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4 Best Practices for QC in a Clinical Testing Lab to Ensure Accurate Results

Posted by Eric Morreale, PhD on Feb 18, 2020 12:00:00 AM


What is a clinical laboratory director’s worst nightmare? That’s an easy one. The thought that, somehow, an inaccurate testing result has escaped their lab and convinced an unsuspecting clinician to make a poor patient care decision.

So much of modern medical care is grounded in treatment decisions based on diagnostic testing results. According to one review of the data, 98 percent of in-patient populations get lab tests.

False negatives can delay life-saving and life-improving patient care. False positives can cause patients to undergo unnecessary treatment, which can result in needless psychological, physical, and financial distress.

No wonder lab directors are troubled by the possibility, no matter how small, of reporting inaccurate results - critical patient care decisions hang in the balance. (Not to mention the professional reputations of lab directors, the reputations of their labs and hospitals, and the trust of patients and clinicians.)

To prevent errors in testing and reporting, quality control is a must. You need to be confident every time you report a result that your assays are working the way they are intended.

Here are four tips for optimizing quality control to ensure accurate results in your clinical lab:

1. Consider the Cost of Poor Quality Control (QC)

In the 30+ years we’ve spent working with clinical labs and lab directors, the number one reason cited for not upgrading their QC practices is the added costs involved. Budgets are tight and the cost of reportable results is calculated down to the penny.

While the cost of implementing additional QC is easily calculated, it’s important to also consider the hidden costs of QC failures when evaluating whether to adopt higher standards. While not always obvious, the following items should be included in any cost-benefit analysis:

  • Failed runs: This is the most readily calculated cost of inadequate QC. As you know, the only results that count are reportable results. Having to rerun a test essentially doubles the cost. Thus, it’s important to understand the overall test failure rate for the lab, and whether adopting additional QC measures would reduce this rate (and overall costs).  
  • Troubleshooting and downtime: That old saying is true - time is money. Assay and instrument failures can lead to a cycle of troubleshooting and equipment downtime as you search for the source of the problem. This is a significant resource drain on lab personnel and impedes their true mission - generating reportable results. Extensive need for troubleshooting can truly jeopardize operations of the entire lab. If downtime is lengthy, it can force expensive outsourcing of testing. And it certainly isn’t a positive for the morale of your staff as the pressure mounts to fix problems, in addition to their regular duties. The questions is - would additional QC pick up troubling trends earlier, reducing downtime and the overall troubleshooting burden placed on the lab?
  • Failed proficiency testing: While employment of a top notch quality control system is not a legal requirement, participation in a proficiency testing (PT) program is. Robust QC has the added benefit of preparing a lab for PT challenges, and minimizing the risk of failure.  Failed PT can lead to costly, but required, investigations and corrective action measures and in the worst case can endanger your lab’s certification from CLIA and state agencies.
  • Reporting of inaccurate results: Finally, false positives and negatives (if you catch them) are the bane of any clinical lab. The cost is immeasurable with respect to damaged reputations, not to mention the human cost of incorrect patient care decisions.

It is true that the third-party reference materials needed for a robust quality control program are not free. But when you run the numbers, you’ll find the cost of improving QC with third-party controls on a per-run basis is relatively low, particularly given the expensive and potentially catastrophic consequences of inadequate QC described above.

2. Run External as Well as Internal Controls

If not doing so currently, the most impactful and immediate QC improvement your lab can make is adding independent, third-party controls to your daily testing regimen. A common misconception is that the controls provided in the IVD manufacturers’ assay kits are sufficient to ensure the test is performing properly. Unfortunately, these internal controls do not provide a truly accurate and independent assessment of performance over time. Because internal controls are typically composed of the same material as the assay calibrators, are designed at relatively high concentrations, and endure frequent lot changes, they are not effective at identifying performance issues that could lead to inaccurate results.

We’re not saying that internal controls should not be utilized - they should be run as specified in the assay’s package insert. But independent, third-party verification can provide a level of certainty that internal controls lack.

3. Pressure Test Your Assays at Their Lower Limits

Where does an assay start to first show signs of failure? Typically, it’s near the limit of detection, where the true assay sensitivity is challenged. This is also where performance failures have the greatest negative consequences, as this is near the clinical decision point.

Internal controls included with test kits tend to mimic strong-positive samples - nowhere near the critical clinical decision point. In contrast, a high-quality third-party control - such as SeraCare’s ACCURUN line of molecular and serology controls - are specifically designed to be a weak positive sample that can catch performance issues at the lower limits of detection. Thus, look to third-party suppliers for external controls that will truly challenge your assays.

4. Run Controls Daily

You probably already know this, but it’s worth reiterating that the standard for quality control in a clinical testing lab is to run external controls at least once a day for each test. Some lab directors insist on the additional security of running controls with each shift change. If an assay has experienced recent performance issues, external QC should be run even more frequently.

Time for a QC Refresh?

With a few simple steps, you can cost-effectively improve your quality control practices, reduce reporting errors, and enhance your confidence. Learn how in our free guide for clinical laboratory personnel, “Best Practices for Clinical Labs: Strategies for Implementing a Best-in-Class Quality Control System.”

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Topics: Molecular & Serology