Investigation of a Commercial ELISA for the Detection of Canine Procalcitonin

Background

Rapid identification of sepsis enables prompt administration of antibiotics and is essential to improve patient survival. Procalcitonin (PCT) is a biomarker used to diagnose sepsis in people. Commercial assays to measure canine PCT peptide have not been validated.

Objective

To investigate the validity of a commercially available enzyme‐linked immunosorbent assay (ELISA) marketed for the measurement of canine PCT.

Animals

Three dogs with sepsis, 1 healthy dog, 1 dog with thyroid carcinoma.

Methods

Experimental study. The ELISA''s ability to detect recombinant and native canine PCT was investigated and intra‐assay and interassay coefficients of variability were calculated. Assay validation including mass spectrometry of the kit standard solution was performed.

Results

The ELISA did not consistently detect recombinant canine PCT. Thyroid lysate yielded a positive ELISA signal. Intra‐assay variability ranged from 18.9 to 77.4%, while interassay variability ranged from 56.1 to 79.5%. Mass spectrometry of the standard solution provided with the evaluated ELISA kit did not indicate presence of PCT.

Conclusions and Clinical Importance

The results of this investigation do not support the use of this ELISA for the detection of PCT in dogs.     

Visualizing certainty of extrapolations from models of land change

This article presents a method to estimate and to visualize the certainty of land change models as they extrapolate beyond the time interval for which empirical data exist. The method to project the certainty relies on measurements of model performance during a validation run with historic data and on the assumption that the model’s accuracy approaches randomness as it predicts farther into the future. A land change model typically predicts each pixel as exactly one category for each year. This article presents a technique to convert those predictions into conditional probabilities. As an example, we use the model Geomod to extrapolate forest change over a century for the Plum Island Ecosystems, which is a Long Term Ecological Research site of the United States’ National Science Foundation. Geomod uses calibration information between 1971 and 1985 in order to predict the changes from 1985 to 1999, at which point the validation procedure measures the model’s predictive accuracy. Then the model is re-calibrated with information from 1985 to 1999 in order to extrapolate into the future, assuming a business as usual scenario. As time progresses, the expected accuracy approaches 0.5, which is the probability at which the model’s prediction is as accurate as a random prediction, since the application involves two categories. The extrapolated accuracy of the prediction for the entire study area in the year 2097 is 68%. The method is designed to work with any number of categories so it can be used with a variety of land change models.     

Validation of the 9-11th rib cut to estimate the chemical composition of the dressed carcass and of the whole empty body of Zebu cattle

This study was conducted to validate the 9-11th rib cut to estimate the chemical composition of the carcass and of the empty body weight (EBW) of Zebu cattle. Nineteen Zebu steers with initial body weight of 266.5±32.2 kg were used. Four steers were slaughtered at the beginning to compose the reference group; three were fed at maintenance level, and the remaining were allotted to different planes of nutrition (5.0%, 35.0% and 65.0% concentrate levels in the diets, DM basis). The 9-11th rib cuts and half of the carcasses were dissected and the weights of fat, muscle and bone tissue were recorded. The components fat, muscle and bone tissue from the 9-11th rib cut and from the half carcass were sampled and chemical analysis of fat, protein, water, ash and minerals determined. The 9-11th rib cut satisfactorily estimated the physical composition of the carcass, but not the chemical composition. The 9-11th rib cut appropriately estimated the chemical composition of the carcass in terms of protein, water, ash and macro mineral content. For the percentage of fat and Ca, an over- and underestimation of 7.84% and 13.34%, respectively, were detected. Regression equations were fitted to estimate the percentage of fat and Ca in the carcass, and that of protein, water and ash in the whole empty body.     

Validation of a competitive ELISA for diagnosis of Brucella melitensis infection in sheep and goats

A competitive enzyme-linked immunosorbent assay (cELISA) was validated for the serodiagnosis of Brucella melitensis infection in small ruminants using 2108 positive and 2154 negative reference sera from sheep and goats. The optimum cut-off values, offering the highest diagnostic sensitivity (DSn) and diagnostic specificity (DSp), determined by receiver operating characteristic analysis, were at 23.6%, 21.8% and 25.0% inhibition of the conjugate control for sheep, goats and both species, respectively. The DSns of the cELISA for sheep, goats and both species at these cut-off values were 89.2% (95% confidence interval 87.1-91.1%), 74.0% (95% CI 71.4-76.5%) and 77.9% (95% CI 76.1-79.7%), whereas DSps were 96.4% (95% CI 95.2-97.4%), 92.9% (95% CI 91.1-94.3%) and 97.2% (95% CI 96.4-97.8%), respectively. Compared to cELISA, indirect ELISA and fluorescence polarisation assay have higher DSns and DSps. However, the results obtained with the cELISA were in good agreement with those of the complement fixation test (CFT) under field conditions using 5735 sheep and goat sera. The cELISA can be used as an alternative to the CFT for diagnosing B. melitensis infection in small ruminants.     

