Specimen Validity Testing

A set of tests designed to establish whether the specimen submitted to a drug-testing laboratory has been adulterated or altered to subvert the testing process is called the Specimen Validity Testing (SVT). Since examination helps to determine the validity of the specimen submitted for testing, conducting these tests is a part of QA. When some reliable data showed that adulteration was a concern, these tests were introduced by SAMHSA and numerous companies used advertising methods for sale to “beat the drug test.” Examining the urine for adulterants such as oxidizing agents constitutes a part of the current SVT (14). Furthermore, measuring creatinine concentration, specific gravity and pH to establish whether they are within the expected physiological range is also included.

Adulterated, substituted, dilute or invalid constitute the four categories describing altered specimen, and analogous to the drug tests, SVT is regulated by it. However, the multiple decision points for determining the category of a specimen differ from the drug tests; in all testing processes, each decision point must be challenged. Since customers react differently to various results, the altered specimen is discriminated into different categories.

If 3.0 > pH > 11.0 or if the specimen constitute of substances, not typically present in urine, that are designed to manipulate with testing, the specimens are considered adulterated. If urine creatinine <2.0mg/dL and 1.0010≥ specific gravity ≥ 1.0200, the category is defined as “substituted”. Since they are subverting the drug-testing system, the donors face harsh consequences by companies with drug-testing programs, in case the donors fall in the 2 categories mentioned above. If 2≤ creatinine < 20 mg/dL and 1.0010< specific gravity < 1.0030, the specimen is categorized as dilute.

Invalid results may be from 3.0≤ pH <4.5, 9.0≤ pH <11, nitrite ≥200 µg/mL, creatinine <2.0 mg/dL and l.0010< specific gravity <1.0200, or creatinine ≥2.0 mg/dL and specific gravity ≤1.0010. When donors have dilute or invalid specimens they may be asked to contribute another specimen.

To challenge decision points, initial creatinine tests must have QC samples in the following ranges: 1.0-1.5, 3.0-20.0, and 21.0-25.0 mg/dL. Confirmation tests must have creatinine controls in the ranges 1.0-1.5 and 3.0-4.0 mg/dL. Initial specific gravity tests on a -decimal-place refractometer require a QC sample targeted at 1.0002 and one in the range of 1.004 to 1.018. A 4 Decimal-place refractometer is required for confirmation of specific gravity and there must be a control targeted at 1.0000, one targeted at 1.0020, one in the range of 1.0040 to 1.0180, and one 1.0200≤ QC <1.0250. Initial pH tests using a colorimetric procedure must have controls in the following ranges: 2.0-2.8, 3.2-4.0, 4.5-9.0, 10.0-10.8, and 11.2-12.0. If the initial pH testing is accomplished with a pH meter, then the QC sample with pH in the range 4.5-9.0 may be deleted. The confirmatory test must use a pH meter and have the same control requirements as the initial pH meter test.

For SVT, published methods are not plentiful and laboratories cannot always find two different methods to certify a result. In these instances, the NLCP allows measurements on 2 different aliquots of the same specimen with the same type of method.

Post a Comment

Your email is never published nor shared. Required fields are marked *

You may use these HTML tags and attributes <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

*
*