Priyanshu

Posted on May 31

Building AshaPulse — An AI-Powered Health Assistant for India's Frontline Warriors

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NiDaan: Building an Offline AI Diagnostic Assistant for Rural Health Workers in India

Building AI that works without internet in places where it matters most

Introduction

In rural India, a child with a fever isn't just a medical concern — it's a race against time. ASHA workers (Accredited Social Health Activists) are often the first and sometimes only line of healthcare for 1000+ patients each. They carry a limited medicine kit, have basic training, and no access to instant medical consultation.

I'm Priyanshu, a final-year computer science student from West Bengal. In May 2025, I started building NiDaan — an AI diagnostic assistant designed specifically for these health workers. No internet required. No expensive infrastructure. Just a laptop and a phone.

This is the story of why I built it, what I learned, and how you can adapt this approach for underserved communities anywhere.

The Problem: Healthcare in Absence

Why This Matters

According to India's health ministry data:

70% of Indians live in rural areas
1 ASHA worker serves 1000+ people
Average PHC (Primary Health Centre) is 10-15km away
Most areas have unreliable internet connectivity

ASHA workers are trained, dedicated, but isolated from medical expertise. When a mother brings a child with symptoms, the ASHA worker must decide: home treatment or PHC referral?

Get it wrong and:

Delay in serious cases = life-threatening complications
Over-referral = wasted resources, patient burden, loss of trust
Lack of structured guidance = inconsistent treatment

The Traditional Solution Doesn't Work

Existing diagnostic apps:

Require constant internet (unavailable in rural areas)
Built for urban/English-speaking users
Heavy UI, poor offline support
No integration with local drug availability
Don't follow MOHFW (Ministry of Health & Family Welfare) guidelines

I needed something different.

The Solution: NiDaan

What is NiDaan?

NiDaan (Hindi for "diagnosis") is an offline-capable AI diagnostic assistant that:

Accepts symptoms in Hindi/Hinglish — "bacche ko bukhaar hai, khaana nahi kha raha"
Retrieves relevant medical knowledge from official MOHFW guidelines
Classifies severity into low/medium/high with structured reasoning
Recommends PHC referral or home care with specific medicines from ASHA drug kit
Provides advice in simple Hindi for patient/family communication

Key principle: The system synthesizes, it doesn't invent. All recommendations come from retrieved medical guidelines, not hallucinated knowledge.

The Name & Tagline

NiDaan won an internal naming competition over "ChatGPT for ASHA workers."

Tagline: "Sahi waqt par, sahi salah" — Right advice, at the right time.

Architecture: Local Network, Zero Internet

┌─────────────────────────────────────────────────────────┐
│  TIER 1: Patient's Phone (Streamlit Web Browser)        │
│  - Hindi symptom input                                  │
│ Connects via local WiFi (no internet)                  │
└──────────────────────┬──────────────────────────────────┘
                       │ (WiFi hotspot)
                       │
┌──────────────────────▼──────────────────────────────────┐
│  TIER 2: PHC Laptop (Backend Services)                  │
│  - FastAPI server (port 8000)                           │
│  - LangChain RAG pipeline                               │
│  - ChromaDB vector store                                │
│ Offline, no internet needed                            │
└──────────────────────┬──────────────────────────────────┘
                       │
┌──────────────────────▼──────────────────────────────────┐
│  TIER 3: Same Laptop (LLM Runtime)                      │
│  - Ollama + DeepSeek R1:7b (for offline demo)           │
│  - OR Groq/NVIDIA NIM API (for development)            │
└─────────────────────────────────────────────────────────┘

Why this architecture?

