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At least 487 records · Page 27Linked to original sources
PubMed2004

An expression of within-plate uncertainty in sandwich ELISA.

This paper puts forward a method to describe an equation of the within-plate uncertainty (relative standard deviation (R.S.D.) of measurements) as a function of analyte concentration in sandwich enzyme-linked immunosorbent assay (ELISA). A kit for thyroid stimulating hormone is taken as an example. The pipetting procedures of analyte solution and chromogen-substrate solution and absorbance inherent to the wells of a microplate are identified as major error sources and their variability is included as parameters in the uncertainty equation. These parameters can be determined by the experiments with distilled water. The theoretical R.S.D. is shown to be in good agreement with the results of the repeated experiments using the real samples. Since the theory gives a continuous plot of R.S.D. against concentration, the uncertainty structure of the ELISA kit can be recognized over a wide concentration range and the detection limit and quantitation range can easily be determined on the plot.

Enzyme-Linked Immunosorbent Assay↗
PubMed2006

Supercritical fluid chromatography-tandem mass spectrometry for fast bioanalysis of R/S-warfarin in human plasma.

Chiral separation for the analysis of enantiomers in biological fluids by HPLC often takes relatively long chromatography time compared to achiral analysis. The advantage of fast mass transfer in packed-column supercritical fluid chromatography (pSFC) and the high-flow compatibility of APCI-MS/MS were applied to develop a fast bioanalytical method for R/S-warfarin in human plasma. Presented here are the main challenges encountered during method development of a semi-automated liquid extraction SFC-MS/MS method. The selection of internal standard, robustness of the SFC equipment, and carryover issues are discussed. The method has high-throughput: the chromatography time is at least two-fold faster than the our fastest previous method; and the liquid/liquid extraction time of 96 samples is less than 20 min using a Tecan Genesis RSP 100 pipetting station and a Tomtec Quadra-96 workstation. The standard curve range was 13.6-2500 ng/ml. Precision of QC concentrations from four validation runs was 7.0% for R-warfarin and 6.0% C.V. for S-warfarin; and the bias was 3.7 and 3.2% R.E., respectively. The method is sensitive, accurate, selective and robust, and was applied to a drug-interaction clinical study with rapid turnaround of sample analysis.

Calibration↗
PubMed2004

Spontaneous synaptic activity in chick vestibular nucleus neurons during the perinatal period.

The principal cells of the chick tangential nucleus are second-order vestibular neurons involved in the vestibuloocular and vestibulocollic reflexes. The spontaneous synaptic activity of morphologically identified principal cells was characterized in brain slices from 1-day-old hatchlings (H1) using whole-cell voltage-clamp recordings and Cs-gluconate pipet solution. The frequency was 1.45 Hz for spontaneous excitatory postsynaptic currents (sEPSCs) and 1.47 Hz for spontaneous inhibitory postsynaptic currents (sIPSCs). Using specific neurotransmitter receptor antagonists, all of the sEPSCs were identified as AMPA receptor-mediated events, whereas 56% of the sIPSCs were glycine and 44% were GABA(A) receptor-mediated events. On exposure to TTX, the frequency of EPSCs decreased by 68%, while the frequency of IPSCs decreased by 33%, indicating greater EPSC dependency on presynaptic action potentials. These data on spontaneous synaptic activity at H1 were compared with those obtained in previous studies of 16-day old embryos (E16). After birth, the spontaneous synaptic activity exhibited increased EPSC frequency, increased ratio for excitatory to inhibitory events, increased percentage of TTX-dependent EPSCs, and faster kinetics. In addition, the ratio for glycine/GABA receptor-mediated events increased significantly. Altogether, these data indicate that at hatching spontaneous synaptic activity of vestibular nucleus neurons in brain slices of the chick tangential nucleus undergoes appreciable changes, with increased frequency of EPSCs and glycinergic activity playing more important roles compared with the late-term chick embryo when GABAergic activity prevailed. The definition of this developmental pattern of synaptic activity in vestibular nucleus neurons should contribute to understanding how vestibular reflex activity is established in the hatchling chick.

Afferent Pathways↗
PubMed2004

Isomers of trans fatty acids modify the activity of platelet 12-P lipoxygenase and cyclooxygenase/thromboxane synthase.

OBJECTIVES: Trans isomers of fatty acids (TFA) have been implicated in the initiation and progression of atherosclerosis. Previous studies have shown that trans-unsaturated fatty acids like their cis-unsaturated counterparts exert a modifying effect on platelet aggregation. The aim of this work was to determine the influence of TFA on the aforementioned enzymes: lipoxygenase and cyclooxygenase/thromboxane synthase. METHODS: Two C18 cis-trans fatty acid pairs: oleic/elaidic and linoleic/linolelaidic were chosen. Fasting blood was sampled from 30 healthy volunteers without any lipid abnormalities and not on medication for at least 7 days prior to sampling. Platelet-rich plasma (PRP) was prepared and the platelet count was adjusted to 3 x 10(8) cells x ml(-1). Fatty acids in hexane were added to a final concentration of 7 microM and evaporated to dryness under nitrogen, 500 microl of PRP was pipetted into each tube, thoroughly mixed and incubated at 37 degrees C for 60 min. 12-P LOX activity was measured with a spectrophotometric method and expressed per mg protein. Cyclooxygenase/thromboxane synthase activity was determined by TXB(2) production with an ELISA-based assay. Statistics were done with the Kruskal-Wallis test and Statistica software package. RESULTS: We have found that the activity of 12-P LOX was suppressed by all cis-trans fatty acids used by us. Cyclooxygenase/thromboxane synthase activity was significantly inhibited by polyunsaturated fatty acids only. Linolelaidic acid was more potent in comparison to its monounsaturated (elaidic acid) counterpart. CONCLUSIONS: We believe that the effects of fatty acids are demonstrated at the membrane level where fatty acids may produce a perturbation in specific lipid domains. TFA are able to interact with the platelet membrane and transmembrane proteins just as the cis isomers. By interacting with proteins exposed on the cytoplasmic membrane, TFA may modify the activity of receptors and other membrane proteins. In this way, changes on the membrane surface are propagated into the cell affecting the activity of cytoplasmic enzymes like 12-P LOX and cyclooxygenase/thromboxane synthase.

Blood Platelets↗
PubMed2005

Nongenomic effects of mineralocorticoid receptor activation in the cardiovascular system.

Fifteen years ago Wehling and colleagues showed unequivocal rapid effects of aldosterone, neither mimicked by cortisol nor blocked by spironolactone, and postulated that these nongenomic effects are mediated via a membrane receptor distinct from the classical mineralocorticoid receptor (MR). Several recent studies have challenged this view. Alzamora et al. showed 11beta-hydroxysteroid denydrogenase 1 and 2 (11betaHSD1, 11betaHSD2) expression in human vascular smooth muscle cells, and that aldosterone rapidly raises intracellular pH via sodium-hydrogen exchange; cortisol is without effect and spironolactone does not block the aldosterone response. When, however, 11betaHSD activity is blocked by carbenoxolone, cortisol shows agonist effects indistinguishable from aldosterone; in addition, the effect of both aldosterone and cortisol is blocked by the open E-ring, water soluble MR antagonist RU28318. In rabbit cardiomyocytes, aldosterone increases intracellular [Na+] by activating Na+/K+/2Cl- cotransport, with secondary effects on Na+/K+ pump activity. Pump current rises approximately 10-fold within 15', is unaffected by actinomycin D or the MR antagonist canrenone, and not elevated by cortisol. Pump current is, however, completely blocked by the open E-ring, water soluble MR antagonist K+ canrenoate and stoichometrically by cortisol. PKCepsilon agonist peptides (but not PKCalpha, PKCdelta or scrambled PKCepsilon peptides) mimic the effect of aldosterone, and PKCepsilon antagonist peptides block the effect. Very recently, cortisol has been shown to mimic the effect of aldosterone when cardiomyocyte redox state is altered by the installation of oxidized glutathione (GSSG) via the pipet, paralleling the effect of carbenoxolone on vascular smooth cells and suggesting possible pathophysiologic roles for an always glucocorticoid occupied MR.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2006

Molecular diagnosis of viral diseases, present trends and future aspects A view from the OIE Collaborating Centre for the Application of Polymerase Chain Reaction Methods for Diagnosis of Viral Diseases in Veterinary Medicine.

