What is the purpose of an 'invalid result' in UDT?

• A. It confirms a positive result.
• B. It indicates the test cannot be interpreted due to technical error or validity test failure, often requiring recollection or reanalysis.
• C. It confirms a negative result.
• D. It indicates the test is complete and final.

Answer: (B)

In urine drug testing, an invalid result means the test could not be interpreted because the specimen or the run failed validity checks. This happens when there are technical issues or problems with the specimen that prevent a reliable determination, such as failure of integrity markers (like improper creatinine, specific gravity, dilution, or signs of adulteration), incorrect temperature, or other procedural or instrument controls not meeting acceptance criteria. When an invalid result occurs, a recollection or reanalysis is usually required to obtain a valid result, often with a new specimen collected under proper conditions. This is not a positive or negative result, nor is it a final result; it’s a flag that the test couldn’t be interpreted as is, prompting retesting to ensure accurate and defensible results.