Beckman Coulter Improves Operational Qualification Program With Advanced Technology for Liquid Delivery Quality Assurance.	Printer Friendly

ARTEL MVS* Provides Information on Accuracy and Precision

By Keith J. Albert, Ph.D., Technical Marketing Manager, ARTEL, Lisa Knapp, Field Project Manager for Automated Solutions, Beckman Coulter, Julie Stanis Farias, Technical Support Engineer, Beckman Coulter, and Angelica Olcott, Applications Manager, Beckman Coulter.

Imagine that you run a primary screening laboratory at a biopharmaceutical company. You use sophisticated automated liquid delivery instrumentation to run anywhere from 100,000 to one million or more compounds per year in assays that can cost up to $100,000 per plate. Your facility is regulated by stringent SOPs, your data could be audited by the FDA and you’re in a fiercely competitive race to bring new drugs to market. There is clearly no room for error.

Because liquid handling is a core component of your drug discovery processes, qualification of automated liquid delivery devices, validation of assays that depend on liquid delivery steps and a standardized measurement method are all necessary. If you had access to technology providing information on the precision of your instruments, would that be enough? For a growing number of Beckman Coulter customers, the answer is no. What’s missing? Knowing that your instrument is also accurate.

Why is accuracy important? Accuracy information is critical to determine the deviation of the dispensed volumes from the target volume. For example, if an instrument is programmed to dispense 100 µL but consistently dispenses 115 µL, the instrument might be found to be operating with perfect precision, even though it was radically over-dispensing. In this example, precision information alone would not detect the 15 µL over-dispense. This result is highly undesirable given that accuracy variability can have a greater impact on the integrity of tests and assays than precision variability. While precision information is important, it only provides details about the closeness of the dispensed volumes to each other.

To satisfy customer demands for accuracy and precision data, and to provide stronger assurance of the integrity of results produced by its equipment, Beckman Coulter has upgraded its Field Service Operational Qualification Program with ARTEL’s MVS (Multichannel Verification System). Based on ratiometric photometry, a technology measuring the absorbance of light by two proprietary dye solutions, the MVS provides verification of the accuracy and precision of dispensed volumes in one simultaneous measurement, and this enhances customer confidence in the performance of Beckman Coulter’s automated liquid handlers.

Implementing the MVS has resulted in an increase in the number of laboratories enrolled in Beckman Coulter’s optional Operational Qualification Program and positive feedback from customers.

The Operational Qualification Process
Operational qualification is important for most life science laboratories, especially those in the clinical and pharmaceutical markets, as it is used to prove that equipment performs within specifications and complies with regulations. Third-party validation of equipment performance also strengthens data integrity and facilitates compliance. For these reasons, many Beckman Coulter customers opt-in to the company’s Field Service Operational Qualification program, including users of the Biomek® FX^P,  Biomek NX^P and Biomek 3000 Laboratory Automation Workstations (liquid handling devices designed for drug discovery laboratories) and VidieraTM NsP (Nucleic Sample Preparation device geared for hospital and reference laboratories). 

Beckman Coulter has several Operational Qualification products, OQ1, 2 and 3. OQ1 documents instrument operation as tested in a standard, non-qualification installation.  OQ2 includes all OQ1 tests and adds a preventive maintenance check, as well as a software confidence and verification test. OQ3 is the highest level of instrument qualification that Beckman Coulter offers, and provides for certification with the MVS system.  The OQ3 product contains all the elements of OQ1 and OQ2 (preventative maintenance check, a software confidence and verification test, instrument functionality tests), and then adds system performance tests using the MVS system.  These MVS tests have been developed to use NIST traceable standards as applicable. The purpose of Beckman Coulter’s on-site Operational Qualification level 3 (OQ3) program is to determine whether equipment is performing within manufacturer’s specifications, which are typically tighter than regulations require. 

The service process for OQ3 is as follows. First, pre-qualification is conducted to determine the as-found performance based on both accuracy and precision dispensing. Tests are run at high volumes as well as at low volumes, with target volumes determined by customer applications and type of head employed (i.e., 384-channel head vs. eight-channel pod) (please refer to Figures 1 and 2). If need be, the instrument, or method, is adjusted so that it operates within the desired tolerances and preventive maintenance is conducted if due, for example, by replacing components with newer versions or performing scheduled cleaning. The final step is an as-left qualification, where service representatives ensure instrument performance within set tolerances and provide documentation proving that the instrument is operational. 

