[Comparison of plasma total homocysteine determinations in 9 French hospital laboratories by using 6 different methods]. / Comparaison du dosage de l'homocystéine plasmatique totale dans neuf laboratoires par six techniques différentes.

A lot of methods are now available for total plasma homocysteine (tHcy) determination. Commercial kits using immunoassay, easier to use, begin to supplant in-house laboratory methods. Our aim is to evaluate the interchangeability of tHcy measurements in 9 French hospital laboratories. Six different method types were used: 2 gas chromatography-mass spectrometry (GC-MS), 2 HPLC with fluorescence detection subdivided in one in-house method and one commercial kit (Bio-Rad ), 3 fluorescence polarization immunoassays (FPIA), 1 enzyme immunoassay, 1 amino acid analyser, 1 capillary electrophoresis coupled with laser-induced fluorescence detection (EC-LIF). Each laboratory analysed 41 patient's plasma samples in which 8 samples contained added homocystine. Results were analysed for imprecision, recovery, and methodological differences. The mean among-laboratory imprecision (CV) ranged from 12.5 to 18% in function of plasma sample type and was identical to the mean among-method variation. In terms of recovery, we obtained underestimated results with immunoassays. The bias relative to the GC-MS method was less than 12.5% except for two laboratories, one using FPIA assay and the other EC-LIF. In conclusion, the interchangeability of tHcy results between laboratories is not satisfactory and does not allow us to evaluate cardiovascular risk linked to moderate increases of tHcy.

Analysis of the effects of rotational larviciding on aquatic fauna of two Guinean rivers: the case of permethrin.

Within the Onchocerciasis Control Programme about 50,000 km of west African rivers have been regularly sprayed with larvicides to control the vector of dermal filariasis caused by Onchocerca volvulus. Since the beginning of the programme invertebrates and fish data were collected to monitor adverse effects on non-target organisms. The regular series of biological and hydrological data collected in two Guinean rivers were analysed to evaluate the effects of rotational larviciding with particular attention to permethrin, as preliminary acute toxicology tests and semi-field experiments suggest it has stronger effects on non-target fauna in respect to other larvicides. Invertebrates and fish variations in biomass and species richness are seasonal and flow-related and the results presented here do not support any evidence of specific effects of permethrin application on the biological targets monitored. Larvicide applications influence community structures, putting pressure on some taxonomic groups, causing, for example, the rarefaction of some taxa. In spite of the above results, the scarcity of some invertebrate systematic units does not result in a significant reduction of total invertebrate density because of the corresponding increase in other systematic units. In nature the studied aquatic communities would rarely be in equilibrium because of frequent natural stresses, such as drought and spate events, the biological variations discussed are to be considered ecologically acceptable.

[Plasma homocysteine measurement: a study of pre-analytical variation factors for conditions for total plasma homocysteine concentration]. / Dosage de l'homocystéine plasmatique: étude des facteurs de variation préanalytiques sur la concentration en homocystéine plasmatique totale.

An increase in homocysteine, a sulphur amino acid, is nowdays considered as a risk factor for cardiovascular diseases, and is independent of other risk factors. Reference range for total plasma homocysteine level in adults is usually 5-15 mmol/l. Hyperhomocysteinemia is defined as a fasting total plasma homocysteine level > 15 mmol/l. There may be also graded increased risks for subjects with homocysteinemia from 10 to 15 mmol/l. However, no threshold has been defined, partly because of the lack of standardization in pre-analytical and analytical steps. The aim of the present work was to evaluate three pre-analytical parameters on plasma homocysteine levels: i) the influence of three anticoagulants (EDTA, sodium citrate and lithium heparin); ii) the delay period of blood sample on ice before centrifugation; and iii) the advantages of strong acidic citrate at room temperature. The mean concentrations of total plasma homocysteine were different in function of the anticoagulant. These differences (EDTA minus lithium heparin or EDTA minus sodium citrate) were less than 10% however the used methods and could explain the good correlation between the results. However we recommend to keep the anticoagulant constant in the same study. When EDTA blood samples were immediately put on crushed ice, the maximum delay period before centrifugation could reach 4 hours. If ice is unavailable, strong acidic citrate at room temperature is a good alternative until for 4 hours.

Lp(a) is increased in hemodialysis patients according to the type of dialysis membrane: a 2-year follow-up study.

AIMS: Patients with chronic renal failure treated by hemodialysis develop lipoprotein abnormalities that may contribute to their increased risk ofatherosclerosis. This study shows lipid parameter follow-up procedure according to the type of dialysis membrane in an unselected population of 33 hemodialysis patients. PATIENTS AND METHODS: The study included 33 patients with end-stage renal disease and 110 healthy blood bank donors of Tenon Hospital. Cholesterol and triglycerides were determined by enzymatic methods, apoA-I, apoB by immunoturbidimetry and Lp(a) by immunonephelemetry. Apo(a) phenotyping was performed by agarose gel electrophoresis followed by immunoblotting. Patients and controls subjects were estimated by Student's t- and chi2-tests. RESULTS: Patients dialyzed with low-flux membranes had Lp(a) concentrations higher than patients dialyzed with high-flux membranes. Patients dialyzed with polyacrylonitrile membranes (AN 69) had an apoA-I concentration significantly lower than patients dialyzed with hemophane or polysulfone membranes. We also confirmed some of the lipid abnormalities and high Lp(a) concentrations in ESRD patients. CONCLUSION: These results may contribute to a more rational choice of the dialysis membrane in hemodialysis patients.