Rigorous Liquid Handling Quality Assurance Helps CardioDx Improve Cardiovascular Care

Jan 30, 2014

A Change of Heart

liquid handlingKnowledge is power and nowhere is this truer than in the healthcare industry. The more relevant information that diagnostic tools can provide about a patient, the more individualized treatment plans can become, resulting in more effective care and improved quality of life. Due to the resulting improvements in patient care, more and more companies are focusing on developing tools to advance personalized medicine and this includes molecular diagnostic testing.

Working to improve cardiovascular care, CardioDx, Inc. is developing clinically validated genomic tests to provide physicians with more precise information about patients suffering from coronary artery disease, cardiac arrhythmias, and heart failure so the ideal therapeutic path can be determined. Compared to imaging-based diagnostic tools, which rely heavily on the skill and experience of a cardiologist for proper diagnosis, CardioDx’s tests are less invasive and more objective. CardioDx’s tests output a numeric score based on a patient’s molecular footprint for an objective, analytical assessment.

Because the test results, i.e., patient test score, will directly lead to medical decisions affecting patient attention and care, quality assay results are of the utmost importance. The ability of CardioDx to produce an accurate test outcome relies on the quality of its laboratory operations. Automated liquid handlers are used extensively at CardioDx throughout numerous volume-dependent assay steps, making instrument quality control crucial.

To ensure laboratory quality, CardioDx uses the MVS® Multichannel Verification System to verify the performance of its automated liquid handlers.  A product of Artel, the MVS rapidly provides traceable measurements of the accuracy and precision of transferred volumes. The results provided by the MVS help CardioDx eliminate automated liquid handling instruments as a source of error and enhance data integrity, resulting in greater confidence in individual treatment decisions for cardiovascular patients.

The Use of Automated Liquid Handlers

Licensed by the state of California as a clinical laboratory, CardioDx adheres to the Clinical Laboratory Improvement Amendments (CLIA) and operates in compliance with CFR part 820, which is the company’s internal quality standard. Part of complying with these regulations is being able to effectively measure instrumentation performance, including automated liquid handlers.

At CardioDx, liquid handling quality assurance is essential during the development of its genomic assays. The proprietary science behind CardioDx’s genomic diagnostic tools is contained in the unique combination of master mix and specific target volumes of reagents used in the company’s assay plates. Each production batch requires the development of several hundred assay plates, and liquid handling error can result in inefficiency, wasted reagents, and outcome variability.

In actual patient testing, automated liquid handlers play a large role in almost every stage of the process, from receipt of a sample through data generation, and many of these steps are highly volume-dependent. Due to the analytical nature of CardioDx’s genomic diagnostic tests, the instruments must transfer explicit volumes of sample and reagent during each module of the assay, including RNA Extraction, RNA Quantitation and Normalization, cDNA generation, and Real-Time qPCR.

“At any time we’re moving samples through the process, accurate transfer of samples and reagents is required for consistency in test results,” said Jon Marlowe, Associate Director of Automation, CardioDx.

 A Change for Confidence

To strengthen confidence in results and streamline its liquid handling quality assurance method, CardioDx switched to the Artel MVS to confirm the performance of its automated liquid handlers. Based on Artel’s ratiometric photometry technology, the MVS measures the absorbance of light by two specially formulated dyes to verify volume.

The MVS provides results traceable to NIST (National Institute of Standards and Technology).  In addition, using the MVS, a 96-channel liquid handler could be verified in less than 15 minutes, including automatic calculation and documentation of results. The automation is achieved through barcodes, located on the system’s microtiter plates, reagents, and calibrator plate, that contain metrological information. The system’s software automatically records the photometric measurements taken by the MVS and rapidly determines both the accuracy and precision of the volume delivered from each individual tip of the automated liquid handler.

“With the Artel MVS, we are confident that we are only measuring error in the instrument and are not observing additional error from the measuring device,” said Marlowe.

Now, CardioDx also uses the MVS to develop liquid handling methods as well as to monitor the performance of its automated liquid handlers over time. Calibration is conducted at least semi-annually for all instruments, while monthly calibrations are performed for those automated liquid handlers most heavily used. This calibration frequency allows the company to quickly detect and correct liquid handler error and have assurance that the results reported for volume transfers are accurate and precise.

Quality Assurance Tools of the Past

Prior to use of the MVS, CardioDx verified the performance of its automated liquid handlers with a homebrew method using fluorescent reagents as well as with gravimetric technology. The fluorescent method required the use of Eosin Red reagents and an internally developed stock solution. This method required lengthy manual calculations to determine the accuracy and precision of transferred volumes.

“With fluorometric calibration, there was no gold standard to assure the reliability of the results,” said Marlowe.

Gravimetric calibration proved even more tedious.  This technique, which weighs liquid quantities on a balance to determine volume, is only able to measure the volume dispensed from one tip of an automated liquid handler at a time.  With a 96-channel automated liquid handler, a performance assessment of a single liquid transfer required approximately one hour to complete.

“We needed to know with certainty that the measuring device was not introducing any error into the calibration process so we could have complete confidence in our liquid handling process,” said Marlowe.  “And this was not possible with gravimetric or fluorometric calibration methods.”

 Staff Support

“The MVS has been a very welcomed solution.  When my colleagues were first introduced to the system, they were amazed by its ease of use and its lack of a learning curve,” said Marlowe.

The use of the MVS has brought about an overall change in staff perception about liquid handling quality assurance.  The MVS has provided objective evidence that automated liquid handlers do not always deliver the target volume and that ongoing performance verification is necessary for true confidence in the integrity of results.

“The MVS allows us to implement our diagnostic tests with the highest level of confidence in our science without questioning the performance of our automated liquid handling equipment,” said Marlowe. “At the end of the day after using the MVS, we have a greater level of assurance and confidence in the quality of the results we’re providing to cardiologists.”


 About CardioDx

CardioDx is a cardiovascular genomic diagnostics company focused on serving cardiologists by offering clinically validated, actionable genomic diagnostics. Their mission is to partner with clinicians in answering complex clinical questions for their patients. CardioDx provides timely and reliable information to help clinicians make individualized treatment decisions and improve patient care. For more information, contact CardioDx at 2500 Faber Place, Palo Alto, CA, 94303; Tel: 650-475-2788; Fax: 650-475-2799; Website: www.cardiodx.com.