![]() For instance, the Parkinson’s disease drug amantadine may give false positive results for amphetamines, while the antipsychotic chlorpromazine and the antihistamine diphenhydramine may give false positive results for methadone.Ĭonfounding factors can interfere with a clear interpretation of the result. Non-negative results may include true positive and false positive results.įalse positive immunoassay results may arise from non-target interference. A negative result is one that is less than the predetermined cut-off value, and a non-negative one is equal to or greater than the cutoff. When performed and interpreted properly, “presumptive tests provide a rapid and reliable method that can be used to distinguish negative from non-negative results,” he said. The analyst must be trained in performing and interpreting point of care results, “and should be tested for colorblindness,” Dr McClure noted. Test results read by the human eye, such as point-of-care colorimetric assays, are subjective. “This is a critical point,” one that affects how results may be interpreted.Ĭhemistry instruments that perform these drug tests are calibrated to the sensitivity and linear range of the assay, and provide an objective result. ![]() ![]() “The assay specificity decreases as the scope of drugs or metabolites detected is increased,” said Dr McClure. Immunoassay drug tests may be targeted for a single compound, or for a whole class. The degree of color change is proportional (or in some cases, inversely proportional) to the amount of drug which may be present in the specimen. The unbound enzyme-labeled drug molecule is active and catalyzes a change in another reagent, giving a color change. When the patient specimen contains the targeted drug, the patient drug competes with the enzyme-labeled drug for antibody binding. When the antibody binds to the enzyme-labeled drug, the enzyme is inactivated. Most presumptive drug tests at Quest Diagnostics will fit the CPT code 80307.Īn example of a presumptive drug test is the enzyme multiplied immunoassay, in which the assay reagents include an antibody to the drug and an enzyme-labeled drug molecule of the same drug that is being tested. Definitive testing typically follows presumptive testing, or may be the test of first choice.ĬPT code: 80305 Drug test(s), presumptive, any number of drug classes, qualitative any number of devices or procedures, (eg, immunoassay) capable of being read by direct optical observation only (eg, dipstick, cups, cards, cartridges) includes sample validation when performed, per date of service (maps to 80300 or G0477).ĬPT code: 80306 Drug test(s), presumptive, any number of drug classes, qualitative any number of devices or procedures, (eg, immunoassay) read by instrumented assisted direct optical observation (eg, dipstick, cups, cards, cartridges) includes sample validation when performed, per date of service (maps to 80300 or G0478).ĬPT code: 80307 Drug test(s), presumptive, any number of drug classes, qualitative any number of devices or procedures, by instrument chemistry and analyzers (eg, utilizing immunoassay ), chromatography (eg, GC, HPLC), and mass spectrometry either with or without chromatography, (DAT, DESI, GC-MS, GC-MS/MS, LC-MS, LC-MS/MS, LDTD, MALDI, TOF) includes sample validation when performed, per date of service (maps to 80301, 80302, 80303, 80304 and G0479). “Definitive” testing is a qualitative or quantitative procedure that identifies the specific drugs and associated metabolites. “A presumptive test is a qualitative test used to detect the possible presence of a drug or drug class,” he explained, based on the definition issued by the American Medical Association in 2015. ![]() Dr McClure outlined these complexities in a recent webinar. But whether a presumptive test is right for your patient depends on many factors, according to Dr Leland McClure, Director, Medical Science Liaison, Medical Affairs at Quest Diagnostics, and understanding the complexities of presumptive testing is vital for making the right testing choice. Presumptive drug testing can give you rapid results that can be used to help improve patient care. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |