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Nitrite ion has been identified as the active ingredient of two commercial adulterants that could cause discrepant results between the immunoassay screening and gas chromatographic-mass spectrometric (GC-MS) confirmation of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in urine. Procedures to chemically convert the nitrite ion at the beginning of sample preparation for GC-MS analysis may not overcome all nitrite adulteration cases because portions of the THCCOOH might have been lost between the time of sample collection and the time of analysis. This study was conducted to further investigate the influence of both urine sample matrix and the duration of nitrite exposure on nitrite interference of THCCOOH detection. Forty clinical "THC-positive samples" that had been screened and confirmed positive for the presence of THCCOOH were spiked with 0.15M or 0.3M of nitrite. The levels of THCCOOH at various time intervals after nitrite spiking were monitored by instrument-based cannabinoids immunoassays (Syva EMIT d.a.u. and/or Roche Abuscreen ONLINE assays) and by an onsite THC immunoassay (Roche ONTRAK TESTSTIK). Results from this report demonstrate that the two outstanding "urine specimen factors" that dictated the effectiveness of the nitrite adulteration were urinary pH and the original drug concentration before nitrite spiking. Significant decreases in the immunoassay results could be observed within 4 h of nitrite treatment in the majority of samples with acidic urinary pH values. Regardless of their original concentration of THCCOOH (GC-MS ranging from 33 to 488 ng/mL), all of the 20 samples that had acidic pH values gave negative immunoassay results 1 day after nitrite adulteration. In contrast, the immunoassay results of samples with neutral or basic pH values were less affected by nitrite exposure in the same studies. Approximately two-thirds of the samples with pH values greater than 7.0 remained immunoassay-positive 3 days after nitrite spiking. Nevertheless, some of the adulterated urine that showed no change in immunoassay results might exhibit significant decrease in GC-MS recoveries even with bisulfite treatment, collaborating with the observations that a portion of samples screened positive with THC immunoassay in the laboratory could fail to confirm with GC-MS analysis. The decrease or loss of immunoassay detectable cannabinoid cross-reactives in acidic "THC-positive samples" can be attenuated by chemically increasing the pH value of the samples to the basic pH range.

Background We developed a porous Ti alloy/PEEK composite interbody cage by utilizing the advantages of polyetheretherketone (PEEK) and titanium alloy (Ti alloy) in combination with additive manufacturing technology. Methods Porous Ti alloy/PEEK composite cages were manufactured using various controlled porosities. Anterior intervertebral lumbar fusion and posterior augmentation were performed at three vertebral levels on 20 female pigs. Each level was randomly implanted with one of the five cages that were tested: a commercialized pure PEEK cage, a Ti alloy/PEEK composite cage with nonporous Ti alloy endplates, and three composite cages with porosities of 40, 60, and 80%, respectively. Micro-computed tomography (CT), backscattered-electron SEM (BSE-SEM), and histological analyses were performed. Results Micro-CT and histological analyses revealed improved bone growth in high-porosity groups. Micro-CT and BSE-SEM demonstrated that structures with high porosities, especially 60 and 80%, facilitated more bone formation inside the implant but not outside the implant. Histological analysis also showed that bone formation was higher in Ti alloy groups than in the PEEK group. Conclusion The composite cage presents the biological advantages of Ti alloy porous endplates and the mechanical and radiographic advantages of the PEEK central core, which makes it suitable for use as a single implant for intervertebral fusion.

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