Repeat Until It Passes: The QC Habit That Hides the Drift
On Tuesday at 7:40 the Level II control on the chemistry analyzer comes up 2.3 SD above the mean. The analyst runs it again from the same vial, and the repeat lands at 0.8 SD. The flag clears, the morning batch goes out, and by nine nobody remembers it.
You know that morning. About 89% of US labs handle a failed control the same way, according to Westgard QC’s 2025 Great Global QC Survey. More than 46% see a failure every day.
Running the control again doesn’t tell you why it failed, and it doesn’t record what you decided. Treat a QC failure as an event. Record what failed, what you decided, what you did, and which results since the last acceptable control are in question. A passing repeat answers none of those.
We’ll follow Tuesday’s batch through that record, whether yours lives on paper or in a laboratory information system.
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