Order Allergenco-D for only $169 per box of 50 cassettes!

Every order includes a certificate for $200 in lab fee discount for new clients

Limited supply. Order NOW!

Last week, we went over the procedure of a quantitative measurement (counting fungal cells in swab samples). After you get the result of the enumeration back, how should you evaluate the data? Although it's not often discussed, understanding the quantitation limit (QL) of an analysis is critical in data interpretation. In order to talk about QL, we need to understand detection limit first.

Detection limit (DL) is the lowest quantity of a substance that can be distinguished from the absence of that substance. For microscopic direct exam, DL is one spore, yeast, or hyphal fragment. For culture method, DL is one colony. This is also called the "Instrument Detection Limit" (IDL) in analytical chemistry. In those two microbiological analyses mentioned above, the "instrument" is human eye. One cell and one colony is the lowest unit an eye can observe. Assuming 200-, 2000- and 20000-fold dilutions of a swab sample were made during sample preparation, one colony (IDL) in an agar plate containing 200-fold diluted sample means the "Method Detection Limit" (MDL) is 200 colony forming unit (CFU) per swab. Assuming a 2 in2 area were swabbed, the "Sample Detection Limit" (SDL) is 100 CFU per in2.

It can be demonstrated as the following calculations.
1 colony/agar plate
= 1 CFU/agar plate
= 1 CFU/(1/200 of the swab)
= 200 CFU/swab
= 200 CFU/(2 in2)
= 100 CFU/in2


If the agar plates for 200- and 2000-fold dilutions were overloaded by too many colonies, the SDL will become 10,000 CFU/in2. SDL is sample-specific and cannot be generically calculated. A simple way to calculate the SDL is to use "one" as the raw count in the analysis and calculation of a particular sample.

We ill continue next week and discuss what quantitation limit is and why it is important to know it.

Click here for more details

We all know that your lab can either be your best friend or your worst enemy! If standing between you and your customers is a "Money-Making Mega Lab" with un- reproducible data and watered-down cheap services, it is no wonder that your business is not growing the way you want it to grow. Quality analyses with personal attention from QLab can help you grow your business like no one else!

We typically help companies that have been frustrated with unsatisfying services from their current microbiology lab on issues such as:
(1) poor technical support
(2) no personal attention
(3) inconsistent results
(4) project delay; slow turnaround time
(5) reports not making sense
(6) lack of ethics

Call us today, and experience how some of your competitors have been gaining their advantage by using QLab's services!

Host: Joe Hughes/Cliff Zlotnik

We are going into our summer break with a show that has been in the making for quite some time. Steven M. Spivak, PhD is a Professor Emeritus, University of Maryland, Technical Advisor to RIA and an icon in the disaster restoration industry. Don't miss this opportunity to hear from one of the top minds in the disaster restoration field. Fire, water, odor, textiles, standards and more on the next episode of IAQ Radio

Scheduled Time:
Date: Fri, August 15, 2008
Time: 12:00 PM EDT