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# Patient Pathway Analysis - Improvement Recommendations
This document outlines recommended improvements to modernize the Patient Pathway Analysis application, based on multi-domain expert analysis.
---
## Executive Summary
| Area | Current State | Recommended Change | Priority |
|------|--------------|-------------------|----------|
| **GUI Framework** | CustomTkinter | **Reflex** (browser-based, native Plotly) | High |
| **Data Storage** | CSV files (90MB+) | SQLite with caching | High |
| **Data Source** | Manual CSV export | Direct Snowflake connection | Medium |
| **Directory Assignment** | Multi-stage fallback | GP diagnosis codes as primary | Medium |
| **Code Quality** | Monolithic, no types | Modular, typed, tested | Low |
---
## 1. GUI Framework: Replace CustomTkinter with Reflex or Flet
### What
Replace the CustomTkinter-based GUI with a modern Python framework. Two strong options:
- **[Reflex](https://reflex.dev)** - React-based, runs in browser
- **[Flet](https://flet.dev)** - Flutter-based, native desktop or browser
### Why
Since Python is approved and standalone `.exe` distribution isn't required, **both frameworks are viable**.
| Criterion | CustomTkinter | Reflex | Flet |
|-----------|---------------|--------|------|
| UI paradigm | Native desktop | Browser (localhost) | Desktop or browser |
| Component richness | Limited | 60+ React components | Material Design |
| Styling | Manual/limited | Full CSS/Tailwind | Flutter theming |
| Plotly integration | External HTML | **Native embed** | WebView needed |
| State management | Manual | Automatic re-render | Manual updates |
| Learning curve | Low | Moderate (React-like) | Low-moderate |
| Community | Small | 22k+ GitHub stars | 12k+ GitHub stars |
| Maturity | Stable | Active (v0.6+) | Active (v0.80+) |
### Recommendation: **Reflex**
Given that:
1. Python is approved for users
2. Standalone `.exe` not required
3. **Interactive Plotly is required** (Reflex has native `rx.plotly()` component)
Reflex is now the better choice because:
- **Native Plotly support** - no need to open external browser windows
- **Modern React-based UI** - cleaner, more customizable
- **Simpler state management** - automatic re-rendering on state changes
- **Better for data apps** - designed for dashboards and data visualization
### How (Reflex)
**Basic app structure:**
```python
import reflex as rx
class State(rx.State):
"""Application state."""
start_date: str = "2019-04-01"
end_date: str = "2025-04-30"
selected_drugs: list[str] = []
selected_trusts: list[str] = []
analysis_running: bool = False
chart_data: dict = {}
async def run_analysis(self):
self.analysis_running = True
yield # Update UI
# Run analysis (async)
df = await self.load_and_process_data()
self.chart_data = generate_plotly_figure(df)
self.analysis_running = False
def index() -> rx.Component:
return rx.box(
rx.hstack(
# Sidebar with filters
rx.vstack(
rx.date_picker(
value=State.start_date,
on_change=State.set_start_date,
),
rx.checkbox_group(
items=drug_list,
value=State.selected_drugs,
on_change=State.set_selected_drugs,
),
rx.button(
"Run Analysis",
on_click=State.run_analysis,
loading=State.analysis_running,
),
width="300px",
),
# Main content - interactive Plotly chart
rx.plotly(data=State.chart_data, layout=chart_layout),
width="100%",
)
)
app = rx.App()
app.add_page(index)
```
**Key components mapping:**
| Current Component | Reflex Equivalent |
|-------------------|-------------------|
| `CTkFrame` | `rx.box`, `rx.vstack`, `rx.hstack` |
| `CTkButton` | `rx.button` |
| `CTkCheckBox` | `rx.checkbox` |
| `CTkSlider` | `rx.slider` |
| `DateEntry` | `rx.date_picker` |
| `CTkScrollableFrame` | `rx.scroll_area` |
| `filedialog` | `rx.upload` |
| Plotly HTML file | **`rx.plotly()`** - native embed! |
**Running the app:**
```bash
# Install
pip install reflex
# Initialize (first time)
reflex init
# Run development server
reflex run
# Opens http://localhost:3000 in browser
```
**Background tasks with progress:**
```python
class State(rx.State):
progress: int = 0
status: str = ""
async def run_analysis(self):
self.status = "Loading data..."
