Is Limit of Detection (LOD) the same as Minimum Detection Limit (MDL)?

Ask the Expert Question:Under the Department of Defense (DOD) Quality Systems Manual 4, the language has changed from Minimum Detection Limit (MDL) to Limit of Detection (LOD) (and Limit of Quantitation (LOQ)). Is the LOD the same thing as MDL? What is TestAmerica's plan on becoming consistent with this new language?

Expert Response:The DOD is using all of these designations at this time.

The MDL definition has not changed and is essentially the lowest level at which a result can be reliably distinguished from a blank.

The LOD is higher than the MDL, and is supposed to be the level at which a true concentration in the sample will reliably give a result that is greater than the MDL.

LOQ definition has not changed and is the lowest quantitative level for the sample.

When reporting data, the LOD is used as the Non-Detect (ND) value, for example, NDs will be reported as < LOD.

Detects, however, are reported down to the MDL, with J flags if below the LOQ.

TestAmerica is reporting data for DOD projects using these conventions. We are not reporting this way to non DOD projects to be consistent with non DOD quality programs.

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