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A A Pappas

Publications and source records attributed to A A Pappas.

At least 37 records · Page 2Linked to original sources
PubMed1991

Analysis of phospholipids in human amniotic fluid by 31P NMR.

A recently described solvent-reagent system for obtaining narrow linewidths in 31P NMR spectra of phospholipid extracts was applied to human amniotic fluid. Resolution of the major components was achieved by manipulating the solvent composition, and assignments were made by spiking samples with standard compounds. Spin-lattice relaxation times were determined and used to optimize data acquisition. NMR estimates of the phosphatidylcholine to sphingomyelin ratio for 33 patients were compared to those obtained by TLC densitometry, a common clinical assay for fetal pulmonary maturity. Estimates of the levels of phosphatidylglycerol and phosphatidylinositol could also be obtained from 31P NMR. High-resolution 31P NMR in this solvent-reagent system provides a relatively straightforward and reliable alternative method for assessing fetal pulmonary status by phospholipid quantitation in human amniotic fluid. The 31P NMR method has the advantage that it is sensitive to total, and not just unsaturated, phosphatidylcholine.

Amniotic Fluid↗
PubMed1991

Isopropanol ingestion: a report of six episodes with isopropanol and acetone serum concentration time data.

The disposition of isopropanol and its major metabolite acetone were observed in six isopropanol ingestion episodes among five patients. Serum admission isopropanol and peak acetone concentrations ranged from 16.5 to 220 mg/dL and 141 to 585 mg/dL respectively. Ingestions ranged from 120 to 300 mL of 70% isopropanol with concomitant ethanol ingestion in two episodes. The isopropanol and acetone apparent half-lives ranged from 2.9 to 16.2 hours (h) and 7.6 to 26.2 h respectively. Two episodes of isopropanol ingestion were observed within a 9 month period in patient one. Isopropanol terminal elimination rate constants were 0.043 and 0.085 per hour (per h) with no marked difference in acetone terminal elimination rate constants (0.025 and 0.033 per h). Discrepancy between the two isopropanol elimination rate constants reflected concomitant ethanol abuse with the first ingestion. Reductions in isopropanol and acetone half-lives were also noted among patients requiring ventilatory support.

1-Propanol↗
PubMed1991

Rapid preparation of plasma for coagulation testing.

Currently recommended minimum centrifugation of whole blood to produce platelet-poor plasma for routine coagulation assays is 1000g relative centrifugal force for 10 minutes. Many clinical laboratories centrifuge blood for routine coagulation assays from 500g to 2000g, with spin times varying from 20 to 5 minutes. Ninety blood samples, routinely submitted to our coagulation laboratory, were prospectively assayed simultaneously for the prothrombin time, activated partial thromboplastin time, and fibrinogen level, comparing centrifugation at 11,000g for 2 minutes with centrifugation at 1000g for 10 minutes. Routine and readily available equipment and supplies were used. Platelet counts were performed on the supernatant plasma in each sample to determine the efficacy of platelet depletion. Excellent correlation of methods was observed for the prothrombin time, activated partial thromboplastin time, and fibrinogen level. Platelet counts on the plasma supernatant showed no significant difference between the two centrifugation methods. We concluded that high-speed centrifugation at 11,000g with a shortened spin time of 2 minutes and with the use of routinely available equipment and supplies can significantly decrease the specimen preparation time for routine coagulation testing.

Blood↗
PubMed1990

Clinical comparison of immunoradiometric assays for intact versus beta-specific human chorionic gonadotropin.

Monoclonal immunoradiometric assays (IRMA) for human chorionic gonadotropin (hCG) are available for either intact hCG (IhCG) or beta subunit hCG (beta hCG). The authors evaluated the clinical applications of both methods. Serum samples (N = 180) were divided into the following five clinical groups: Group 1: elevated luteinizing hormone (LH), follicular stimulating hormone (FSH), and thyroid-stimulating hormone (TSH), which share alpha subunits with hCG; Group 2: pregnancy; Group 3: trophoblastic tumors; Group 4: malignancy; and Group 5: positive rheumatoid factor or anti-nuclear antibody (ANA). The values of beta hCG versus IhCG for Group 1 showed statistical significance but no clinical significance, indicating negligible cross-reactivity in the alpha subunit group. beta hCG values, although exceeding the IhCG values, correlated well (r = 0.97) in intrauterine pregnancies; however, these values were not believed to be clinically significant. There is negligible interference by alpha subunits, elevated rheumatoid factor, ANA, or malignancy in the determination of IhCG versus beta hCG. The authors conclude that either the IhCG or beta hCG assays may be used in clinical conditions in which a potential exists for interference of alpha subunits, autoantibodies, or heterophile antibodies or in malignancy.

