In drug of abuse testing, which pairing is used for screening and confirmation?

• A. Tlc for screening and GC-MS for confirmation
• B. Immunoassay for screening and HPLC for confirmation
• C. Tlc for screening and HPLC for confirmation
• D. GC-MS for screening and TLC for confirmation

Answer: (A)

Screening is meant to quickly sift through many samples for possible positives, while confirmation provides a definite, specific identification of the substance present. Thin-layer chromatography offers a simple, low-cost way to screen samples: it’s easy to perform, can handle multiple specimens, and gives a quick indication that a drug-like compound may be present. For confirmation, gas chromatography–mass spectrometry is used because it separates the compound and then identifies it with a unique mass spectrum, giving a precise fingerprint for the exact drug and reliable quantification. This pairing blends speed with specificity, which is why it’s a classic combination in drug-of-abuse testing. Immunoassays are fast for screening but can cross-react and aren’t definitive without a confirmatory test; HPLC can confirm, but without mass spectrometric data it’s less definitive than GC-MS.