Reducing the need for repeating urine drug testing with the gray zone determined by the measurement uncertainty.

Background: On an initial urine screening test for illegal substances, if the concentration of a substance is at or above the determined legislative threshold, it is reported as positive. Repeating testing with the same sample to verify it before reporting is a common practice in clinical laboratories. This study aimed to determine whether measurement uncertainty (MU) results can be used to detect a grey zone to reduce repeat testing. Methods: A retrospective study was conducted using data from the laboratory information system between January 1, 2020, and July 1, 2022. Samples studied twice within one hour before reporting for the same urine sample were analyzed. The MU values for urinary amphetamine, cannabinoid, cocaine, and opioid parameters were calculated using ADVIA Chemistry reagents on a Siemens ADVIA 1800 chemical analyzer. The grey zone was defined as the cut-off value ± MU.

Effects of altitudes on secondary metabolite contents of Origanum majorana L.

Altitude is an important ecological factor that significantly affects essential oil content, yield and composition. In this study, conducted to examine the effects of altitude on essential oil content and composition of O. majorana, plant samples were collected from the southern region of Türkiye at the beginning of flowering period from seven different altitudes (766 m, 890 m, 968 m, 1079 m, 1180 m, 1261 m and 1387 m) at 100 m intervals. The highest percentage of essential oil (6.50%) obtained by hydro-distillation was determined at 766 m altitudes. The GC-MS analyses revealed that low altitude affected some essential oil components positively. The linalool ratio, which is the major component of the essential oil of O. majorana species, was the highest at 766 m (79.84%) altitudes. Borneol, linalool oxide, trans-linalool oxide, caryophyllene, a-humulene, germacrene-D and bicyclogermacrene components yielded high values at 890 m altitudes. Thymol and α-terpineol, which have an important place in the essential oil composition, increased at 1180 m altitudes; a-terpinene, cis-sabinene hydrate, terpinene-4-ol and carvacrol increased at 1387 m altitudes.