self.progress = 10
yield
df = load_data()
self.status = "Processing..."
self.progress = 50
yield
result = process_data(df)
self.status = "Complete"
self.progress = 100
yield
```
### Alternative: Flet
If you prefer a more desktop-like feel, Flet remains a good option:
```python
import flet as ft
def main(page: ft.Page):
page.title = "HCD Analysis"
async def run_analysis(e):
# Background task
page.run_task(do_analysis)
page.add(
ft.Row([
# Sidebar
ft.Column([
ft.DatePicker(),
ft.ElevatedButton("Run", on_click=run_analysis),
]),
# Chart area (opens in browser for interactivity)
ft.ElevatedButton("View Chart", on_click=open_chart),
])
)
ft.app(target=main) # Desktop window
# OR
ft.app(target=main, view=ft.WEB_BROWSER) # Browser
```
### Effort Estimate
- Learning Reflex basics: 2-3 days
- Rewriting GUI: 1-2 weeks
- Testing and polish: 3-5 days
---
## 2. Data Storage: SQLite Architecture
### What
Replace CSV-based data loading with a SQLite database that stores reference data in normalized tables and caches processed patient data.
### Why
| Aspect | Current (CSV) | SQLite |
|--------|---------------|--------|
| Startup time | 90MB+ file read + full processing | Load reference data once (< 1MB) |
| Memory usage | Entire dataset in memory | Incremental queries |
| Incremental updates | Full reprocess required | Only process new/changed records |
| Query performance | Pandas groupby/merge | Indexed SQL with CTEs |
| Data consistency | Multiple CSVs can drift | Single source of truth with FK constraints |
| Caching | None | Materialized views |
**Expected improvements:**
- 60-80% faster startup
- 50-70% memory reduction
- 90%+ time savings on incremental updates
### How
**Recommended schema (simplified):**
```sql
-- Reference tables
CREATE TABLE ref_drug_names (
drug_name_raw TEXT PRIMARY KEY,
drug_name_std TEXT NOT NULL
);
CREATE TABLE ref_organizations (
org_code TEXT PRIMARY KEY,
org_name TEXT NOT NULL
);
CREATE TABLE ref_directories (
directory_id INTEGER PRIMARY KEY,
directory_name TEXT UNIQUE NOT NULL
);
CREATE TABLE ref_drug_directory_map (
drug_name_std TEXT,
directory_id INTEGER,
is_single_valid BOOLEAN DEFAULT FALSE,
PRIMARY KEY (drug_name_std, directory_id)
);
-- Patient data (fact table)
CREATE TABLE fact_interventions (
intervention_id INTEGER PRIMARY KEY,
upid TEXT NOT NULL,
provider_code TEXT,
drug_name_std TEXT NOT NULL,
intervention_date DATE NOT NULL,
price_actual REAL,
directory_id INTEGER,
directory_assignment_method TEXT,
data_load_batch_id INTEGER
);
-- Critical indexes
CREATE INDEX idx_upid ON fact_interventions(upid);
CREATE INDEX idx_upid_drug ON fact_interventions(upid, drug_name_std);
CREATE INDEX idx_intervention_date ON fact_interventions(intervention_date);
-- Materialized view for patient summaries (cached aggregations)
CREATE TABLE mv_patient_treatment_summary (
upid TEXT PRIMARY KEY,
first_seen DATE,
last_seen DATE,
total_cost REAL,
drug_count INTEGER,
last_refresh TIMESTAMP
);
-- File tracking for incremental updates
CREATE TABLE processed_files (
file_path TEXT PRIMARY KEY,
file_hash TEXT NOT NULL,
last_processed TIMESTAMP
);
```
**Migration strategy:**
1. **Phase 1**: Create schema, load reference tables from existing CSVs
2. **Phase 2**: Develop incremental load scripts for patient data
3. **Phase 3**: Build materialized views for aggregations
4. **Phase 4**: Modify `dashboard_gui.py` to query SQLite instead of processing CSVs
**Key query replacing pandas aggregation:**
```sql
-- Replaces ~200 lines of pandas groupby/merge
WITH patient_drugs AS (
SELECT
upid,
drug_name_std,
MIN(intervention_date) as first_date,
MAX(intervention_date) as last_date,
COUNT(*) as intervention_count,
SUM(price_actual) as drug_cost
FROM fact_interventions
WHERE intervention_date BETWEEN :start_date AND :end_date
AND provider_code IN (:trust_filters)
GROUP BY upid, drug_name_std
)
SELECT * FROM patient_drugs;
```
### Effort Estimate
- Schema design and setup: 2-3 days
- Migration scripts: 3-4 days
- Query optimization: 2-3 days
- Integration testing: 2-3 days
---
## 3. Snowflake Integration
### What
Enable direct download of HCD activity data from Snowflake servers, replacing manual CSV exports.
