QUALITY CONTROL CHART

QUALITY CONTROL CHART

graphical tool used in laboratories to monitor the stability and performance of an analytical test over time

It is utilized to observe and detect analytic errors such as inaccuracy and imprecision.

GAUSSIAN CURVE

A symmetrical, bell-shaped curve that represents how data points (such as QC results) are distributed around a mean value.

CUMULATIVE SUM GRAPH(CUSUM)

A type of control chart that monitors the cumulative deviation of QC results from a target value (mean) over time

Common method: V-mask

This plot will give the earliest indication of systematic errors (trend)

It is very sensitive to small, persistent errors that commonly occur in the modern, low calibration-frequency analyzer.

1.0 or 100%

The total area under the curve is?

YOUDEN/TWIN PLOT

A two-dimensional graph used in external quality assessment (EQA) or proficiency testing

It displays the results of the analyses by plotting the mean values for one specimen on the ordinate (y-axis) and the other specimen on the abscissa (x-axis).

The points falling from a center but on the 45° line suggest a proportional error, and points falling from the center but not on the 45° line suggest a constant error.

SHEWHART LEVEY-JENNINGS CHART

A graphical QC tool where control results are plotted over time.

Shows whether the testing process remains stable or if systematic/random errors occur.

It is a graphic representation of the acceptable limits of variation in the results of an analytical method.

Widely used in internal quality control (IQC) of laboratories.

Trend

It is formed by control values that either increase or decrease for six consecutive days.

Main cause: Deterioration of reagents

Shift

It is formed by control values that distribute themselves on one side or either side of the mean for six consecutive days.

Main cause: Improper calibration of the instrument

Outliers

These are control values that are far from the main set of values

These are highly deviating values.

These are caused by random or systematic errors.

WESTGARD MULTIRULE QC RULES

A set of decision rules applied to quality control (QC) results plotted on a Levey-Jennings chart.

used the term control rule whether an analytical run is in control (acceptable) or out of control (reject, investigate).

12s

Refers to the control rule that is commonly used with a Levey-jennings chart.

Happens when a control reaches 2sd and serves as a warning

13s

Happens when one control goes to 3sd

22s

Happens when two consecututive 2sds happen

R4S

Happens when a control goes beyond the mean and into the other side

for example from -2sd into +2sd

41s

4 controls that did not reach or cross the mean

8x

8 consecutive controls that fall on one side of the mean

10x

10 consecutive controls that fall on one side of the mean

12x

12 consecutive controls that fall on one side of the mean

SIX SIGMA

It is a performance Improvement program, in which the goal is to improve the process by eliminating variations or errors: improved performance, improved quality, improved bottom line, improved customer satisfaction, and improved employee satisfaction

It is a tool that can be used to reduce laboratory errors, increase productivity and improve quality in the clinical laboratory.

Main Goal: To reduce the number of defects to near zero

SIX SIGMA DEFECTS

anything that does not meet customer requirements- laboratory result error, delay

generally measured per million opportunities (DPMO).

Sigma (σ)

standard deviation, a measure of variation

TREND

Gradual change in the analytic process

SHIFT

Abrupt change in the analytical process. Sudden and sustained change in one direction in control sample values