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T R Koch

Publications and source records attributed to T R Koch.

83 records · Page 5Linked to original sources
PubMed1977

Evaluation of automated glucose oxidase methods for serum glucose: comparison to hexokinase of a colorimetric and an electrometric method.

Two automated glucose oxidase methods have been evaluated with respect to accuracy, precision, recovery, linearity and various potential interferences. Trinder's method on an AutoAnalyzer II had a between-day coefficient of variation (C.V.) of 2.6% (mean 228 mg/dl), was linear to 500 mg/dl, and produced a mean recovery of 99.7%. Comparison of Trinder's method with a manual, blanked hexokinase method yielded the regression equation: TR=--1.95 + HEX (1.04); Spearman's rho correlation coefficient was: 0.974. The Beckman System I glucose method had a between-day C.V. of 1.6% (mean 198 mg/dl), was linear to 500 mg/dl, and recovered an average of 98.0% of added glucose. Comparison with the same hexokinase method yielded: SYI = 1.27 + HEX (1.02: Spearman's rho = 0.991. None of the possible interfering compounds tested caused significant deviation of results by either method within the range of concentrations encountered physiologically. Trinder's method on the AutoAnalyzer II and the System I method are accurate, precise methods and are highly recommended for routine use in the clinical laboratory.

Autoanalysis↗
PubMedDate not supplied

Serial capillary gas chromatography/Fourier transform infrared spectrometry/mass spectrometry (GC/IR/MS): qualitative and quantitative analysis of amphetamine, methamphetamine, and related analogues in human urine.

A method using serial capillary gas chromatography/Fourier transform infrared spectroscopy/mass spectrometry (GC/IR/MS) for the analysis of derivatized amphetamine, methamphetamine, and related analogues was developed. The GC/IR/MS was configured and optimized with a Hewlett-Packard (HP) 5890A gas chromatograph with a 12-m x 0.32-mm i.d. HP-5 capillary column serially interfaced through an HP 5965A infrared detector to an HP 5970 mass selective detector with a fused-silica 1.2-m x 0.10-mm i.d. column. Urine samples are extracted and derivatized as heptafluorobutyryl (HFBA) derivatives. For quantitation GC/MS in the selected ion monitoring (SIM) mode was used, with D,L-amphetamine-D5 as the internal standard. Gas chromatography/Fourier transform infrared spectrometry (GC/FT-IR) quantitation uses a selected wavelength chromatogram, spectral subtraction, double internal standard method using both D,L-amphetamine-D5 and 4-phenyl butylamine. Sensitivity for the combined GC/MS and GC/FT-IR system for amphetamine and methamphetamine shows limits of linearity of 100 to 5000 ng/mL, a limit of detection of 25 ng/mL, and a limit of quantitation of 98 ng/mL. The overall recovery for amphetamine and related analogues was greater than 85%. Precision studies for concentrations over the range of 200 to 1500 ng/mL showed coefficients of variations ranging from 2.8 to 13.0%. Correlation studies for quantitative GC/MS SIM and GC/FT-IR are greater than 0.98 for amphetamine, methamphetamine, and related analogues. Each analysis includes GC/MS SIM and GC/FT-IR quantitation, qualitative nonselective full spectra GC/FT-IR, and GC/MS scans of HFBA derivatives cross-referenced with an internal drug library, which provides high confidence and a means for the surveillance of amphetamine-like chemical analogues.

Amphetamine↗
PubMedDate not supplied

Improved screening for benzodiazepine metabolites in urine using the Triage Panel for Drugs of Abuse.