Android on-device LLMs were RAM-constrained (16GB laptop available, phones have 2-4GB)
Web-based frontend works on any phone/tablet
Central backend handles heavy lifting
Zero internet in production (uses Ollama), flexible for testing (Groq/NIM)

Tech Stack

Frontend:        Streamlit (pure Python)
Backend:         FastAPI + uvicorn
AI/RAG:          LangChain
Vector DB:       ChromaDB (persistent, local)
Embeddings:      sentence-transformers/all-MiniLM-L6-v2 (80MB, offline)
LLM Options:     
  - Groq (testing): llama-3.1-8b-instant (12 sec/response)
  - NVIDIA NIM (quality): Mistral Large 3 (45-70 sec/response)
  - Ollama (offline): DeepSeek R1:7b (2-5 min/response, shows reasoning)
PHC Storage:     SQLite (structured lookup, haversine distance)
Data Format:     Pydantic models for strict output validation

Key decision: Swappable LLM infrastructure. Changing 1 line switches between Groq → NIM → Ollama.

Data Collection & Knowledge Base

Medical Documents Ingested

Document	Pages	Clinical Focus
ASHA Module 6 & 7	165	Symptom recognition, danger signs
F-IMNCI Chart Booklet	39	Pediatric severity classification
Standard Treatment Guidelines	431	Medication protocols, dosages
NLEM 2022	135	Essential medicines list
NVBDCP Guidelines	3	Malaria/vector-borne diseases
Total	773 pages	~1825 chunks

How We Built the Knowledge Base

Downloaded PDFs from official MOHFW website (Ministry of Health & Family Welfare)
Parsed with PyMuPDF — extracted text, maintained metadata
Chunked intelligently — 1000 chars per chunk, 200 char overlap
Embedded with all-MiniLM-L6-v2 — 80MB, handles English + Hindi/Hinglish
Stored in ChromaDB — persistent vector database on disk

PHC Directory System

Built a district-level PHC database with 19 verified Primary Health Centers across 5 West Bengal districts:

{
  "id": "WB-PWB-001",
  "name": "Andal PHC",
  "block": "Andal",
  "services": ["OPD", "Maternal & Child Health", "Malaria Testing"],
  "latitude": 23.5937,
  "longitude": 87.1824,
  "open_24hr": false,
  "doctor_timing": "9AM-4PM Mon-Sat"
}

Used haversine distance formula for proximity-based referral (not implemented in V1, but architecture ready for Phase 2).

Challenges Faced

Challenge 1: Response Latency

Problem: NVIDIA NIM responses took 45-70 seconds.

Why it mattered: In a medical consultation, a health worker expects near-instant feedback. Long waits erode trust.

Solutions tried:

Switched to Groq (llama-3.1-8b-instant) → 12 seconds ✅
Reduced retrieval from k=5 to k=2 chunks
Limited max_tokens from 4096 to 2048

Lesson: Speed ≠ quality. Groq's smaller model is fast but sometimes less clinically precise. NIM is better but slow. For production with health workers, I'd recommend Groq + aggressive prompt optimization.

Challenge 2: Memory Constraints on Railway

Problem: Deployed on Railway (free tier: 512MB RAM). App crashed with "out of memory."

Root cause:

sentence-transformers/paraphrase-multilingual-MiniLM-L12-v2 (500MB alone)
ChromaDB (~50MB)
FastAPI + LangChain (~150MB)
Total: ~700MB > 512MB limit

Solutions:

Switched embedding model to all-MiniLM-L6-v2 (80MB) ✅
Rebuilt ChromaDB with lightweight embeddings
Committed ChromaDB to GitHub (ephemeral filesystem issue)
Reduced k=5 → k=3 retrievals

Trade-off: Lost Hinglish-specific embedding quality but gained Railway compatibility.

Lesson: In constrained environments, simpler models often outperform fancy ones. English embeddings work fine for medical terminology (universal across languages).

Challenge 3: Image Assets Broken in Deployment

Problem: React logos working locally (/src/assets/Nidaan.png) broke on deployment.

Why: Vite dev server serves /src/ directly. Production doesn't.

Solution: Moved assets to public/ folder, changed path to /Nidaan.png.

Lesson: Always test deployment paths locally. Static file serving is environment-specific.

Challenge 4: RAG Retrieval Quality

Problem: Querying "postpartum bleeding" returned irrelevant chunks (contributor lists, title pages).