### Why
- Eliminates manual export step
- Enables date-range filtering at query level (faster)
- Automatic caching with TTL
- Graceful fallback to local files if Snowflake unavailable
### How
**Authentication: SSO Browser Login**
Using `externalbrowser` authenticator - opens system browser for SSO authentication:
```python
import snowflake.connector
conn = snowflake.connector.connect(
account="your_account.region",
user="your.email@nhs.net",
authenticator="externalbrowser",
warehouse="ANALYTICS_WH",
database="data_hub",
schema="dwh"
)
```
**Note**: User will see browser popup on first connection each session.
**Configuration (`config/snowflake.toml`):**
```toml
[snowflake]
account = "your_account.region"
warehouse = "ANALYTICS_WH"
database = "DataWarehouse"
schema = "dwh"
[query]
default_timeout = 300
chunk_size = 100000
[cache]
enabled = true
ttl_hours = 24
directory = "./data/cache"
```
**Core connector pattern:**
```python
from snowflake.connector import connect
class SnowflakeConnector:
def fetch_activity_data(self, start_date, end_date, provider_codes=None):
query = """
SELECT
"Provider Code",
"PersonKey",
"ProductDescription" as "Drug Name",
"Intervention Date",
"Price Actual",
-- ... other columns
FROM DataWarehouse.dwh.FactHighCostDrugs
WHERE "Intervention Date" BETWEEN :start_date AND :end_date
"""
with self.connect() as conn:
cursor = conn.cursor()
cursor.execute(query, {'start_date': start_date, 'end_date': end_date})
return cursor.fetch_pandas_all()
```
**Caching strategy:**
| Scenario | Action |
|----------|--------|
| Same date range within 24 hours | Use cache |
| Date range includes today | Query Snowflake (data may be updating) |
| User clicks "Refresh" | Query Snowflake |
| Snowflake unavailable | Fallback to local CSV/Parquet |
**Data loader with fallback:**
```python
class DataLoader:
def load_data(self, start_date, end_date, force_refresh=False):
# 1. Try cache
if self.cache and not force_refresh:
cached = self.cache.get(start_date, end_date)
if cached is not None:
return cached, "cache"
# 2. Try Snowflake
try:
df = self.snowflake.fetch_activity_data(start_date, end_date)
self.cache.set(df, start_date, end_date)
return df, "snowflake"
except SnowflakeConnectionError:
pass
# 3. Fallback to local files
if self.fallback_file.exists():
return pd.read_parquet(self.fallback_file), "local_file"
raise RuntimeError("No data source available")
```
**Dependencies to add:**
```toml
dependencies = [
"snowflake-connector-python[pandas]>=3.12.0",
"cryptography>=42.0.0",
]
```
### Effort Estimate
- Snowflake connector setup: 2-3 days
- Caching layer: 1-2 days
- GUI integration (data source selector): 1-2 days
- Testing with real data: 2-3 days
---
## 4. GP Diagnosis Code Integration
### What
Use GP diagnosis codes as the **primary source** for directory/specialty assignment, with existing logic as fallback.
