Quality Control and Assurance

Gaussian Distribution

Normal, symmetrical distribution around the mean

Gaussian distribution is assumed for all ______ statistics.

quality control

Confidence intervals are the limits between we expect a specified ______ of a population to lie.

proportion

The percent coefficient of variation (%CV) is ______ expressed as a percent.

SD

%CV allows comparison of variation between two sets of data/methods that have different ______.

means

The higher the %CV, the more ______ is expected with those results.

variation

Sensitivity is ______ related to specificity.

inversely

What are the two types of sensitivity?

Analytical and clinical

Analytical sensitivity is the ability of a test to detect the analyte regardless of its ______.

amount (limit of detection)

Clinical sensitivity is the assay's ability to correctly identify patients ______ a disease.

with

Clinical sensitivity is like a ______.

screening

Clinical sensitivity equation

TP/(TP + FN)

Analytical specificity is the ability of a test to detect the ______ analyte.

intended

Clinical specificity is an assay's ability to correctly identify patients ______ as negative.

without

Clinical specificity is like a ______.

confirmation

Clinical specificity equation

TN/(TN + FP)

The prevalence compares what two things?

positive and negative predictive value

Prevalence is dependent on ______.

population

Analytical sensitivity/specificity are both ______ specific.

lab

What are the consequences of a false negative?

- Delay treatment

- Can spread disease

- Worsening disease

What are the consequences of a false positive?

- Stress

- Unnecessary treatment

- Legal action (illegal drug use)

Linearity is the relationship between ______ and ______ values over the range of analytical measurements.

measured, expected

Analytical range of method is the ______ and ______ test results that are reliable and can be reported.

lowest, highest

A control material is run in large batches (50-100 samples) to get a ______.

reference range

Often, a ______ of control material is used for analytical testing.

combination

An analyte standard has a known concentration and is used for ______.

calibration

The ______ of a control is plotted on a chart.

concentration

A known control needs to be determined if it is ______ or ______.

normal, abnormal

If a control is unknown, it will need to be ______.

identified

A ______ is when a patient result is compared to a previous result from the same patient.

delta check

An analyte used in a delta check should be ______ in healthy individuals.

stable

Delta checks can be reported as an ______ or ______ between values.

absolute number, % change

A Levey-Jennings chart is a visual indication of if a test is ______.

working well

On a Levey-Jenning chart, a perfect control would show 8-9 points between the ______ limits and ______ limits on each side of the mean.

1s, 2s

A ______ is an abrupt change in data pattern.

shift

A ______ is a gradual change in the pattern of data points.

trend

If data is rejected from Westgard rules, the patients results are ______ until the problem is fixed.

not reported

1(2s) Westgard Rule violation

1(3s) Westgard Rule violation

R(4s) Westgard Rule violation

2(2s) Westgard Rule violation

4(1s) Westgard Rule violation

10x Westgard Rule violation

Which Westgard Rule violations are due to random error?

- 1(2s)

- 1(3s)

- R(4s)

Which Westgard Rule violations are due to systematic error?

- 2(2s)

- 4(1s)

- 10x

Accuracy is the ability of an analytical method to obtain true/correct results after a number of ______.

replicates

Precision is the ______ of a method.

reproducibility

The narrower a distribution of results after a number of replicate analyses, the ______ the precision.

better

______ is the amount by which analysis varies from the correct result.

Bias

Example:

Expected value = 50

Result value = 47

Bias = ______.

3 units

What are the 3 types of error in the clinical lab?

Pre-analytical, analytical, post-analytical

Examples of pre-analytic error

Test order entry, pt. identification, specimen collection/transport, etc.

Analytical error is associated with the performance of the ______.

method/instrument

What are the two types of analytical error?

Random and systematic

Random analytical error affects ______ of the result.

reproducibility

What are some causes of random analytical error?

Air bubbles in reagent, improperly mixed reagents, imprecise pipette, etc.

Systematic analytical error causes a shift to the ______ over time.

mean

Systematic analytical error is ...

Constant and porportional

Systematic analytical error is caused frequently by ______.

instrument calibration

What are some examples of systematic analytical error?

Interfering substances, deterioration of reagents/calibrators/photometric light source, etc.

Post-analytical error occurs when the results are ______.

reported/released

What are some examples of post-analytic error?

Transcription mistakes, using wrong units, delays, etc.