Distinguish between screening results and confirmatory results.

Distinguish between screening results and confirmatory results.

• A. Screening results are definitive; confirmatory results are less specific.
• B. Screening results are presumptive and may be positive/negative; confirmatory results use a specific, definitive method with identification and quantification.
• C. Screening results measure metabolites only; confirmatory results measure parent drug.
• D. They are identical.

Answer: (B)

Screening tests are designed to be rapid and broad, giving presumptive results that can be positive or negative. They use methods like immunoassays that prioritize throughput, but they can cross-react with other substances or miss low levels, so they aren’t definitive. Confirmatory testing, on the other hand, uses a highly specific method to identify the exact substance and quantify how much is present. This step provides a definitive identification and an exact concentration, which is why it’s used to confirm any presumptive screening result. So, the best choice captures that screens are presumptive and may be positive or negative, while confirmatory tests employ a specific, definitive method with both identification and quantification. The other statements don’t fit because screening isn’t definitive, confirmatory isn’t limited to metabolites, and the two results are not identical.

Screening tests are designed to be rapid and broad, giving presumptive results that can be positive or negative. They use methods like immunoassays that prioritize throughput, but they can cross-react with other substances or miss low levels, so they aren’t definitive.

Confirmatory testing, on the other hand, uses a highly specific method to identify the exact substance and quantify how much is present. This step provides a definitive identification and an exact concentration, which is why it’s used to confirm any presumptive screening result.

So, the best choice captures that screens are presumptive and may be positive or negative, while confirmatory tests employ a specific, definitive method with both identification and quantification. The other statements don’t fit because screening isn’t definitive, confirmatory isn’t limited to metabolites, and the two results are not identical.