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A drug test (also often toxicology screen or tox screen) is a technical analysis of a biological specimen, for example urine, hair, blood, breath, sweat, or oral fluid/saliva—to determine the presence or absence of specified parent drugs or their metabolites.
It gives a negative test-result for 25I-NBOMe and many other non-indole-related psychoactives. The reagent will also give a positive result for opium, because of the presence of tryptophan in natural opium. [3] Pyridoxine, present in vitamin supplements, can give positive results to the Ehrlich test, showing a pink colour change. [4]
The false positive rate (FPR) is the proportion of all negatives that still yield positive test outcomes, i.e., the conditional probability of a positive test result given an event that was not present. The false positive rate is equal to the significance level. The specificity of the test is equal to 1 minus the false positive rate.
Since the antibodies do not bridge between antigens, no agglutination occurs. Because no agglutination occurs, the test is interpreted as negative. In this case, the result is a false negative. The range of relatively high antibody concentrations within which no reaction occurs is called the prozone. [5]
Reagent testing is one of the processes used to identify substances contained within a pill, usually illicit substances. With the increased prevalence of drugs being available in their pure forms, the terms "drug checking" or "pill testing" [1] may also be used, although these terms usually refer to testing with a wider variety of techniques covered by drug checking.
Because the test pad reaction is dependent on pH, false positive results can occur if the urine is highly alkaline. [60] [62] Conventional test strips are not sensitive enough to reliably detect microalbuminuria, a condition in which urine albumin levels are slightly elevated, [64] although dipsticks specialized for this measurement exist. [62]
The strips change color depending on the pH of the fluid. The strips will turn blue if the pH is greater than 6.0. A blue strip means it's more likely the membranes have ruptured. This test, however, can produce false positives. If blood gets in the sample or if there is an infection present, the pH of the vaginal fluid may be higher than normal.
As the lipophilicity of ionizable compounds is strongly dependent of pH, the distribution coefficient logD, or a logP vs pH curve may be used instead. Potency at the biological target. High potency (high value of pIC 50) is a desirable attribute in drug candidates, as it reduces the risk of non-specific, off-target pharmacology at a given ...