# STI Tx Guide vs Diagnosaurus® DDx

The clearest difference is rating: Diagnosaurus® DDx at 4.8 against STI Tx Guide's 3.5. Diagnosaurus® DDx also leads on ratings volume (2.5K vs 36) and review sentiment (53% vs 36%). STI Tx Guide's advantage is in-app purchases (none vs 1) and update cadence (every 2 months vs every 10 months). On price, ads and iOS requirement there is nothing between them.

Both are free to download. Diagnosaurus® DDx sells 1 one-off in-app purchase. STI Tx Guide asks for nothing beyond the download.

Diagnosaurus® DDx holds the better App Store score, 4.8 against 3.5. That said, the two scores are not equally well evidenced: Diagnosaurus® DDx has 2.5K ratings behind it against 36, so its average is the more settled of the two. Written reviews point the same way: 36% of STI Tx Guide's written reviews are positive against 53% of Diagnosaurus® DDx's.

STI Tx Guide ships an update every 2 months, Diagnosaurus® DDx every 10 months. The most recent releases landed on October 23, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | STI Tx Guide | Diagnosaurus® DDx |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.5 (36 ratings)](https://appshunter.io/ios/app/sti-tx-guide/id655206856/reviews) | **[4.8 (2.5K ratings)](https://appshunter.io/ios/app/diagnosaurus-ddx/id833728910/reviews)** |
| Number of ratings | 36 | **2.5K** |
| Positive reviews | 35.7% of reviews | **53.2% of reviews** |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | **Every 2 months** | Every 10 months |
| Monetization | **Free** | Free with in-app purchases |
| Size | 36 MB | 19 MB |
| Requires iOS | 15.0 | 15.0 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod, Mac** |
| Age rating | 12+ | 17+ |
| Developer | [Centers For Disease Control and Prevention](https://appshunter.io/developer/439259253) | [Unbound Medicine, Inc.](https://appshunter.io/developer/300420400) |

## What reviewers say

### STI Tx Guide

[App page](https://appshunter.io/ios/app/sti-tx-guide/id655206856)

Provides healthcare professionals with up-to-date, evidence-based recommendations for the prevention, diagnosis, and treatment of sexually transmitted infections. Features include clinical care guidance, sexual history resources, and patient materials for effective patient management.

**Highlights:** STI prevention recommendations, Diagnosis guidance, Treatment protocols, Clinical care assistance, Sexual history resources, Patient management tools

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### Diagnosaurus® DDx

[App page](https://appshunter.io/ios/app/diagnosaurus-ddx/id833728910)

This medical reference tool assists healthcare professionals in performing differential diagnoses quickly and confidently. It offers a searchable database of over 1,000 diagnoses, cross-referenced for related conditions, and allows users to save favorite entries and make custom notes.

**Highlights:** Over 1,000 differential diagnoses, Search by organ system, symptom, or disease, See Related DDx feature, Save favorite entries, Highlight and make custom notes, Universal Index Search

**Features:** Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Diagnosaurus DDx | $4.99 | one-time |

**What reviewers like**

- 👍 User-friendly interface
- 🚀 Quick access to differential diagnoses
- 💡 Helpful for building differential diagnoses
- 👍 Comprehensive coverage of conditions
- 👍 Useful for medical students and practitioners

**What reviewers complain about**

- 🐛 Lack of in-depth information
- 🐛 Incomplete differential diagnoses
- 🐛 Lack of links to explain conditions
- 🐛 Requires in-app purchase to access full content
- 🐛 Unreliable update mechanism

**Reported bugs**

- Subscription issues and inability to restore purchases
- Blank pages and non-functional content
- Compatibility issues with newer iOS versions

**Requested features**

- Add ability to edit or add custom differential diagnoses
- Improve search functionality and navigation
- Provide more detailed information on conditions
- Integrate with other medical resources and databases
- Improve support for older devices and iOS versions


## Frequently asked questions

### Is STI Tx Guide free?

STI Tx Guide is free to download, with no in-app purchases.

### Is Diagnosaurus® DDx free?

Diagnosaurus® DDx is free to download, with in-app purchases available.

### Which has better reviews, STI Tx Guide or Diagnosaurus® DDx?

Diagnosaurus® DDx is rated higher. STI Tx Guide averages 3.5 out of 5 from 36 ratings, while Diagnosaurus® DDx averages 4.8 from 2.5K ratings.

### Do STI Tx Guide or Diagnosaurus® DDx have ads?

Neither STI Tx Guide nor Diagnosaurus® DDx shows ads.

### Which is updated more often, STI Tx Guide or Diagnosaurus® DDx?

STI Tx Guide ships an update every 2 months, and Diagnosaurus® DDx every 10 months. Most recently, STI Tx Guide was updated on October 23, 2026 and Diagnosaurus® DDx on October 24, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*