Quality control samples are special specimens inserted into the testing process and treated as if they were patient samples by being exposed to the same operating conditions. The purpose of including quality control samples in analytical runs is to evaluate the reliability of a method by assaying a stable material that resembles patient samples. Quality control is a measure of precision or how well the measurement system reproduces the same result over time and under varying operating conditions.
Quality control samples are special specimens inserted into the testing process and treated as if they were patient samples by being exposed to the same operating conditions. The purpose of including quality control samples in analytical runs is to evaluate the Assayed controls definition of a method by assaying a stable material that resembles patient samples.
Quality control is a measure of precision or how well the measurement system reproduces the same result over time and under varying operating conditions. Pathologists need to be involved in development of quality control protocols, the selection of quality control materials, long term review of quality control data, and decisions about repeating patient samples after large runs are rejected.
These quality control activities play an important part in assuring the quality of laboratory tests. Quality control material is usually run at the beginning of each shift, after an instrument is serviced, when reagent lots are changed, after calibration, and when patient results seem inappropriate.
A quality control scheme must be developed that minimizes reporting of erroneous results, but does not result in excessive repitition of analytical runs.
The manufacturer should recommend in their product labeling the period of time within which the accuracy and precision of the instruments and reagents are expected to be stable. Each laboratory should use this information to determine their analytical run length, taking into consideration sample stability, reporting intervals of patient results, cost of reanalysis, work flow patterns, and operator characteristics.
The user's defined run length should not exceed 24 hours or the manufacturer's recommended run length. Quality control samples must be analyzed at least once during each analytical run. Manufacturers should recommend the nature of quality control specimens and their placement within the run.
Random Assayed controls definition of quality control samples yields a more valid estimate of analytical imprecision of patient data than fixed placement and is preferable. Quality control materials should have the following characteristics.
They should have the same matrix as patient specimens, including viscosity, turbidity, composition, and color. For example, a method that assays serum samples should be controlled with human serum based controls.
Quality control material should be simple to use because complicated reconstitution procedures increase the chance of error.
Liquid controls are more convenient than lyophilized controls because they do not have to be reconstituted. Controls should have minimal vial to vial variability, because variability could be misinterpreted as systematic error in the method or instrument.
Quality control materials should be stable for long periods of time. Controls with short shelf lives necessitate frequent reordering and verification against the outgoing material, creating more unnecessary work.
Quality control material should be available in large enough quantities to last at least one year. Purchasing a large batch decreases the number of times that control ranges have to be established.
Controls should have target values that are close to medical decision points. Quantitative tests should include a minimum of one control with a target value in the healthy person reference interval and a second control with a target value that would be seen in a sick patient. If three control levels are run, an abnormally low patient range should be included.
Quality control levels for therapeutic drug monitoring should mirror therapeutic, toxic, and trough values. If a test is qualitative, giving either negative or positive results, a negative control and a weak positive control with a concentration at the lowest detectable level are recommended.
Both assayed and unassayed control material are available. Assayed controls are measured by a reference method and sold with published target values.
They are more expensive than unassayed controls and are not cost effective for routine quality control in a hospital or reference laboratory.
Assayed controls are recommended for physician office laboratories. Unassayed controls must be analyzed by the laboratory to determine the target value and acceptable range.
Comparison studies need to be run between the current and new unassayed control materials. If the new control material is from the same manufacturer, only five samples of the new control material need to be run to establish a mean. If the mean is close to the mean of the outgoing quality control material, the new control material can be accepted.
No data points should be excluded unless they are known to be result of operational errors. The standard deviation of the outgoing controls is adopted for use until enough data points are collected for calculation.
Interpretation of quality control data involves both graphical and statistical methods. Quality control data is most easily visualized using a Levey-Jennings control chart.
The dates of analyses are plotted along the X-axis and control values are plotted on the Y-axis. The mean and one, two,and three standard deviation limits are also marked on the Y-axis. Inspecting the pattern of plotted points provides a simple way to detect increased random error and shifts or trends in calibration.
With a correctly operating system, repeat testing of the same control sample should produce a Gaussian distribution. This means that 1 data point in 20 should fall between either of the 2 s and 3 s limits and 1 data point in will fall outside the 3 s limits in a correctly operating system.Both assayed and unassayed control material are grupobittia.comd controls are measured by a reference method and sold with published target grupobittia.com are more expensive than unassayed controls and are not cost effective for routine quality control in a hospital or reference grupobittia.comd controls are recommended for physician office.
Define unassayed. unassayed synonyms, unassayed pronunciation, unassayed translation, English dictionary definition of unassayed. adj 1. untried; not attempted 2. not subjected to an analysis or experiment Regardless of whether you use an 'assayed' control or an unassayed Part 2.
Both Immunotrol[TM]controls are supplied in . Controls and Assay Validation. Assay Validation particular definition for PCR assays (discussed shortly). Basic Lessons in Laboratory Quality Control Written by Greg Cooper, CLS, MHA Manager of Clinical Standards and Practices Published by Bio-Rad Laboratories, Inc.
Assayed and Unassayed Controls Assayed controls have been analyzed by the manufacturer so that the range of values for the analytes they contain is known. Unassayed controls are unknowns.
Basic Lessons in Laboratory Quality Control Written by Greg Cooper, CLS, MHA Manager of Clinical Standards and Practices Published by Bio-Rad Laboratories, Inc.