The emergence and re-emergence of transboundary animal diseases (TADs), e.g., foot-and-mouth disease, classical swine fever and the highly pathogenic avian influenza strongly indicate the need for the development of powerful and robust new diagnostic methods. The experiences of an OIE-Collaborating Centre and of two EU project consortia are summarised on the diagnostic application of gel-based PCR, general PCR systems, phylogeny, molecular epidemiology, real-time PCR (TaqMan, Molecular Beacons, Primer-Probe Energy Transfer), amplification without thermocycling (Invader), multiplex PCR, nucleic acid extraction and pipetting robotics, automation and quality control, including internal controls. By following the steps of OIE validation, the diagnostic assays are nationally and internationally standardised. The development of padlock probes and microarrays, as well as ultra rapid PCR and sequencing methods is further improving the arsenal of nucleic acid based molecular diagnosis. Further trends of diagnostic development are also mentioned, in order to combat TADs and other viral infections more effectively in the future.

Animals↗
PubMed2005

Parasitemia in an immunocompetent horse experimentally challenged with Sarcocystis neurona sporocysts.

Equine protozoal myeloencephalitis (EPM) is a serious neurological disease of horses in Americans. Most cases are attributed to infection of the central nervous system with Sarcocystis neurona. Parasitemia has not been demonstrated in immunocompetent horses, but has been documented in one immunocompromised foal. The objective of this study was to isolate viable S. neurona from the blood of immunocompetent horses. Horses used in this study received orally administered S. neurona sporocysts (strain SN 37-R) daily for 112 days at the following doses: 100/day for 28 days, followed by 500/day for 28 days, followed by 1000/day for 56 days. On day 98 of the study, six yearling colts were selected for attempted culture of S. neurona from blood, two testing positive, two testing suspect and two testing negative for antibodies against S. neurona on day 84 of the study. Two 10 ml tubes with EDTA were filled from each horse by jugular venipuncture and the plasma fraction rich in mononuclear cells was pipetted onto confluent equine dermal cell cultures. The cultures were monitored weekly for parasite growth for 12 weeks. Merozoites grown from cultures were harvested and tested using S. neurona-specific PCR with RFLP to confirm species identity. PCR products were sequenced and compared to known strains of S. neurona. After 38 days of in vitro incubation, one cell culture from a horse testing positive for antibodies against S. neurona was positive for parasite growth while the five remaining cultures remained negative for parasite growth for all 12 weeks. The Sarcocystis isolate recovered from cell culture was confirmed to be S. neurona by PCR with RFLP. Gene sequence analysis revealed that the isolate was identical to the challenge strain SN-37R and differed from two known strains UCD1 and MIH1. To our knowledge this is the first report of parasitemia with S. neurona in an immunocompetent horse.

Animals↗
PubMed1997

A questionnaire survey of the ergonomic problems associated with pipettes and their usage with specific reference to work-related upper limb disorders.

This study has considered the ergonomic problems associated with the use of pipettes through a questionnaire study of users. The study groups comprised an exposed (i.e. pipette users) and a non-exposed (i.e. non-users) cohort. Eighty questionnaire responses were returned by pipette users and 85 by non-users from six organisations; a response rate of approximately 55% for each of the study cohorts. The reported occurrence of elbow and hand complaints [using the general version of the Nordic musculoskeltal questionnaire (Kuorinka et al, 1987)] was significantly higher in the pipette user population as compared to the control population. There is an increase in the percentage of those reporting hand complaints as the duration of the working period involving continuous use of pipettes increases. Almost 90% of subjects in the longest exposure group (continuous use for more than 60 min) reported hand complaints. Users identified a number of features which made plunger operated pipettes more difficult to use: almost all of the female population who reported difficulties identified plunger operation as a design deficiency. Users also identified features of the general working environment which made the pipetting tasks more difficult. The study concludes that a number of work-related factors may affect the efficiency and comfort of staff performing laboratory tasks using pipettes.