Previous Methodology
Before switching to ARTEL’s MVS, Beckman Coulter employed a photometric method using a bead-based solution to verify that equipment was performing within precision specifications, as determined per instrument for both ends of the volume spectrum. To test volumes at the high end, a target volume was determined, for example 200 microliters, and the instrument being qualified was instructed to pipette 200 µL of the bead-based solution into one microtiter plate. These plates were read in a microplate reader to find the percent CV. However, this technology only provided precision data. While it was useful to know that the instrument was performing consistently (i.e. precisely), there was no proof to confirm that the instrument was dispensing accurately. 

In addition, this technology was problematic at low temperatures. If the bead-based solution froze, in transit for example, the beads would be physically altered after thawing, and this rendered the solution useless. Service technicians also had to manually record the results, lengthening the amount of time spent at customer facilities and increasing the propensity for error and doubt. All of these issues coupled with growing customer demand for data about the accuracy of their instruments led Beckman Coulter to source a new technology for its Operational Qualification program.

Accuracy and Precision in One Experiment
It was important to Beckman Coulter that its qualification program easily produce accuracy and precision information, and that the technology be capable of interacting with the complete range of the company’s automated liquid delivery devices, from one-channel through 384-channel instruments. 

Traditionally, laboratories have used gravimetry to verify the accuracy and precision of liquid delivery devices. However, this method, which verifies volume by weighing liquid quantities on a balance, is time consuming and prone to environmental and manual error, especially at small volumes. In addition, gravimetric calibration is not ideal for multichannel devices because it only provides an aggregate assessment of all channels as opposed to information regarding how each individual channel is performing. 

Conversely, ARTEL’s MVS is based on proprietary ratiometric photometry, which employs a dual-dye, dual-wavelength absorbance method for accurate and precise measurement of small target volumes. This technology relies on two colorimetric dyes with distinct absorbance maxima at 520 nm (red) and 730 nm (blue). Using calculations derived from the Beer-Lambert Law, the MVS is used to quantify both the precision and accuracy of each dispensing channel in one experiment by measuring the absorbance of these dyes.

The Beer-Lambert law states that when light passes through a solution containing some concentration of dye, the amount of light absorbed by the dye solution is proportional to both the concentration of dye and the interaction pathlength of the light with the solution. If both the molar absorptivity and concentration of the dye solution are known and closely controlled, which is the case with the MVS, the law can be used to determine an unknown pathlength traversed by a light beam. By measuring the pathlength through the solution and knowing the dye concentration, the unknown volume can be calculated through a series of equations.

This process is accomplished by ARTEL’s determination of the absorbance per unit pathlength of the red and blue dyes. This NIST-traceable information is recorded on a barcode on each reagent bottle, further reducing measurement variability and uncertainty. Barcodes on the system’s microtiter plates, sample solutions and calibrator plate contain performance information that is passed to the system’s software through a bar code reader. The plate reader collects photometric measurements of the dye solutions dispensed into the microtiter wells by the liquid delivery device. These measurements, together with the bar code information, are used to rapidly determine both the precision and accuracy of the volume delivered from each tip of the device being tested. 

The MVS measurement results are also traceable to international standards, allowing comparability of all Beckman Coulter devices regardless of model, location or number of dispensing channels.  ARTEL’s MVS system reads at 517 nm, which is close to the wavelength used for Eosin Y, a dye commonly used previously for pipetting validation.

Trust in Results
With the MVS, Beckman Coulter’s Operational Qualification program provides more information to customers for a full assessment of liquid delivery device performance, facilitating assay validation and method transfer. In addition, the automated documentation feature of the MVS eliminates the time consuming and error-prone step of manually recording results. This, coupled with NIST-traceable results provides stronger reliability. With regular use, the Operational Qualification system for pipetting validation can also help monitor the pipetting performance of an instrument over time. Figure 3 shows results for a Biomek p200 96-channel head from regularly scheduled testing over a year-long period.

