Bayer Immuno 1 PSA Assay: an automated, ultrasensitive method to quantitate total PSA in serum.

The Bayer Immuno 1 PSA Assay measures total PSA in human serum and demonstrates excellent performance with an interassay CV < or = 3.4% and a biological detection limit of 0.03 microgram/L. No significant interference from common hormonal and chemotherapeutic drugs, kallikrein, prostatic acid phosphatase, and trypsin, or elevated levels of total bilirubin, hemoglobin, triglycerides, and IgG was observed. The 95th percentile values for healthy individuals increased with age from 3.0 micrograms/L for males 50-59 years and 3.3 micrograms/L for males 60-69 years, to 4.6 micrograms/L for males > or = 70 years. Clinical studies with retrospective samples demonstrated correspondence between serial measurements of PSA and clinical outcome for 98% of 159 prostate cancer patients. Clinical sensitivity for patients with clinical evidence of disease, untreated at the time of specimen draw, increased with increasing stage from 77.5-100%. Specificity of 60-70% for BPH and other benign urogenital diseases was consistent with previous findings. Bayer Immuno 1 PSA Assay values for 2131 specimens from healthy subjects and patients with prostate cancer, BPH, and other malignant and nonmalignant diseases correlated well with the Abbott IMx PSA Assay over the range 0.0-6,238 micrograms/L (Y = 1.10 x + 0.02). The Bayer Immuno 1 PSA Assay provides automated ultrasensitive, precise, and equimolar measurement of total PSA in human serum.

Quantitative metabolic profiling of valproic acid in humans using automated gas chromatographic/mass spectrometric techniques.

An automated gas chromatographic/mass spectrometric assay is described for the antiepileptic drug valproic acid (VPA) and 14 of its metabolites in plasma or urine. Quantitative analysis of the parent drug and its biotransformation products was carried out with the aid of trimethylsilyl derivatives, and was performed by selected ion monitoring gas chromatography/mass spectrometry (normally of [M-CH3]+ species) using an HP 5790 mass selective detector (MSD) quadrupole mass spectrometer. The analysis was fully automated, in that simple injection, data acquisition, integration, quantification and report functions were carried out during unattended operation by an HP 59970C ChemStation computer system. The method exhibits good accuracy and high precision, with correlation coefficients greater than 0.990 for all standard curves. Replicate analyses of pooled plasma samples over a 4 month period exhibited an inter-day variation of less than 15% for the parent drug and ten of its metabolites. Moreover, the high dynamic range of the MSD instrument permitted quantification of VPA and minor metabolites thereof (e.g. the hepatotoxic terminal olefin, delta 4-VPA) at levels as disparate as 260 micrograms ml-1 (VPA) and 14 ng ml-1 (delta 4-VPA) in a single analysis. The high stability and sensitivity of the assay, combined with the fully automated features of the instrumentation, make the method ideally suited to expanded clinical studies and for the routine monitoring of potentially high-risk patients on VPA therapy.