Sterility testing is the field on a certificate of analysis most likely to say “pending” — and the one buyers seem most confused by. We spoke with a microbiology lab technician (who asked to remain unnamed, since she isn't authorized to speak for her employer) about what's actually happening during that gap.

Why does sterility take longer than purity testing?

“Purity is a machine measurement — you run the sample through an instrument and you get a number back in under an hour, sometimes faster. Sterility is a biological test. You're checking whether anything grows. Growth takes time, by definition. USP <71>, which is the standard method, calls for a fourteen-day incubation period before you can call a result negative with any confidence.”

Fourteen days? That seems long for a retail product.

“It is long, relative to how fast everything else moves. That's exactly why you see so many COAs ship with purity finalized and sterility marked pending — the purity result is real and complete, and the supplier isn't willing to hold the whole batch off the market for two weeks waiting on the slower test. Whether that's the right call is a business decision, not a lab decision. But it does mean pending isn't a red flag by itself.”

“Pending isn't a red flag by itself. A pending result that never gets updated — that's the actual problem.”

— the lab technician we interviewed

So when should a buyer actually worry?

“When pending becomes permanent. If a COA says pending and it's dated two months ago, that result should exist by now — fourteen days plus reporting time is not two months. At that point either the test never got completed, or it did and the result isn't being shared, and neither of those is a good sign.”

Is there a faster method that gives the same confidence?

“Rapid PCR-based sterility screening exists and it's much faster — same-day, in some cases — but it's testing for something slightly different: presence of specific microbial DNA rather than actual growth over time. It's a genuinely useful screening tool, but it's not interchangeable with a full USP <71> result, and a COA should tell you which one you're looking at.”

What would you want to see change?

“Just update the pending fields once the real result comes back. That's it. That's the whole ask. It's not a testing problem, it's a paperwork problem, and it's the easiest one on this entire list to fix.”