Screening for benzodiazepines is an important component of many drug testing programs. Current immunochemical methods are limited by a lack of sensitivity to many of the 35 forms of benzodiazepines available and because the antibodies used are insensitive to the glucuronic acid conjugates that constitute the major metabolites in urine. The Triage Panel for Drugs of Abuse (Biosite Diagnostics), a new screening device, is a competitive immunoassay containing monoclonal antibodies directed against glucuronide metabolites of benzodiazepines. We tested this device on 326 urine specimens, which were also tested by two other immunoassay methods (FPIA and EMIT) and by GC/MS. We found a sensitivity of 97.5% and a specificity of 94.3% for the Triage assay when it was applied to a population in which approximately 50% of the specimens were positive; a distribution of eight different benzodiazepines was found in the positive samples. Other immunoassays performed with lower sensitivity or specificity or both. We found no significant difference between two analysts using the Triage test. We conclude that the Triage method represents a superior method for benzodiazepine screening when compared with other immunoassay methods.

Anti-Anxiety Agents↗
PubMedDate not supplied

Employment profiles in neuromuscular diseases.

Consumer and rehabilitation provider factors that might limit employment opportunities for 154 individuals with six slowly progressive neuromuscular diseases (NMD) were investigated. The NMDs were spinal muscular atrophy (SMA), hereditary motor sensory neuropathy (HMSN), Becker's muscular dystrophy (BMD), facioscapulohumeral muscular dystrophy (FSHD), myotonic muscular dystrophy (MMD), and limb-girdle syndrome (LGS). Forty percent were employed in the competitive labor market at the time of the study, 50% had been employed in the past, and 10% had never been employed. The major consumer barrier to employment was education. Other important factors were type of occupation, intellectual capacity, psychosocial adjustment, and the belief by most individuals that their physical disability was the only or major barrier to obtaining a job. Psychological characteristics were associated with level of unemployment. However, physical impairment and disability were not associated with level of unemployment. There also were differences among the types of NMDs. Compared with the SMA, HMSN, BMD, and FSHD groups, the MMD and LGS groups had significantly higher levels of unemployment, lower educational levels, and fewer employed professional, management, and technical workers. Nonphysical impairment factors such as a low percentage of college graduates, impaired intellectual function in some individuals, and poor psychological adjustment were correlated with higher unemployment levels in the MMD group. Unemployment in the LGS group was correlated with a failure to complete high school. Major provider barriers to employment were the low level of referrals to Department of Rehabilitation by physicians and the low percentage of acceptance into the State Department of Rehabilitation. The low rate of acceptance was primarily attributable to the low number of referrals compounded by a lack of counselor experience with individuals with NMD. Both consumer and provider barriers may contribute to the lack of interest in obtaining a job.

Adult↗
PubMedDate not supplied

Gut hormone release in patients after spinal cord injury.

Gastrointestinal disorders including abdominal pain, abdominal distention, ileus, and constipation are common after spinal cord injury. In physiologic studies of patients with spinal cord injury, slow gastric emptying, ileal dilation, and abnormal rectosigmoid motility have been found. However, it is not yet known whether abnormal gut hormone release is important in the development of these abnormalities. In healthy volunteers, there are postprandial increases in plasma peptide YY and motilin levels, which appear related to neural mechanisms. We hypothesized that abdominal sympathetic pathways provide tonic inhibition of peptide YY and motilin release and that postprandial increases in these gut hormones are mediated through spinal pathways. Fasting serum was obtained from normal volunteers, paraplegic patients, and tetraplegic patients. In studies in which patients were fed, serum was obtained from normal volunteers, paraplegic patients, and tetraplegic patients before and at 30-min intervals after a 280 kcal meal. Serum motilin and peptide YY levels were measured by radioimmunoassays. In fasting studies, there was a trend (P = 0.23) toward increased fasting serum motilin in paraplegic patients, and this result did not support tonic inhibition of motilin release. Fasting peptide YY levels were not increased in spinal cord injury patients, which did not support tonic inhibition of peptide YY release. In fed studies, there were strong trends toward postprandial increases in serum peptide YY in volunteers and paraplegic patients and a significant postprandial rise in serum peptide YY in tetraplegic patients (P = 0.04). This was evidence against involvement of spinal pathways in postprandial release of peptide YY.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