INTERNIST-I/ CADUCEUS

A medical diagnostic assistant expert system

Created By: Dr. Harry Pople, Dr. Jack Myers, and Randolph Miller

Goal

Cover a broad area of the internal medicine domain.Make accurate classification of the diseases that patients haveExplain what caused the disease(s)

Reasoning Like a Doctor

Try to model the method that doctors follow in diagnosisAssumptions: Doctors quickly narrow down possible

disease(s) The patient is assumed to have one

disease until otherwise shown. (reduces the search space)

The System

Task: Classification & SynthesisCode: InterLispData: 500 diseases 3500 manifestations This covers 70-75% of internal

medicine

Data Structure

Pathophysiological(causal) Model – A causal interaction of diseases,

symptoms, derangements, abnormal lab values, etc…

Nosological Structure A Taxonomy of disease (not a strict

hierarchy)

Terms

Manifestation – Findings Symptom, sign, abnormal lab

values… (Shock, Common duct stone, jaundice,…)

Disease Entity – Actual Disease Gilbert’s Disease, Viral Hepatitis, …

Causal Model

caused by

- Manifestation

- Disease States

… …

Findings (Manifestations) Disease Entities

Syndromes,pathological derangements, and other entities

A is CAUSED BY B

caused by

Causal Model

AA is a Symptom

- Manifestation

- Disease States

BB is a

Disease Entity

CC is a

syndrome

D D is a Disease EntityE

E is an Abnormal Lab Value

A is CAUSED BY B OR CA is CAUSED BY C is CAUSED BY DE is CAUSED BY D

Causal Model

Nosological Structure

INTERNIST-I

Causal Model Disease profile: (evoking strength,

frequency) Manifestation: (import value)

Method Create a list of possible diseases

evaluate the hypothesis to conclude a disease. Score = Explained – Unexplained

Manifestation*Evoking

Manifestation*Frequency

Manifestation*Import

INTERNIST-I ExampleINITIAL POSITIVE MANIFESTATIONS: + AGE GTR THAN 55 + ARTHRITIS HX + DEPRESSION HX + SEX FEMALE + THYROIDECTOMY HX + ULCER PEPTIC HX + URINE DARK HX + WEIGHT INCREASE RECENT HX + ANOREXIA …+ STOMACH BARIUM MEAL HIATAL HERNIA + DENY  INITIAL NEGATIVE FINDINGS: -ALCOHOLISM CHRONIC HX -DIARRHEA CHRONIC -FECES BLACK TARRY -FEVER -PRESSURE VENOUS INCREASED ON INSPECTION …-ESOPHAGUS BARIUM MEAL VARICES -STOMACH BARIUM MEAL ULCER CRATER -T3 RESIN UPTAKE INCREASED -T4 TOTAL BLOOD INCREASED -GO

DISREGARDING: DEPRESSION HX, WEIGHT INCREASE RECENT HX, CHEST PAIN LATERAL EXACERBATION WITH BREATHING, CHEST PAIN LATERAL SHARP, …, GLUCOSE BLOOD 130 TO 300, AMMONIA BLOOD INCREASED, ASCITIC FLUID WBC 100 TO 500, GLUCOSE TOLERANCE DECREASED  CONSIDERING: AGE GTR THAN 55, SEX FEMALE, URINE DARK, ANOREXIA, FECES LIGHT COLORED, JAUNDICE, LIVER ENLARGED MODERATE, SKIN PALMAR ERYTHEMA, …, PROTHROMBIN TIME INCREASED, RHEUMATOID FACTOR POSITIVE.  DISCRIMINATE: HEPATITIS CHRONIC ACTIVE, BILIARY CIRRHOSIS PRIMARY   

INTERNIST-I ExamplePlease Enter Findings of LIPID(S) BLOOD GO  CHOLESTEROL BLOOD DECREASED? N/A

Please Enter Findings of INSPECTION AND PALPITATION SKIN GO  SKIN XANTHOMATA? NO  Please Enter Findings of BLOOD COUNT AND SMEAR  GO  RBC TARGET(S)? NO

… CONCLUDE: HEPATITIS CHRONIC ACTIVE

DISREGARDING: DEPRESSION HX, CHEST PAIN LATERAL EXACERBATION WITH BREATHING, CHEST PAIN LATERAL SHARP, … 

CONSIDERING: WEIGHT INCREASE RECENT HX, ABDOMEN DISTENTION, ASCITIC FLUID PROTEIN 3 GRAM(S) PERCENT OR LESS ...  CONCLUDE: TRANSUDATIVE ASCITES  DISREGARDING: ... CONSIDERING: ASTERIXIS, PULSE PRESSURE INCREASED, TACHYCARDIA, AMMONIA BLOODINCREASED  PURSUING: HEPATIC ENCEPHALOPATHY  CSF FLUID OBTAINED? N/A  CONCLUDE: HEPATIC ENCEPHALOPATHY

INTERNIST-I TestingNo. of instances

Category INTERNIST-I

Clinicians

Discussants

Definitive, correct 17 23 29

Tentative, correct 8 5 6

Failed to make correct diag.

18 15 8

Definitive, incorrect 5 8 11

Tentative, incorrect 6 5 2

Total incorrect 11 13 13

Total no. errors in diagnosis

29 28 21

Total possible diagnoses 43 43 43

Problems

Knowledge-base errors Data base incomplete/omissions (2) Data base incorrect (2) Lack of anatomic knowledge (1) Failure to represent degree of severity (2)

Computer-program faults Lack of temporal reasoning (3) Failure of scoring algorithm (3) Failure to seek global overview (1) Improper attribution of findings to a concluded

diagnosis (6)

Solution: CADUCEUS

New Data Structure Combine Causal and nosologic

hierarchies

New Method: State space search with evaluation

across states. Eliminate possible areas of

hierarchies

Data Structure

CADUCEUS Results

CADUECUS is better then INTERNIST-IGets to answer faster Less consultations to the doctor Eliminates huge parts of the search

right away

Lack of temporal reasoning

Conclusion

Goal Met: INTERNIST-I and CADUCEUS do cover

a large area of internal medicine

Goal not met: Accurately classify a patients

diseases Explain systems results to the user

Questions

Combinations