Preliminary results on the postmortem measurement of 3-beta-hydroxybutyrate in liver homogenates.

The concentrations of 3-beta-hydroxybutyrate (3HB) in blood and two liver samples were retrospectively examined in a series of medicolegal autopsies. These cases included diabetic ketoacidosis, nondiabetic individuals presenting moderate to severe decompositional changes and nondiabetic medicolegal cases privy of decompositional changes. 3HB concentrations in liver sample homogenates correlate well with blood values in all examined groups. Additionally, decompositional changes were not associated with increases in blood and liver 3HB levels. These results suggest that 3HB can be reliably measured in liver homogenates when blood is not available at autopsy. Furthermore, they suggest that metabolic disturbances potentially leading or contributing to death may be objectified through liver 3HB determination even in decomposed bodies.

Usefulness of methadone plasma concentration measurement in patients receiving nevirapine or efavirenz.

Objective: To determine methadone plasma trough and peak concentrations in patients presenting opiate withdrawal symptoms after introduction of nevirapine or efavirenz. To describe the disappearance of these symptoms after methadone titration based on plasma concentrations rather than on the symptoms. Methods: Nine patients undergoing highly active antiretroviral therapy (HAART) and either nevirapine or efavirenz treatment were monitored daily for opiate withdrawal in a specialized drug addiction center. Methadone dose was titrated daily, and plasma concentrations were measured. The data are retrospective (case series). Results: Several patients complained of symptoms such as nausea, vomiting, accelerated intestinal transit, or insomnia. Even after methadone titration based on clinical symptoms, patients and health-care providers trained in infectious disease did not classify these as withdrawal symptoms and considered them as the side effects of HAART or anxiety. Methadone plasma trough concentration showed low levels of (R)- and (R,S)-methadone. Further methadone dose adjustment according to plasma level resulted in the disappearance of these withdrawal symptoms. The daily methadone dose was split when the peak/trough (R)-methadone ratio was more than 2. Conclusions: When introducing efavirenz or nevirapine to patients undergoing methadone treatment, withdrawal symptoms should be monitored, especially those such as insomnia, vomiting, or nausea. Methadone plasma trough and peak measurements can be of value in preventing unnecessary side effects of HAART.

Activity assays and immunoassays for plasma Renin and prorenin: information provided and precautions necessary for accurate measurement.

BACKGROUND: Measurement of plasma renin is important for the clinical assessment of hypertensive patients. The most common methods for measuring plasma renin are the plasma renin activity (PRA) assay and the renin immunoassay. The clinical application of renin inhibitor therapy has thrown into focus the differences in information provided by activity assays and immunoassays for renin and prorenin measurement and has drawn attention to the need for precautions to ensure their accurate measurement. CONTENT: Renin activity assays and immunoassays provide related but different information. Whereas activity assays measure only active renin, immunoassays measure both active and inhibited renin. Particular care must be taken in the collection and processing of blood samples and in the performance of these assays to avoid errors in renin measurement. Both activity assays and immunoassays are susceptible to renin overestimation due to prorenin activation. In addition, activity assays performed with peptidase inhibitors may overestimate the degree of inhibition of PRA by renin inhibitor therapy. Moreover, immunoassays may overestimate the reactive increase in plasma renin concentration in response to renin inhibitor therapy, owing to the inhibitor promoting conversion of prorenin to an open conformation that is recognized by renin immunoassays. CONCLUSIONS: The successful application of renin assays to patient care requires that the clinician and the clinical chemist understand the information provided by these assays and of the precautions necessary to ensure their accuracy.

Influence of reconstruction parameters during filtered backprojection and ordered-subset expectation maximization in the measurement of the left-ventricular volumes and function during gated SPECT.

