Single-laboratory Study Research Articles

In Vivo Experimental Intracranial Aneurysm Models: A Systematic Review

Animal models are necessary to develop and test innovations in aneurysm therapy before clinical introduction. This review aims at identifying the most likely candidates for standardizing preclinical testing of aneurysm devices. We systematically searched electronic databases for publications on animal aneurysm models from 1961-2008 to assess the methodologic quality of the studies and collect data on the patency and angiographic and pathologic outcomes of treatments. There has been a steady increase in the annual number of publications with time. Species that were most frequently used were dogs, rabbits, and rodents, followed by swine. Most publications are single-laboratory studies with variables and poorly validated outcome measures, a small number of subjects, and limited standardization of techniques. The most appropriate models to test for recurrences after endovascular occlusion were the surgical bifurcation model in dogs, and the elastase-induced aneurysm model in rabbits. A standardized multicenter study is needed to improve the preclinical evaluation of endovascular devices in aneurysm therapy.

Acute Ischemic Stroke Treatment in 2007

A variety of interventions have proven effective in reducing the risk of a first stroke.1 Nevertheless, each year, more than 700 000 Americans have strokes and more than 150 000 die, making stroke the country’s third-leading cause of death.2 More than 25% of stroke survivors older than age 65 years are disabled 6 months later.2 On the basis of the results of prospective randomized clinical trials and other studies performed over the past decade, the general approach to the management of acute stroke has evolved from nihilism to active intervention. A large volume of experimental studies delineates the various aspects of the ischemic cascade. The results of the single laboratory study shown in Figure 1 provide a conceptual framework that guides the current clinical approach to patients with acute ischemic stroke.3 The experiment, performed in awake monkeys, shows that focal symptoms (in this case, paralysis) develop when local cerebral blood flow drops below a certain threshold (in this experiment, <23 mL · 100 g−1 · min−1). In Figure 1, the hatched area between the development of symptoms and infarction is a graphic representation of the so-called penumbra, an area of brain that is functionally inactive but structurally intact and potentially salvageable. Neurological function is completely recoverable if local cerebral blood flow is restored promptly. For a given level of reduced blood flow, the likelihood of sustaining irreversible injury (ie, ischemic stroke) increases as a function of time. This essential biology is the basis of the mantra, “Time lost is brain lost.” Timely restoration of blood flow to ischemic brain offers the chance of reversing or limiting the injury. Figure 1. Relationship between cerebral blood flow, time, functional impairment, and infarction. Even within 3 hours, ischemic tissue might go on to infarction or be …

Development and implementation of the CCME Reference Method for the Canada-Wide Standard for Petroleum Hydrocarbons (PHC) in soil: a case study

Petroleum hydrocarbons have historically been analyzed by a wide variety of test methods. Interlaboratory studies have shown that standardization of both extraction and gas chromatographic analysis improved interlaboratory variability in hydrocarbon analysis. The Canadian Council of Ministers of the Environment has required a reference method for use with the Canada-wide standard for petroleum hydrocarbons. The process for developing and validating this method is described. This method requires the determination of 4 hydrocarbon fractions, namely, F1 (nC6 to nC10), F2 (>nC10 to nC16), F3 (>nC16 to nC34) and, F4 (nC35+), using GC-FID or gravimetry. The Tier 1 method was validated in a single laboratory study. This validated method was subjected to interlaboratory studies to determine its applicability and precision.

Feasibility of Multicentric Assessment of MRD in All by Flow-Cytometry: Standardization and Experience of the I-BFM-ALL FCM-MRD Study Group.

