Quality Control

quality assurance

system that encompasses preanalytical, analytical, and postanalytical factors

quality control

a system for recognizing and minimizing analytical errors

it monitors analytical processes, detects analytical errors and prevents the reporting of incorrect pt values

QC is one component of a QMS program

quality management system

approach that focuses on process improvement that encompasses all management activities needed to support the lab’s QA and QC

continuous quality improvement

activities designed to evaluate and improve quality pt care

a part of QMS used to determine and address the causes of problems identified by QA and QC

statistics

science of gathering, analyzing, interpreting and presenting data

standard deviation

commonly used equation used to calculate the dispersion of groups of data

coefficient of variation

equation that compares similar data using the SD and mean

Levey-Jennings Chart

a visual representation of plotted data points

random error

error that occurs by chance

can be positive or negative

EX) air bubbles in reagent line, different techniques, specimen characteristics

systemic error

type of analytical error that makes results continuously higher or lower than the actual value

EX) poorly made reagents, failing instruments, poorly written procedure

reference intervals

ranges calculated using the SD

quality control reference ranges

established using control materials

normal pt reference ranges

ranges established using normal pt specimens

drs use to determine the health of pts

standards

solutions of known concentration used in calibration

reference materials/calibrators

controls

substances that closely resemble simulated specimens in physical and chemical characteristics

chemistry: 2 levels, immunochemistry: 3 levels

accuracy

closeness of results to true value

precision

closeness of results to each other

trend

gradual rise/decline in analyzed values away from the mean

shift

sudden change in plotted data falling to one side of the mean

Gaussian distribution curve

the normal distribution curve, bell-shaped, shows results of plotted data

dispersion

spread of data

What is the purpose of QA

to ensure quality pt outcomes throughout the total testing process

why must QC be performed on every procedure

the controls monitor the procedures and detect analytical errors

how many test values are needed to establish reference ranges

20

what % of data fall under SD

1 SD: 68.2%

2 SD: 95.5%

3 SD: 99.7%

what is the purpose of a Levey-Jennings chart

a visual representation of how well a procedure is in control

clinically significant pt shift

a change in reported pt results that is different enough to possible affect the pt’s diagnosis or treatment

Westgard rules

list specific limits on how much error is acceptable in control values before pt test results are rejected

how does the lab use westgard rules

need to analyze two different levels of controls (abnormal and normal) with pt specimens

what happens when QC is out of control

pt results are not to be reported until QC is back in control

proficiency testing

external quality control programs where labs are sent unknown samples, analyze them, and report back to the program. The results are compiled and compared to other labs

point of care testing (POCT)

analytical testing performed outside the lab (lab testing goes to pt)