Deep Dive: DDO vs. PICO (Aligned with DEPTh + Design Triad)
- Mayta
- 11 minutes ago
- 2 min read
🧠 Think "DEPTh" First—Not Framework
Before choosing DDO or PICO, classify the clinical challenge:
Type | Description | Examples |
Diagnosis | What feature helps us identify X? | What predicts scrub typhus? |
Etiognosis | What causes or increases risk? | Does PM2.5 cause preterm birth? |
Prognosis | What predicts outcome? | What predicts ICU mortality in sepsis? |
Therapeutic | Does intervention improve outcome? | Does metronomic chemo increase OS? |
Methodologic | How should we best measure/study? | Is this tool valid/reliable? |
🚦 Match framework to challenge type:
Use DDO for diagnosis, etiognosis, prognosis, and most therapeutic cohort studies.
Use PICO for randomized therapeutic trials.
🧩 Framework Dissection: DDO vs PICO
Feature | DDO | PICO |
Full Name | Domain–Determinant–Outcome | Patient–Intervention–Comparator–Outcome |
Best for | Observational, causal, prognostic, diagnostic | Randomized therapeutic interventions |
Structure | Who → What X → What Y | Who → Treatment A vs B → What Y |
Analysis Mapping | Easy to plug into `Y = f(X | confounders)` | Direct for superiority/inferiority analysis |
Flexibility | High: allows causal/predictive logic | Narrow: fits RCT-specific logic |
🔍 Secret Insight: PICO assumes a "treatment effect" structure. If you’re not randomizing, PICO can mislead your method logic.
🧪 Advanced Examples with CECS Mapping
🌱 Causal Inference (Etiognosis)
"Does high air pollution exposure increase preterm birth risk?"
DEPTh: Etiognosis
DDO:
Domain: Pregnant women in polluted cities
Determinant: PM2.5 exposure
Outcome: Preterm delivery
Occurrence Equation:
Preterm = f(PM2.5 | Age, BMI, Comorbidities)
Design:
Method: Retrospective cohort
Analysis: Multivariable logistic regression
🧬 Diagnostic Accuracy
"What symptoms help distinguish leptospirosis from other febrile illnesses?"
DEPTh: Diagnosis
DDO:
Domain: Suspected febrile illness cases
Determinants: Mud exposure, conjunctival suffusion, WBC count
Outcome: Lab-confirmed leptospirosis
Analysis: ROC curve, AUC, LR+, LR−
💉 Therapeutic RCT (PICO justified)
"Does metronomic chemo extend survival in unfit AML patients vs best supportive care?"
DEPTh: Therapeutic
PICO:
P: Unfit AML patients
I: Metronomic chemo
C: Best supportive care
O: Median survival at 6, 12 months
Design: Pragmatic RCT
Analysis: Kaplan–Meier curves, Cox model
🧠 Why Bad Questions Derail Good Research
🛑 Common Errors:
PICO logic used for prognostic studies → misfit
DDO variables unclear → domain/determinant conflated
Outcome not operationalized → “better outcome” ≠ measurable endpoint
🔍 Secret Insight: Ask yourself, “Can I sketch an occurrence equation?” If not, the framework isn't ready.
✅ Key Takeaways
DDO is your Swiss Army knife for most study types, especially observational, prognostic, and diagnostic.
PICO is laser-focused: use when testing an intervention in RCT logic.
DEPTh helps you align clinical logic to research logic.
Research design flows from clinical challenge → structured question → objectives → design → analysis.
A solid occurrence equation helps align all decisions downstream.
Comments