Top 5 Reasons You Received an Invalid Spore Test

reasons for invalid spore tests

Biological Monitoring, or spore testing, is an important component of any infection prevention program. Utilizing a mail-in spore testing product is the easiest and most cost-effective way to ensure CDC recommended biological testing procedures are done on a regular basis. Also by using this type of product an outside test lab is verifying your weekly spore test results, which provides you with a 3rd party verification of test results.

But the evaluation process takes place in an FDA regulated facility.  This means that if certain criteria are not met, you might receive an invalid spore test result. So it’s important to meet the criteria! Let’s take a moment to review the five most common reasons a spore test might be marked invalid.

Test cycle began more than 30 days before lab received it

The lab must receive the spore test within thirty days of its start date; otherwise, it will automatically be marked invalid. Keep in mind that the lab cannot change the date the tester records, even if there’s an obvious mistake. Say you wrote down 2016 when you obviously meant 2017. Well, that’s unfortunate—but by FDA regulation, the lab can’t change the date for you. Expect an invalid test result.

You used an expired test envelope

All mail-in test envelopes have a stated expiration date. If the envelope has expired prior to the test date, then the test is invalid. Watch those expiration dates!

You forgot to include the spore strips

The test requires a test strip and a control strip to be in the envelope. The control strip should always stay in the envelope, but some forget to place the test strip back in the envelope prior to mailing.  Be sure to put the test strip back in the envelope prior to sending or your test is invalid.

You wrote down two sterilizer serial numbers 

Some offices have more than one sterilizer. Be sure you are referencing only one serial number on the test envelope. One serial number for one sterilizer—more than that, and the test lab will not know which autoclave was tested.

Blue protective sleeve on the test strip was removed

Don’t remove the test strip from the the blue sleeve—we mean the blue glassine protective sleeve. If you remove it, the test will be immediately invalid.

Now You Know

Your infectious disease prevention isn’t complete without an accurate, effective spore test. In fact, the CDC recommends you perform spore tests once a week, and most states have their own, more stringent requirements.

HealthFirst can help you perform this important biological monitoring! HealthFirst offers mail-in and in-office solutions—either of which will help you keep your patients safe.

Visit today to learn more.


Dr. Donald Cohen, a trusted figure and key opinion leader, has been a licensed and practicing dentist for over 30 years. Additionally, Dr. Cohen has 20 years of teaching experience at Columbia University SDOS, and 20 years as an Attending Dentist at Columbia Presbyterian Hospital in New York City. With his many years of experience in the field and in the classroom, “Dr. Don” is an expert in the areas of dental compliance, regulations, and best practices.


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