柳州市健康人群血清蛋白及A/G比值参考值调查

目的 建立柳州市健康人群血清总蛋白(TP)、清蛋白(ALB)及A/G比值的参考范围.方法 对柳州市2 091名健康人群的TP、ALB进行检测,计算A/G比值,对结果进行统计分析.结果 TP参考范围为68.61～85.51 g/L.男性ALB、A/G明显高于女性(P＜0.001);男性参考范围为:ALB 41.18～57.22 g/L,A/G 1.13～2.47;女性参考范围为:ALB 41.72～55.12 g/L,A/G 1.11～2.25.男女各年龄阶段TP、ALB、A/G的参考范围也存在不同程度差异.结论 柳州健康人群TP、ALB、A/G的参考范围在性别、年龄组间是不同的.旧的参考范围已不适用于当今人群,各实验室应建立本室的参考范围.     

Full Ventricular Capture Indicated by the QT Interval Function

The atrioventricular (AV) interval is critical in dual chamber (DDD) pacing in patients with hypertrophic obstructive cardiomyopathy (HOCM) to obtain full ventricular capture (FVC) with maximal reduction of the left ventricular (LV) outflow gradient and optimal LV diastolic filling. We studied the relationship of FVC, fusion, spontaneous AV conduction, and the QT interval. Methods: 11 patients with various cardiac diseases and stable AV conduction received a QT sensing Diamond (tm) Vitatron, DDD pacemaker. Software was downloaded into the pacemaker. In the DDD pacing mode, with the QT interval measured from the ventricular pacing stimulus to the end of the T wave, the AV interval was shortened from 400 ms, in 20-ms steps, to 90 ms. At 90 ms the stimulation rate was increased by 30 beats/mm and the AV interval was increased stepwise. FVC and fusion was examined on the surface ECG, Results: At 400 ms interval, spontaneous AV conduction inhibited the pacemaker. Shortening the AV interval resulted in pacing with a short QT interval. Further reduction of the AV interval resulted in a longer QT interval up to a point where the QT interval became stable. This point, the bending point in the plot of measured QT interval versus shortened AV intervals, coincided with the point of FVC. The relation of the QT-AV interval plot and the point of fusion was comparable when lengthening the AV interval at a 30 beats/mm faster stimulation rate. Conclusion: The bending point in the QT interval versus AV interval plots showed a good correlation with the FVC and fusion points observed on ECG. The results suggest that automatic discrimination between fusion and full capture using QT interval measurements may be feasible.     

Circadian Variations of Heart Rate and STIMT Interval: Adaptation for Nighttime Pacing

In order to determine the optimal pacing rate for pacemaker patients at night, 150 normal subjects with regular sinus rhythm and free of manifest heart disease, were studied using 24-hour Holter monitoring. Minimum and average heart rates were analyzed on an hourly basis. The study group was divided into six age groups, 25 subjects each, ranging from 20-29 years to 60-69 years. The minimum heart rate during the night was found to be lower than 65 ppm for all groups. The youngest subjects showed the largest variation in the minimum heart rate. The results suggest that an automatic lowering of the pacing rate during the night would allow for longer periods of sinus rhythm, thereby improving hemodynamic performance and reducing pacemaker power consumption. Suitable sensors for automatic lowering of the pacing rate include inbuilt 24-hour clock systems and the QT interval that lengthens during sleep.     

Reference intervals for free thyroxine, total triiodothyronine, thyrotropin and thyroglobulin for Quebec newborns, children and teenagers

OBJECTIVE: Paediatric reference values, although essential for interpreting patients' results, are scarce. Moreover, they are often population- and instrument-dependent. We have measured free thyroxine (Free T(4)), total triiodothyronine (Total T(3)), thyroglobulin (Tg) and thyrotropin (TSH) in samples obtained from groups of newborns, children and adolescents. SUBJECTS AND METHODS: Blood samples collected from healthy children and teenagers (100 girls and 100 boys) of age groups ranging between 9-10, 11-14 and 15-17 years and selected randomly from a cohort representative of the Quebec population, were used. Samples from infants of age ranging between 1 day and 2 years (n = 99) were obtained from a hospital-based population with benign conditions unlikely to affect thyroid function. Variables were measured on the Access 2 immunosystem. RESULTS: Free T(4), Tg and TSH levels declined significantly with age. However, Total T(3) level presented a nonlinear variation with age, being lower in the first month of life.     

Cumulative effect of preceding pacing cycle length on ventricular repolarization after a pause

This study was designed to investigate if the components of the QT interval after a pause are influenced by the preceding pacing cycle length. Ten patients (seven women and three men; age 79 +/- 9 years, means +/- SD) with complete atrioventricular block or sick sinus syndrome whose own heart rate was < 40 beats/min were examined. All patients had already undergone implantation of a permanent pacemaker. Ventricular pacing protocol was performed with simultaneous recording of a 12-lead electrocardiogram. One set of regular stimuli for 30 seconds (S1) with a variable cycle length (1,000, 700, and 400 ms) was followed by a single stimulus (S2) with a fixed coupling interval of 1,500 ms. QT intervals in response to the last S1 (S1-QT) and S2 (S2-QT) were measured. The QT interval was divided into two components, the interval from start of Q wave to the peak of T wave (QaT) and that from the peak to end of T wave (Tae). The S2-QT and S1-QT interval shortened in association with a decrease in the S1S1 interval. The abbreviation of S2-QT interval was not associated with a significant change in the Tae interval. The results demonstrated that the QT interval after a pause shortened by reducing the preceding pacing cycle length. This shortening is probably due to a homogenous abbreviation of action potential duration across the ventricular wall.     

