Sensitivity and specificity of autoantibody tests in the differential diagnosis of lupus nephritis.

Several studies have investigated the potential of various autoantibody tests in the diagnosis of systemic lupus erythematosus (SLE). Many lupus patients initially present with glomerulonephritis. In that clinical situation the main differential diagnosis are other forms of glomerulonephritis. In this study the diagnostic value of nine test kits for autoantibody against ANA, dsDNA, circulating immune complexes, C1q, nucleosomes, histones and Sm as well as C3 and C4 levels was evaluated in 39 patients with biopsy-proven lupus nephritis in comparison to 43 patients suffering from other forms of glomerulonephritis. The most useful test was an anti-nucleosome antibody enzyme-linked immunosorbent assay (ELISA) with a sensitivity of 90% and a specificity of 88%. All tests for anti-dsDNA antibodies (Crithidia luciliae Anti-dsDNA, BINDAZYME Anti-dsDNA, FARRZYME high avidity Anti-dsDNA) were of moderate sensitivity and very good specificity. Decreasing the cut-off for the conventional anti-dsDNA ELISA (BINDAZYME) considerably increased its sensitivity (87%) without loss of specificity (90%). Tests for anti-C1q and immune complexes performed worse than the antidsDNA tests. As anti-histone and Sm antibodies are present only in a minority of lupus nephritis patients they are of limited value in diagnosing the disease. In conclusion, testing for anti-nucleosome antibodies and the conventional anti-dsDNA ELISA with lower cut-off provide the best diagnostic aids for differentiation of lupus nephritis from other forms of glomerulonephritis.

Anti-CCP: history and its usefulness.

Antibodies directed to cyclic citrullinated peptides (anti-CCP) are highly specific for rheumatoid arthritis (RA) and can easily be detected in sera by using commercially available immunoassays. The second version of the anti-CCP test (anti-CCP2) demonstrated high specificity (89-98%) and good sensitivity (41-88%) for RA. Commercially available ELISA methods from three different companies are on the market. All three CCP2 assays show similar results as all CCP2 assays use the same antigen-coated plates. This study was an evaluation of a new automated method for the determination of anti-CCP2 in a routine laboratory setting. Five hundred and forty three serum samples were tested for anti-CCP2 within normal routine diagnostic using a commercially available ELISA and retested with a prelaunch version of a new and fully-automated method (EliA). The results were comparable. The new automated assay is easy to use and demonstrated a diagnostic sensitivity of 80% and specificity of 97%.

Rapid estimation of octanol-water partition coefficients using synthesized vesicles in electrokinetic chromatography.

Vesicle electrokinetic chromatography (VEKC) using vesicles synthesized from the oppositely charged surfactants cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS) and from the double-chained anionic surfactant bis(2-ethylhexyl)sodium sulfosuccinate (AOT) was applied to the indirect measurement of octanol-water partition coefficients (log Po/w). A variety of small organic molecules with varying functional groups, pesticides, and organic acids were evaluated by correlating log Po/w and the logarithm of the retention factor (log k') and comparing the calibrations. A linear solvation energy relationship (LSER) analysis was conducted to describe the retention behavior of the vesicle systems and compared to that of octanol-water partitioning. The solute hydrogen bond donating behavior is slightly different with the vesicle interactions using CTAB-SOS vesicles as compared to the octanol-water partitioning model. The AOT vesicle and octanol-water partitioning systems showed similar partitioning characteristics. VEKC provides rapid separations for determinations of log Po/w in the range of 0.5 to 5 using CTAB-SOS vesicles and 0 to 5.5 using AOT vesicles.

Determination of octanol-water partition coefficients of pesticides by microemulsion electrokinetic chromatography.

Microemulsion electrokinetic chromatography (MEEKC) was evaluated as a screening tool for the indirect measurement of octanol-water partition coefficients (log Po/w) of pesticide compounds. Over 80 pesticide compounds representing a variety of structural characteristics were studied, and good correlation of log Po/w with the logarithm of the retention factor was found. The microemulsion system studied allowed the separation of compounds in the log Po/w range of -1 to 7. In addition, a smaller set of simple organic molecules that vary in structural features was evaluated and compared to the pesticide log Po/w calibration. The pesticide and simple organic molecule log Po/w calibration lines were statistically similar. This suggests that a universal set of standard compounds may be employed for the log Po/w calibration to provide measurements for a variety of compounds with good accuracy.

Manual and verbal responses to completely masked (unreportable) stimuli: exploring some conditions for the metacontrast dissociation.