### Why
- More accurate: Diagnosis directly indicates specialty
- Reduces "Undefined" assignments
- Leverages existing NHS data linkage
- Maintains current logic as safety net
### How
**NHS diagnosis code landscape:**
| Code System | Usage | Notes |
|-------------|-------|-------|
| **SNOMED CT** | GP systems (mandatory since 2018) | Primary source |
| **ICD-10** | Secondary care | Maps FROM SNOMED CT |
| **Read Codes** | Legacy only | Historical records |
**New priority chain:**
```
1. Drug has single valid directory → use that (unchanged)
2. [NEW] GP diagnosis available → map SNOMED/ICD-10 to directory
3. Extract from clinical data fields (existing)
4. Most frequent for same patient/drug (existing)
5. UPID-based inference (existing)
6. Default to "Undefined" (existing)
```
**ICD-10 to Directory mapping (examples):**
```python
ICD10_TO_DIRECTORY = {
# Neoplasms (Chapter II)
"C": ["MEDICAL ONCOLOGY", "CLINICAL ONCOLOGY", "CLINICAL HAEMATOLOGY"],
# Blood diseases (Chapter III)
"D5": ["CLINICAL HAEMATOLOGY"],
"D6": ["CLINICAL HAEMATOLOGY"],
# Endocrine (Chapter IV)
"E10": ["DIABETIC MEDICINE"], # Type 1 diabetes
"E11": ["DIABETIC MEDICINE"], # Type 2 diabetes
# Eye (Chapter VII)
"H0": ["OPHTHALMOLOGY"],
"H1": ["OPHTHALMOLOGY"],
"H2": ["OPHTHALMOLOGY"],
"H3": ["OPHTHALMOLOGY"],
# Musculoskeletal (Chapter XIII)
"M05": ["RHEUMATOLOGY"], # Rheumatoid arthritis
"M06": ["RHEUMATOLOGY"],
"M32": ["RHEUMATOLOGY"], # SLE
# Genitourinary (Chapter XIV)
"N0": ["NEPHROLOGY"],
"N1": ["NEPHROLOGY"],
"N18": ["NEPHROLOGY"], # CKD
}
```
**Multi-diagnosis resolution:**
```python
def resolve_directory_from_diagnoses(diagnoses, drug_valid_dirs):
"""
When patient has multiple diagnoses:
1. Filter to diagnoses mapping to directories valid for this drug
2. Oncology diagnoses take priority (ICD-10 chapter C)
3. Use most recent active diagnosis
4. Default to first alphabetically (deterministic)
"""
valid_matches = []
for dx in diagnoses:
icd10_prefix = dx.icd10_code[:3]
possible_dirs = ICD10_TO_DIRECTORY.get(icd10_prefix, [])
matching = set(possible_dirs) & set(drug_valid_dirs)
if matching:
valid_matches.append({
'directories': matching,
'is_oncology': dx.icd10_code.startswith('C'),
'date': dx.diagnosis_date
})
if not valid_matches:
return None # Fall back to existing logic
# Oncology priority
oncology = [m for m in valid_matches if m['is_oncology']]
if oncology:
return sorted(oncology[0]['directories'])[0]
# Most recent
valid_matches.sort(key=lambda x: x['date'], reverse=True)
return sorted(valid_matches[0]['directories'])[0]
```
**Data source options:**
1. **Snowflake linked data** (recommended): Query `data_hub.dwh.DimClinicalCoding` joined via `PatientPseudo`
2. **Local CSV cache**: Pre-extracted GP diagnosis data for offline use
3. **Hybrid**: Cache with Snowflake refresh
**GP Diagnosis Query (confirm column names via Snowflake MCP):**
```sql
SELECT
PatientPseudo,
SNOMEDCode, -- or similar
ICD10Code, -- may need mapping from SNOMED
DiagnosisDate,
DiagnosisStatus -- Active/Resolved if available
FROM data_hub.dwh.DimClinicalCoding
WHERE PatientPseudo IN (:patient_pseudo_list)
ORDER BY DiagnosisDate DESC
```
**New reference file needed (`./data/diagnosis_directory_map.csv`):**
```csv
icd10_prefix,directory,priority,notes
C,MEDICAL ONCOLOGY,1,All malignancies
C81,CLINICAL HAEMATOLOGY,1,Hodgkin lymphoma
C90,CLINICAL HAEMATOLOGY,1,Multiple myeloma
E10,DIABETIC MEDICINE,1,Type 1 diabetes
E11,DIABETIC MEDICINE,1,Type 2 diabetes
G35,NEUROLOGY,1,Multiple sclerosis
H0,OPHTHALMOLOGY,1,Eye disorders
M05,RHEUMATOLOGY,1,Rheumatoid arthritis
N18,NEPHROLOGY,1,Chronic kidney disease
```
**Tracking assignment source (for audit):**
```python
df['Directory_Source'] = pd.NA # New column
# After each assignment step:
df.loc[assigned_mask, 'Directory_Source'] = 'DRUG_SINGLE' # Step 1
df.loc[assigned_mask, 'Directory_Source'] = 'GP_DIAGNOSIS' # Step 2 (NEW)
df.loc[assigned_mask, 'Directory_Source'] = 'CLINICAL_EXTRACT' # Step 3
# ... etc
```
### Prerequisites
- Explore `data_hub.dwh.DimClinicalCoding` schema to confirm exact column names (use Snowflake MCP)
- Map `PatientPseudo` to your HCD data (may need to add PatientPseudo to your data extract)
- Obtain SNOMED CT to ICD-10 mapping table from NHS TRUD (if DimClinicalCoding only has SNOMED)
### Effort Estimate
- Mapping table creation: 2-3 days
- Snowflake GP query development: 2-3 days
- Integration with existing logic: 2-3 days
- Validation and testing: 3-5 days
---
## 5. Code Quality Improvements
### What
Modernize the codebase with better structure, type hints, error handling, and testing.
