Systematic review of the biological variation data for diabetes related analytes

BACKGROUND

Objective interpretation of laboratory test results used to diagnose and monitor diabetes mellitus in part requires the application of biological variation data (BVD). The quality of published BVD has been questioned. The aim of this study was to quality assess publications reporting BVD for diabetes-related analytes using the Biological Variation Data Critical Appraisal Checklist (BIVAC); to assess whether published BVD are fit for purpose and whether the study design and population attributes influence BVD estimates and to undertake a meta-analysis of the BVD from BIVAC-assessed publications.

METHODS

Publications reporting data for glucose, HbA_1c, adiponectin, C-peptide, fructosamine, insulin like growth factor 1 (IGF-1), insulin like growth factor binding protein 3 (IGFBP-3), insulin, lactate and pyruvate were identified using a systematic literature search. These publications were assessed using the BIVAC, receiving grades A, B, C or D, where A is of highest quality. A meta-analysis of the BVD from the assessed studies utilised weightings based upon BIVAC grades and the width of the data confidence intervals to generate global BVD estimates.

RESULTS

BIVAC assessment of 47 publications delivered 1 A, 3 B, 39C and 4 D gradings. Publications relating to adiponectin, C-peptide, IGF-1, IGFBP-3, lactate and pyruvate were all assessed as grade C. Meta-analysis enabled global BV estimates for all analytes except pyruvate, lactate and fructosamine.

CONCLUSIONS

This study delivers updated and evidence-based BV estimates for diabetes-related analytes. There remains a need for delivery of new high-quality BV studies for several clinically important analytes.

Effect of grain size and heavy metals on As immobilization by marble particles

The effect of grain size and the interaction of heavy metals on As sorption by marble waste with different particle sizes was investigated. Acidic solutions containing only arsenic and a mixture of arsenic, lead, zinc, and cadmium were put in contact with the marble waste. The amount of metal(loid)s that were immobilized was calculated using the difference between the concentration in the acidic solution and in the liquid phase of the suspensions. Approximately 420 μg As m(-2) was sorbed onto the marble grains, both nonspecifically and specifically, where ≥ 80 % of the total arsenic in the acidic solution remained soluble, which suggests that this amendment is not effective to immobilize arsenic. However, in mixed contamination, relatively stable Pb-Ca arsenates were formed on the surface of the marble particles, and the soluble arsenic was reduced by 95 %, which indicates that marble particles can effectively immobilize arsenic and lead when both appear together.

Spreading of pollutants from alkaline mine drainage. Rodalquilar mining district (SE Spain)

In the Rodalquilar mining district of SE Spain, a total of 46 soil samples that were between 0 and 20 cm in depth were taken from the tailings dump, stream sediments, and surfaces that were presumably were unaffected by mining. In each soil sample, organic carbon content, pH, particle size distribution and total and soluble trace element content were analysed. Pollutants were scattered by runoff from two source areas: tailings from Au mining (Sn, Sb, As and Se) and wastes from Pb mining (Pb, Cu and Zn). Sn, Pb, and Sb were spread mostly in the solid phase of the runoff, while Cu, Zn, As and Se were spread in both the solid and soluble phases of the runoff. The pollutants with the highest soluble concentrations were As and Se, which were scattered at greater distances from the source. Some evidence suggests that tailings from Au mining could also be scattered by wind, but no farther than 1500 m from the source.

Effectiveness of amendments on the spread and phytotoxicity of contaminants in metal-arsenic polluted soil

A metal-arsenic polluted soil from sulphide-mine waste was treated, in all possible combinations, with two different amounts of marble sludge (98% CaCO3), compost (41% organic carbon), and Byferrox (70% Fe). Lixiviate and pore water from each treated and untreated soil were analysed, and lettuce-seed bioassays were performed. None of the treatments decreased the electrical conductivity of lixiviates or the concentrations of all pollutants found in both solutions. Marble sludge and compost increased the pH values and decreased the zinc, cadmium, copper, and lead concentrations in both solutions while increasing the arsenic concentrations in the lixiviates. Byferrox did not alter the physicochemical parameters or the concentrations of zinc, cadmium, copper, or lead in either solution but significantly decreased the arsenic concentrations in pore water. Compared with the Byferrox treatment, the mixture of marble sludge and Byferrox decreased redox potential values, increasing the arsenic concentrations in both solutions and the electrical conductivity of the pore water. All lixiviates were highly phytotoxic and seeds did not germinate. Pore-water phytotoxicity was related to electrical conductivity values and heavy-metal concentrations. The combination of marble sludge and compost was most effective at diminishing toxicity in lettuce. The soils treated with Byferrox, alone or mixed with marble sludge or compost, were the most phytotoxic.