Detection of minimal residual disease (MRD) in ALL using flow cytometry (FC) is feasible in nearly 100% of patients (pts.) and gives superior prognostic information. This has been evidenced by several single-laboratory studies. It is, however, not known to date whether FC MRD detection can reliably be standardized, so that multiple laboratories could collaborate to provide MRD information of similar quality in large and international treatment trials. On the basis of the current AIEOP-BFM-ALL 2000 trial, which comprehensively includes children with ALL from Austria, Germany, Italy, and Switzerland, a multicenter observational study of FC-MRD was initiated in 2000 in 4 collaborating laboratories. Until 2004, n=395 pts. have been prospectively recruited to this investigation (consecutive per center). Samples for evaluation were blood (PB) and bone marrow (BM) from early treatment time-points (diagnosis, days 8, 15, 22, 33, 52, 78). Lineage-specific, standardized 3-(5)-tube staining panels were based on 4-color FC. To foster inter-laboratory standardization, an extensive quality program was launched. This included full-staff meetings twice yearly (including list-mode data review), personnel exchange, assessment of concordance in list-mode data analysis, and sample exchange. We report now on results of the latter two issues. List-mode data files from 93 samples (from 15 pts., i.e. (3)-4 consecutive pts. per center selected by a certain time-point) were shared between all 4 centers for parallel analysis. By peer-review, 48/93 samples (51,5%) were finally regarded as MRD-positive. Concordance of all 4 centers in positive-negative estimates was reached in 71% of samples (66/93), and of at least 3 centers in 95,7% (89/93). In MRD-positive samples, concordance in quantitative estimates (<5x- difference) from all 4 centers was evident in 70,8% (34/48), and from at least 3 centers in 81% (39/48). Lowest concordance was reached in samples with very low amounts of MRD (<10−4). Surveying the available 369 single MRD-results (data from 93 samples x 4 centers), 341 (92,4%) were correct regarding positive-negative estimates (range by centers: 88,0 – 97,8%). From 174 positive MRD-measures, correct log-levels were documented in 167 (96%) overall (range by centers: 93,2 – 97,8%). Sample exchange (n=38 follow-up samples from 10 consecutive pts.) by express mail yielded a 2-center concordance of 92% regarding positive-negative MRD-estimates. Quantitative results in MRD-positive samples (n=21 paired data sets) were highly concordant (in 86% <5x-difference) despite transportation, and differences in FC instrumentation and software usage. In conclusion, multicenter MRD-evaluation by FC in large treatment trials for ALL is feasible, but extensive quality standardization is necessary. Performance should be monitored throughout the trial period to warrant comparable results when assessed in multiple centers (Figure 1. Concordance: MRD-positive samples per series). [Display omitted]

Evaluation of E Test, disk diffusion and broth microdilution to establish tentative quality control limits and review susceptibility breakpoints for two aerobic actinomycetes

A single laboratory study was carried out to compare E Test with broth microdilution and disk diffusion to establish tentative quality control ranges for Nocardia asteroides ATCC 19247 and Rhodococcus equi ATCC 6939 against a panel of eight antimicrobial agents. Reproducibility testing was performed on 12 consecutive days to establish tentative quality control ranges. A total of 36 clinical strains of the Nocardia asteroides complex and 5 Rhodococcus strains were used in the study. Both candidate control strains and clinical strains grew well on cation-adjusted Mueller-Hinton agar. Adequate growth occurred at 48 to 72 h for the Nocardia isolates and 24 to 48 h for Rhodococcus. A standardized primary inoculum of 5 × 10 4 CFU/mL was used for performance of E Test and disk diffusion for the Nocardia isolates. Tentative population-based error rates were calculated using current breakpoints for Enterobacteriaceae for E Test compared with disk diffusion for the 36 clinical strains of Nocardia species. Significant very major error rates were observed for imipenem (22%) and minor error rates varied from 2.7% to 50%. These methods require more extensive validation before definitive breakpoint criteria can be established.

Absence of toxicity of Bacillus thuringiensis pollen to black swallowtails under field conditions.

