Latent class models for medical diagnostic tests in multicenter trials

Medical diagnostic tests must enjoy appropriate validity and high reliability in order to qualify as adequate assessment tools. Without a gold standard test, available medical diagnostic tests are not perfect; hence, the reliability of such tests must be evaluated precisely. Kappa coefficient statistics are often utilized to assess reliability of tests when there are two or more medical diagnostic tests. However, the statistics are imprecise for a typical case when the prevalence rate of a target disease is unknown. Although latent class models could be used to assess reliability, the models cannot estimate reliability in the case of two tests, due to unidentifiability or the lack of degrees of freedom. An alternative approach to assess reliability for the case of two tests is stratifying a two‐by‐two contingency table under the assumption that sensitivities and specificities between the two tests be equal over all strata and that prevalence rates in the strata be different from each other. Because stratification is basically a multi‐sample analysis, it should not be applied to the situation where subsamples (i.e., centers) are randomly selected from a larger population. In this article, a type of mixed‐effect model is proposed to evaluate the reliability of two tests for trials in randomly selected multiple centers. Several types of distributions for prevalence rates over subpopulations are considered. Simulation studies show that our proposed method performs nicely. Analysis of real data is also reported. Copyright © 2013 John Wiley & Sons, Ltd.     

密闭系统中四种共培养植物光合作用效率研究

目的 探讨大型密闭系统中几种共培养植物的光合效率等特性,为开展人与植物的物质交换实验提供基础数据.方法 利用受控生态生保系统集成实验平台植物舱开展常压下生菜等4种共培养色拉型蔬菜的光合效率研究.植物共培养面积为36.0 m2;采用Hoagland营养液培养;光源为90％红+10％蓝LED组合光源,光照强度为450μmol·m-2·s-1PPF,光照周期为24 h;根据植物不同生长阶段调节CO2浓度,控制范围为0.2％ ～0.8％.结果 系统运行平稳,环境参数控制状态良好,植物生长状态基本正常;共培养植物产O2量和CO2吸收量平均分别为0.915 kg·d-1和1.204 kg·d-1,植物平均每天能产生约1.1人呼吸所需的O2,同时吸收其排出的CO2.结论 通过该实验,基本掌握植物共培养技术及系统放O2和吸收CO2的能力,可为开展多人多天的受控生态生保系统集成试验研究提供技术支持.     

招收飞行学员听力检查标准探讨

目的 探讨修改空军招收飞行学员听力检查标准的可行性. 方法 ①收集招收飞行学员听力检查资料5673份,按现行的空军招收飞行学员听力检查标准(标准1)统计听力合格例数及合格率.②将低中频(0.25、0.5、1、2、3 kHz)听力损失不超标准1且双耳高频(4、6、8 kHz)听力损失总和≤270 dB者,按双耳高频听力损失之和的大小分为3组:A组(≤210 dB),B组(＞210 dB且≤240 dB)及C组(＞240 dB且≤270 dB).按5 dB档差统计A组听力较差耳4 kHz听力损失＞45 dB的例数,以及B组和C组听力较差耳4 kHz听力损失≤45 dB的例数.③将标准1高频部分修改为4 kHz听力损失≤45 dB,且双耳高频听力损失总和≤240 dB(标准2),或4 kHz听力损失≤45 dB且双耳高频听力损失总和≤270 dB(标准3).按标准2和标准3统计合格例数及合格率;分别统计符合3个标准的合格者中的0.5、1、2、4 kHz平均听阈＞25 dB的例数及所占百分比.比较3个标准的合格率及合格者中有听力障碍的百分比. 结果 ①按标准1统计,合格5310例.②A组4 kHz听力损失＞45 dB的63例,B组4 kHz听力损失≤45 dB的30例,C组4 kHz听力损失≤45 dB的25例.③按标准1、标准2及标准3统计的合格率分别为93.60％(5310/5673)、93.02％(5277/5673)及93.46％(5302/5673),差异无统计学意义;按标准1、标准2及标准3统计的合格者中0.5、1、2、4 kHz平均听阈＞25 dB的比率分别是2.56％(136/5310)、1.57％(83/5277)及1.77％(94/5302),按标准1统计的比率比标准2、标准3统计均高(x2=12.76、7.77,P＜0.01),而标准2与标准3之间差异无统计学意义. 结论 将现行空军招收飞行学员听力检查标准的高频修改为4 kHz听力损失≤45 dB,双耳高频听力损失之和≤240 dB是科学合理的,既降低了合格者中轻度听力障碍的比例,又对合格率没有明显影响.     

Skin Sensitization in School Children in Northern and Southern Norway

It has been suggested that environmental exposures and living conditions can explain some of the worldwide variation in atopic disorders. Norway has large environmental contrasts within the country. We compared skin prick sensitization rates among school children living in the southern subarctic and in the northern artic part of Norway. Approximately one quarter of the children were sensitized, mostly against pollen and animal dander, while mite and mould sensitization seemed to be a minor problem. Sensitization rates and profiles were similar in the north and south despite differences in living conditions and environmental exposures.     

