SI- Diagnosis

diagnosis

the process that labels patients, classifies their illnesses, and that propels us toward specific treatments in the confidence that they will do more good than harm

Medical Diagnosis

-traditionally: the role of the physician/ geared toward identification of pathology

-imaging studies

-blood work

-tissue culture

Diagnosis examination

-patient history

-systems review

-physical examination

-tests and measures

diagnosis evaluation

-clinical judgment

-synthesis

-decision and/or action

evidence based approach

knowing how to select and interpret diagnostic tests in order to confirm or exclude a diagnosis

based on: precision, accuracy, expense, safety

goals of evidence based approached

1. assess the quality of diagnostic study

2. introduce quantitive interpretation of diagnostic accuracy

3. decide- can the dest be applied to confirm or exclude a suspected diagnosis

Diagnostic Study

P- population of patients of interest

D- diagnostic test being studied

R- reference standard

A- accuracy of diagnostic test

P in diagnostic study

population or patients of interest

D in diagnostic study

Diagnostic test being study

R in Diagnostic study

Reference Standard

A in Diagnostic study

accuracy of diagnostic test

population descriptors

Demographic descriptors: age, sex

Include those with suspected target disorder: type of disorder, severity of disorder, diagnostic dilemma

diagnostic test

well described - needs to be repeatable

adequate rationale for test

Reference standard

gold standard, criterion standard, diagnostic standard

result is accepted as “the diagnosis'‘

if it is unacceptable, study is invalid

accuracy

number of correct matches- reference and diagnostic tests agree: both positive, both negative

number of incorrect matches- reference and diagnostic tests disagree: one positive and one negative

sensitivity

tells the clinician how good the test is a correctly identifying patients with the condition of interest. ability of a test to detect true positives

proportion of patients with the target disorder and positive diagnostic test result

indicates how often a diagnostic test detects a disease or condition when it is present

specificity

tells the clinician how good the test is at correctly identifying the absence of disease. ability of a test to detect true negatives

proportion of patients without target disorder and negative diagnostic test result

likelihood ratios

combine sensitivity and specificity into a single measure that better reflects how much a test result changes the probability of a disease being present or absent

quantifies relationship- pretest odds or probability, test result (+or-), post-test odds or probability

positive LLR

how much more likely a positive test result is in someone with a desease compared to someone without it. “rules in”