[Multicenter evaluation of four homogenous LDL-cholesterol assays]. / Evaluation multicentrique de quatre méthodes de dosage direct du cholestérol-LDL.

International guidelines emphasize the importance of LDL cholesterol (LDL-C) assay in the care and follow-up of patients with cardiovascular risk. Most studies and common practice use Friedewald's formula for LDL-C calculation. The accuracy of the result depends closely on the precision of the input parameters (total cholesterol, triglycerides (TG) and HDL cholesterol), and discrepancies between calculated LDL-C and measurement by reference methods appear when TG exceed 4.5 mmol/L, or in the presence of abnormal lipoproteins. These restrictions and uncertainties in calculations have prompted the recent development of direct and homogeneous methods that fit all analyzers. A multicenter evaluation of four direct assays of LDL-C (Daiichi, Denka Seiken, Kyowa, Wako) was carried out on 45 serum samples (TG below 3.1 mmol/L) in eight laboratories using different analyzers. For three methods (Daiichi, Kyowa, Wako), the interlaboratory reproducibility was markedly improved relative to that of calculation. A strong correlation was found for all new methods when compared with a beta-quantification assay. Average bias in Denka Seiken assays was greater than Kyowa's and Daiichi's (although less dispersed for the latter) and for Wako all bias were positive. The relationship between bias variations and the lipid parameters of the samples was studied. Three methods, Daiichi, Kyowa and Wako, revealed a significant positive correlation between bias and serum VLDL-C/TG ratio, clearly indicating that cholesterol enrichment of VLDL was a source of variability in these assays. Specificity of the four methods was tested in situation of dyslipidemia by spiking isolated lipoproteins (chylomicrons, VLDL and HDL). This experiment revealed differences in behavior, most evidently upon addition of VLDL. No method was truly specific, but up to 8 mmol/L of TG the variations were acceptable. In the presence of type III hyperlipoproteinemia, however, only the Denka Seiken method was reliable. Linearity up to 20 mmol/L (Daiichi, Denka Seiken) or 14 mmol/L (Kyowa, Wako) of LDL-C allows these tests to be used in main routine cases. New direct assays are an obvious technological advance in terms of analytical performance and conveniency. Their use for the diagnosis and follow-up of hyperlipidemic patients offers an alternative that overcomes the limitations of the Friedewald calculation.

Resting energy expenditure and substrate utilisation rate in children with constitutional leanness or obesity.

BACKGROUND & AIM: The influence of energy expenditure on body weight regulation, in the absence of organic disease, has never been studied in a paediatric population covering a broad range of body weights. The aim of this study was to investigate resting energy metabolism in children with constitutional leanness, normal body weight, or common obesity. METHODS: Fourteen children with constitutional leanness, 16 children with obesity, and controls were studied. Resting energy expenditure and postabsorptive substrate utilisation rate were measured by indirect calorimetry and body composition was assessed from skinfold thicknesses. RESULTS: As compared to the predicted value calculated from the regression equation of resting energy expenditure on fat-free mass in the controls, resting energy expenditure was decreased in lean children (P=0.002), whereas no difference was found in obese children. In obese children and the overall population, fat mass was positively correlated with fat oxidation rate. In each group and in the overall population, fat oxidation rate was positively correlated to resting energy expenditure. CONCLUSIONS: Constitutionally lean children have a low resting metabolic rate, probably adaptive in nature. In obese children, resting energy expenditure is increased in proportion to the fat-free mass, and fat balance is the main determinant of energy balance. These data suggest a constitutional regulation of body weight.

[Acute meningitidis, acute phase proteins and procalcitonin]. / Les méningites aiguës, protéines inflammatoires et procalcitonine.

