Intro to Quality Control (Medialab)

Which of the following is NOT a Westgard rule violation and would not be a cause for rejecting a QC run? - 12S - 13S - 22S - R4s

12S

systematic / random error: 13S

random

unassayed / assayed control : Not linked to specific method systems

unassayed control

Which of the following types of controls can be used to measure accuracy of a laboratory's methods? - Assayed commercially prepared control - Unassayed commercially prepared control - Patient samples tested in duplicate

- Assayed commercially prepared control - Unassayed commercially prepared control

Which of the following may be included in a quality control plan? - Method for recording patient test results - Proficiency testing guidelines and requirements - Procedures for troubleshooting QC errors

- Proficiency testing guidelines and requirements - Procedures for troubleshooting QC errors

Random error affects the precision of a test (reproducibility). Some things that could cause random errors are:

- bubbles in reagents or reagent lines - instrument instability - temperature variations - operator variability, such as variation in pipetting

Systematic error causes inaccurate results that are consistently low or high. Some things that could cause systematic errors include:

- change in reagent lot - change in calibration - assigning the wrong calibrator values - reagents that were improperly prepared or are deteriorating - pipettor maintenance error - deteriorating photometric light source in instrument

There are two types of errors that one should look for when examining quality control charts. What are they?

- random errors - systematic errors

Which of the Westgard multi-rules does the following control data violate?

13S

Which of the Westgard rules have been violated according to the control charts shown below that represent 2 levels of daily controls for 10 days? (choose all that apply)

13S, R4S

What is the mean of the following data set? 15, 16, 18, 16, 14, 10, 20, 12, 14

15

Which of the Westgard multi-rules does the control data violate?

22S

What is the standard deviation of the following data set, rounded to the nearest whole number? 15, 16, 18, 16, 14, 10, 20, 12, 14

3

For a certain method, a control has a mean result of 12 with a standard deviation (SD) of 2. What is the acceptable 95% range for this control?

8-16

Which of the following best describes random error? - Results may be either above or below the mean. - Results will consistently be below the mean. - Results will consistently be above the mean.

Results may be either above or below the mean.

Ideally, what testing should be done prior to starting a new lot of control material in order to establish its mean and standard deviation?

Should be tested at least 20 times over 20 days

If a commercial lyophilized reagent is diluted using slightly more water than indicated, what type of error will occur?

Systematic

accuracy / precision: - Systematic errors will affect a system's accuracy. - Bias is an estimate of systematic error.

accuracy

accuracy / precision: refers to the closeness of the measured quantitative value to the reference value.

accuracy

unassayed / assayed control : Have assigned analyte values provided by the manufacturer of the control material

assayed control

unassayed / assayed control : May only be suitable for certain method systems

assayed control

______________: A measure of imprecision that is expressed as a percentage

coefficient of variation

T/F: If a laboratory is part of a system, it can compare its proficiency testing (PT) results with other laboratories in the system prior to submitting the results to the PT provider.

false

The standard deviation will be larger / smaller if the data are spread out and smaller if the data are closely clustered about the mean

larger

______________: The average of the data points

mean

accuracy / precision: - Random errors will affect a test system's precision. - Standard deviation and coefficient of variation are measures of imprecision.

precision

accuracy / precision: refers to the agreement of results upon replicate testing of a material or similar material under specified conditions.

precision

systematic / random error: R4S

random

______________: are statistical fluctuations (in either direction) in the measured data due to the precision limitations of the measurement device

random errors

______________: Relates to the distribution of the control results around the central point

standard variation

systematic / random error: 22S

systematic

______________: by contrast, are reproducible inaccuracies that are consistently in the same direction. Systematic error is more subtle and harder to detect.

systematic errors

unassayed / assayed control : Generally less expensive

unassayed control