Week 1

Question 1

List five things blood donations are tested for:

Answer 1

HIV
HBV
HTLV
HCV
ABO and Rh blood types

Also:
West Nile Virus
Syphilis
Trypanosoma cruzi (Changa Disease)

Question 2

When someone gets their blood drawn there are many components of that blood that could be used for different cases: describe four components of the blood that can be used, what they are each used for, and how long they can be stored.

Answer 2

1. RBC: trauma/surgery, severe anemia-Storage for 10yrs in freezer
2. Plasma: to treat shock from extreme blood loss or burns, correct deficiency in coagulation factors-Storage 1yr in freezer
3. Concentrate of Platelets: low platelet levels, dysfunctional platelets-Storage for 5 days room temp
4. Cryoprecipitate: fibrinogen deficiencies-Storage for 1 yr in freezer

Question 3

Standard precautions tell us to treat all human blood and certain body fluids as if they were known to be infectious for:

Answer 3

HIV, HBV, HCV and other blood borne pathogens

Question 4

List some common important Screening tests:

Answer 4

Pap (cervical cancer)
HPV (cervical cancer)
HIV
TB
PKU (PhenylKetoneUria=> impaired metabolism of Phenylalanine)
Colonoscopy (colorectal cancer, lesion, polyps)
DEXA (Dual Energy Xray Absorptiometry, bone mineral density)
PSA (Prostate Specific Antigen, could indicate prostate cancer or
inflamed prostate (or just ejaculated))

Question 5

When is a screening test most valuable (at what stage of disease can it detect imbalance)?

Answer 5

Screening tests are most valuable because the pick up on disease when it is detectable only through screening tests, but is pre-clinical(before clinical symptoms arise)

Question 6

A test is Reliable if…

A test is Valid if…

Answer 6

A test is reliable if it gets the Same result each time

A test is valid if it gets the Correct result

Question 7

Sensitivity v.s. Specificity

Answer 7

Sensitivity= True positives detected/(all people who actually had the disease aka=> true positives + false negatives)

-Sensitivity is the percentage of individuals WITH the disease who have a POSITIVE test result (how many positives did it detect out of all the positives)

Specificity: true negatives/(true negative +false positives)

-Specificity is the percentage of individuals WITHOUT the disease who have a NEGATIVE test result

Question 8

Positive Predictive Value vs. Negative Predictive Value

Answer 8

PPV = True positives/(True positives + False positives)

NPV = True negatives/(True negatives + False negatives)

Question 9

As a small 2x2 table, each quadrant labeled a,b,c,d, respective with true positive (a), False positive (b)
false negative (c), true negative (d)

Describe Sensitivity, Specificity, PPV, and NPV as equations using these letters:

Answer 9

Sensitivity = a/(a+c)
Specificity = d/(d+b)
PPV = a/(a+b)
NPV = d/(c+d)

Question 10

When establishing a diagnosis there are several different approaches. See if you can list some and point out which requires the least thought and is also the most expensive:

Answer 10

• Shotgun approach (least thought, most expensive); just run a bunch of tests and hope the results tell you something
• Hypothesis deduction
• Medical Algorithm
• Pattern Recognition

Question 11

Reference or “normal” ranges for screening tests should be taken with a grain of salt. Why?

Answer 11

A small but definite group of clinically normal persons may have undetected disease

Normal ranges are sometimes calculated from too small of a population

Population tested for normal range may not be representative of the population being tested

Normal ranges will vary between different lab techniques

Some percent of the population with the disease will have normal lab results

Question 12

Individual levels during screening may vary due to what factors?

Answer 12

Is the patient fasting?
Do the results vary depending on the time of day?
Do the results vary depending on the age or gender of the patient?

Question 13

Where do most sources of invalid results come from? Pre-analytical stage or post-analytical stage?

Answer 13

Pre-analytical errors outside of lab = 20%
-patient id and prep, phlebotomy and site prep, test collection procedures, specimen handling, storage, and processing, transport

Pre-analytical errors in lab = 40%
-registration, storage, centrifugation, distribution, sample prep

Post-analytical errors = 23%
-incorrect data entry, oral miscommunication of results, error in reporting EMR, provider does not receive results, etc….