22. Diagnosis, Screening, and complications of Overuse

Question 1

symptoms

Answer 1

• sensations that are abnormal
• we all have them, all of the time
• rarely due to disease
• patients vary in sensitivity or interest in reporting

Question 2

disease

Answer 2

“condition that impairs normal functioning and typically manifested by signs and symptoms

• ICD-9/10 for $
• can be asymptomatic
• many ‘diseases’ not well defined (eg back pain, baldness, etc)
• job is to make patients better….so only diagnose if it helps, otherwise it is symptom management

Question 3

testing

Answer 3

• common
• recent development
• ideally reduce uncertainty
• tests are often helpful, but few tests are perfect (need to be ordered appropriately)
• test results can harm

Question 4

sensitivity

Answer 4

ability to identify all WITH disease

• proportion of persons with a disease who have a POSITIVE test
• = TP/(TP+FN)
• people with disease = TP + FN

Question 5

specificity (general definition)

Answer 5

only identify the disease (not negatives); those WITHOUT disease

• proportion of persons without disease who have a NEGATIVE test
• = TN/(TN + FP)
• people without disease = TN + FP

Question 6

what is a true positive?

Answer 6

test positive and disease present (a)

Question 7

what is a true negative?

Answer 7

test negative and disease absent (d)

Question 8

what is a false negative?

Answer 8

test negative and disease present (c)

Question 9

what is a false positive?

Answer 9

test positive and disease absent (b)

Question 10

pre test probability

Answer 10

probability of disease before any diagnostic testing (based on clinical symptoms) = PREVALENCE
- small pre-test probability means the disease is unlikely

Question 11

positive predictive value

Answer 11

how likely you are to have disease if you test positive = a/(a+b) = TP/(TP+FP) = true positives/all positives

Question 12

**sensitivity and specificity are properties of the ______, predictive values vary according to ________.

Answer 12

test; population tested

Question 13

what comes with diagnosis?

Answer 13

• reassures/worries patients and providers
• requires follow up testing/procedures
• limits uncertainty of providers
• identifies possible treatments
• provides guess at prognosis
• illness condition for patient to view of self
• (insurance)

Question 14

screening vs diagnostic tests

Answer 14

screening test: identify people at LOW RISK

• maximizes SENSITIVITY (few with disease are missed)
• NO symptoms***

diagnostic test: determine who among those at risk ACTUALLY HAS DISEASE

• maximizes SPECIFICITY (few false positives)
• SYMPTOMS

Question 15

levels of prevention

Answer 15

• primary: before disease (prevent disease, eg flu shot, abstinence/condoms)
• secondary : with disease, no symptoms
• tertiary: after symptoms, improve outcomes

Question 16

criteria for screening

Answer 16

• important health problem
• acceptable form of treatment
• natural history understood (needs to be a mild stage where the disease can be prevented)
• recognizable latent stage (can distinguish from normal)

Question 17

can a test be used for screening and diagnosis?

Answer 17

yes - eg chlamydia NAAD is diagnosis for a teen with discharge or screening for an asymptomatic, sexually active teen

Question 18

what is the detectable pre-clinical phase?

Answer 18

period between when a disease is detectable by screening test and when it is detectable by the patient (symptoms)

Question 19

Bayes’ Theorem

Answer 19

• more simple than it seems
• interpretation of new information depends on what you already know about the patient
• converts pre-test likelihood of disease to post-test likelihood of disease

Question 20

bottom line for a screening program?

Answer 20

does it improve outcome (survival/quality of life)?

what harm does it cause?

Question 21

overuse

Answer 21

• medical care in which harms outweigh benefits
• when benefits are negligible
• when fully informed patients would forego medical care (includes overdiagnosis and overtreatment)

Question 22

overdiagnosis

Answer 22

diagnosis of abnormalities not related to disease (false positives)

Question 23

overtreatment

Answer 23

• overdiagnosed with disease
• wrong practice
• unwanted care

Question 24

cascade events

Answer 24

findings not related to presenting problem that leads to more testing or procedures

Question 25

why is overuse important?

Answer 25

• patient safety (avoiding harms and treating appropriately)
• patient satisfaction (less burden of care)
• artificial elevation of rates, problems with comparisons, costs

Question 26

problems with tests

Answer 26

• false-negatives
• false-positives
• overdiagnosis
• cascades (incidentalomas)

Question 27

for a rare disease with no symptoms, what is necessary in the screening test/

Answer 27

minimize false +