A crucial method for investigating patients with coronary artery disease (CAD) is the calculation of the left ventricular ejection fraction (LVEF). It is, consequently, imperative to precisely estimate the value of LVEF--a process that can be done with myocardial perfusion scintigraphy. Therefore, the present study aimed to establish and compare the estimation performance of the quantitative parameters of the reconstruction methods filtered backprojection (FBP) and ordered-subset expectation maximization (OSEM). METHODS: A beating-heart phantom with known values of end-diastolic volume, end-systolic volume, and LVEF was used. Quantitative gated SPECT/quantitative perfusion SPECT software was used to obtain these quantitative parameters in a semiautomatic mode. The Butterworth filter was used in FBP, with the cutoff frequencies between 0.2 and 0.8 cycles per pixel combined with the orders of 5, 10, 15, and 20. Sixty-three reconstructions were performed using 2, 4, 6, 8, 10, 12, and 16 OSEM subsets, combined with several iterations: 2, 4, 6, 8, 10, 12, 16, 32, and 64. RESULTS: With FBP, the values of end-diastolic, end-systolic, and the stroke volumes rise as the cutoff frequency increases, whereas the value of LVEF diminishes. This same pattern is verified with the OSEM reconstruction. However, with OSEM there is a more precise estimation of the quantitative parameters, especially with the combinations 2 iterations × 10 subsets and 2 iterations × 12 subsets. CONCLUSION: The OSEM reconstruction presents better estimations of the quantitative parameters than does FBP. This study recommends the use of 2 iterations with 10 or 12 subsets for OSEM and a cutoff frequency of 0.5 cycles per pixel with the orders 5, 10, or 15 for FBP as the best estimations for the left ventricular volumes and ejection fraction quantification in myocardial perfusion scintigraphy.

Mesurer l'amplitude articulaire du genou: goniométre universel ou smartphone [Measurement of the knee range of motion: standard goniometer or smartphone?].

Universal standard goniometer is an essential tool to measure articulations' range of motion (ROM). In this time of technological advances and increasing use of smartphones, new measurement's tools appear as specific smartphone applications. This article compares the iOS application "Knee Goniometer" with universal standard goniometer to assess knee ROM. To our knowledge, this is the first study that uses a goniometer application in a clinical context. The purpose of this study is to determine if this application could be used in clinical practice.

A new approach to accurate measurement of uniaxial joint angles based on a combination of accelerometers and gyroscopes.

A new method of measuring joint angle using a combination of accelerometers and gyroscopes is presented. The method proposes a minimal sensor configuration with one sensor module mounted on each segment. The model is based on estimating the acceleration of the joint center of rotation by placing a pair of virtual sensors on the adjacent segments at the center of rotation. In the proposed technique, joint angles are found without the need for integration, so absolute angles can be obtained which are free from any source of drift. The model considers anatomical aspects and is personalized for each subject prior to each measurement. The method was validated by measuring knee flexion-extension angles of eight subjects, walking at three different speeds, and comparing the results with a reference motion measurement system. The results are very close to those of the reference system presenting very small errors (rms = 1.3, mean = 0.2, SD = 1.1 deg) and excellent correlation coefficients (0.997). The algorithm is able to provide joint angles in real-time, and ready for use in gait analysis. Technically, the system is portable, easily mountable, and can be used for long term monitoring without hindrance to natural activities.

Validation of methane measurement using headspace-GC-MS and quantification by a stable isotope-labeled internal standard generated in situ.

A previous study has shown the possibility to identify methane (CH4 ) using headspace-GC-MS and quantify it with a stable isotope as internal standard. The main drawback of the GC-MS methods discussed in literature for CH4 measurement is the absence of a specific internal standard necessary to perform quantification. However, it becomes essential to develop a safer method to limit the manipulation of gaseous CH4 and to precisely control the injected amount of gas for spiking and calibration by comparison with external calibration. To avoid the manipulation of a stable isotope-labeled gas, we have chosen to generate a labeled gas as an internal standard in a vial on the basis of the formation of CH4 by the reaction of Grignard reagent methylmagnesium chloride with deuterated water. This method allows precise measurement of CH4 concentrations in gaseous sample as well as in a solid or a liquid sample after a thermodesorption step in a headspace vial. A full accuracy profile validation of this method is then presented.

Measurement of ß-tryptase in postmortem serum, pericardial fluid, urine and vitreous humor in forensic setting