Adult↗
PubMed1980

Analysis of adhesion of large vesicles to surfaces.

An experimental procedure that can be used to measure the interfacial free energy density for the adhesion of membranes of large vesicles to other surfaces is outlined and analyzed. The approach can be used for both large phospholipid bilayer vesicles and red blood cells when the membrane force resultants are dominated by isotropic tension. The large vesicle or red cell is aspirated by a micropipet with sufficient suction pressure to form a spherical segment outside the pipet. The vesicle is then brought into close proximity of the surface to be tested and, the suction pressure reduced to permit adhesion, and the new equilibrium configuration is established. The mechanical analysis of the equilibrium shape provides the interfacial free energy density for the surface affinity. With this approach, the measurable range of membrane surface affinity is 10(-4)-3 erg/cm2 for large phospholipid bilayer vesicles and 10(-2)-10 erg/cm2 for red blood cells.

Adhesiveness↗
PubMed1981

Thermoelasticity of large lecithin bilayer vesicles.

Micromechanical experiments on large lecithin bilayer vesicles as a function of temperature have demonstrated an essential feature of bilayer vesicles as closed systems: the bilayer can exist in a tension-free state (within the limits of experimental resolution, i.e., less than 10(-2) dyn/cm). Furthermore, because of the fixed internal volume, there is a critical temperature at which the vesicle becomes a tension-free sphere. Below this temperature, thermoelastic tension builds up in the membrane and the vesicle's internal pressure increases while the surface area remains constant. Above this temperature, the vesicle's surface area increases while the tension and internal pressure are negligible. Without mechanical support, the vesicles fragment into small vesicles because they have insufficient surface rigidity. In the upper temperature range we have measured the increase of surface area with temperature. These data established the thermal area expansivity to be 2.4 X 10(-3)/degrees C. At constant temperature, we used either pipet aspiration with suction pressures up to 10(4) dyn/cm2 or compression against a flat surface with forces up to 10(-2) dyn to produce area dilation of the vesicle surface on the order of 1%. The rate of increase of membrane tension with area dilation was calculated, which established the elastic area compressibility modulus to be 140 dyn/cm. The tension limit that produced lysis was observed to be 3-4 dyn/cm (equivalent to 2-3% area increase). The product of the elastic area compressibility modulus, the thermal area expansivity, and the temperature gives the reversible heat of expansion at constant temperature for the bilayer. This value is 100 ergs/cm2 at 25 degrees C, or approximately 5 kcal/mol of lecithin. Similarly, the product of the thermal area expansivity multiplied by the area compressibility modulus determines the rate of increase of thermoelastic tension with decrease in temperature when the area is held constant, i.e., -0.34 dyn/cm/degrees C.

Elasticity↗
PubMed1984

Channel properties of the purified acetylcholine receptor from Torpedo californica reconstituted in planar lipid bilayer membranes.

The electrophysiological properties of the cation channel of the purified nicotinic acetylcholine receptor (AChR) reconstituted in planar lipid bilayers were characterized. Single-channel currents were activated by acetylcholine, carbamylcholine and suberyldicholine. The single channel conductance (28 pS in 0.3 M NaCl) was ohmic and independent of the agonist. Single channel currents increased with Na+ concentration to a maximum conductance of 95 pS and showed a half-saturation point of 395 mM. The apparent ion selectivity sequence, derived from single-channel current recordings, is: NH+4 greater than Cs+ greater than Rb+ greater than or equal to Na+ Cl-, F-, SO2-(4). The distribution of channel open times was fit by a sum of two exponentials, reflecting the existence of at least two distinct open states. The time constants depend on the choice of agonist, being consistently longer for suberyldicholine than for carbamylcholine. Similar channel properties were recorded in bilayers formed from monolayers at the tip of patch pipets . Single-channel currents occur in paroxysms of channel activity followed by quiescent periods. This pattern is more pronounced as the agonist concentration increases, and is reflected in histograms of channel-opening frequencies. Computer simulations with a three-state model, consisting of two closed (unliganded and liganded) and one open state, do not resemble the recorded pattern of channel activity, especially at high agonist concentration. Inclusion of a desensitized liganded state reproduces the qualitative features of channel recordings. The occurrence of paroxysms of channel activity thus seems to result from the transit of AChR through its active conformation, from which it can open several times before desensitizing.