Impact of unconfined sulphur-mine waste on a semi-arid environment (Almería, SE Spain)

Thirty-five soil samples were taken from unconfined mine waste, stream sediments, and surfaces unoccupied by mining and presumably unaffected by it, in a sulphur-mining zone surrounded by carbonate material and characterized by a semi-arid climate with short torrential storms. These samples were analysed and the results compared to estimate the spread of pollution in the landscape and to assess potential environmental risk. The mean concentrations of S, Zn, Cd, Pb, and As in mine waste were between 3.5-fold (As) and 50-fold (S) greater than unaffected soils. Oxidation of S led to a sharp drop in pH, strong weathering of minerals, and solubilisation of the constituent elements, forming a toxic acidic mine drainage with highly concentrated pollutants that were discharged into the drainage channels. Successive acid mine drainage into the soil on the valley floor spreads acidification and pollution downstream. The high carbonate content in surrounding soils played an important role in the increase of the pH and precipitation of S, Pb, and Al of the affected soils. Meanwhile, high mobility of Zn, Cd and As under basic conditions and a low Fe concentration explain the broad spread of these elements, as high concentrations were detected in soil more than 2000 m from the source. Only the soil solutions from near the waste dump (first 500 m) were highly phytotoxic, and moderately phytotoxic from 500 to 1500 m away. The concentration of pollutants in the leachates was clearly higher than in soil solutions, even in the soils located over 2000 m from the source, implying that the size of the polluted area will increase with time.

Use of liming in the remediation of soils polluted by sulphide oxidation: a leaching-column study

Pure CaCO(3) in ascending quantities was added to a soil to study the effect of liming after contamination by an acidic solution from the oxidation of pyrite tailings. The samples were placed in percolation columns, and soils and leachates were monitored. In the soil samples, the mineralogy, pH, CaCO(3), iron, and total content in Cu, Zn, As, Cd, and Pb were determined. The presence of CaCO(3) in the soils considerably limited their acidification, favouring the precipitation of Cu, Zn, and Cd, and promoting precipitation of iron and SO(4)(2-) ions in the form of iron hydroxysulphates and gypsum. The iron hydroxysulphates tended to retain the less mobile elements (As, and Pb) near the top of the soil. The more mobile elements (Zn, Cd and Cu) precipitated in deeper layers, directly related mainly to the CaCO(3) added and to pH. The CaCO(3) clearly did not reduce Zn and Cd toxicity effectively enough, given that the concentrations of both elements were above the toxic level in all leachates. The amounts of liming needs to be properly controlled, as excessively high pH limits As fixing, at the same time as the effectiveness of CaCO(3) is limited by coating precipitation, reducing its capacity to react with the acidic solution.

Ambient trace element background concentrations in soils and their use in risk assessment

The definition of ambient background concentrations (ABCs) is used in this study to assess the potential environmental risk of trace elements in soils and parent materials from Granada, Spain. Two different layers of soil (0-20 and 20-40 cm) and parent material samples were collected at 93 sites. From cumulative frequency distribution curves, ABCs for As, Co, Cu, Cr, Ni, Pb and Zn were estimated at 3.5-20, 7-23, 13-25.6, 29-66, 7-20, 15-36, and 5.5-76 mg kg(-1), respectively. Tukey box-plots were used to discriminate different concentration classes and identify potentially contaminated sites. Weakly-weathered soils (Entisols) over carbonate materials showed the lowest background contents, the most developed soils (Alfisols) over metamorphic rocks the highest ones. Outliers were mainly found near a former iron mine where arsenic concentrations were by far exceeding the corresponding regional ABC. These soils were however, not toxic to Escherichia coli and Vibrio fischeri. The prediction of site-specific ABCs together with bioavailability and toxicity assessment is a valuable tool for giving further insight into the risk of trace elements in soils.