L'activation des mastocytes se produit dans plusieurs conditions pathologiques et est principalement observée chez des patients développant une réaction anaphylactique. Dans la pratique clinique, la mesure de l'histamine et de ses métabolites dans le plasma et dans l'urine du patient peut être effectuée et montre parfois des résultats aussi précis que la mesure de la beta-tryptase dans le sang lorsqu'il est nécessaire de confirmer une activation mastocytaire. En revanche, la mesure de la beta tryptase dans l'urine dans un but diagnostic n'a que rarement été effectuée sur des personnes vivantes et a montré des résultats contradictoires. Dans le domaine de la médecine légale, la mesure de la beta-tryptase dans un but diagnostic est effectuée dans le sérum postmortem obtenu à partir de sang prélevé au niveau fémoral. Cependant, le sang peut être partiellement ou complètement indisponible dans certains cas spécifiques, dans les autopsies de nourrissons ou de corps sévèrement mutilés par exemple. Un des buts de notre étude est d'évaluer la pertinence de la mesure de la beta-tryptase dans des échantillons biologiques alternatifs, à savoir dans l'urine, l'humeur vitrée et le liquide péricardique. Pour cela nous avons sélectionné 94 cas d'autopsies comprenant 6 cas de réaction anaphylactique suite à l'administration de produits de contraste radiologique, 10 cas d'hypothermie, 10 cas d'acidocétose diabétique, 10 cas de suicide par arme à feu, 18 cas de décès consécutif à une injection d'héroïne, 10 cas de décès traumatiques, 10 cas de mort subite avec peu ou pas d'athérosclérose coronarienne, 10 cas de décès avec une athérosclérose coronarienne sévère mais sans signe d'infarctus du myocarde et 10 cas de décès consécutif à un infarctus du myocarde avec une athérosclérose coronarienne sévère. Dans tous les cas de réaction anaphylactique suite à l'administration de produit de contraste radiologique, les concentrations de beta-tryptase, mesurées dans le sérum postmortem et dans le liquide péricardique, ont montré des valeurs plus élevées que le seuil clinique de référence (11 ng/l) et le seuil postmortem de référence (45 ng/l). La concentration de beta-tryptase mesurée dans l'urine et l'humeur vitrée a montré des valeurs inférieures au seuil clinique dans tous les cas de notre étude. La mesure de la concentration de beta tryptase dans le liquide péricardique semble donc une alternative valable à la mesure dans le sérum postmortem, lorsque le sang fémoral n'est pas disponible durant l'autopsie, afin de poser un diagnostic de réaction anaphylactique.

Random measurement error and regression dilution bias.

Summary points: - The bias introduced by random measurement error will be different depending on whether the error is in an exposure variable (risk factor) or outcome variable (disease) - Random measurement error in an exposure variable will bias the estimates of regression slope coefficients towards the null - Random measurement error in an outcome variable will instead increase the standard error of the estimates and widen the corresponding confidence intervals, making results less likely to be statistically significant - Increasing sample size will help minimise the impact of measurement error in an outcome variable but will only make estimates more precisely wrong when the error is in an exposure variable

Dyadic pulsations as a signature of sustainability in correspondence networks

In this paper, we introduce the concept of dyadic pulsations as a measure of sustainability in online discussion groups. Dyadic pulsations correspond to new communication exchanges occurring between two participants in a discussion group. A group that continuously integrates new participants in the on-going conversation is characterized by a steady dyadic pulsation rhythm. On the contrary, groups that either pursue close conversation or unilateral communication have no or very little dyadic pulsations. We show on two examples taken from Usenet discussion groups, that dyadic pulsations permit to anticipate future bursts in response delay time which are signs of group discussion collapses. We discuss ways of making this measure resilient to spam and other common algorithmic production that pollutes real discussions

A wearable system for multi-segment foot kinetics measurement.

This study aims to design a wearable system for kinetics measurement of multi-segment foot joints in long-distance walking and to investigate its suitability for clinical evaluations. The wearable system consisted of inertial sensors (3D gyroscopes and 3D accelerometers) on toes, forefoot, hindfoot, and shank, and a plantar pressure insole. After calibration in a laboratory, 10 healthy elderly subjects and 12 patients with ankle osteoarthritis walked 50m twice wearing this system. Using inverse dynamics, 3D forces, moments, and power were calculated in the joint sections among toes, forefoot, hindfoot, and shank. Compared to those we previously estimated for a one-segment foot model, the sagittal and transverse moments and power in the ankle joint, as measured via multi-segment foot model, showed a normalized RMS difference of less than 11%, 14%, and 13%, respectively, for healthy subjects, and 13%, 15%, and 14%, for patients. Similar to our previous study, the coronal moments were not analyzed. Maxima-minima values of anterior-posterior and vertical force, sagittal moment, and power in shank-hindfoot and hindfoot-forefoot joints were significantly different between patients and healthy subjects. Except for power, the inter-subject repeatability of these parameters was CMC>0.90 for healthy subjects and CMC>0.70 for patients. Repeatability of these parameters was lower for the forefoot-toes joint. The proposed measurement system estimated multi-segment foot joints kinetics with acceptable repeatability but showed difference, compared to those previously estimated for the one-segment foot model. These parameters also could distinguish patients from healthy subjects. Thus, this system is suggested for outcome evaluations of foot treatments.