Insufficient sample quantity — Samples must be at least 2mL in volume. Improper labeling — Specimens must be labeled with patient name, DOB, SS number/medical record number, and order number. Specimen leakage — Leaks can cause potential cross-contamination, making them unsuitable for analysis. Specimen has been adulterated — The ratio of the parent drug to its metabolites can show evidence of adulteration. Specimen has violated stability requirements — Specimens that have exceeded storage limits may be rejected.