ABSTRACT
We aimed to evaluate the interference of lamotrigine (LMG) on the synthetic cannabinoids metabolite-K2/1 (SCm/K1) urine test by Homogeneous Enzyme Immunoassay (Immune-SCm/K1). This study consists of two parts: case-control and interference effect research. In the case-control study, two groups using LMG and a non-use of LMG were formed, all of them non-SC users. In the interference effect research, four groups were formed by adding either a LMG stock solution or a LMG user's urine to a SCm/K1 negative urine, and Immune-SCm/K1 test calibrators and quality control (QC) materials. Immune-SCm/K1, SCm/K1 by LC/MS-MS and LMG tests were performed on all samples in the study. The case-control study was performed on a total of 55 participants (mean age 39.76 ± 9.84 years). Both groups were statistically insignificant in terms of age and gender. Urine LMG levels were 5.71 ± 10.61 mg/L in the LMG group and <0.30 mg/L in the control group. Immune-SCm/K1 results were 35.84 ± 7.62 ng/mL in the LMG group, <3.00 ng/mL in the control group and the LC/MS-SCm/K1 urine test of both groups were found to be 'NEGATIVE'. Results were interpreted as a cross-reaction in the interference study and a statistically significant relationship was found between LMG levels and Immune-SCm/K1 levels in the SCm/K1 negative samples (groups 1 and 2) (R2 = 0.9341 and R2 = 0.9941, respectively; p < .001). LMG interference was observed in SCm/K1 positive samples ranging from -6.17 to 714.77%. LMG in the specimen interferes with the Immune-SCm/K1 screening test and causes false positivities.