The reference change value: a proposal to interpret laboratory reports in serial testing based on biological variation

BACKGROUND

A proposal to calculate and use the reference change value (RCV) as an objective guide for interpreting the numerical results obtained in clinical laboratory serial testing is introduced in this study.

METHODS

A database showing the results of a compilation of 191 publications on biological variation and including information on a number of analytes provided the standardized criterion based on biology for calculating the RCVs.

RESULTS

For each of the 261 analytes included in the study, the RCV was determined using Harris's formula, replacing analytical imprecision with the desirable specification of analytical quality based on half the within-subject biological variation at 95% probability levels. The result is a guide for a common criterion to identify clinically significant changes in serial results.

CONCLUSIONS

The RCV concept is an approach that can be offered by laboratories to assess changes in serial results. The RCV data in this study are presented as a point of departure for a widely applicable objective guide to interpret changes in serial results.

The Catalan Healthcare Intercultural Mediation Training Project of “la Caixa” Social and Cultural Outreach Projects

Known by many different names-culture broker, community interpreter, medical interpreter, and communication facilitator-the intercultural mediator has as a primary task the facilitation of communication and the therapeutic relationship in the presence of linguistic and/or cultural difference. The Immigration Plan of “la Caixa” Social and Cultural Outreach Projects has undertaken an ambitious project to train all of the cultural mediators in Spain, including both those currently working and those newly entering the field, to meet existing needs. In the first phase of the project, the training was developed in Catalunya, in collaboration with the the Catalan Department of Health, executed by the Psychiatry Department of the Vall d'Hebron University Hospital (Autonomous University of Barcelona) and certified by the Health Studies Institute of the Department of Health. Drawing from the four years experience of the NGO SURT and the Department of Psychiatry of the Vall d'Hebron University Hospital, the program provides 200 hours of theoretical and 1200 hours of practical training. 50 currently employed intercultural mediators and 30 novices are being trained. In subsequent phases the training will be adapted to needs of other autonomous regions of Spain. Modules include medical anthropology, Western biomedicine, community health, linguistic interpretation, cultural competence, professional identity, and ethics. Small group supervision provides a supportive environment to facilitate the application of theory to practice. Finally, high quality training materials were developed specifically for the course. Preliminary evaluations of the project are positive despite some unanticipated complications.

Remediation measures and displacement of pollutants in soils affected by the spill of a pyrite mine

The soils affected by the spill of a pyrite mine were analysed in 100 sampling points at three depths (0-10, 10-30, and 30-50 cm) in 1998 (after the tailings were removed), 1999 (after the cleaning of the highly contaminated areas), and 2004 (after the tilling of the upper 20-25 cm). The comparative study reveals that the removal of the tailings left a heterogeneous distribution pattern of the contaminants, with highly polluted spots alternating with less contaminated areas. The cleanup did not substantially lower the concentration in the highly polluted soils, and the spread of the pollutants increased the concentration in As and Pb in the uppermost 10 cm of 60% of the soils, while the Zn and Cd concentrations increased in only 30% of the soils. Given the high concentration of pollutants in the topsoil (especially As), the tilling of the upper 20-25 cm, despite reducing the average concentration of pollutants in the uppermost 10 cm, did not substantially lower the percentage of soils that exceeded the concentration of 40 mg As kg(-1) dry soil and almost doubled the percentage of soils that surpassed this concentration between 10 and 30 cm. Meanwhile, the displacement of Zn and Cd within the soil supported the reduction in the percentage of soils that in the upper 10 cm exceeded the reference concentrations of these elements (900 mg Zn kg(-1) dry soil and 2 mg Cd kg(-1) dry soil), and the percentage of soils exceeding these concentrations between 10 and 50 cm in depth did not increase. Six years after the spill and at the end of all remediation measures, the intervention levels defined by the Environmental Agency of the Regional Government of Andalusia for natural parks were exceeded in the uppermost 10 cm in 35% of the soils.

