Question

Immunoassays 1. What are the basic mechanisms involved in the attempted adulteration of urine samples and are they equally effective in producing false negatives.

Answer 1

Adulterants are foreign substances either ingested or added directly to urine to prevent positive results mainly in drug tests.These adulterants include common house hold items to specific chemical additives obtained from various sources. Common house hold items include citric acids (vinegar) ,ammonia,bleach,laundry detergent,salt etc.These alter the pH of the sample and which measure whether the sample is abnormally acidic or basic.Common products such as lemonade,soft drinks,etc,donor some times directly add these products to urine or simply substitute with sample.Adding eye drop to urine sample help to give false negative for drug screening.Chemical additives that alter the test result include Glutraldehyde(urine aid) Nitrate and chromates and halogens.Gulteraldehyde effect the result of screening test for drugs.Many chemicals named stealth( containing peroxidase and peroxide), Urine luck(pyridinium chlorochromate, PCC ) and Klear (potassium nitrate) available can invade screening tests and confirmation tests and can give false negative results.

When NaCl is added to the sample urine it could alter the protein structure which will affect the enzymatic activities of test.And the high salt concentration could precipitate the drug which will give false negative results.The acidic pH caused by acids and alkaline pH caused by bleaches could alter the binding and reaction rates which alter the results.Some chemicals also affect the drug test by oxidation reactions.Soap may alter the reaction by increasing drug binding site on antibody resulting decreased assay reaction.Addition of some adulterants also change the optical measurement of urine sample interfering its absorbance measurements.Some urine adulterants can be detected by routine specimen integrity tests(creatinine,pH,temperature and specific gravity) and some adulterants by specific adulterant detection tests.