A single laboratory study on monarch butterflies has prompted widespread concern that corn pollen, engineered to express Bacillus thuringiensis (Bt) endotoxin, might travel beyond corn fields and cause mortality in nontarget lepidopterans. Among the lepidopterans at high potential risk from this technology is the black swallowtail butterfly, Papilio polyxenes, whose host plants in the midwestern U. S. are located principally in narrow strips between roads and crop fields. A field study was performed to assess whether mortality of early instar black swallowtails was associated either with proximity to a field of Bt corn or by levels of Bt pollen deposition on host plants. Potted host plants were infested with first instar black swallowtails and placed at intervals from the edge of a field of Bt corn (Pioneer 34R07 containing Monsanto event 810) at the beginning of anthesis. We confirmed by ELISA that pollen from these plants contained Cry1Ab endotoxin (2.125 +/- 0.289 ng/g). Although many of the larvae died during the 7 days that the experiments were run, there was no relationship between mortality and proximity to the field or pollen deposition on host plants. Moreover, pollen from these same plants failed to cause mortality in the laboratory at the highest pollen dose tested (10,000 grains/cm(2)), a level that far exceeded the highest pollen density observed in the field (200 grains/cm(2)). We conclude that Bt pollen of the variety tested is unlikely to affect wild populations of black swallowtails. Thus, our results suggest that at least some potential nontarget effects of the use of transgenic plants may be manageable.

Evaluation of EPA Method 8120 for Determination of Chlorinated Hydrocarbons in Environmental Samples

Abstract Method 8120 of EPA Manual SW-846 has been evaluated in a singlelaboratory study. Several modifications made to the current method were implemented to allow determination of selected chlorinated hydrocarbons in complex environmental samples. The 2 packed gas chromatographic columns specified in Method 8120 were replaced with 2 megabore fused-silica open tubular columns chemically bonded with trifluoropropylmethyl siloxane and polyethylene glycol, respectively. The list of target compounds was expanded from 15 to 22 to include all possible trichlorobenzenes, tetrachlorobenzenes, and hexachlorocyclohexane (BHC) isomers. The Florisil cleanup procedure was modified to allow quantitative recovery of 20 of the 22 target compounds. A procedure that uses 1 g Florisil disposable cartridges and hexane-acetone (9:1) eluant was developed. This latter procedure gives quantitative recovery of all 22 target compounds from all matrixes tested. The revised method was tested with a variety of sample matrixes. Detection limits for water samples ranged from 1.4 ng/L for hexachlorobutadiene to 1300 ng/L for 2-chloronaphthalene; detection limits for 15 compounds were below 40 ng/L. Because of background contamination, detection limits for soil and sediment samples need to be determined on a case-by-case basis.

Diagnostic studies for systemic necrotizing vasculitis. Sensitivity, specificity, and predictive value in patients with multisystem disease.

Forty patients with multisystem disease and suspected systemic necrotizing vasculitis were evaluated with a protocol designed to confirm the diagnosis with sequential testing. All patients underwent initial laboratory testing. Subsequent studies were individualized to the patient starting with "safe" tests (skin, muscle, rectal biopsies) and progressing to "invasive" tests (arteriography, kidney and lung biopsies). No single laboratory study was found to have adequate predictive value. Skin biopsy, rectal biopsy, and arteriography were insensitive, nonspecific, or had poor predictive values. Muscle biopsy was the most valuable safe procedure (sensitivity, 50%; specificity, 100%; predictive value, 100%; predictive value of negative biopsy, 76%; efficiency, 64%). A diagnostic approach to the patient with possible systemic necrotizing vasculitis is described.

Diagnostic Studies for Systemic Necrotizing Vasculitis

• Forty patients with multisystem disease and suspected systemic necrotizing vasculitis were evaluated with a protocol designed to confirm the diagnosis with sequential testing. All patients underwent initial laboratory testing. Subsequent studies were individualized to the patient starting with "safe" tests (skin, muscle, rectal biopsies) and progressing to "invasive" tests (arteriography, kidney and lung biopsies). No single laboratory study was found to have adequate predictive value. Skin biopsy, rectal biopsy, and arteriography were insensitive, nonspecific, or had poor predictive values. Muscle biopsy was the most valuable safe procedure (sensitivity, 50%; specificity, 100%; predictive value, 100%; predictive value of negative biopsy, 76%; efficiency, 64%). A diagnostic approach to the patient with possible systemic necrotizing vasculitis is described. (<i>Arch Intern Med</i>1989;149:161-165)

Single-Laboratory Evaluation of EPA Method 8080 for Determination of Chlorinated Pesticides and Polychlorinated Biphenyls in Hazardous Wastes

