automation Status

REQ ID	Automation Status	Notes
REQ-RULES-WDCT-001	Automated	Data-driven test with parameterized inputs
REQ-RULES-WDCT-002	Automated	Data-driven test with parameterized inputs
REQ-RULES-WDCT-003	Automated	Data-driven test with parameterized inputs

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Traceability to Existing Tests

Requirement	Jira Tests	Status
REQ-RULES-WDCT-001	BT-5133, BT-5305, BT-5244, BT-5328, BT-5261, BT-5700, BT-5369	Existing
REQ-RULES-WDCT-002	BT-5308, BT-5307	Existing
REQ-RULES-WDCT-003	BT-5368, BT-5367	Existing

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Gap Analysis

Identified Gaps

Gap	Requirement	Description	Priority	Owner
None	-	All acceptance criteria have corresponding test vectors	-	-

Remediation Plan

No gaps identified. All requirements have:

• Complete condition coverage via decision tables
• Boundary value testing for thresholds
• End-to-end integration scenarios
• Traceability to existing Jira test tickets