Basic QC Practices

There are manufacturer controls and then there are third party independent controls. What happens when they don't agree?

Manufacturer Controls vs 3^rd Party Controls: Who’s Wrong, Who’s Wright, and Who hates being caught in the middle?

March 2026
Sten Westgard, MS

During the “How Europe QC’s” webinar in February, one of the questions we received involved the struggle of a laboratory using independent controls on an even more independent instrument:

“When we troubleshoot analyzer issues, our analyzer manufacturer insists on running their QC materials. They will only agree we have an issue if we are outside their 3 SD range. How do we deal with this?”

This is a refrain I am hearing more and more these days. Labs running 3^rd party controls that give them an “out” signal, but instrument manufacturers refuse to agree with that signal, and instead insist on accepting only the verdict of their own manufacturer controls.

The 3^rd party controls say the test is out. The manufacturer controls say that the test is in. What’s a laboratory to do?

Remember why independent controls are recommended.

ISO 15189:2022 made about as strong a statement as it can without making it mandatory: “The use of third-party IQC material should be considered, either as an alternative to, or in addition to, control material supplied by the reagent or instrument manufacturer.”

In other words, when it comes to test methods, trust but verify. Healthy skepticism of manufacturer controls is encouraged. Best practice is to run independent controls. This is not only encouraged by ISO, but can be found in CLSI C24 guidance on QC.

Why can’t we trust the manufacturer controls?

Part of the problem is the essential conflict of interest a manufacturer has in making its own controls.

Manufacturer controls, often, are about controlling the customer, not controlling the method. Since these controls are often provided “free” to the customer as part of the instrument purchase price, all the costs, burdens and expenses associated with QC are borne by the manufacturer, not the laboratory. Thus, there is a strong incentive to minimize those costs through wider ranges and other advice.

While the controls themselves might not be especially poor, the “ranges” that are recommended to the laboratory customer can be. Determining your own mean and SD is still considered best practice, but manufacturers often provide ranges along with their controls. These ranges are supposed to be used only temporarily while the laboratory gathers enough data to determine their own mean and SD. Unfortunately, the modern laboratory is over-worked and under-staffed, and they adopt the manufacturer ranges not temporarily, but permanently. Sometimes the manufacturer even explicitly recommends that labs only use the manufacturer controls.

The manufacturer range is often too wide. The SD from this range is built typically on a group of laboratories, which will then include much more variation. What may be presented as a 2 SD range by the manufacturer will actually be far wider, if measured by the individual laboratory SD. One study found that hematology ranges being recommended by the manufacturer were not actually 2 SD, but were in fact as wide as 6 SD. https://onlinelibrary.wiley.com/doi/10.1111/ijlh.14220

In my own experience, I have worked with laboratories where the manufacturer told the customer to adopt the manufacturer ranges, despite the fact that they were as wide as 10 SD. In case you are wondering, control charts with 10 SD limits look a lot like straight lines.

What happens with these wide manufacturer ranges? We call this Blind Man QC. The visibility of variation and errors is lost. That straight line of QC is actually an illusion. The laboratory operates blissfully unaware that significant errors could be occurring and escaping the lab.

In more recent times, this practice has become even more coercive. I have talked with customers who diligently calculate their own mean and SD, only to have them automatically overridden by the manufacturer software. Seeing the manufacturer actively preventing the customer from using their own mean and SD for QC is a new level of control.

What is strange, of course, is that the customer is supposed to be right. It’s the laboratory that is paying the manufacturer, after all, and thus the manufacturer should be responsive to the customer. But instead, we are seeing that the manufacturer is flexing their power and forcing ranges onto the customer and refusing to accept the judgment of 3^rd party controls. When this happens, the manufacturer controls not only the QC, but also the customer.

If you walk into a Vegas casino and sit down at a blackjack table, you expect a standard (independent) deck of cards. If the casino instead presents you with a customized deck, one that was built just for their casino, and was “tailored” specially for your game, you might not be surprised to find out that it lacks all the kings and aces. 

Part of this new power relationship comes from the modern, massive scale of these instrument deals. Today’s diagnostic contracts are coming from outside the laboratory, from the accounting centers and executive boardrooms. The laboratory might not have had a voice in the purchase decision, and they have less of a voice in the actual operational day-to-day. The contract is signed, the money is flowing, and a lab tech is not empowered to change that. The instrument is here to stay, regardless of whether or not the QC is “out.”

Is it possible the 3^rd party control – or even (shudder) the laboratory itself – is actually wrong?

Laboratories don’t help themselves with how they run QC. As our 2025 survey found, most labs are using relic ranges – 2 SD – that are painfully tight and cause daily out-of-control flags that are overwhelmingly the result of false rejection. Thus, the instrument manufacturer has a point: if the lab is using the wrong QC rule and does not understand why the flags don’t represent real errors, the only defense/response the manufacturer feels they have is to suggest a wider range. If a laboratory insists on using the 1:2s rule, the manufacturer subverts them by offering a different SD. This new SD, as we mentioned earlier, is not actually 2 SD, but could be much wider. The laboratory “wrong” is met with a manufacturer “wrong”, and those two wrongs make a "wright." Except of course, two incorrect applications of QC don’t magically cancel each other out. The real error conditions can get lost.

3^rd party control providers don’t help the situation when they encourage labs to continue using the 1:2s rule, to continue repeating the control, to run new controls, and repeat new controls, and on and on. While encouraging these poor practices certainly helps the profit margin of the control manufacturer, it does not help the lab, the instrument manufacturer, or the clinician and patient.

The better alternative: 3^rd party control with the right QC.

Using 3^rd party control is best when the laboratory is using their own mean, their own SD, and adjusting the QC rules being implemented to the test method context. That means taking into account the quality goal (TEa, allowable total error), as well as the measurement of imprecision and bias. From that, laboratories can calculate an analytical Sigma metric and use Westgard Sigma Rules to reduce the number of QC rules to the optimal minimum.

What if you are caught in the middle?

While it’s easy for us to recommend an ideal solution, there are plenty of labs that remain caught in the finger-pointing. The manufacturer refuses to accept the lab’s verdict. The 3^rd party control manufacturer insists their QC is correct. How do you resolve the standoff?

1. Make sure the lab is not complaining about self-inflicted wounds. If the 1:2s is generating a lot of out-of-control events, the manufacturer is probably justified in pushing back. If other rules are being violated, too, not so much.
2. Break the tie. Are there patient values that are clearly impacted by errors? Do you have other signs outside of the QC that the clinical results are not reliable? Are clinicians complaining? Are EQA or peer group results showing the same problem? The weight of evidence is now on your side.
3. Can you tie the problem to a specific event or change? Did things begin going south after a new reagent lot or calibrator was introduced? Or after a particular part was replaced or maintenance performed? Or software changed?

Ultimately, the laboratory is paying the bill. While the customer is not always right, the manufacturer should respect the complaints and provide a reasonable response. “Widen your ranges until you stop complaining” is not appropriate or acceptable advice.

[postscript: What if you are the manufacturer? Or the 3^rd party control provider?]

[Before making any accusations about the other party, make sure the customer is doing QC correctly. Is this problem a result of false rejection caused by the wrong QC rule? This is one of the hardest challenges of a vendor: telling your customer that they might be wrong. Gently, gently guide the customer toward a better approach to QC.

Oh, and stop with the ranges as wide as the universe. You're not fooling anyone.]