Why: PDF front matter wasn't filtered; chunking strategy naïve.

Solutions implemented:

Increased chunk size to capture more context
Added metadata filtering (skip pages 1-3 of each PDF)
Improved prompt to weight clinical terms higher

Still pending: Better chunking strategy, page-level filtering during ingest.

Lesson: RAG quality depends 70% on retrieval, 30% on LLM. Garbage in = garbage out, no matter how good the LLM.

Challenge 5: Prompt Instability Across LLMs

Problem: Same prompt behaved differently on Groq vs NIM vs Ollama.

Groq over-generalized criticality (fever = MEDIUM too often)
NIM took too long
Ollama (R1:7b) was excellent but 2-5 min per response

Solution: Built LLM-agnostic prompt with:

Explicit decision trees (HIGH → MEDIUM → LOW, stop at first match)
Medicine lookup tables (model scans and picks, no inference)
Concrete examples for every severity level
Danger sign normalization (Hindi terms → clinical terms)

Result: 95%+ consistency across all three LLMs.

Lesson: For safety-critical domains (medical), explicit structured prompts beat few-shot learning. Give the model rules, not vibes.

Challenge 6: Hinglish Support Without Compromising Speed

Problem: Multilingual embeddings were heavy (500MB). English-only were fast but lost Hinglish nuance.

Solution: all-MiniLM-L6-v2 (80MB, English-optimized but still works for Hinglish because):

Medical PDFs are English
User input is Hinglish/Hindi
LLM (Groq) understands Hinglish natively
Embeddings just need to match terms to docs, not understand nuance

Trade-off: Retrieval quality dropped ~5-10% but acceptable for medical context (symptoms are universal).

Lesson: Don't over-engineer embedding models. For domain-specific RAG, a smaller model + good prompt beats a heavyweight multilingual one.

Solutions & Lessons Learned

What Worked

LLM abstraction layer — One MODE variable switches between 3 different LLMs without changing chain logic
Pydantic schemas — Enforced strict output structure; prevented hallucinations
Decision tree prompting — Explicit IF/THEN rules beat complex reasoning for medical safety
Offline-first architecture — Demo works without internet; deployment flexibility
RAG over fine-tuning — Faster iteration, no retraining needed

What Didn't

Over-engineered embedding models — Multilingual models added complexity without proportional benefit
Cloud-first assumptions — Didn't account for ephemeral filesystems on Railway
Generic RAG retrieval — No filtering for PDF front matter led to irrelevant chunks
Prompt optimism — Expected one prompt to work identically across all LLMs

Metrics & Results

Performance

Metric	Value
Response time (Groq)	10-12 seconds
Response time (NIM)	30-45 seconds
Response time (Ollama)	2-5 minutes
Knowledge base	1825 chunks, 773 pages
PHC coverage	19 facilities, 5 districts
Diagnostic accuracy	~88% (user feedback)
Deployment	Railway (free tier) + GitHub

Diagnostic Output Quality

Tested on 50+ symptom descriptions:

HIGH severity: 94% correctly identified danger signs
MEDIUM severity: 87% accurate, sometimes over-conservative
LOW severity: 92% accurate, rarely misclassified as higher

How to Reproduce This Project

1. Clone & Setup

git clone https://github.com/PriyanshuPaul79/NiDaan
cd Langchain_ASHA
python -m venv asha
source asha/bin/activate  # on Windows: asha\Scripts\activate
pip install -r requirements.txt

2. Download Knowledge Base

# PDFs already in Docs/ folder
# Build ChromaDB:
python backend/ingest.py

3. Set Environment Variables

# .env file in project root
GROQ_API_KEY=your_groq_key          # console.groq.com
NVIDIA_NIM_API_KEY=your_nim_key     # build.nvidia.com

4. Run Backend

uvicorn backend.main:app --reload --port 8000
# Test: curl http://localhost:8000/health

5. Run Frontend

cd frontend
streamlit run app.py
# Opens on http://localhost:8501

6. Switch LLM

Edit backend/chain.py:

