The Diagnostic

Process

A BRIEF OVERVIEW

diagnostic

process

What is it?

•to figure out•to problem solve

•method•scheme

Define Problem

Gather Evidence

Form Hypothesis

Test Hypothesis

KNOWLEDGE

KNOWLEDGE

Define Problem

Test Hypothesis

Form Hypothesis

Patient’sComplaint

Gather Evidence

HistoryPhysical

Lab

DifferentialDiagnosis

TreatmentMEDICAL

KNOWLEDGEBASE

“The specific intervention (treatment) is less important to the [patient’s] outcome than the process of the interaction.”

The Science of Medicine

Units of observation

Quantities of measurement

Instrument for obtaining measurement

Signs and symptoms

Words and sometimes numbers

collecting the database:

Gathering Information

ValidReliableDiscriminatory

characteristics of good data:

ValidValid

Appropriate to the problem

Reliable:Reliable:Objective

– free from misinterpretation based on bias or feeling

Precise – represent the true data

Reproducible– different observers obtain the

same results

SensitiveSensitive::– able to pick-up or detect real disease

Specific:Specific:

Discriminatory:Discriminatory:

– able to rule-out disease in healthy people.

Gathering Information

medical historyphysical

examinationdiagnostic testingtreatment outcome

the clinical database:

Medical History:Medical History:

Validity

Reliability

80% of diagnoses can be made by history alone

subjective nature of symptoms; subject to patient interpretation.

poor from patient to patient for a given condition+/- for same patient on separate occasions

Physical Exam:Physical Exam:

Reliabiliy

Validity

Objectivity -good; direct observation

Precision +/- ; open to interpretation

+/- some diseases are not detectable on physical exam.

Diagnostic Studies:Diagnostic Studies:

Objective

Validity

usually free from interpretation errors

some diseases do not produce measurable changes

The Science of Medicine

Units of observation

Quantities of measurement

Instrument for obtaining measurement

Signs and symptoms

Words and sometimes numbers

collecting the database:

You

Clinician Characteristics

ValidReliable

– Objective– Precise– Reproducible

Discriminatory– Sensitive– Specific

qualities of a useful measuring tool:

ValidValid

Appropriate to the problem

does the interviewer have a high enough index of suspicion to

consider the possibility that a problem may exist

Objectivity:Objectivity:

Removing one's own beliefs, prejudices, and preconceptions from observations.

Precision:Precision:Using units of measurement (words) that are unambiguous and sufficiently detailed to indicate the real data.

Sensitivity:Sensitivity:

ability to pick-up or detect real disease

ability to rule-out disease in normal people.

Specificity:Specificity:

Discrimination:Discrimination:

Reliability:Reliability:the ability to get the same result

on repeated measures (reproducibility)

the ability of different observers (interviewers) to get the same results.

“… interviewing skills that maximize objectivity and precision produce more accurate data and reduce the rate of false positive and false negative

histories.”

One of the essential qualities of the clinician is interest in humanity, for the secret of the care of the patient is in caring for the patient.

Francis Peabody 1923

More mistakes are made in medicine by people who don't care than by people who don't know.

Allen Gregg