As reported by Neumann and Klotz [1994, in Attention and Performance XV: Conscious and Nonconscious Information Processing Eds C Umiltà, M Moscovitch (Cambridge, MA: MIT Press) pp 123-150], a geometric shape masked by metacontrast can affect response latency (RT) even if it is not visible, i.e. if it yields a d' value of zero in a signal-detection (SD) task (metacontrast dissociation). In the initial study as well as in most subsequent experiments, the RT task was manual and the SD task was verbal. Hence tasks and output modes were confounded. In the present study, two experiments were conducted to find out which of these factors is responsible for the metacontrast dissociation. In experiment 1, participants performed an RT task in either a manual or a verbal output mode. In experiment 2, these output modes were compared in an SD task. Independently of output modes, the masked primes affected RT but could not be detected in the SD task. It is concluded that tasks, but not output modes, are crucial for the metacontrast dissociation. Implications for the mechanisms underlying the metacontrast dissociation and for the functional difference between judgments and responses are discussed.

High-performance capillary gel electrochromatography with replaceable media.

Capillary gel electrochromatography is evaluated with an entangled polymer solution which is pumped into the capillary and run under fritless conditions. The polymer used has an acid backbone with grafted hydrophobic segments, the polyacid giving the electroosmotic flow and the hydrophobe segments providing the retentive component. Experimental evaluation of this type of system reveals performance similar to capillary electrophoresis and other forms of electrochromatography. The analysis of plate height data demonstrates that zone broadening is primarily due to diffusion with little contribution from nonequilibrium zone broadening. Hence, operation at high velocities (high voltages) is most desirable as opposed to most chromatographic methods. Some of the advantages of this type of experiment include being able to replace the retentive media in a few minutes, fast and reproducible high-performance separation, and having a retention mechanism similar to reversed-phase liquid chromatography. Disadvantages include a low retentive phase concentration and hence low sample loadability and limited solvent compatibility of the polymer. A number of different separations are demonstrated including separation of alkyl benzoates, alkylphenones, alkylbenzenes, oxidation inhibitors, and PAHs.

The effect of a masked stimulus on the response to the masking stimulus.

Four experiments are reported in which the subjects had to respond to a target that masked a preceding prime via metacontrast masking. In one part of Experiment 1, the subjects discriminated the target's shape (square or diamond) by a motor-choice reaction, and in another part they had to respond with a simple reaction. The prime was neutral (circular) with respect to the target's shape. The data showed a facilitation effect. In both tasks the reaction time was reduced by the masked prime. However, the reduction was more pronounced with simple reaction than with choice reaction. In the other experiments, additional primes were used with the same angular shapes as the targets. In Experiments 2 and 3, after discriminating the target's shape by a choice reaction, the subjects had to judge the prime's shape in a signal-detection task. While neither the d' value for discriminating the angular primes from the circular ones (Exp. 2) nor the d' value for distinguishing between the angular primes (Exp. 3) was different from zero, the choice-reaction data showed a congruency effect. With a congruent prime (i.e., a prime that had the same shape as the target), the reaction times were reduced. With an incongruent prime, the reaction times grew. In Experiment 4 the errors were investigated. The facilitation effect was present in the RT, but not in the number of errors, whereas the congruency effect was present in the number, but not in the RT of errors. While the facilitation effect can be attributed either to an unspecific activation by the masked prime or to an influence of the prime on attentional processes, the congruency effect can be explained by the assumption that the masked prime directly activates the specific response, which corresponds to the prime's shape.

Differential effects of visual-spatial attention on response latency and temporal-order judgment.

Theorists from both classical structuralism and modern attention research have claimed that attention to a sensory stimulus enhances processing speed. However, they have used different operations to measure this effect, viz., temporal-order judgment (TOJ) and reaction-time (RT) measurement. We report two experiments that compared the effect of a spatial cue on RT and TOJ. Experiment 1 demonstrated that a nonmasked, peripheral cue (the brief brightening of a box) affected both RT and TOJ. However, the former effect was significantly larger than the latter. A masked cue had a smaller, but reliable, effect on TOJ. In Experiment 2, the effects of a masked cue on RT and TOJ were compared under identical stimulus conditions. While the cue had a strong effect on RT, it left TOJ unaffected. These results suggest that a spatial cue may have dissociable effects on response processes and the processes that lead to a conscious percept. Implications for the concept of direct parameter specification and for theories of visual attention are discussed.