Negative controls and reagent blanks provide a means to detect contamination from reagents. Laboratories should run quality control checks on reagents prior to use in casework. These checks assist in determining if a reagent is free of contamination at that time. Negative controls can then be assessed on an ongoing basis to demonstrate that they remain contaminant free.
Including and assessing negative controls and reagents blanks are critical quality control steps. These controls provide a means of detecting reagent contamination and, on occasion, sporadic contamination. Because many contamination events are sporadic, negative results in these controls do not necessarily mean that samples from the same batch are contaminant free. Additionally, the detection of contamination in these controls does not mean that all batch samples have been affected.
Some consumables can be treated with ultraviolet (UV) light and/or autoclaved. These preventive measures may be useful in limiting contamination events. Other consumables, such as centrifugal filter units and filtered pipette tips, cannot be pretreated. In these instances, establishing a method for detecting contamination from these items is very important.
Laboratories can perform quality control checks of consumables similarly to those for reagents, but the process is not as clear-cut. Some laboratories have established procedures whereby a percentage of consumables from each lot number is evaluated prior to use in casework. This may be especially useful for laboratories that have observed contamination suspected to be from consumable products. While this approach will not prevent contamination, it can provide data from any profile(s) developed during these checks, which can be used for future evaluation of potential contamination events.
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