Real time validation of paediatric biochemical reports using the Valab-Biochem system.

Validation of biochemical reports must be fast and clinically accurate to be of assistance to clinicians. Considerable skill is required to analyse the consistency of different data in the report and to consider influences on the data. When performed throughout the day, such analysis is time-consuming and uncertain. We therefore decided to use a computer-assisted validation system, Valab-Biochem. Its decisions result from a decision tree based primarily on the intrinsic consistency of the data, validation ranges and patients' sex, age and hospital ward. Three hundred randomly chosen reports were simultaneously submitted to Valab-Biochem and to five biologists in order to analyse the computer's findings. The sensitivity of Valab-Biochem was 80% compared to biologists' consensus decision, which was taken as the gold standard. The specificity was 78%. This system provided autonomous assessment of the reports and could be used as an initial screen to assist biologists and focus attention on potentially inconsistent reports.

Moyamoya disease in a child with glycogen storage disease type Ia.

A three-year-old child affected by glycogen storage disease (GSD) type Ia presented with acute hemiplegia secondary to Moyamoya disease. So far, the association of moyamoya with GSD Ia had only been reported twice. The rarity of both conditions makes their association unlikely to be a chance event and an etiological relationship between them must be considered.

Hydroperoxides of erythrocyte phospholipid molecular species formed by lipoxygenase correlate with alpha-tocopherol levels.

The hydroperoxides corresponding to the main molecular species of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were determined after lipoxygenase treatment of erythrocyte membranes from healthy children. This work was a preliminary study prior to applying this analytical procedure to erythrocyte membranes from children with diseases associated with vitamin E deficiency. The total molecular species corresponding to 20:4 and 22:6 associated with 16:0 and 18:0 were significantly higher in PE (26.94 +/- 4.70 nmol/mg protein) than in PC (20.14 +/- 6.70 nmol/mg protein); these concentrations represented 63% of the total molecular species in PE and 22% in PC. However, the concentrations of hydroperoxides produced from these polyunsaturated fatty acid molecular species were in the same order of magnitude in PC (3.98 +/- 1.56 nmol/mg protein) and in PE (3.61 +/- 1.63 nmol/mg protein). In contrast, the molecular species concentrations containing two double bonds, such as 16:0/18:2 and 18:0/18:2 and their corresponding hydroperoxides, were clearly more elevated in PC than in PE. There was a positive relationship between the concentrations of alpha-tocopherol and each hydroperoxide of PC and PE, and this association was particularly strong in PE (P < or = 0.0001). These results suggest that alpha-tocopherol exerts a stabilizing effect toward hydroperoxides, limiting their further degradation into peroxyl radicals. The protective effect of alpha-tocopherol could be more effective in PE because more polyunsaturated fatty acids were present.

Determination of cortisol and associated glucocorticoids in serum and urine by an automated liquid chromatographic assay.

We describe a method for the determination of urinary free cortisol and glucocorticoids in plasma, used in the diagnosis of adrenal disorders, based on automated reverse-phase high-performance liquid chromatography (HPLC). The within-day and day-to-day CVs were less than 5.5 and 8.0%, respectively. The calibration curves for cortisol and 11-deoxycortisol were linear up to 2000 nmol/L. Cortisol concentrations as low as 3.5 nmol/L in 1 mL of plasma or urine can be measured. Correlation of HPLC results for 40 plasma specimens with those by radioimmunoassay showed r = 0.965. This method is sensitive and free from the interference habitually encountered in immunoassays, and can thus be proposed for research and as a potential reference method.

Simultaneous determination of the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their corresponding hydroperoxides obtained by lipoxygenase treatment.

A method for the simultaneous determination of the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their corresponding hydroperoxides is described. Hydroperoxides were formed by incubation of phospholipids with lipoxygenase at pH 9.2. Silicic acid column chromatography (silica Sep-Pak column) was used to separate the phospholipids into phosphatidylcholine and phosphatidylethanolamine. A single C-18 reverse-phase column was employed to separate the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their hydroperoxides by high-performance liquid chromatography. The mobile phase consisted of 5% 10 mM ammonium acetate at pH 5 and 95% methanol. The molecular species of phosphatidylcholine and phosphatidylethanolamine were detected at 205 nm; the eluate was mixed with a chemiluminescence reagent (isoluminol and microperoxidase) and monitored by fluorometry. Under the experimental conditions used, three individual molecular species of both soybean phosphatidylethanolamine and phosphatidylcholine (18:3/18:2, 18:2/18:2 and 16:0/18:2), together with their corresponding hydroperoxides, were identified and quantitated.

[Update of a selected technique for uric acid determination in plasma and serum. Experimental study and value of derivative spectrophotometry]. / Mise au point d'une technique sélectionnée de dosage de l'acide urique dans le plasma et le sérum. Etude expérimentale et intérêt de la spectrophotométrie dérivée.