Clinical pharmacokinetics of ferric natural protein in iron-deficient females

Although iron therapy is very common, few studies have assessed iron absorption or iron kinetics in general, particularly with Fe(3+). This was the primary objective of this study, with assessment of tolerance as a secondary objective. Eight nonsmoking iron-deficient females without other associated pathologies, with an average age of 21.62 +/- 1.69 years, were studied. The diagnosis of iron deficiency was established by determination of sideraemia (28.7 +/- 13.5 microg/dl), iron binding capacity (380.5 +/- 70.2 microg/dl) and ferritin (5 +/- 1.4 microg/L) on the prestudy visit. The women remained in the Phase I Unit during days 0, 1, 2 and 3 of the study. A serum iron concentration curve was obtained daily from blood samples drawn at 0, 1, 2, 4, 6, 8 and 12 hours postdose. Therapy with ferric natural protein (ferrimannitol ovoalbumin) 40mg twice daily was started on day 1 of the study and continued for 30 days. The following parameters were evaluated: area under the curve (AUC(0-12h)), peak iron concentration (C(max)) and time to reach peak concentration (t(max)). Serum iron concentration-time curves were practically flat on day 0, but showed an increase following ferric therapy (Friedman, p < 0.05), confirming the usefulness of the postabsorption test and good absorption of ferric iron (Fe(3+)). The increase in AUC (314.65 +/- 67.9 to 1174.44 +/- 1071.8 microg/dl.h) and C(max) (49 +/- 24.4 to 146 +/- 101.9 microg/dl) from day 1 and the correlation between both parameters (r(2) > 0.85, p </= 0.008) supported the use of either parameter. The t(max) ranged from 4 to 6 hours. Ferric therapy was well tolerated by all patients. This study shows that ferric iron contained in this preparation is well absorbed and provides a satisfactory method for evaluation of iron absorption.

Background arsenic concentrations in Southeastern Spanish soils

The arsenic content in the province of Granada (SE Spain) was quantified, based on 93 soils at two different depths and their corresponding parent materials. The arsenic concentrations fit a log-normal distribution. Four different statistical procedures to estimate the arsenic background range in the region were tested. Upper background limits clearly exceeded limits reported for natural soils when based on the Tukey box plot or means and standard deviations of the dataset (M+/-2sdev) or of the calculated distribution function (Mf+/-2sigma) but not when based on median values (Md+/-2MAD). The relative cumulative frequency curve not only adequately estimates the background range but also delivers a clear and detailed visualisation of the data distribution and identifies subpopulations with specific background ranges related to combinations of parent materials and degree of soil development.

Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings

To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed.

Soil pollution by a pyrite mine spill in Spain: evolution in time

Soil pollution was studied after the spill of the Aznalcóllar pyrite mine between 1998 and 2001, analyzing As, Zn, Cd, Cu and Pb both in total concentrations as well as in soluble and bioavailable forms. The main remediation measures were: clean-up of the tailings and polluted soils, plus application of amendment materials (liming). The results indicate that, after three years, 50-70% of the acidic soils and 25-30% of the basic soils are still highly polluted in total arsenic. The limit of 0.04 mg kg(-1) for water-soluble arsenic is exceeded in 15-20% of all soils. The EDTA-extractable arsenic (bioavailable) exceeds the limit of 2 mg kg(-1) only in the acidic sectors. After clean-up, the homogenization of the upper 20-25 cm of the soils appears to be the most recommended measure in the reduction of pollution.

Migration of trace elements from pyrite tailings in carbonate soils

In the carbonate soils contaminated by a toxic spill from a pyrite mine (Aznalcóllar, southern Spain), a study was made of a thin layer (thickness = 4 mm) of polluted soil located between the pyrite tailings and the underlying soil. This layer, reddish-yellow in color due to a high Fe content, formed when sulfates (from the oxidation of sulfides) infiltrated the soil, causing acidification (to pH 5.6 as opposed to 8.0 of unaffected soil) and pollution (in Zn, Cu, As, Pb, Co, Cd, Sb, Bi, Tl, and In). The less mobile elements (As, Bi, In, Pb, Sb, and Tl) concentrated in the uppermost part of the reddish-yellow layer, with concentration decreasing downward. The more mobile elements (Co, Cd, Zn, and Cu) tended to precipitate where the pH was basic, toward the bottom of the layer or in the upper part of the underlying soil. The greatest accumulations occurred within the first 6 mm in overall soil depth, and were negligible below 15 mm. In addition, the acidity of the solution from the tailings degraded the minerals of the clay fraction of the soils, both the phyllosilicates as well as the carbonates. Also, within the reddish-yellow layer, gypsum formed autigenically, together with complex salts of sulfates of Fe, Al, Zn, Ca, and Mn, jarosite, and oxihydroxides of Fe.