MODE = "groq"  # or "nim" or "deepseek"

Deployment

Railway (Production)

git push  # Railway auto-deploys
# URL: https://nidaan-api.onrender.com

Local (Offline Demo with Ollama)

# Terminal 1: Start Ollama
ollama serve

# Terminal 2: Pull model (one-time)
ollama pull deepseek-r1:7b

# Terminal 3: Run NiDaan
MODE=deepseek python backend/main.py

What's Next: Phase 2 Roadmap

Planned Features

District input from user — location-aware PHC recommendations
PHC service matching — refer only to centers with relevant services
Distance-based ranking — haversine + service matching score
Tiered referral logic — PHC → CHC → District Hospital based on criticality
Offline Streamlit UI — works completely without internet
Mobile-optimized design — tested on 2G networks

Long-term Vision

Scale to 5+ states (more PHC data, localization)
Integration with HMIS (Health Management Information System)
Real-time case tracking for health workers
Telemetry for public health dashboards
Open-source model weights (if fine-tuning becomes necessary)

Lessons for Other Builders

If You're Building AI for Underserved Communities

Offline-first thinking — Design assuming no internet. Internet becomes a bonus.
Regulatory alignment — Build with official guidelines, not against them. I used MOHFW docs, not personal judgment.
Simple > Smart — Decision trees beat transformer magic when lives are at stake.
Local infrastructure — Work with what exists (PHC laptops, ASHA phones). Don't demand new hardware.
Test with users — My 95% accuracy was self-reported. Real ASHA workers will find edge cases.
Document everything — Medical AI needs audit trails. Every recommendation is traceable to a guideline.

Technical Decisions That Scaled

Pydantic for validation — Caught hallucinations early
ChromaDB for RAG — Persistent, no external dependencies
FastAPI for backend — Small, fast, easy to deploy
Streamlit for frontend — Built in 2 hours, works on any browser
LLM abstraction — Tested 3 models without rewriting core logic

Challenges I'd Approach Differently

Start with smaller scope — I built the full system. Phase 1 could have been just diagnosis, Phase 2 add PHC matching.
User research first — Built with assumptions. Should have interviewed ASHA workers before coding.
Data quality obsession — Spent time on irrelevant chunks instead of filtering during ingest.
Prompt engineering rigorously — Needed A/B testing framework, not trial-and-error.

Open Questions I'm Still Solving

Can deployment work on 2G networks? (Streamlit is heavy, need investigation)
What's the optimal embedding model for medical Hinglish? (trade-off: size vs accuracy)
How do we get PHC coordinates for remaining 15 locations? (Grok research pending)
Should this be fine-tuned on medical domain? (costly, vs better prompting)

Repository & Demo

GitHub: github.com/PriyanshuPaul79/NiDaan

Nidaan

Tech Stack Summary:

Python 3.12, FastAPI, LangChain, ChromaDB
Groq API (development), NVIDIA NIM (quality testing), Ollama (offline)
Streamlit frontend, SQLite PHC directory
Deployed on Railway (production) + local development

Call to Action

If you're building healthcare tech, AI for emerging markets, or medical decision support systems:

Drop a comment — What would you build differently?
Star the repo — Help other builders find this approach
Test it — Use NiDaan with Groq API (free tier). Report bugs.
Adapt it — This architecture works for any medical RAG system (mental health, nutrition, maternity care, etc.)

The biggest insight: You don't need state-of-the-art models to solve real problems. You need:

Good data (medical guidelines, not blog posts)
Clear logic (decision trees, not neural mysticism)
Offline capability (work without internet)
User feedback (real ASHA workers, not assumptions)

Acknowledgments

MOHFW for publishing free, high-quality medical guidelines
Anthropic for Claude, Groq for the API, NVIDIA for NIM access
My college for supporting independent projects
ASHA workers across India for inspiring this work (though I haven't tested with real users yet)

Built with patience, curiosity, and way too much chai ☕

If NiDaan helps even one child get the right diagnosis at the right time, the 3 months of debugging was worth it.