How do I know my pipettes are accurate?
Clinical labs should calibrate their pipettes before putting them into service, and calibrate and perform preventive maintenance on them periodically thereafter. Vendors calibrate pipettes before shipping them to laboratories, providing documentation at that time about a pipette’s bias and imprecision, as well as the method used to calibrate it.
A pipette’s bias and imprecision must meet a laboratory’s requirements, and laboratories should archive vendors’ certificates with this information. Labs also need to document their vendor’s shipping method to ensure the method had a low risk of impacting pipette calibration.
If lab personnel have any doubt about a pipette’s accuracy, they should recalibrate the instrument before putting it into use. Some labs go the route of calibrating pipettes themselves, but many others in the interest of quality use external vendors to calibrate and maintain their pipettes. An external pipette calibration vendor should be ISO 17025-accredited as a testing and calibration laboratory to ensure the calibration service performed is reliable.
What services do pipette calibration vendors provide?
Calibration vendors service a wide range of laboratories including academic, clinical, and forensic, as well as laboratories that follow Good Laboratory Practice and Good Manufacturing Practice regulations. Three of the common options in pipette calibration services are: the label, Found As values, and Left As values. The label is critical to clinical laboratories in documenting a pipette’s calibration and date of service. The Left As value tells a laboratory that a pipette was accurate after service. The Found As value, in turn, determines if a pipette was calibrated before service. These inputs tell anyone looking at the record that a pipette was accurate both before and after any servicing.
My pipette was not accurate. What should I do?
Pipettes are not always found to be within a laboratory’s specifications at the time of service. This leads to a very important question: What impact did the inaccurate pipettes have on testing? A pipette’s imprecision can be a source of error, and its affect on patient testing needs to be investigated and documented.
The investigation should start with determining how a pipette was being used by tracing it to a specific process or step in a testing process. An example of this would be pinpointing that pipette X is located at a specific workspace in the laboratory where DNA extractions are processed. Next, the lab should assess the impact of the pipetting bias on that specific process.
In some cases, this might be as simple as looking at quality control values for the process before and after the pipette’s calibration. In others, the lab might need to dive into a more thorough assessment by retesting patient samples that were run with the pipette in question.
The impact on testing can be assessed by looking at the bias introduced by the pipetting error. If the lab finds that patient testing has been affected, then it may need to notify providers and/or issue corrected reports.
Overall, pipettes are critical to quality results in clinical laboratories. A lab should not ignore their potential as a source of error when routine calibration services find pipettes that have not been performing to the lab’s required specifications.
James Fuller, PhD, DABCC, FAACC, DLM(ASCP), is the chief scientific officer of Lighthouse Lab Services and consults with clinical laboratories on quality and compliance. He also is the project manager for the development of new clinical laboratories across the United States. Email: firstname.lastname@example.org