Soil pollution by oxidation of tailings from toxic spill of a pyrite mine

On the 25th April 1998, toxic water and tailings from a pyrite mine of Aznalcóllar (southern Spain) spilled into the Agrio and Guadiamar River Basin affecting some 40 km2. In five sectors throughout the basin, we monitored the physical and chemical properties of the tailings as well as the degree of pollution in the soils on four different sampling dates: 5 May, 20 May, 4 June and 22 July 1998. The characteristics of the tailings deposited on the soils are shown to be related to distance from the spill. The oxidation rate of the tailings and the solubilization of the pollutant elements were more pronounced in the middle and lower sectors of the basin, where the particle size was finer, the sulfur content higher and the bulk density less. The increases in water-soluble sulfates, Zn. Cd and Cu were very rapid (the highest values being reached 25 days after the spill) and intense (reaching 45% of the total Cu, 65% of the total Zn and Cd). Meanwhile, the increases in water-soluble As, Bi, Sb, Pb and Tl were far lower (ranging between 0.002% of the total Tl and 2.5% of the total As) and less rapid in the case of As, Bi and Pb (the highest values for these elements being reached 40 days after the spill). These soluble elements infiltrated the soils with the rainwater, swiftly augmenting the soil pollution. Twenty-five days after the spill, when the rainfall ranged between 45 and 63 mm, the first 10-cm of the soils in the middle and lower sectors of the basin exceeded the maximum concentration permitted for agricultural soils in Zn, Cu and Tl. At 40 days after the spill, when the rainfall ranged between 60 and 89 mm, all the soils reached or exceeded the maximum permitted concentrations for As and Tl. Nevertheless, the pollutants tended to concentrate in the first 10 cm of the soils without seriously contaminating either the subsoil or the groundwaters. Consequently, a rapid removal of the tailings and the ploughing of the first 25-30 cm of the soils would be urgent measures to diminish pollutant concentration in the soils affected by the spill.

[Pharmacovigilance study of azithromycin tablets (500 mg) in the treatment of adult patients with respiratory tract infections]

Our aim was to study a new form of azithromycin (500 mg tablets) in order to evaluate the tolerability and the influence of the ingestion of food on tolerability, the efficacy and treatment compliance in a large number of patients with respiratory tract infections. We carried out an open, non-comparative, multicenter, observational and prospective pharmacovigilance study of 3223 outpatients with respiratory tract infections randomly assigned to receive a daily dose of azithromycin for three months taken either during or outside meals. Patients were evaluated during an initial visit and two later ones in order to record the adverse events and establish the clinical efficacy. The diagnostics were as follows: pharyngotonsillitis (1200), acute otitis media (394), acute bronchitis (1134), exacerbation of chronic bronchitis (436), and community-acquired pneumonia (53). The overall therapeutic efficacy was satisfactory (cure or improvement) in 96% to 97% at the second visit and in 93% to 94% in the third (pharyngotonsillitis, 93%; acute otitis media, 91%; acute bronchitis, 94%; exacerbation of chronic bronchitis, 94%; and community-acquired pneumonia, 96%). A total of 170 adverse events were reported in 141 patients (4.4%); 12 were severe yet not related to the study medication. Eighty-eight patients showed adverse events presumed to be related to azithromycin; most were in the digestive tract. No differences in tolerability were observed in relation to food intake. Treatment compliance was high (97%). The elevated clinical efficacy, adequate compliance and the excellent tolerability profile of azithromycin tablets make them a safe and effective alternative in the treatment of respiratory tract infections.

