Isabel Healthcare

What is Isabel and who sells it?

Isabel Healthcare Ltd is a UK company (Companies House 04759944) co-founded in 1999 by Jason and Charlotte Maude after their daughter Isabel was nearly fatally misdiagnosed. Jason Maude is CEO. The company is based in Surrey, and the Isabel Medical Charity became a shareholder in 2004.

Isabel sells more than one product: DDx Companion for clinicians, Self-Triage for institutions and platforms, Clinical Educator for learners, and an API. The vendor says Isabel is used in over 90 countries and available in 14 languages (isabelhealthcare.com).

What does DDx Companion do?

The clinician enters demographics and free-text or autocomplete features, drawn from more than 25,000 phrases. The tool covers over 10,000 conditions and returns a ranked list with a likelihood bar in under 90 seconds, according to the vendor. It also shows red-flag "don't miss" diseases and a check for drugs that could cause the symptoms (isabelhealthcare.com/products/isabel-ddx-companion).

It links to DynaMed and DynaMedex from EBSCO and Best Practice from BMJ. The Standard plan adds Merck Manual and PubMed links. The Premium plan adds a large-language-model layer that uses the Isabel differential as its starting point, then produces a diagnosis compare table, in English only. The vendor says this avoids the hallucination and variability of a plain LLM, which is its claim.

Self-Triage asks 11 standard questions and takes less than a minute. Isabel says DDx Companion is available in the Cerner App Gallery, that Epic clients can have info-button access, and that an API has existed since 2010. The vendor does not state HIPAA, SOC 2 or BAA status or a UK or EU medical-device class, and the FDA 510(k) database has no Isabel entry.

What does the evidence say?

The vendor claims the correct disease appears in the top ten differential with 96% accuracy. That is a vendor-reported figure with no stated validation date. A vendor press release claims 98% on journal-collected cases.

A 2025 study in Orphanet Journal of Rare Diseases (PMID 41194125) compared expert clinicians and AI in 100 rare-disease patients, setting the Isabel DDx Companion against an interdisciplinary case conference. The correct diagnosis in Isabel's top ten matched at least one conference diagnosis in 28% of cases. The authors say standalone effectiveness may be limited because the tool filters on the history entered.

A separate comparison of Isabel Pro and ChatGPT-4 favored Isabel on reproducibility and citation accuracy (PMC12169417). Against a general-purpose language model, Isabel's pitch is a repeatable differential with references, and that comparison supports it on reproducibility.

How much does Isabel cost?

Isabelhealthcare.com sells individual plans by the year: Standard at $149 (EUR 139 including VAT) and Premium at $199 (EUR 179 including VAT), as of October 2026. Students and residents pay $49 per year, except EU students, and listed emerging economies get 50% off. The site offers a free 30-day trial. Institutional and enterprise plans are by demo request with no price.

Who is it for?

A resident working up an unclear presentation can use it to check what was missed. An emergency physician can run the red-flag list on a vague complaint. A medical educator can use Clinical Educator for case-based teaching. A clinician with a rare, undiagnosed patient should not expect it to replace a case conference.

The verdict

Buy Standard at $149 a year if you are a resident or emergency physician who wants a second look at a differential, and add Premium only if the LLM compare table matters to you. Skip it if you hope it will solve a rare undiagnosed case on its own, since the one head-to-head study against a case conference matched in 28% of cases.