The prognosis of bacterial meningitis is critically dependent on a rapid causal diagnosis and implementation of an accurate treatment. However, clinical and biological parameters available within the few hours that follow the patient's admission are not reliable enough, except when bacteria are to be found in cerebrospinal fluid under the microscope. Therefore, the initial treatment of acute meningitis is still most of time presumptive so that the definitive diagnosis, however difficult, is often established when the therapeutic management has already been initiated. The use of biological markers, especially lymphokines and acute-phase proteins, has been proposed to facilitate the accuracy of the initial diagnosis. Today, C-reactive protein (CRP) is the most widely used inflammatory marker in emergency departments with aim to discriminate bacterial from viral infections. In 1998, Gerdes et al. published a meta-analysis from 35 studies questioning the usefulness of CRP in discriminating bacterial meningitis from viral meningitis. They outlined that the majority of authors proposed to use this inflammation marker as an additional tool for discriminating bacterial meningitis from viral meningitis, without having evaluated its independent contribution relative to other parameters such as white blood cell count, cerebrospinal fluid (CSF) white cell count, protein or glucose. Procalcitonin (PCT) is an acute-phase protein with faster kinetics than CRP, its concentration in serum rising within the few hours that follow the inception of a bacterial infection. Two French studies published in 1997 and 1998 have shown that, using a cut-off range of 0.5 through 2 ng/mL, the sensitivity and specificity of PCT were 100% in discriminating bacterial meningitis from viral meningitis. Some of the seven studies published since seemed to demonstrate the usefulness of PCT in diagnosing meningitis. Finally, PCT was used effectively to shorten unnecessary antibiotic treatment for children seen in an hospital in Paris (France) during summer 2000.

Weight loss and changes in energy metabolism in massively obese adolescents.

OBJECTIVE: To investigate the energy metabolism modifications induced by energy restriction and weight loss in massively obese adolescents. SUBJECTS: Ten massively obese girls (179 +/- 31% of ideal body weight; age, 13.3-16.4 y) after 2-5 weeks on a low-energy diet and 4.5-11.5 months later, that is, after a substantial weight loss, and eight controls. MEASUREMENTS: Resting energy expenditure (REE) and carbohydrate-induced thermogenesis (CIT) after a sucrose load (by indirect calorimetry), plasma glucose and insulin before and after the sucrose load. RESULTS: After 2-5 weeks on a low-energy diet, REE (7415 +/- 904 kJ/d) was lower than the expected value calculated from the regression equation of REE on fat free mass in controls (P = 0.005). After a 37 +/- 17% reduction in excess weight, REE decreased (6405 +/- 613 kJ/d) and remained lower than the expected value (P = 0.005). At the early stages of weight loss, the area under the plasma glucose response curve was negatively correlated with CIT (r = -0.80, P = 0.01) and was higher in the six obese adolescents with low CIT than in the four with normal CIT (396 +/- 52 vs 283 +/- 26 mmol.l-1.min-1, P = 0.01). After substantial weight loss, the area under the plasma insulin response curve decreased by 32% (P = 0.02), and both CIT and the area under the plasma glucose response curve became similar in obese patients with low and normal CIT prior to weight loss. CONCLUSION: These results indicate that in massively obese adolescents, REE for fat-free mass is decreased at the very beginning of the process of losing weight and remains decreased as long as energy restriction and weight reduction carry on. They also indicate that the impaired CIT sometimes observed returns to normal after weight reduction suggesting that it is secondary to a decrease in glucose uptake induced by obesity-associated insulin resistance.

Sucrase-isomaltase deficiency: changing pattern over two decades.

Twenty-two cases of sucrase-isomaltase deficiency (SID) were observed over a period of 20 years. Since 1977 delay of introduction of sucrose and its decrease in infants' diets have modified the symptomatology. In general, onset of diarrhea has not taken place immediately but 15 days to 2 months after introduction of sucrose. Out of 12 cases with dehydration, five occurred 3 to 7 months after the beginning of sucrose diet. Hypotrophy was not constant (11 of 22 cases), thus diagnosis was delayed in 17 of 22 cases. A yellow complexion due to rising carotene levels in the blood is a striking feature. Because of falsely positive sucrose load tests (four out of 14 nonSID infants) and failure of the hydrogene breath test (one out of five studied cases), disaccharidase determination remains the key to diagnosis. Despite the genetic difference symptoms seem to depend on infant feeding practices.

Energy balance in children and young adults receiving haemodialysis for chronic renal failure.

This study was designed to determine the contribution of energy expenditure to the energy imbalance seen in uraemic children. Resting energy expenditure (REE) was measured using open-circuit indirect calorimetry in eight uraemic haemodialysed subjects aged 9.3-20.4 years and in 10 healthy children. Linear correlations between REE and both body weight and fat-free mass as measured by anthropometry were found in both controls and uraemic subjects (respectively: r = 0.76 and r = 0.88 for body weight and r = 0.73 and r = 0.90 for fat-free mass). Measured REE in uraemic patients was not different from the value predicted by using actual body weight and fat-free mass in the regression equation of REE on body weight and fat-free mass in controls (paired t test: p = 0.70 and p = 0.19 respectively). These data suggest that the energy imbalance seen in uraemic children is not due to increased energy expenditure and is therefore probably due to decreased food intake.