A Mother Speaks

Eosinophilic pneumonia was confirmed by bronchoalveolar lavage fluid examination and transbronchial lung biopsy. Aspergillus niger was cultured from the patient's pharyngeal swab and bronchoalveolar lavage fluid. Inhalation bronchoprovocation test with A. niger antigen was positive. Although the patient's condition improved promptly with 10 mg/day prednisolone administration, dry cough recurred approximately 2 months after completion of this therapy. Severe coughing disappeared on oral cleansing with 300 mg/day amphotericin B, and he recovered completely on 100 mg/day amphotericin B administration. Oral cleansing with amphotericin B may be efficacious in preventing relapses of eosinophilic pneumonia caused by allergic reaction to fungal antigen.     

Increased Asymptomatic Airway Hyper-Responsiveness in Obese Individuals

Objective. Asymptomatic airway hyper-responsiveness (AHR) represents a risk of further accelerated decline in lung function, and of asthma. Due to the fact that rare and contradictory results exist concerning the impact of obesity on BHR, we re-assessed the prevalence of bronchial hyper-responsiveness (BHR) in a large cohort of 60 lean, 84 overweight, and 360 class 1–3 obese non-asthmatic individuals, by coupled plethysmography and spirometry. Methods. Baseline-specific airway conductance (SGaw) and spirometric values were measured and then a methacholine challenge testing (MCT) was performed and considered as positive when a ≥200% increase in specific airway resistance (SRaw = 1/SGaw) was reached. Results. Compared to lean and overweight subjects, obese subjects of any class presented about a twice more frequent AHR (～ 50% in obese vs. 17 and 26% in lean and overweight subjects, respectively). However, the bronchial sensitivity (methacholine dose doubling SRaw) and the shape of the relationship between SGaw and cumulative methacholine doses were the same in the five groups of individuals. Conclusion. The present data show a more frequent AHR in obese subjects. The association of plethysmography with spirometry, by taking into account the bronchodilator effect of the lung inflation (preceding the expiratory flow measurement) in some individuals, permitted to include some MCT which would have been otherwise excluded.     

Parietal Cell and Intrinsic Factor Antibodies in a Finnish Rural Population Sample

Parietal cell and intrinsic factor antibodies were studied in the sera of 156 inhabitants of Pornainen. Parietal cell antibodies were found in 8 per cent of the ‘random sample’, consisting of 135 subjects, and in 34 per cent of the ‘high risk group’ consisting of 29 subjects with decreased gastric secretion. Intrinsic factor antibodies were found in 3 cases in the ‘high risk group’. Two of these had manifest and one latent pernicious anaemia. It seemed that the determination of gastric antibodies may be of some value in screening for severe atrophic gastritis and pernicious anaemia.     

Efficacy of a new Antihypertensive Agent (Indenolol) Assessed by Ambulatory Blood Pressure Monitoring

The effects of two-week treatment periods with indenolol (I) and metoprolol (M) were examined by 24-hour mean blood pressure (BP) monitoring in control conditions and during exercise stress test in 7 patients with essential hypertension, using the Oxford method. Both drugs induced a significant reduction in mean BP and heart rate (HR) as compared to pretreatment values (mean BP: from 1173 mmHg to 1064 after I, p < 0.05 and to 1023 after M, p < 0.01; HR: from 782 bpm to 662 after I, p < 0.01 and to 672 after M, p < 0.01). I and M induced a significant reduction in systolic and diastolic BP throughout the day and most of the night. During bicycle ergometer the basal and peak values of systolic and diastolic BP were significantly lower after both treatments as compared to the pretreatment values (both p < 0.01). Our data suggest that I once a day possesses a substantial and consistent antihypertensive action, effective over most of the 24 hours.     

Postnatal Protein Malnutrition Affects Inhibitory Avoidance and Risk Assessment Behaviors in Two Models of Anxiety in Rats

Abstract

Protein malnutrition induces structural, neurochemical and functional alterations in the central nervous system, leading to alterations in behavioral function. In order to study the effects of early protein malnutrition on inhibitory avoidance and escape behaviors we used the elevated T-maze (ETM), while the risk assessment behaviors were evaluated by the canopy stretched attend posture (SAP) test. Rat pups were fed by lactating females receiving 16% (control) or 6% (malnourished) protein diets during the lactation period. After weaning the animals received the same diets until 49 days of age, when all animals started receiving a lab chow diet. Behavioral tests were started at 70 days of age. ETM results showed lower inhibitory avoidance in malnourished animals, without differences in escape behavior. SAP test results showed higher exploration and lower risk assessment behaviors in malnourished animals compared to control. These results suggest that malnourished animals are less anxious and/or more impulsive as measured by these two animal models and that malnutrition seems to affect differently behavioral strategies underlying fear and anxiety responses.