Pollution of soils by the toxic spill of a pyrite mine (Aznalcollar, Spain)

On 25 April 1998 the retention walls broke open in a pond containing the residues from a pyrite mine of Aznalcollar (southern Spain), spilling some 45 x 10(5) m3 of polluted water and toxic tailings into the Agrio and Guadiamar River basin, affecting some 55 km2. On 5 May, seven sectors in the affected area were studied, analysing tailings, polluted water, and contaminated as well as uncontaminated soils. The principal pollutants were: Zn, Pb, Cu, As, Sb, Bi, Cd and Tl. The range of total contamination of each element was extremely broad, as penetration of the tailings depended on the soil characteristics. Most of the Cu, Zn and Cd penetrated the soil in the solution phase of the spill, while the other elements penetrated mostly as part of the solid phase. Zn exceeded the maximum concentrations permitted by the international community in four of the seven sectors studied, As in three, and the other elements only in one sector. Drying and consequent aeration of the tailings rapidly oxidized sulphides to sulphates, lowered the pH and solubilized the pollutants. Therefore, future rains could aggravate the pollution problem, if the tailings are not quickly removed.

Our experience with Wallstent self-expanding metal prostheses in 65 patients with malignant dysphagia

OBJECTIVE

to document the usefulness of self-expanding metal stents in patients with malignant dysphagia.

METHOD

from January 1992 to January 1997 we implanted 75 Wallstent prostheses (28 uncovered AV, 20 uncovered Unistep, 15 covered Telestep, and 2 covered double-mesh Permalume stents) in 65 patients with malignant dysphagia.

RESULTS

mean survival time was 100 days in patients with uncovered stents, and 215 days in patients with covered stents. Oral feeding was possible throughout the post-implantation course in 58 of 65 patients. Only two severe complications occurred: esophageal perforation with mediastinitis, and migration of the stent from the distal esophagus into the stomach. All implantation procedures were done under radiological guidance. For AV and Unistep prostheses we used a nasal approach without sedation, and for Telestep and Permalume stents we used an oral approach with sedation.

CONCLUSIONS

Wallstent self-expanding metal stents are useful in palliating malignant dysphagia. The placement and implantation of these stents are straightforward.

Current databases on biological variation: pros, cons and progress

A database with reliable information to derive definitive analytical quality specifications for a large number of clinical laboratory tests was prepared in this work. This was achieved by comparing and correlating descriptive data and relevant observations with the biological variation information, an approach that had not been used in the previous efforts of this type. The material compiled in the database was obtained from published articles referenced in BIOS, CURRENT CONTENTS, EMBASE and MEDLINE using "biological variation & laboratory medicine" as key words, as well as books and doctoral theses provided by their authors. The database covers 316 quantities and reviews 191 articles, fewer than 10 of which had to be rejected. The within- and between-subject coefficients of variation and the subsequent desirable quality specifications for precision, bias and total error for all the quantities accepted are presented. Sex-related stratification of results was justified for only four quantities and, in these cases, quality specifications were derived from the group with lower within-subject variation. For certain quantities, biological variation in pathological states was higher than in the healthy state. In these cases, quality specifications were derived only from the healthy population (most stringent). Several quantities (particularly hormones) have been treated in very few articles and the results found are highly discrepant. Therefore, professionals in laboratory medicine should be strongly encouraged to study the quantities for which results are discrepant, the 90 quantities described in only one paper and the numerous quantities that have not been the subject of study.

Commutability and traceability: their repercussions on analytical bias and inaccuracy

The commutability of calibrators and accuracy control materials affects the traceable link between patient sample results and standards. We sought to identify the repercussions of commutability on various aspects of laboratory practice (calibration, control of bias and accuracy assessment) and to discover the solutions that can reduce the problems produced by non-commutability with presently available resources. Ten serum constituents, ten comparison procedures and 37 analytical procedures were studied. The information concerning accuracy and bias provided from materials found to be commutable in previous works was challenged with native serum results for each routine and reference method compared, using Passing-Bablok regression and decision limits derived from biological variation. We found that: (1) Use of commutable control materials did not assure reliable information on the bias (systematic component of analytical error) of analytical procedures, and (2) Results from native serum and commutable controls were very highly concordant, indicating that these materials provide a good indication of the inaccuracy (total analytical error) of results. We suggest that the performance of individual laboratories would be better evaluated by occasional use of native sera with values assigned by reference methods in EQAS schemes. Moreover, our findings support the idea that manufacturers should assign values to calibrators using reference methods and native sera to reduce matrix effects and promote traceability.

