Intro to Lab Medicine Med Terms

Question 1

Reference Range

Answer 1

range of values within a population of people who do NOT have a given disease
- upper and lower limits
- usually central 95% (5% of people without disease fall outside of reference range)
- aka standard range or “normal range”

Question 2

Desirable Range

Answer 2

• prognosis-related ranges
• associate laboratory results with clinical outcomes

Question 3

Therapeutic Range

Answer 3

• measures effectiveness of medication
• screens for possible toxicity due to medication

Question 4

Threshold

Answer 4

for certain lab tests, presence of disease is associated with a value above a given THRESHOLD
- there can be overlap in values between those with disease and those without disease

Question 5

Sensitivity

Answer 5

focuses on population of individuals who have the diseases**
- capacity to identify individuals with the disease
- many screening tests have high sensitivity (low diagnostic threshold), which leads to potential for false positives

Question 6

Sensitive Test

Answer 6

low diagnostic threshold (higher false positives)
- detects disease in people who have it, but may be + in healthy people (false positive)

Question 7

Specificity

Answer 7

focuses on population of individuals without the disease
- everyone without the disease would have a negative result in an effective test

Question 8

Specific Test

Answer 8

high diagnostic threshold (higher false negatives)
- healthy people have a normal/negative result, but may miss the disease in someone who has it (false negative)

Question 9

Positive Predictive Value

Answer 9

focuses on people with a + test result
- likelihood that a positive test result identifies someone WITH the disease
- ex: TB test in a community with a lot of TB cases

Question 10

Negative Predictive Value

Answer 10

focuses on people with a - test result
- likelihood that a negative test result identifies someone WITHOUT the disease
- ex: D-dimer for pulmonary embolism

Question 11

Prevalence

Answer 11

number of existing cases in a population
- usually expressed as a % of the population
- ex: 48% of American adults have hypertension (high BP)

Question 12

Incidence

Answer 12

number of new cases occurring within a period of time
- usually within one year
-ex: sore throat (many new cases each year!)

Question 13

Reasons for Ordering Lab Tests

Answer 13

1. Diagnosis of disease -> proper treatment
2. Monitoring of Disease/Interventions
3. Screening for Disease
4. Research
   bottom line: answering clinical questions

Question 14

Questions to Ask Before Ordering Lab Tests

Answer 14

1. Why is this test being ordered?
2. What are the consequences of not ordering the test?
3. How good is the test in discriminating between health vs disease?
4. How are the test results interpreted?
5. How will the test results influence patient management and outcome?

Question 15

Laboratory Testing Cycle

Answer 15

1. Pre-Analytic Phase
2. Analytic Phase
3. Post-Analytic Phase

Question 16

Pre-Analytic Phase

Answer 16

where prepping and getting the sample occurs
most errors occur in this stage of testing process
ways to avoid errors:
- ask the right questions
- use the right supplies
- label a sample correctly
- handle and transport sample correctly
- obtain proper quantity of sample
- order the test properly

Question 17

Factors Impacting Test Results

Answer 17

1. Biological: age, sex
2. Behavioral: diet, BMI, smoking, alcohol intake, caffeine intake, exercise, stress
3. Clinical: diseases, drug therapy, pregnancy
4. Specimen Collection & Handling

Question 18

Hypothesis Deduction

Answer 18

use H&P to formulate differential diagnosis, then select labs likely to confirm a diagnosis

Question 18

Pattern Recognition

Answer 18

comparing patient’s pattern for results for several laboratory tests
- medical algorithms
- logical and sequential
- maximize clinician’s efficiency
- can minimize ordering unnecessary tests

Question 19

Rifle vs Shotgun Approach

Answer 19

A. Rifle: ordering a specific test based on diagnostic accuracy and predictive value
B. Shotgun: indiscriminately order a large number of tests

Question 20

Clinical Diagnosis is based on…

Answer 20

1. Thorough hx and physical exam
2. Pt demographics
3. Dz incidence and prevalence
4. Critical thinking
5. Pattern recognition
6. Diagnostic tests/labs (only if needed)

Question 21

Best Practices

Answer 21

• if there is a screening test available order that first (usually cheaper)
• limit tests to those relevant to patient’s presentation
• avoid taking blood fro someone already very sick
• unnecessary tests can lead to more testing!