General Clin Chem

Question 1

Reference intervals (define / purpose)

Answer 1

“Interval of values w/in which the MAJORITY of the HEALTHY patient values lie”

-used for making comparisons

Question 2

How are reference intervals established?

Answer 2

1. Choose selection criteria (healthy)
2. Obtain representative values from ~120 animals
3. Include 95% (mean +/- 2SD)

Question 3

What are some considerations in establishing intervals?

Answer 3

Top 2 = “Healthy” & Same species

Animal factors

1. healthy
2. Demographics –species, age
3. Environmental –Diet, fasted, Excitement

PreAnalytical Factors

1. Specimen collection
2. Handling -time til analysis, storage condition

Laboratory Factors

1. Analytical Factors –instrument, method, reagents, calibration
2. Statistical methods used –bell vs skewed population

Question 4

Meaning of 3rd SD value

Answer 4

Bc only 95% of healthy patient numbers are w/in the interval, there is 5% that is not (even tho they are healthy)–these animals are in the 3rd SD

Question 5

How to distinguish 3 SD value from True positive.

Answer 5

True positive will usuallyhave:

• HIGHER abnormalities
• SUPPORTING test data
• CLINICAL SIGNS associated

Question 6

Biochemical profiling (define / advantage & disadvantage)

Answer 6

“Grouping related/complementary clinical chemistry tests together”

Advantages

1. consistant, orderly approach to interpretation
2. Integrate data (ex. elytes + acid base)
3. increased confidence in results (supporting tests)
4. increased discrimination (high BUN w/ normal Creatinine –Possible 3rd SD?)

Disadvantage

1. More tests–> more false positives
2. Cost

Question 7

Advantage of sequential data

Answer 7

-Diverse population –> wide range –> decrease sensitivity for dz detection
Doing self tests, limits the diversity of the population and therefore makes small changes in values more significant