Evaluation of the immunospecificity of the porin Om1 of Vibrio anguillarum serotype O1

Three methods of immunoanalysis (immunoblot, ELISA and dot-blot) were used to evaluate the immunospecificity of the antiserum against the porin Om1 of Vibrio anguillarum serotype O1 with respect to all the serotypes of V. anguillarum, different Vibrio species and other Gram-negative genera. In the immunoblot analysis of the outer membrane proteins, this antiserum cross-reacted with the main outer membrane protein (MOMP) of all the Vibrio strains studied but not with other genera, except Plesiomonas shigelloides. However, when analyses were performed using whole cells as antigens (ELISA and dot-blot), the antiserum was more specific for V. anguillarum.

Synthesis and evaluation of tacrine-huperzine A hybrids as acetylcholinesterase inhibitors of potential interest for the treatment of Alzheimer's disease

Seventeen polycyclic compounds related to tacrine and huperzine A have been prepared as racemic mixtures and tested as acetylcholinesterase (AChE) inhibitors. The conjunctive pharmacomodulation of huperzine A (carbobicyclic substructure) and tacrine (4-aminoquinoline substructure) led to compound 7jy, 2.5 times less active than tacrine as AChE inhibitor, but much more active than its (Z)-stereoisomer (7iy). Derivatives 7dy and 7ey, lacking the ethylidene substituent, showed to be more active than tacrine. Many other structural modifications of 7jy led to less active compounds. Compounds 7dy and 7ey also showed to be much more active than tacrine in reversing the partial neuromuscular blockade induced by d-tubocurarine.

Procedure for studying commutability validated by biological variation

In the field of laboratory medicine, the two quantitative approaches designed to identify the stabilized materials that produce results that are commutable with results from patients' samples were found to differ. In commutability evaluations, the responses of each material and each method studied are specific, thus, it is vital to standardise the procedure used for determining this characteristic. We incorporated statistical components from the two described methods that seemed to be consistent, and added a new element based on biological variation, to validate the criterion of acceptability that determines whether or not a material is commutable. The three methods for studying commutability (using the confidence interval [alpha = 0.05], the +/- 2s(yx) formula, and the limit based on biological variation as acceptability criteria) were applied to creatinine results from 31 stabilised materials and serum samples analysed with seven instruments, when compared against a reference method for creatinine analysis. Over the wide range of concentrations studied, the confidence interval limit and the biological variation limit coincided in the identification of commutable materials, whereas the +/- 2s(yx) was excessively permissive at normal and low concentration levels. We therefore recommend the use of Passing-Bablok regression with its confidence interval (alpha = 0.05) in studies concerning commutability. Using this method, commutability is simple to calculate with available software and, as validated by biological variation, results are reliable.

Commutability between stabilized materials and fresh human serum to improve laboratory performance

With the recent advances in laboratory technology, many quality-related problems have been improved. However, the issue of commutability, a factor that greatly affects daily decisions concerning patient status, still remains to be solved. This paper determines the commutability between 27 stabilized materials (controls and calibrators) and clinical specimens for five serum quantities, using carrier-bound reagent chemistry and conventional wet methods. Our aim was to pinpoint the specific problems related to non-commutable calibrators and controls in our setting, and minimize their effect in daily practice. We found major difficulties in selecting appropriate accuracy controls in carrier-bound reagent techniques, and in finding materials commutable for several analytes simultaneously. Several suggestions for reducing problems related to non-commutability, such as procedures for assigning values to multicalibrators, are proposed. We explain the apparent incongruencies observed in daily quality surveillance, when data from different control materials (internal quality control and external quality assessment) are evaluated. The conclusions emphasize the need for a combined effort (manufacturers, organizers of external quality assessment schemes and individual laboratories) to find the cause of, and eliminate, the negative repercussions on laboratory performance produced by non-commutability.