Antibodies, Antinuclear↗
PubMed1989

Interpretation of urine quantitative 11-nor-delta-9 tetrahydrocannabinol-9-carboxylic acid to determine abstinence from marijuana smoking.

Verification of abstinence from cannabinoid use after initial identification requires documentation of falling quantitative levels of urinary 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) over an extended time period. We present a case in which normalization of quantitative urinary THC-COOH results to urinary creatinine is required to correctly interpret a series of quantitative levels and confirm abstinence from marijuana smoking.

Creatinine↗
PubMed1988

Vancomycin serum protein binding determination by ultrafiltration.

Sixty-two serum concentrations were obtained from 12 infected patients enrolled in a vancomycin pharmacokinetic study. Both unbound and total serum vancomycin concentrations were measured using ultrafiltration and a commercial fluorescent polarization immunoassay. Ultrafiltrates were obtained by centrifugation at 1000 X g for ten minutes at room temperature and their assay indicated a range in protein binding from 7.9 to 71 percent. The mean protein binding (mean +/- SD) was 41.95 +/- 14.15 percent. No measurable adsorption of vancomycin onto the ultrafiltration membrane was noted. Orthogonal regression of unbound versus total vancomycin concentrations was described by the equation y = 0.597x-0.362 with a correlation coefficient of 0.948.

Adult↗
PubMed1987

Total and free disopyramide by fluorescence polarization immunoassay and relationship between free fraction and alpha-1 acid glycoprotein.

Disopyramide is an antiarrhythmic drug with concentration dependent protein binding within the therapeutic range. We found good agreement between fluorescence polarization immunoassay (FPIA, Abbott TDX) and high performance liquid chromatography (HPLC) for total disopyramide among 27 admission patients' sera (FPIA = 1.12 (HPLC) -0.002, r = 0.982, SEE = 0.378 mg/l). Agreement between FPIA and HPLC for free disopyramide was similarly good (FPIA = 0.867 (HPLC) -0.003, r = 0.986, SEE = 0.09 mg/l, n = 27). Serum alpha 1 acid glycoprotein concentration (AAG) and free fraction (FF) percent of disopyramide correlated inversely (FF = -0.0112 (AAG) + 31.3 r = 0.707, SEE = 6.41 mg/l, n = 24), and the free disopyramide fraction varied greatly. For two pooled sera with 12 different disopyramide concentrations (range from 0.5-20.0 mg/l), the proportion of free fraction ranged from 6.5 to 73.2%. Overall, we found the free disopyramide fraction variable with each individual, total drug, and protein concentration. Therefore, free drug concentration should be monitored in disopyramide therapy, and FPIA is reliable for free as well as total drug assay.

Chromatography, High Pressure Liquid↗
PubMed1987

Carbamazepine and erythroid arrest.

A patient who developed anemia with an isolated erythroid toxicity following chronic carbamazepine administration is reported. The anemia quickly resolved with discontinuation of this drug. Other hematologic toxicities of carbamazepine are well described; however, an isolated erythroid toxicity is unusual. In addition, the onset of this drug-induced toxicity developed later than is expected for carbamazepine-associated hematological toxicities. This case demonstrates the suddenness with which hematological toxicities can occur with carbamazepine, and affirms the need for regular monitoring of patients. Any significant decrease in the patient's hemoglobin or hematocrit level requires close monitoring for the sudden development of serious anemia.

Adult↗
PubMed1987

Financial unbundling reduces outpatient laboratory use.