Animals↗
PubMed1992

A sensitive measure of surface stress in the resting neutrophil.

The simplest parameterized model of the "passive" or "resting receptive" neutrophil views the cell as being composed of an outer cortex surrounding an essentially liquid-like highly viscous cytoplasm. This cortex has been measured to maintain a small persistent tension of approximately 0.035 dyn/cm (Evans and Yeung. 1989. Biophys. J. 56:151-160) and is responsible for recovering the spherical shape of the cell after large deformation. The origin of the cortical tension is at present unknown, but speculations are that it may be an active process related to the sensitivity of a given cell to external stimulation and the "passive-active" transition. In order to characterize further this feature of the neutrophil we have used a new micropipet manipulation method to give a sensitive measure of the surface stress as a function of the surface area dilation of the highly ruffled cellular membrane. In the experiment, a single cell is driven down a tapered pipet in a series equilibrium deformation positions. Each equilibrium position represents a balance between the stress in the membrane and the pressure drop across the cell. For most cells that seemed to be "passive," as judged by their spherical appearance and lack of pseudopod activity, area dilations of approximately 30% were accompanied by only a small increase in the membrane tension, indicative of a very small apparent elastic area expansion modulus (approximately 0.04 dyn/cm). Extrapolations back to zero area dilation gave a value for the tension in the resting membrane of 0.024 +/- 0.003 dyn/cm, in close agreement with earlier measures. A few cells showed virtually no change in cortical tension and fit the persistent cortical tension model of Evans and Yeung (1989. Biophys. J. 56:151-160). However, other cells that also appeared "passive," as judged by their spherical appearance, had membrane tensions that increased as the apparent surface area was increased. Thus, the postulated,persistent "cortical tension" does not appear to be a unique and constant parameter for all cells as the membrane area is dilated.This measurement of membrane tension could represent a sensitive indication of the first stages of cell activation and the"passive-active" transition.

Cell Membrane↗
PubMed1995

Mechanically stimulated cytoskeleton rearrangement and cortical contraction in human neutrophils.

A mechanical test with micropipets is used to characterize cytoskeleton rearrangement and contraction induced by mechanical stresses in human neutrophils. The yield shear resultant of the cell cortex is on the order of 0.06 to 0.09 mN.m-1. The measured yield shear resultant suggests that the neutrophil cortex is a weakly cross-linked structure. When a tether is pulled out from the cell surface, a polymer structure starts to fill it and spreads out from the cell body. The rate of advancement of the polymerization front is almost constant and, therefore, is not diffusion limited. The measured rate is much smaller than the one of spontaneous actin polymerization, suggesting that the limiting process is either the dissociation of actin monomers from their dimers with the capping proteins or the rate of formation of new nucleation sites or both. Polymerization is also observed after applying sufficient mechanical stresses on a small portion of the cell surface. The polymerization is followed by mass transfer from the cell into the prestressed region and later on by contraction of the main cell body. The pressure generating the flow is located in the prestressed region and most probably is a result of its "swelling" and contraction. The contraction of the main cell body is very similar (in its time dependence and magnitude) to the contraction during phagocytosis. The measured maximum cortical tension is on the order of 0.5 mN.m-1, which for a 3.5-microns diameter pipet corresponds to a maximum contraction force of 11 nN.

Adult↗
PubMed1997

Micropipette aspiration of human erythrocytes induces echinocytes via membrane phospholipid translocation.