Characterization of a porin from the outer membrane of Vibrio anguillarum

The outer membranes of the 10 serovars of Vibrio anguillarum showed a common major protein with a size of around 40 kDa. Antibodies against the major outer membrane protein (MOMP) of V. anguillarum AO18 (serovar O1) cross-reacted with the MOMPs of all the other serovars but not with the outer membrane proteins of Escherichia coli. The MOMP of V. anguillarum serovar O1 was isolated, reconstituted to two-dimensional crystals, and structurally characterized by electron microscopy and image processing. The unit cell structure of the crystalline MOMP, as well as the secondary structure composition of the protein with a high amount of beta-structure, is strongly reminiscent of that of bacterial porins. The functional properties of the pores were investigated by conductance measurements with the MOMP reconstituted in planar lipid membranes. The V. anguillarum MOMP is characterized by a relatively weak cation selectivity and a moderate surface charge, and it shows voltage-dependent conductance effects. The MOMP is functionally similar to OmpF from E. coli, and it can be classified as a general diffusion porin.

[Transferability of results in hematologic determinations]

PURPOSE

To evaluate inaccuracy of the results attained in several Servei Catalá de la Salut laboratories in order to assess if quality purposes are accomplished and results are transferable between them.

MATERIAL AND METHODS

Two types of haematological analysers are used: those based upon volumetric measurements and those using light dispersion for particle counting. Inaccuracy was ascertained in accordance to the inter-laboratory quality control programme. The inter-series study was performed with commercial control material in each laboratory with their own data, the monthly coefficient of variation being found, and the mean of the CV of 12 months was then calculated. Intra-series inaccuracy with commercial control material was assessed in each laboratory three times a day for 10 days, and the inaccuracy with fresh patient blood was examined daily in triplicate. The analytical inaccuracy attained in patient samples was also compared with that attained with stabilized control materials.

RESULTS

The inaccuracy quality limits were exceeded in the haematological constituents under study. Quality objectives were accomplished in the inter-series inaccuracy study for red cell count, white cell count, MCV, granulocytes and lymphocytes. Repeat fresh patient-blood assays can be used to assess intra-series inaccuracy for red and white cell counts, but not for platelet count.

CONCLUSIONS

Inaccuracy of the blood constituents studied is not transferable. Inaccuracy for the commonest haematological values is transferable between laboratories. Intra-series inaccuracy for red and white cell counts can be assessed by repeated use of fresh patient-blood when control material is not available. Patient samples are not advisable as a control of the white cell differential count for intra-series inaccuracy studies in those systems using volumetric principles.

Biological variation in urine samples used for analyte measurements

To determine the influence of biological variation on the reliability of data from different types of urine specimens, we measured nine analytes in first-morning, randomly collected, and 24-h samples of urine from 53 healthy individuals (14 men and 39 women). The urines were collected once a week for 10 weeks. The data obtained were used as a basis for specimen collection and to gain insight into the influence of urine quantities in the diagnosis, screening, and monitoring of patients. We found that 24-h urine expressed in output rather than concentration units is the most reliable specimen for diagnosis and monitoring for most of the analytes studied. On the basis of the ratio between estimated within- and between-subject variation, the tests with greatest medical usefulness for diagnosis and screening of specific pathologies are those measuring protein and sodium. Moreover, the results indicate that urine creatinine may be a poor test for diagnosis, monitoring, and screening.

Biological variation in urine samples used for analyte measurements

To determine the influence of biological variation on the reliability of data from different types of urine specimens, we measured nine analytes in first-morning, randomly collected, and 24-h samples of urine from 53 healthy individuals (14 men and 39 women). The urines were collected once a week for 10 weeks. The data obtained were used as a basis for specimen collection and to gain insight into the influence of urine quantities in the diagnosis, screening, and monitoring of patients. We found that 24-h urine expressed in output rather than concentration units is the most reliable specimen for diagnosis and monitoring for most of the analytes studied. On the basis of the ratio between estimated within- and between-subject variation, the tests with greatest medical usefulness for diagnosis and screening of specific pathologies are those measuring protein and sodium. Moreover, the results indicate that urine creatinine may be a poor test for diagnosis, monitoring, and screening.