Previous studies have examined methods of reducing laboratory use, without great success. We studied the effects of the financial unbundling of clinical biochemistry determinations in a university outpatient clinic. After eliminating the charge structure that promoted panel use, the ordering of chemistry 19 panels fell dramatically, accompanied by an increase in orders for electrolyte and chemistry 6 panels. The total number of biochemical assay determinations fell by one third after this administrative intervention. Only orders for potassium and creatinine measurements remained relatively unchanged and eventually increased. The ordering of five analytes of the chemistry 19 profile was reduced by at least 50%. Reassessment of the intervention six months later demonstrated the sustained decline in laboratory use. We conclude that physicians are attuned to price inefficiencies in basic laboratory testing and can alter their ordering behavior accordingly. Facilities can change patterns of use by altering charge structures alone. The decline in laboratory testing also indicates that physicians receive unnecessary clinical data when they order biochemical profiles. Financially bundled chemistry profiles could be replaced by physiologically based test groupings.

Arkansas↗
PubMed1986

Acquired von Willebrand syndrome due to an inhibitor specific for von Willebrand factor antigens.

A patient with acquired von Willebrand syndrome associated with polycythemia rubra vera is described. Her plasma factor VIII procoagulant activity (67 U/dl) and factor VIII-related antigen (117 U/dl) were normal but no von Willebrand factor activity could be detected. Factor VIII crossed immunoelectrophoresis revealed decreased levels of less anodic polymeric forms of factor VIII. Mixture of her plasma or immunoglobulin G (IgG) fraction with normal plasma resulted in complete recovery of factor VIII activity and related antigen but no measurable von Willebrand factor activity, confirming the presence of an unique inhibitor. The limited specificity of this inhibitor to antigenic sites solely on the von Willebrand portion of the factor VIII bimolecular complex is distinct from all previous reports of this syndrome. This unique inhibitor offers a molecular probe to examine the von Willebrand factor: platelet interaction.

Antigens↗
PubMed1986

A computerized system for rapid retrieval and compilation of critical or interesting patient data.

The timely availability and presentation of critical and interesting patient data is essential to ensure quality patient care as well as ease of recognition and, secondarily, to provide material for teaching and research. The ability to accomplish these goals expeditiously in a complex and busy clinical laboratory may be difficult to acquire. An on-line, computerized system has been developed which automatically searches each patient record for up to 600 different laboratory tests, compares each result against individually established limits, and then formats pertinent test results for maximum discrimination. The report format also includes patient and specimen collection data, diagnosis, attending physician's name, and other desired associated test results. An additional feature of the system is that selected critical or interesting results for each laboratory division may be displayed on video display terminals located throughout the laboratory and at nursing stations. The system was written using the FORTRAN programming language and runs on a Control Data Cyber 18 computer.

Clinical Laboratory Techniques↗
PubMed1986

Rapid sample preparation and high performance liquid chromatographic determination of total and unbound serum disopyramide.

A rapid sample preparation procedure, which requires no solvent extraction or concentration, for the high performance liquid chromatographic (HPLC) determination of disopyramide is described. The chromatography is performed on a C-18 radial compression mu-Bondapak column and detection by absorbance at 254 nm with a run time of 12 min. The mobile phase is 10 mM sodium acetate (pH 4.5)/acetonitrile (3:1 vol/vol). For the total drug assay, 50 microliter 30% (wt/vol) trichloroacetic acid is added to 500 microliter serum, which causes the precipitation of protein. Following centrifugation, 100 microliter of supernatant is mixed with 25 microliters of internal standard (25 micrograms/ml, ethyl p-aminobenzoate), and 50 microliters of this mixture is injected into the HPLC. Unbound disopyramide is separated from protein-bound drug by filtration with an Amicon Centrifree filter, which removes 99.6% of protein and does not retain disopyramide. To 100 microliters of this filtrate is added 25 microliters of internal standard, and 50 microliters is injected into the HPLC. The assay is linear to at least 20 micrograms/ml. The total drug assay shows an average recovery of 93.0% with an average coefficient of variation (CV) of 3.4%. The unbound drug assay shows an average CV of 4.1%. The percentage of free drug in a sample containing 4.85 g/dl protein varies from 68.0 to 83.5% at concentrations of 2.5-10 micrograms/ml, which illustrates the concentration-dependent nature of the protein binding, and the need to measure the unbound fraction of drug. Of 31 drugs tested for interference, none was found to interfere.

Chromatography, High Pressure Liquid↗