When a discocytic erythrocyte (RBC) was partially aspirated into a 1.5-microns glass pipette with a high negative aspiration pressure (delta P = -3.9 kPa), held in the pipette for 30 s (holding time, th), and then released, it underwent a discocyte-echinocyte shape transformation. The degree of shape transformation increased with an increase in th. The echinocytes recovered spontaneously to discocytes in approximately 10 min, and there was no significant difference in recovery time at 20.9 degrees C, 29.5 degrees C, and 37.4 degrees C, respectively. At 11 degrees C the recovery time was significantly elevated to 40.1 +/- 6.7 min. At 20.9 degrees C the shape recovery time varied directly with the isotropic RBC tension induced by the pipetting. Sodium orthovanadate (vanadate, 200 microM), which inhibits the phospholipid translocase, blocks the shape recovery. Chlorpromazine (CP, 25 microM) reversed the pipette-induced echinocytic shape to discocytic in < 2 min, and the RBC became a spherostomatocyte-II after another 30 min. It was hypothesized that the increase in cytosolic pressure during the pipette aspiration induced an isotropic tension in the RBC membrane followed by a net inside-to-outside membrane lipid translocation. After a sudden release of the aspiration pressure the cytosolic pressure and the membrane tension normalized immediately, but the translocated phospholipids remained temporarily "trapped" in the outer layer, causing an area excess and hence the echinocytic shape. The phospholipid translocase activity, when not inhibited by vanadate, caused a gradual return of the translocated phospholipids to the inner layer, and the RBC shape recovered with time.

Blood Specimen Collection↗
PubMedDate not supplied

Rheological behavior of rat mesangial cells during swelling in vitro.

The response of cells to mechanical forces depends on the rheological properties of their membranes and cytoplasm. To characterize those properties, mechanical and electrical responses to swelling were measured in rat mesangial cells (MC) using electrophysiologic and video microscopic techniques. Ion transport rates during hyposmotic exposures were measured with whole-cell recording electrodes. Results showed that cell swelling varied nonlinearly with positive internal pressure, consistent with a viscoelastic cytoplasm. The extrapolated area expansivity modulus for small deformations was estimated to be 450 dyne/cm. Cell swelling, caused either by positive pipet pressure or hyposmotic exposure (40-60 mOsm Kg-1), rapidly induced an outwardly rectifying membrane conductance with an outward magnitude 4-5 times the baseline conductance of 0.9 +/- 0.5 nS (p < .01). Swelling-induced (SI) current was weakly selective for K+ over Na+, partially reversed upon return to isotonicity, and was antagonized by 0.5 mM GdCl3 (p < 0.02; n = 6). Isolated cells treated with GdCl3 rapidly lysed after hypotonic exposure, in contrast to untreated cells that exhibited regulatory volume decrease (RVD). Our results indicate that volume regulation by MC depends upon a large swelling-induced K+ efflux, and suggest that swelling in MC is a viscoelastic process, with a viscosity dependent on the degree of swelling.

Animals↗
PubMed1999

Effects of hyperosmolarity and ion substitutions on amino acid efflux from the ischemic rat cerebral cortex.

