External quality assessment of multi-analyte chromatographic methods in oral fluid

Abstract

Methods: Qualitative results were evaluated using sensitivity and specificity. Quantitative results were evaluated using z-scores and the standard deviation of Horwitz.Results: Specificity was above 99% in each round, sensitivity per analyte varied between 81.7 and 100%, 20 out of 22 analytes had a sensitivity above 90%. The percentage of satisfactory z-scores increased from 79.4% to 89.2%. This trend was seen for all drug classes, except zopiclone. Results were discussed with participating laboratories and problems were addressed.Conclusions: Because of these corrective actions, DRUID laboratories have a lower variation in results than previously published PT schemes in oral fluid.

A validated method for the detection and quantitation of 50 drugs of abuse and medicinal drugs in oral fluid by gas chromatography–mass spectrometry

“…Despite the variation noticed in the accuracy and precision studies during the validation, the results for zopiclone were precise in these rounds. During the quality control testing it was noticed that zopiclone was a substance that many of the laboratories involved in DRUID had problems with [22].…”

“…4). The quantitativity of the method was evaluated with Z-scores that were calculated according to Pil et al [22]. The Z-scores were |Z| < 2 for all compounds except for MDA on round 2/2008, when the Z-score was 3.1.…”

Development of an electrospray LC‐MS/MS method for quantification of Δ9‐tetrahydrocannabinol and its main metabolite in oral fluid

“…The analytes were extracted from oral fluid samples using a mixedmode SPE material, composed of a non-polar C 8 phase and a strong anion exchange sorbent (see Experimental section), similar to established procedures in the literature, which usually utilize mixed-mode cartridges containing cation exchange [14,18,23,25] and/or reversed-phase sorbents. [9,13] In our experiments, the chosen combination showed excellent efficiency for simultaneous extraction of THC and its metabolite THCCOOH.…”

Oral fluid for workplace drug testing: Laboratory implementation

“…Taking into account that many of the laboratories had not previously analyzed oral fluid, the results showed significant improvement as the facilities gained testing experience. In the final round, very low rates of false negative (0.9%) and false positives (0.4%) were reported 27. In addition, the UK offers an oral fluid proficiency testing scheme, UKNEQAS; and an oral fluid program from Italy, OralVeq, has been available for several years 28…”

“…In the final round, very low rates of false negative (0.9%) and false positives (0.4%) were reported. [27] In addition, the UK offers an oral fluid proficiency testing scheme, UKNEQAS; and an oral fluid program from Italy, OralVeq, has been available for several years. [28] All reports from proficiency programmes show that experience in testing is the key to excellent analytical performance.…”