Determination of iodide in serum and urine by ion-pair reversed-phase high-performance liquid chromatography with coulometric detection.

An HPLC method is described for the determination of iodide in serum and urine using ion-pair chromatography with coulometric detection. After adding hexadecyltrimethylammonium chloride, the ions pairs formed with the iodide in the sample are extracted using an organic solvent. The solvent is then evaporated and the dry residue obtained is mixed with an appropriate volume of mobile phase so as to concentrate the sample prior to injection into the chromatograph. For a sample of 0.5 ml of serum, the method features a limit of detection (signal-to-noise ratio of 3) of 0.2 microgram l-1, sufficient to be applied in paediatric assays for the diagnosis of both iodide deficiency and excess.

Resting energy expenditure in infants with cystic fibrosis.

To evaluate the contribution of energy expenditure to the energy imbalance seen in cystic fibrosis patients, resting energy expenditure was measured using open-circuit indirect calorimetry in eight infants with cystic fibrosis, aged 2-7 months (mean, 4), without overt lung disease and in 10 healthy age-matched controls. In both groups, we found close, significant, linear correlations between resting energy expenditure and body weight and between resting energy expenditure and fat-free mass as measured by anthropometry. Cystic fibrosis patients had a 26% increase in resting energy expenditure per kilogram of fat-free mass as compared with controls and a 32% increase in resting energy expenditure as compared with predicted values for fat-free mass. These data from young infants free of clinical symptoms suggest a constitutional metabolic disorder in cystic fibrosis and support the need for early nutritional therapy in cystic fibrosis patients.

Resting energy expenditure and food-induced thermogenesis in obese children.

Nineteen overweight girls 14.54 +/- 0.38 years of age were studied. Results were compared with those obtained in eight age-matched (14.07 +/- 0.51 years) and sex-matched normal weight controls. Energy expenditure (EE) was determined using open-circuit indirect calorimetry at rest, both after a 12-h fast and after an oral sucrose load of 3 g/kg ideal body weight. Food-induced thermogenesis (FIT) was evaluated by computing the area under the curve of the EE response above resting energy expenditure (REE) during the first 3 h after the sucrose load, REE (kcal/day) was higher in the overweight patients (1,818 +/- 46 vs. 1,527 +/- 67; p = 0.002); REE standardized by fat-free mass (FFM) (kcal/kg FFM/day) was lower in obese children than in controls (35.2 +/- 1.0 vs. 44.9 +/- 1.9; p = 0.0001). A linear correlation between REE and FFM was evidenced in both controls and overweight subjects (r = 0.78 and 0.68, respectively; p = 0.05 and p < 0.001, respectively). Actual REE in the obese children was significantly lower than the value predicted by applying the regression equation of REE on FFM in controls to the actual FFM in obese children (paired t test; p = 0.003). FIT was identical in overweight and normal weight subjects, regardless of whether it was expressed in absolute value, as the percentage calorie intake, or standardized by FFM.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of rheumatoid factors on results for determination of antitoxoplasms IgM antibodies by immunofluorescence and agglutination technics (author's transl)]. / Influence des facteurs rhumatoïdes sur la détermination des anticorps antitoxoplasmes IgM par immunofluorescence et par agglutination.

Simultaneous presence of antitoxoplasm IgG antibodies and of rheumatoid factors gives rise to an IgM-type immunofluorescence reaction in 44 p. cent of cases. Three experiments showed that association of the two antibodies can give rise to false positives in the Remington test ; the mixture of the two antibodies renders the reaction positive in the majority of cases. On the other hand, after absorption of negative rheumatoid factors and separation of serum IgM and IgG, IgM fluorescence is no longer seen ; if they are again mixed, then a positive reaction will result. Interference of antitoxoplasm IgG antibodies and rheumatoid factors does not occur in direct toxoplasm agglutination tests. The presence of the rheumatoid factor is rare in the pregnant female. Nevertheless, it is necessary to test for rheumatoid factors using the latex test. If results are here positive, then serum should be absorbed on aggregated human IgG and the Remington test repeated. The probably rare simultaneous presence of antitoxoplasm IgG antibodies and of rheumatoid factors cannot be differentiated from these false positives without fractionation of the serum, separating IgM and IgG.