Validation of candidate reference methods based on ion chromatography for determination of total sodium, potassium, calcium and magnesium in serum through comparison with flame atomic emission and absorption spectrometry

Objectives: We report on the validation of candidate reference methods based on ion chromatography for the determination of total sodium, potassium, calcium, and magnesium in serum. The current study is a continuation of previous investigations in which we were able to show the potential of ion chromatography to serve as a reference method principle. The validation consisted of comparison of the ion chromatographic methods with generally recognized reference methods based on flame atomic emission (for sodium/potassium) and absorption (for calcium/magnesium) spectrometry.

Methods: Sample preparation consisted of acidic dilution and pre-purification with reversed phase cartridges. Ion chromatography with suppressed conductivity was performed with polymeric stationary phases chemically modified with carboxylate and sulfonate functional groups for sodium/potassium and calcium/magnesium, respectively. Single-point calibration was used in combination with individual adaptation of serum sampling and diluting to give similar responses in samples and standards. In the study, more than 25 control sera were analyzed in parallel with the ion chromatographic methods and the traditional reference methods. The measurement protocol consisted of quadruplicate analysis of each sample per run, in 3 different runs. In each measurement series, internal quality control with certified reference materials from the National Institute of Standards and Technology and the Bureau Communautaire de Référence was applied. The performance criteria to fulfill were predefined (i.e., the maximum within-day and overall coefficient of variation, the confidence interval, the daily and overall deviation from the certified value and the maximum total analytical error).

Results: The comparison is presented as difference plot (i.e., deviation of the results obtained with ion chromatography from those obtained with the respective traditional reference methods). The mean deviations were +0.9% for sodium, +1.0% for potassium, ±0.0% for calcium, and +0.1 % for magnesium. With the exception of 2 values each for sodium and potassium, all deviations were within the limit of 2 times the allowed total analytical error. From the data obtained for internal quality control during the different measurement campaigns, we further estimated the long-term precision and accuracy of our methods. The overall coefficient of variation (respectively the bias) amounted to 0.7% (+0.1%) for sodium, 0.9% (−0.3%) for potassium, 1.3% (−0.1 %) for calcium, and 1.0% (±0.0%) for magnesium.

Conclusion: From the precision and accuracy reached by our ion chromatographic methods, we conclude that they can be proposed as candidate reference methods for the determination of total sodium, potassium, calcium, and magnesium in serum.     

Reference values for cardiopulmonary exercise testing in healthy subjects – an updated systematic review

Introduction: Reference values for cardiopulmonary exercise testing (CPET) parameters provide the comparative basis for answering important questions concerning the normalcy of exercise responses in patients, and significantly impacts the clinical decision-making process.

Areas covered: The aim of this study was to provide an updated systematic review of the literature on reference values for CPET parameters in healthy subjects across the life span.

A systematic search in MEDLINE, Embase, and PEDro databases were performed for articles describing reference values for CPET published between March 2014 and February 2019.

Expert opinion: Compared to the review published in 2014, more data have been published in the last five years compared to the 35 years before. However, there is still a lot of progress to be made. Quality can be further improved by performing a power analysis, a good quality assurance of equipment and methodologies, and by validating the developed reference equation in an independent (sub)sample. Methodological quality of future studies can be further improved by measuring and reporting the level of physical activity, by reporting values for different racial groups within a cohort as well as by the exclusion of smokers in the sample studied. Normal reference ranges should be well defined in consensus statements.     

Standardization of hemipelvis alignment for in vitro biomechanical testing

Although in vitro biomechanical tests are regularly performed, the definition of a suitable reference frame for hemipelvic specimens is still a challenge. The aims of the present study were to: (i) define a reference frame for the human hemipelvis suitable for in vitro applications, based on robust anatomical landmarks; (ii) identify the alignment of a hemipelvis based on the alignment of a whole pelvis (including right/left and male/female differences); (iii) identify the relative alignment of the proposed in vitro reference frame with respect to a reference frame commonly used in gait analysis; (iv) create an in vitro alignment procedure easy, robust and inexpensive; (v) quantify the intra‐operator repeatability and inter‐operator reproducibility of the procedure. A procedure to univocally identify the anatomical landmarks was created, exploiting the in vitro accessibility of the specimen's surface. Through the analysis on 53 CT scans (106 hemipelvises), the alignment of the hemipelvis based on the alignment of a whole pelvis was analyzed: differences between male/female and right/left hemipelvises were not statistically significant To overcome the uncertainty in the identification of the acetabular rim, a standard acetabular plane was defined. An alignment procedure was developed to implement such anatomical reference frame. The intra‐operator repeatability and the inter‐operator reproducibility were quantified with four operators, on male and female hemipelvises. The intra‐operator repeatability was better than 1.5°. The inter‐operator reproducibility was better than 2.0°. Alignment in the transverse plane was the most repeatable. The presented procedure to align hemipelvic specimens is sufficiently robust, standardized, and accessible. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1645–1652, 2018.