QA and QC

MLT 114

What stage of QA may have the most errors?

Pre-analytical phase

What is QA?

Quality assurance that ensures reliability of results

What is accuracy?

Reliability, the closeness of values being the actual/true value

What is precision?

Reproducibility, if a test was repeated, how close to the same value would it be?

What is inherent variability?

The expectation that no method would give the exact same result each time. These errors are not significant in reporting results

What is normal distribution?

The distribution of values that fall within normal references based on the mean, median, and mode

What is a Gaussian curve?

A bell-shaped graph displaying the normal distribution with 68% of expected results in the middle of the curve and 99.7% of expected results to fill the length of the curve

What is the mean/average?

The sum of all values divided by number of values

What is the median?

The middle value of all values organized numerically. If two values are central, take the average of the two values.

What is mode?

The most occurring value

What is the range?

Highest value minus lowest value, or displayed as a low to high range

What is standard deviation?

Defines the degree of imprecision, the higher SD = the lower precision of a method

What is the SD formula?

How do you calculate ±1SD, ±2SD, and ±3SD?

±1SD: Mean + and - 1(SD)

±2SD: Mean + and - 2(SD)

±3SD: Mean + and - 3(SD)

What does ±1SD represent?

68% of results fall within ±1SD 

What does ±2SD represent?

95% of results fall within ±2SD

What does ±3SD represent?

99.7% of results fall within ±3SD

How is a reference range established?

Take the range of values that fall within ±2SD (95% of results)

What are the confidence limits?

68%, 95%, and 99.7% as calculated by SD

What is the coefficient of variation (CV)?

Expresses SD as a percentage and is used to compare SD values to find the most accurate method

Method 1 has an SD of 5

Method 2 has an SD of 4

Which method is most precise?

Method 2

Method 1 has a mean of 100mg/dL and an SD of 2.5mg/dL

Method 2 has a mean of 5.0mg/dL and an SD of 0.5mg/dL

Which method is more precise?

Method 1

How is the CV calculated?

(SD/mean) x 100

What is inherent change?

A minor change in reproducibility that could indicate either an inherent error, or that a method/treatment isn’t effective

What is a real change?

A significant change in reproduced results that could indicate a treatment is working

What does “QC is in” mean?

When QC results fall within acceptable limits

What does “QC is out” mean?

When QC results fall out of the acceptable QC range, and results cannot be reported.

Improper pipetting, improper sample mixing, and fluctuations in temperature are examples of what kind of error?

Random error

What sort of variance in results derive from a systematic error?

Trends and shifts

Accumulation of debris in tubing, aging reagents, deterioration of controls, deterioration of light source, are examples of what kind of error?

Systematic trend error

A change of reagent or lot, instrument maintenance, change in room temperature, inaccurate calibration, are examples of what kind of error?

Systematic shift error