Method 8080, as published in the Second Edition of "Test Methods for Evaluating Solid Waste," EPA Manual SW-846, has been evaluated in a single-laboratory study. The Florisil procedure recommended in Method 8080 for sample cleanup does not separate organochlorine pesticides (OCPs) from the polychlorinated biphenyls (PCBs). Consequently, gas chromatographic analysis of OCPs on the packed column recommended in the method may result in false identifications or in no identifications at all when PCBs are present. Therefore, silica gel was substituted for Florisil, a capillary column was substituted for the packed column, and a sulfur cleanup procedure was incorporated in the method. The revised method was evaluated with samples spiked at 3 concentrations. Precision and accuracy indicate that the revised method can be reliably applied to the determination of OCPs and PCBs in liquid and solid matrixes. Detection limits for liquid matrixes range from 0.02 to 0.09 micrograms/L for OCPs and from 0.5 to 0.9 micrograms/L for PCBs. Detection limits for solid matrixes range from 1 to 6 micrograms/kg for OCPs and from 60 to 70 micrograms/kg for PCBs.

Single-laboratory evaluation and modification of U.S. EPA methods 7470 and 7471 for the determination of mercury in aqueous and solid hazardous wastes

The current U.S. Environmental Protection Agency (U.S. EPA) protocols for mercury determinations in aqueous and solid waste samples (SW-846 Methods 7470 and 7471) using recirculating cold-vapor atomic absorption spectrometry (CV-AAS) have been evaluated. The U.S. EPA methods are not sufficiently flexible to permit special quality control (QC) measures, have limited detectability for low-level mercury concentrations, and are plagued by spectral interferences caused by the nonspecific absorption of primary mercury radiation by volatile organic vapors. The U.S. EPA protocols have been modified in a single-laboratory study to facilitate additional QC measures, to enhance detectability for low-level mercury concentrations, and to eliminate nonspecific vapor absorption interferences. Volumetric manipulations for additional QC measures, if required, are facilitated by performing the sample digestions in Erlenmeyer flasks rather than in the current Biochemical Oxygen Demand (BOD) reduction-aeration bottles. Typical manipulations for additional QC measures that are now feasible include dilution of concentrated samples and multiple aliquot sampling for post-digestion spike and replicate analyses. Instrument detectability is improved 10-fold by using a gas sparging bottle as a dedicated reduction-aeration vessel and a silver wool-amalgamation CV-AAS system operated in an open configuration. The on-line amalgamation/thermal desorption process of the modified CV-AAS system eliminates interfering water and organic matrix vapors prior to the mercury absorption measurement. Good accuracy and precision have been obtained with the amalgamation CV-AAS system for the analyses of four reference sediment materials. The amalgamation CV-AAS measurements on the reference sediment digests have been successfully performed at absolute mercury concentration levels that are only 1 to 4 times above the instrumental detection limit of the U.S. EPA recirculating CV-AAS method.

Isolated angiitis of the central nervous system: Prospective diagnostic and therapeutic experience

Isolated angiitis of the central nervous system is an uncommon clinicopathotogic entity characterized by vasculitis restricted to the vessels of the central nervous system without other apparent systemic vasculitis. Experience with the diagnosis, treatment, and follow-up evaluation in four patients with this disease is presented. Early manifestations of disease include severe headaches, altered mental function, and focal neurologic deficits. The pattern of progression from headaches and altered mental status to multifocal neurologic deficits is particularly suggestive of the diagnosis of vasculitis of the central nervous system. Systemic symptoms such as fever, myalgia, arthralgia, and arthritis, which occur frequently in other vasculitic syndromes, are generally not present in patients with isolated angiitis of the central nervous system. Mo single laboratory study can firmly establish or completely exclude the diagnosis; consequently, tissue diagnosis with biopsy of the brain parenchyma and leptomeninges may be required. In two patients, recurrent disease developed despite treatment with corticosteroids alone. Sustained clinical remission was induced in all four patients with a regimen of dally cyclophosphamide and alternate-day prednisone therapy. Cyclophosphamide and alternate-day prednisone therapy are considered the treatment of choice in severe, progressive, or corticosteroid-resistant isolated angiitis of the central nervous system.