The contributions of sodium and chloride ions and of osmotic stresses to the ischemia-evoked efflux of excitotoxic and other amino acids were explored using a rat four vessel occlusion model. Replacement of Na+ with choline or N-methyl-D-glucamine (NMDG) and of Cl- with sulfate or gluconate was used to evaluate the contribution that these ions make to amino acid efflux. The contribution of ischemia-evoked swelling to amino acid release was studied by applying mannitol or sucrose to minimize the cell volume increases and the compensatory regulatory volume decrease evoked efflux of amino acids. Aliquots of artificial cerebrospinal fluid (aCSF), appropriately adjusted for ion replacement or 150 mM mannitol or sucrose, were pipetted into cortical cups 35 min prior to ischemia and perfusate samples were obtained prior to, during and following ischemia (20 min) and reperfusion (40 min). Replacement of Na+ by NMDG depressed basal (normoxic) efflux of most amino acids, with choline substitution having little effect. During ischemia NMDG substitution increased glutamate and GABA efflux and choline enhanced the release of aspartate, glutamate, GABA and taurine. A reduction in extracellular Na+ would facilitate reversal of Na+-dependent transporters with extrusion of amino acids. Another possible explanation for the elevated release is that the absence of Na+ would inhibit the Ca2+/Na+ counter transport system, with a deleterious accumulation of intracellular Ca2+. Chloride replacement with sulfate or gluconate enhanced the efflux of aspartate, glutamate, GABA and taurine during ischemia. Removal of Cl- would depolarize cells, and block the Cl--dependent action of inhibitory amino acid transmitters, with both actions enhancing the ischemic injury and, consequently, amino acid release. Exposure to hyperosmotic mannitol (150 mM) aCSF enhanced ischemia-evoked release of some amino acids (taurine, GABA) and decreased that of aspartate and phosphoethanolamine. Sucrose aCSF enhanced the ischemia-evoked release of most amino acids. A potential explanation for these observations is that both agents may be able to rapidly penetrate the plasma membranes of ischemic neurons, actually contributing to the release of other osmolytes. The unanticipated nature of many of the observations made during these manipulations of the aCSF serves to accentuate the complex nature of the mechanisms responsible for the ischemia-evoked amino acid efflux into the interstitial spaces.

Animals↗
PubMed2003

Signify ER Drug Screen Test evaluation: comparison to Triage Drug of Abuse Panel plus tricyclic antidepressants.

Signify ER Drug Screen Test (Signify ER) and Triage Drug of Abuse Panel plus TCA (Triage DOA Panel) rapid drug screening devices were compared at four laboratories. Both assay systems are point of care immunoassays, measuring phencyclidine, barbiturates, amphetamine, cocaine metabolite, methamphetamine, tricyclic antidepressants, opiates, marijuana metabolite, and benzodiazepines in human urine. The performance of these two assay systems, including a cutoff verification and cross-reactivity using spiked urine specimens and accuracy using clinical urine samples, was investigated. The cutoff verification study showed that the Signify ER had 95.4% precision for all drugs tested at concentrations of 50%, 75%, 125%, 150%, and 200% of cutoffs compared to 90% precision obtained with Triage DOA Panel. Accuracy studies testing 53 negative urine samples demonstrated that both Signify ER and Triage DOA Panel have 100% specificity. Testing of 693 positive urine samples demonstrated that Signify ER and Triage DOA Panel have sensitivities of 99.8% and 99.3%, respectively, with an accuracy of 99.9% and 99.6%. A total of 527 compounds were tested for the cross-reactivity study. Eighty-seven structurally related drugs and metabolites were found to cross-react with at least one of the nine tests of the Signify ER. Four hundred forty structurally unrelated compounds that can be found in human urine were shown not to cross-react with the Signify ER. In terms of operating characteristics, the Signify ER device is simpler since only a single pipetting step is required, and reaction completed within 8 min.

Antidepressive Agents, Tricyclic↗
PubMed1998

Technologies for implementation of quality assurance in the clinical laboratory.

To face the rapid evolution of the clinical laboratory activity from sample analysis towards an in-vitro diagnostic network, a Total Quality Management system must be implemented by laboratory professionals. Technological advances make it possible to introduce new tools and techniques for many issues surrounding the analytical process, as has happened for analysis automation and laboratory management. Preanalytical steps should benefit from extended traceability, using new identification devices such as electronic labels. This may promote the improvement of sample handling in this phase, such as during transportation or centrifugation. Another field is the expansion of metrology. Many factors can now easily be controlled in the clinical laboratory. New reliable automated systems are available to evaluate the performance of pipetting devices. Autonomous miniaturized recorders and probes connected to monitoring softwares allow traceable temperature monitoring. In this paper, some examples are presented to illustrate how technical solutions can support the implementation of Quality Assurance in the clinical laboratory.

Clinical Laboratory Information Systems↗