Therefore, assuming there were 3 false positive results, the probability that a positive result has identified a patient who is adherent is: Predictive value calculations take into account the pre-test probability, which is pivotal in determining the true value of clinical laboratory data.
Clark JD. Gary M.
Sensitivities may vary to such a degree within a drug class that screening assays may be incapable of detecting specific members of the class. Controlled substance abuse and illicit drug use in chronic pain patients: Because the span between the signals produced by the negative control and the threshold calibrator set to zero was greater after the lot change and recalibration, it was assumed that the new reagent lot had greater sensitivity for morphine and codeine.
Forensic Sci Int 1996 ; 77: There also were instances in which no information about prescribed medications appeared on the lab order form, but the PCP contacted the lab for follow-up.
Conversely, in mostly adherent patients, there will be few false positives, and the predictive value of positive results will be high Equation 3. Urine drug testing UDT is an emerging standard of care in the evaluation and treatment of chronic non-cancer pain patients with opioid analgesics.
Percent cross-reactivity of several commercially-available urine opiate screening methods with opiate metabolites and analogues.
In this case, co-administered rifampin, a CYP 3A4 and 2D6 inducer, appeared to be responsible for the accelerated metabolism of the opioid and, hence, this pseudo-false negative test. Reviews of opioid prescribing guidelines have advocated the use of UDT in patients who receive chronic opioid therapy.
The value of a clinical laboratory test can be measured in several dimensions. Pseudo-false positive tests.
Decreased signal in Emit assays of drugs of abuse in urine after ingestion of aspirin: J Opioid Manag 2006 ; 2: The drug library can be modified by the user, so the instrument can be customized for specific applications.
Laboratory error. Or the presence of a central nervous system depressant may help guide the management of an unresponsive patient. Article Contents. Some adulterants are designed to interfere with the assay itself, and are not detectable by routine integrity checks for substitution or dilution.
In three cases, the signal for the patient urine was less than the negative control, but the specimen was referred for confirmatory analysis at the request of the PCP.
Generally, UDT methods are sufficiently sensitive to detect drug use within the preceding 24—48 h, but exceptions exist when the analytical method has limited sensitivity for a specific drug.
In this example, 22 of the 25 non-adherent patients will test negative for the drug, but so will 15 of the adherent patients. In an increasingly sophisticated game of cat and mouse, as the proprietary ingredients in commercially available urine adulterants become known and as tests are developed to detect them, manufacturers of these adulterants reformulate their products in order to avoid detection.