### Why
- `generate_graph()` is 267 lines with complexity >30
- Zero type hints across entire codebase
- Global variables create hidden state
- No automated tests
- Print statements instead of logging
### How
**Quick wins (implement first):**
1. **Replace global variables** with dataclass:
```python
@dataclass
class AnalysisFilters:
start_date: date
end_date: date
last_seen: date
minimum_patients: int
selected_trusts: list[str]
selected_drugs: list[str]
selected_directories: list[str]
custom_title: str = ""
def validate(self) -> list[str]:
errors = []
if self.start_date >= self.end_date:
errors.append("Start date must be before end date")
return errors
```
2. **Externalize configuration:**
```python
@dataclass
class PathConfig:
data_dir: Path = Path("./data")
@property
def drug_names_file(self) -> Path:
return self.data_dir / "include.csv"
@property
def org_codes_file(self) -> Path:
return self.data_dir / "org_codes.csv"
# ... etc for all 7 reference files
def validate(self) -> list[str]:
"""Check all required files exist at startup."""
errors = []
for file_path in [self.drug_names_file, self.org_codes_file, ...]:
if not file_path.exists():
errors.append(f"Required file not found: {file_path}")
return errors
```
3. **Add logging:**
```python
import logging
logging.basicConfig(
level=logging.INFO,
format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
handlers=[
logging.FileHandler("./logs/analysis.log"),
logging.StreamHandler()
]
)
logger = logging.getLogger("PatientPathway")
# Replace all print() with:
logger.info("Starting analysis...")
logger.error(f"Failed to load file: {e}")
```
4. **Extract `generate_graph()` into smaller functions:**
```python
def generate_graph(df, filters: AnalysisFilters, config: PathConfig):
df = prepare_data(df, filters) # ~50 lines
stats = calculate_statistics(df) # ~80 lines
hierarchy = build_hierarchy(df, stats) # ~60 lines
chart_data = prepare_chart_data(hierarchy) # ~40 lines
return render_icicle_chart(chart_data, filters.custom_title) # ~40 lines
```
**Recommended project structure:**
```
project/
├── gui.py # Entry point only
├── core/
│ ├── config.py # PathConfig, AnalysisFilters
│ ├── models.py # Data models
│ └── exceptions.py # Custom exceptions
├── data_processing/
│ ├── loader.py # File/Snowflake loading
│ ├── transformer.py # Data transformations
│ └── validator.py # Data validation
├── analysis/
│ ├── pathway_analyzer.py # Patient pathway calculations
│ └── statistics.py # Statistical calculations
├── visualization/
│ └── plotly_generator.py # Graph generation
└── tests/
├── test_data_processing.py
├── test_analysis.py
└── test_config.py
```
**Add development dependencies:**
```toml
[project.optional-dependencies]
dev = [
"pytest>=8.0.0",
"pytest-cov>=4.1.0",
"mypy>=1.8.0",
"black>=24.0.0",
"ruff>=0.2.0",
]
```
**Priority tests to write:**
```python
# tests/test_data_processing.py
def test_drop_duplicate_treatments_ascending():
"""Verify first intervention kept when ascending=True."""
# ...
def test_drop_duplicate_treatments_descending():
"""Verify last intervention kept when ascending=False."""
# ...
# tests/test_config.py
def test_path_config_validates_missing_files():
"""Verify validation catches missing reference files."""
# ...
def test_analysis_filters_validates_date_range():
"""Verify start date must be before end date."""
# ...
```
### Effort Estimate
- Dataclasses and config: 1-2 days
- Logging setup: 0.5 days
- Extract `generate_graph()`: 2-3 days
- Add type hints (public API): 1-2 days
- Basic test coverage: 2-3 days
---
## Implementation Roadmap
### Phase 1: Foundation (2-3 weeks)
1. Create `PathConfig` and `AnalysisFilters` dataclasses
2. Set up logging infrastructure
3. Design and create SQLite schema
4. Migrate reference data CSVs to SQLite
### Phase 2: Data Layer (2-3 weeks)
1. Implement Snowflake connector with SSO browser auth
2. Build caching layer with TTL
3. Create data loader with fallback chain
4. Migrate `dashboard_gui.py` to use SQLite queries
### Phase 3: Diagnosis Integration (2-3 weeks)
1. Explore `data_hub.dwh.DimClinicalCoding` schema via Snowflake MCP
2. Create ICD-10 to directory mapping table
3. Implement GP diagnosis lookup using `PatientPseudo` linkage
4. Integrate into `department_identification()` as step 2
5. Add `Directory_Source` tracking column
### Phase 4: GUI Modernization (3-4 weeks)
1. Learn Reflex fundamentals
2. Recreate main window and navigation with `rx.vstack`/`rx.hstack`
3. Implement filter panels (date pickers, checkbox groups)
4. Integrate Plotly charts with native `rx.plotly()` component
5. Test with `reflex run`
### Phase 5: Quality & Polish (1-2 weeks)
1. Add type hints to public API
2. Write priority unit tests
3. Extract `generate_graph()` into smaller functions
4. Documentation and cleanup
---
## Configuration Decisions
Based on requirements, the following decisions have been made:
| Question | Decision |
|----------|----------|
| **Snowflake auth** | SSO browser login (`authenticator='externalbrowser'`) |
| **GP diagnosis data** | `data_hub.dwh.DimClinicalCoding` |
| **Patient linkage** | Use `PatientPseudo` (anonymized identifier) - NOT UPID |
| **Plotly interactivity** | Must be interactive - **Reflex has native `rx.plotly()` component** |
| **Distribution** | Python script (`reflex run`) - no .exe needed |
### Implications
**Snowflake SSO**: Connection code becomes:
```python
conn = snowflake.connector.connect(
account="your_account.region",
user=os.environ.get("SNOWFLAKE_USER"),
authenticator="externalbrowser", # Opens browser for SSO
warehouse="ANALYTICS_WH",
database="data_hub",
schema="dwh"
)
```
**Patient Linkage**: The GP diagnosis query needs to join on `PatientPseudo`, not UPID:
```sql
SELECT
cc.PatientPseudo,
cc.SNOMEDCode, -- Confirm actual column names
cc.ICD10Code,
cc.DiagnosisDate
FROM data_hub.dwh.DimClinicalCoding cc
WHERE cc.PatientPseudo IN (:patient_list)
```
**Note**: You'll need to confirm the exact column names in `DimClinicalCoding` - explore via Snowflake MCP or SQL client.
**Plotly Interactivity**: Reflex solves this elegantly with native embedding:
```python
# Interactive Plotly chart directly in the Reflex app
rx.plotly(data=State.chart_data, layout=chart_layout)
```
Full interactivity (zoom, pan, hover tooltips) works in the browser-based app - no external HTML files needed.
---
## References
- [Reflex Documentation](https://reflex.dev/docs/)
- [Reflex Plotly Component](https://reflex.dev/docs/library/graphing/plotly/)
- [Flet Documentation](https://flet.dev/docs/) (alternative)
- [Snowflake Python Connector](https://docs.snowflake.com/en/developer-guide/python-connector/python-connector)
- [NHS SNOMED CT](https://digital.nhs.uk/services/terminology-and-classifications/snomed-ct)
- [NHS ICD-10 Classifications](https://isd.digital.nhs.uk/trud/users/guest/filters/0/categories/28)