A critical study of the candidate reference method for evaluation of uric acid in plasma proposed by the American Association of Clinical Chemistry is followed by testing in six laboratories. The dispersion of results is wide (CV greater than 5%). The importance of turbidity remaining after the deproteinization by trichloracetic acid is clearly demonstrated. This turbidity is really not reproducible from an operation to another one on the same serum. It is very likely responsible of the great dispersion of the results. After that, other deproteinization methods are tried. Ultrafiltration and ultracentrifugation give both defect errors because uric acid is in part bound to proteins. So it is necessary to find another technic which cancels the effects of turbidity on the absorbance readings in the ultra-violet domain. Experimental studies showed that uric acid may be evaluated with a good accuracy by derivative spectrophotometry, in lipid solutions as well as in cloudy ones. Turbidity was created by intralipid suspension additions. Various parameters hitting the method were examined (linearity, smoothing window...), taking as criterion the measure of overloaded serums at different levels. At last, the method is successfully transferred in several sites. In the case of blood serum, the respective influences of derivation and of repetition of final centrifugations are studied in order to estimate the effect of remaining turbidity. By the use of derivative spectrophotometry the improvement of the method of evaluation of uric acid proposed by A.A.C.C. is very noticeable; it reduces the variation coefficient between sites to less than 2%.

Protein A-sepharose used to measure free insulin in plasma.

Diabetic patients receiving insulin therapy generally develop anti-insulin antibodies that must be eliminated, usually by extraction with polyethylene glycol (PEG), before determining the concentration of free (active) insulin in plasma. We describe a new method for removing such antibodies, with the use of Protein A coupled to Sepharose microspheres. The results correlate well with those by the PEG method, although values are systematically higher or lower for given samples, according to the initial titer of the antibody measured in terms of binding capacity. Further studies are required to clarify this observation.

Semi-automated fluorometric assay for urinary total and B N-acetyl-beta-D-glucosaminidase: analytical investigation.

Total N-acetyl-beta-D-glucosaminidase (NAG) and NAG-B isoenzyme determination are determined in order to investigate renal tubular function. Here, we propose a semi-automated adaptation of Sandman's manual method for the Monarch centrifugal analyzer. Fluorescence of the released 4-methylumbelliferone is automatically read and results are directly expressed in nanokatal/l. Mean (1 SD) values expressed in nanokatal/millimole creatinine in urine from healthy female (n = 30) and male (n = 30) subjects were 8.2 (4.0) and 7.8 (2.9) for total NAG and 1.9 (1.4) and 1.5 (0.7) for the NAG-B isoenzyme activity. The assay of six patients with various renal disorders shows definite increase in total NAG and NAG-B isoenzyme activities.

[A recommended method for determination of uric acid in serum]. / Méthode recommandée pour le dosage de l'acide urique dans le sérum.

SFBC work group on uric acid propose a method for evaluation in blood serum which is modeled on the one defined by American Association for Clinical Chemistry. Serum is deproteinized by trichoracetic acid and the supernatant, buffered to pH 8.5, is submitted to uricase action. The disappearing of the strong band of uric acid in UV is measured by derivative spectrophotometry; this procedure vanished the effect of trouble which remains in the supernatant. This spectrophotometric technic permit to reach, in multiple sites, a variation coefficient near of 1 p. cent.

[Agglutination of intravenous lipid emulsions by acute phase proteins of inflammation]. / Agglutination des émulsions lipidiques intraveineuses par les protéines de la phase aiguë de l'inflammation.

Agglutination of intravenous fat emulsions (IVFE) by sera of acutely ill children was studied in vitro in 23 patients. C-Reactive protein (CRP) has been showed to agglutinate with IVFE; after discarding CRP, serum of acutely ill patients still agglutinate with IVFE. The agglutination score in generalized sepsis is significantly highest than in localized sepsis. We studied agglutination during three periods: first days of treatment by antibiotics (period 1), between the fourth day and the end of treatment (period 2), and after the end of treatment (period 3). In period 2, when orosomucoid concentrations; nevertheless, the observation of an agglutination in periods 1 and 3 where the mean orosomucoid level is within normal range, strongly suggests that one or more others acute phase proteins are also involved in occurrence of agglutination.

[Selenium and vitamin E in mucoviscidosis]. / Sélénium et vitamine E au cours de la mucoviscidose.

Selenium and vitamin E are two important components which protect membrane lipids from oxidative damage. Recently an abnormal fatty acid turnover in the membrane phospholipids was found in cystic fibrosis (CF). We studied vitamin E and selenium status in 26 CF children compared to a control group. we measured selenium concentration in plasma and erythrocytes using flameless atomic absorption. The measure of erythrocyte glutathione peroxidase activity allowed a functional assessment of selenium. Total plasma tocopherol concentrations (HPLC) were referred to total lipids. The vitamin E and selenium levels in not yet treated children (n = 6) were very low, with an important decrease in glutathione peroxydase activity. The antioxidative agents deficiency was mild in children with pancreatic enzyme replacement and vitamin E supplementation (n = 20). In the 2 groups, this deficiency was combined and may play a role in CF membrane abnormalities.

