Designing Clinical Decision Support

Required Documents

• Clinical guideline or evidence source document
• Current alert inventory for the target clinical domain (to assess overlap and fatigue burden)
• EHR CDS capability matrix (available trigger types, data elements accessible at runtime)
• Override reason code taxonomy currently in use
• Baseline quality measure data if the CDS targets an eCQM or HEDIS measure

Step 1 --- Define Trigger Logic

Specify the computable conditions that activate the CDS rule:

• Patient inclusion criteria --- Demographics (age, sex), problem list entries (SNOMED CT concepts), active medication list (RxNorm CUIs), lab results (LOINC codes with value thresholds), encounter type
• Action trigger --- What user action initiates evaluation? (New order for drug class X, opening a patient chart, completing a flowsheet row)
• Temporal conditions --- Time-based logic (e.g., "no HbA1c result in past 90 days" requires date arithmetic against LOINC 4548-4)
• Exclusion criteria --- Conditions that suppress the alert: documented allergy contraindication, active hospice status, patient refusal on file
• Boolean logic structure --- Write the full trigger as a structured boolean expression:

  IF (active_medication IN [RxNorm class]) 
  AND (lab_result[LOINC] < threshold OR lab_result_age > 90d) 
  AND NOT (problem_list CONTAINS [SNOMED exclusion concept])
  THEN fire_alert
  

Step 2 --- Design the Intervention

Structure the CDS output following the CDS Five Rights:

• Alert type classification --- Interruptive (hard stop, soft stop) vs. non-interruptive (info button, dashboard indicator, inbox message). Default to non-interruptive unless evidence supports interruption
• Content specification --- Write the exact alert text. Include: (a) what was detected, (b) why it matters with severity, (c) recommended action, (d) link to evidence. Keep below 3 sentences for interruptive alerts
• Action options --- Define the response buttons: Accept recommendation (with pre-populated order), Override with reason (from coded reason list), Defer/snooze (with time limit), Cancel triggering action
• CDS Hooks integration --- For SMART on FHIR CDS Hooks implementations, specify the hook type (patient-view, order-select, order-sign, medication-prescribe), the prefetch query, and the card response structure
• Suggested actions --- For order-based CDS, pre-populate the recommended order with appropriate defaults (dose, route, frequency) to minimize clinician effort

Step 3 --- Assess and Mitigate Alert Fatigue

Before deployment, evaluate the fatigue impact:

1. Estimated firing frequency --- Query historical data to estimate how often the trigger criteria are met. Express as alerts per provider per shift
2. Positive predictive value projection --- Of estimated firings, what percentage represent truly actionable clinical situations?
3. Tiering strategy --- Classify severity: Tier 1 (hard stop, life-threatening), Tier 2 (soft stop, clinically significant), Tier 3 (informational, non-interruptive). Only Tier 1 and 2 justify interruption
4. Duplicate/overlap check --- Compare trigger logic against all existing active CDS rules. Identify rules that would fire on the same patient population and order type
5. Suppression rules --- Define auto-suppression for repeat firings (e.g., "do not re-fire this alert for the same patient within 24 hours if overridden")
6. Override reason analysis plan --- Design structured override reasons that produce analyzable data for post-deployment refinement

Step 4 --- Specify Knowledge Maintenance

CDS rules are clinical content that requires lifecycle management:

• Evidence review schedule --- Define review frequency based on evidence velocity: annual for stable guidelines, quarterly for rapidly evolving domains (e.g., oncology protocols)
• Trigger for urgent update --- FDA safety communication, guideline withdrawal, formulary change, new contraindication
• Version control --- Each rule version gets a unique identifier with effective date, author, approving committee, and clinical evidence citation
• Retirement criteria --- Override rate > 90% for 3 consecutive months triggers mandatory review. Measure-based CDS retires when the quality measure is retired or topped out

Step 5 --- Build and Test

Execute the CDS rule implementation:

• Unit testing --- Create test patients covering: positive trigger (alert fires correctly), negative trigger (alert correctly suppressed), boundary conditions (values at exact thresholds), exclusion criteria (alert suppressed for excluded populations)
• Integration testing --- Test within the full clinical workflow: place the triggering order, verify the alert appears at the correct workflow point, confirm the recommended action executes correctly
• Performance testing --- Measure alert rendering latency. CDS that takes > 2 seconds to display at order entry will be perceived as system slowness, not decision support
• User acceptance testing --- Have 3-5 representative clinicians walk through the alert in simulated encounters. Document feedback on clarity, actionability, and workflow disruption

Step 6 --- Deploy and Monitor

Post-deployment surveillance is mandatory:

• Phased rollout --- Deploy to a pilot unit or provider group first. Monitor for 2 weeks before enterprise deployment
• Monitoring metrics --- Track daily: firing rate, override rate by reason code, acceptance rate, time-to-action after alert display, adverse events in the target population
• Feedback channel --- Establish a mechanism for clinicians to report CDS issues directly to the clinical informatics team (not just the IT help desk)
• 30-day review --- Formal post-deployment review with the CDS governance committee. Present metrics, clinician feedback, and recommendations for tuning

Checkpoint B --- Design Completeness Review

Before submitting for governance committee approval:

• Trigger logic is fully specified with coded data elements (SNOMED, LOINC, RxNorm)
• Evidence base is cited with guideline strength and quality rating
• Alert type (interruptive vs. non-interruptive) is justified with fatigue analysis
• Alert text is reviewed for clinical accuracy and health literacy
• Override reason codes are defined and mapped to the organization's taxonomy
• Suppression and de-duplication rules are specified
• Test cases cover positive, negative, boundary, and exclusion scenarios
• Knowledge maintenance schedule is defined with responsible owner
• Estimated firing frequency and PPV are documented

Quality Audit

• CDS rule addresses a documented clinical need with evidence support (not vendor suggestion alone)
• Interruptive alerts are limited to Tier 1 and Tier 2 severity
• Estimated alert frequency does not exceed organizational threshold per provider per shift
• All coded elements use current terminology versions (SNOMED CT, ICD-10-CM, LOINC, RxNorm)
• CDS Hooks specification follows HL7 standards if applicable
• Override data capture is structured for post-deployment analysis
• Clinical informaticist and subject matter expert sign-off documented
• Post-deployment monitoring plan has defined metrics and review milestones
• Rule version is catalogued in the organizational CDS knowledge base

Guidelines

• Default to non-interruptive CDS formats unless clinical evidence demonstrates that interruption prevents significant harm. The burden of proof is on the case for interruption, not against it
• Never deploy CDS rules without a defined retirement or review process. Orphaned rules are the primary driver of alert fatigue accumulation
• Use coded clinical data (SNOMED CT, LOINC, RxNorm) for all trigger criteria. Free-text triggers are fragile and unauditable
• Include the evidence citation in the alert display. Clinicians are more likely to accept recommendations they can verify
• Design CDS as a system, not individual rules. Every new rule must be evaluated against the existing rule inventory for interaction effects
• Track the override rate as a signal, not a problem. High override rates indicate poor rule design, not poor clinician behavior
• For CDS Hooks implementations, minimize prefetch data to what the rule actually needs. Over-fetching degrades FHIR server performance
• Maintain alignment with ONC certification criterion 170.315(a)(9) for CDS configuration requirements