The provision of per-channel information by the MVS also facilitates and enhances service. As shown in Figure 4, individual tips within a device can be directly compared. This can help detect errors that occur when users of automated liquid delivery devices sometimes draw foreign objects into instrument channels, clogging the pathway and altering volume. Using the MVS, the malfunctioning channel can be immediately identified and resolved. Alternatively, the bead-based method provided an aggregate assessment of total system performance, making accurate problem diagnosis difficult and time consuming.

The Importance of Accuracy
The importance of accuracy information can be demonstrated through an example of a Biomek user who found inconsistencies in assay results when automating a manually developed method, a common occurrence in many laboratories. In this particular case, the user was not obtaining the same results with its Biomek as with the manually pipetted method, and contacted Beckman Coulter for service.

This specific customer application required the addition of 15 µL of the assay’s rate-limiting reagent, a critical determinant of the assay results. The Beckman Coulter service representative ran the critical assay volume through ARTEL’s system and determined that the instrument was operating well within specifications, dispensing a volume of 14.84 microliters, producing accuracy results within 1 percent and precision results within 1.3 percent at 10 µL. Yet the automated assay was returning very different results than was the manually developed method. After evaluating the manually pipetted results using ARTEL’s system, it was determined that the manual pipetting process was dispensing 15.75 µL, 5 percent over the target volume. The service representative simply adjusted the automated liquid handler to over-pipette by the same amount so that it produced the same assay results as the manually pipetted method. Here, precision information alone would not have determined the root cause of the difference in assay results produced by the manual and automated devices.

As Beckman Coulter continues its phased rollout of the new MVS-based Field Service Operational Qualification program and specifies accuracy requirements in the SOPs for a growing number of instruments, the demand for its services continues to expand. Because service representatives can more efficiently complete service visits and more accurately diagnose and solve issues, Beckman Coulter can meet this need and enhance customer satisfaction in its instrumentation.

About the Authors
Keith Albert, Ph.D., is Technical Marketing Manager at ARTEL, and is responsible for automated liquid delivery system performance research, customer education and assay/method validation services associated with ARTEL’s LHQA* (Liquid Handling Quality Assurance) services. Dr. Albert applies his expertise and scientific knowledge to help laboratories optimize their liquid delivery processes and maintain compliance. Dr. Albert's research includes investigation of highly sensitive measurement systems and he has been published in scientific journals and presented papers on more than 20 occasions. He earned his BA in Chemistry at Colby College and his Ph.D. in Bio-Analytical Chemistry at Tufts University.

Lisa Knapp is Field Project Manager for Automated Solutions at Beckman Coulter.

For information on the PCS, MVS, LHQA service suite, other ARTEL solutions for liquid delivery quality assurance or Ratiometric Photometry, contact: ARTEL, 25 Bradley Drive, Westbrook, ME 04092; Tel: 207-854-0860; Fax: 207-854-0867; Website: www.ARTEL-usa.com.

For information on Beckman Coulter’s automated liquid delivery devices or its Field Service Operational Qualification Program, contact 4300 N. Harbor Blvd, PO Box 3100, Fullerton, CA 92834; Tel: 800-742-2345; Fax: 800-643-4366; Website: www.beckmancoulter.com.

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Figure 1.  Biomek NX Multichannel P200 head qualification
Volumes for Plate 1 (µL):

Plate 1 Statistics:

Figure 2.  Span 8 with 1 mL tip qualification (inaccurate well is highlighted in orange)

Group 2 Well Volumes (µL):

Group 2 Channel Statistics:

Figure 3.  Monitoring performance trending over time.

Average of three repeat dispenses is shown per data point.

Figure 4.  Performance Data for Every Tip on a Multichannel instrument.

Data shown from 96-tip Biomek® head at a 5 µL Target Volume, performed with three replicates.

* All trademarks are the property of their respective owners. Where applicable, the PCR process is covered by patents owned by Roche Molecular Systems, Inc., and F. Hoffmann-LaRoche, Ltd.

**This OQ3 service is currently offered in the US, Canada, Europe and Australia. This service is not offered in Asia Pacific at this time.

For Research Use Only; not for use in diagnostic procedures.

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