Urinary excretion of N-acetyl-glucosaminidase and beta-2-microglobulin as early markers of gentamicin nephrotoxicity in neonates.

A prospective study in 16 healthy and 16 gentamicin-treated neonates was undertaken to compare the urinary excretion of proximal tubular markers such as beta 2-microglobulin (beta 2-m) and total N-acetyl-beta-D-glucosaminidase (NAG) and its isoenzymatic form NAGB. beta 2-m excretion was not related to postnatal age in control full-term neonates; it was significantly increased in gentamicin-treated full-term neonates. The urinary excretion of the lysosomal markers, total NAG and NAGB, rose significantly with postnatal age in control group. fMean values for total NAG and NAGB were significantly higher in the treated group but the isoenzymatic profile (NAGB/total NAG X 100) was not modified by gentamicin treatment.

Immunoturbidimetric assay for alpha 1-acid glycoprotein in serum with a centrifugal analyzer.

This is a simple immunoturbidimetric method for the rapid assessment of alpha 1-acid glycoprotein in serum with the "Flexigem" microcentrifugal analyzer. Results obtained for a pediatric population (n = 95) agree with those by radial immunodiffusion (x) and yield the regression equation: y = 1.4x + 0.017 (r = 0.98). Results are printed automatically after a procedure that takes only about 15 min. Within-run precision (CV) ranged from 2.2 to 2.5% for concentrations of 0.35 to 2.4 g/L. Day-to-day CV was 4.25% for an average concentration of 0.9 g/L.

Rapid assessment of albumin concentration by immunoturbidimetry.

The dye-binding methods involving bromcresol green and bromcresol purple may seriously overestimate albumin in serum that has a below-normal albumin/globulin ratio, particularly in nephrotic syndrome hypoalbuminemia. To overcome this problem, we developed a new immunoturbidimetric method for albumin with use of a centrifugal analyzer. Results by this method (y) and by radial immunodiffusion (x) agreed well and yielded the regression equation: y = 0.91x + 1.33 (n = 40, r = 0.96). Compared with laser immunonephelometry, our method is easier and faster (15 min for the overall determination). Thus, the proposed immunoturbidimetric method is particularly suitable for the rapid indirect assessment of oncotic pressure and indirectly for monitoring intravascular body fluids.

[Biotin deficiency in the germ-free rat and propionic acidemia]. / Carence en biotine chez le rat axénique et acidémie propionique.

Biotin deficiency was induced in germ-free rats using three experimental protocols. The results showed the important role of biotin during gestation and suckling. The earlier the deprivation, the earlier the deficiency and the severer the symptoms. In this vitamin deficiency, symptoms occurred that were not observed in the control rats, such as the formation of an intestinal volvulus in rats ingesting an L-isoleucine-supplemented diet. The main biochemical anomalies characteristic of propionic acidemia (ketoacidosis and increased urinary elimination of propionic acid) due to propionyl CoA carboxylase deficiency in man were not observed in the rats that were deprived of biotin for 200 days even after a dietary load of L-isoleucine. Only a small urinary excretion of propionyl-glycine and tiglylglycine was observed. We observed a drop in enzymatic propionyl CoA carboxylase activity in the liver that was proportional to the severity of the vitamin deficiency.

Metabolic abnormalities observed in the rat after administration of sodium dipropylacetate.

Sodium dipropylacetate (DPA) was administered to 10 normally fed rats and 5 biotin-deficient rats. The effects of DPA were measured on propionic acid and glycine levels in urine and blood; and on hepatic propionyl-CoA carboxylase (PCC) activity. No abnormal amounts of propionic acid were found in the blood and urine of the treated rats. Hyperglycinemia and significant constant hyperglycinuria were observed in all animals given DPA, but without significant differences between normal and biotin-deprived rats. DPA treatment did not affect PCC activity in vivo or vitro. These results indicate that the abnormalities of the glycine metabolism are not linked to an accumulation of propionic acid due to PCC inhibition by DPA.

Metabolism of sodium [1-14C] and [3-14C] propionate in the non-deficient and biotin deficient rat.

The fixation and elimination kinetics of [1-14C] propionate were studied using autoradiographic technique in the non-deficient and biotin deficient mouse. To quantitate these results, radioactivity was evaluated in the principal organs and excreta over 24 hours from non-deficient and biotin deficient rats, after intravenous injection of sodium [1-14C] and [3-14C] propionate. Radioactivity was eliminated principally via the lungs in the non-deficient rat. Fecal and urinary elimination was weak. Tissular fixation of the radioactivity 24 hours after [14C] propionate injection was carried out principally on the glandular tissues. Almost identical results were obtained in the biotin deficient animal, in which the hepatic propionyl CoA carboxylase activity is decreased by 80 per cent.