Guided Case: From Screen to Definitive Result

A hospital chemistry bench tests a urine specimen under local non-federal clinical policy. The specimen was collected at 09:40 and received at 10:05, with no unusual odor and a yellow, clear appearance. Creatinine is 45 mg/dL, specific gravity is 1.018, pH is 6.2, and no oxidant flag is present. These findings do not suggest dilution or substitution by the federal criteria, while the clinical report still follows local policy.

The presumptive local screen reports opiates positive at 300 ng/mL, oxycodone negative at 100 ng/mL, and for fentanyl no assay signal met the 2 ng/mL cutoff for the tested target in this specimen; this does not exclude exposure outside the target, cutoff, specimen timing, or detection window. The current medication list documents morphine given the evening before collection. A positive opiate screen is compatible with that medication, but it remains a class reaction. The separate negative assays do not alter what the opiate assay detected.

Definitive GC-MS or LC-MS/MS testing detects morphine at 1,150 ng/mL and does not detect 6-acetylmorphine, codeine, fentanyl or norfentanyl, or oxycodone or oxymorphone within the tested panel. This identifies morphine within that definitive method and argues against heroin marker detection in this specimen. It cannot establish the administered dose, route, exact timing, impairment, or all possible remote exposures. Reconcile the definitive analyte result with the documented medication and release only the conclusion supported by the tested panel.