Analytical validation of commercially available methods for acute phase proteins quantification in pigs

The aim of this study was to validate commercially available methods for porcine haptoglobin (Hp), C-reactive protein (CRP), serum amyloid A (SAA) and major acute phase protein (Pig-MAP) determinations. Intra and inter assay coefficients of variation (CVs) were lower than 20% in all cases with exception of inter assay CVs for CRP and Pig-MAP assays with samples of low acute phase proteins concentration, and for SAA assay at any acute phase proteins concentration. All methods showed good linearity and detection limits were low enough to detect APPs levels in healthy animals. Hp and SAA were very affected by haemolysis. Lipaemia influenced mainly on SAA determination. Over 15-fold increase was observed in CRP and SAA concentrations after artificially induced inflammation by a single subcutaneous dose of turpentine, whereas Hp and Pig-MAP increased less than 5-fold.     

Validation of computerized Swedish horse insurance data against veterinary clinical records

The aim was to evaluate the agreement between computerized insurance data in a large Swedish horse insurance database and the information in the corresponding clinical records (CR). A random sample of 400 veterinary care and 140 life claims was included. Information on name of the horse, breed and gender, year of birth, specific diagnosis and system diagnosis (e.g. joints, digestive and skeletal) was compared between sources. The concordance for demographic variables was categorized as agreement, disagreement or data missing. For diagnostic information, the categories were agreement, minor disagreement and major disagreement and for system information agreement or disagreement. There were missing values for demographic information in the CR, varying from 2% for name to 16% for breed. The overall agreement for demographic information was >94% (disregarding missing data), 92% for system and 84% for specific diagnosis. For veterinary care and life claims, the observed agreement for diagnosis was 85 and 83%, minor disagreement 6 and 5%, and major disagreement 9 and 12%, respectively.

Using the CR data as gold standard, for the systems evaluated (joints, digestive, skeletal, skin and hooves), sensitivity varied between 62% (skin) and 89% (digestive) whereas the specificity was >96% for all systems. The positive predictive values ranged from 86% (skin) to 97% (digestive). Logistic regression analysis was used to examine factors associated with agreement for diagnosis. Analyses were performed separately for veterinary care and life claims. Factors examined were type of visit (clinic/field), treating veterinarian/clinic (categorized as district veterinarians, private practitioners, small clinics, medium clinics and, for the clinics with ≥20 claims, the specific clinics), computerized or manual CR, processing clerk, whether the CR was included in the paper file, if the claim was rejected or reimbursed, system diagnosis and if a immediate settlement (in analysis for veterinary care claims) or death certificate (in analysis for life claims) was included in the paper file. For veterinary care claims, in the logistic regression model type of visit was significantly associated with agreement, with clinic visits generating better agreement than field visits.     

CENTURY模型在川西北高原草原的适用性研究

利用草地生态模型评价气候变化对草地生产力的影响,对于草地的可持续利用有重要意义。本文选取川西北高原的石渠和若尔盖为代表站点,基于试验站多年牧草观测资料,对草地生态系统模型（CENTURY）在川西北高原草地的适用性进行研究。结果表明：CENTURY模型模拟的石渠和若尔盖牧草地上部生物量的模拟值与观测值比较吻合,决定系数分别为0.85和0.48,均通过了0.05的显著性检验,均方根误差分别为5.4 g·m^-2和122.4 g·m^-2,CENTURY模型能够较好的模拟牧草地上部生物量,适用于气候变化对川西北高原草地生产力的影响研究。基于验证后的CENTURY模型对1961-2017年牧草地上生物量的模拟结果显示,近57年来石渠和若尔盖牧草地上生物量均呈显著增加趋势,增加速率分别为5.4 g·m^-2·（10a）^-1和17.2 g·m^-2·（10a）^-1。     

2002-2010年青藏高原植被含水量微波遥感动态监测

水分是衡量植被生理状态和形态结构的重要参数。青藏高原在区域生态环境和全球气候变化等方面扮演重要角色,但对其在植被含水量时空变化动态及其与气候的关系方面缺乏系统研究。基于236个地面样方实测数据和AMSR-E每日亮温数据,利用留一法交叉验证方法确立了青藏高原植被含水量的遥感反演模型。同时,估算了青藏高原植被含水量空间分布,分析了2002-2010年植被含水量的时间动态及其与气候变化的关系,结果表明,1)微波极化指数(MPI)优于微波植被指数(MVI),18 GHz的MPI乘幂模型AWC=128.93×MPI^-0.67可以很好地反映植被绝对含水量(AWC)空间变化动态;2)青藏高原7月份日植被含水量由西北向东南呈带状递增的趋势。其中,西北部至中部的大部分地区植被含水量主要集中在800 kg/hm²以下,东南部植被含水量较西北地区明显增加,主要集中在800～4 000 kg/hm²之间;3)多年平均月际间的植被含水量存在明显的空间异质性,其变差系数具有由西向东逐渐增加的趋势;4)温度和降水与植被含水量之间具有一定的相关关系,其中降水对植被含水量的影响存在明显的滞后性。     

Soil texture, climate and management effects on plant growth, grain yield and water use by rainfed maize–wheat cropping system: Field and simulation study

In sub-mountain tract of Punjab state of India, maize (Zea mays, L.) and wheat (Triticum aestivum L.) crops are grown as rainfed having low crop and water productivity. To enhance that, proper understanding of the factors (soil type, climate, management practices and their interactions) affecting it is a pre-requisite. The present study aims to assess the effects of tillage, date of sowing, and irrigation practices on the rainfed maize–wheat cropping system involving combined approach of field study and simulation. Field experiments comprising 18 treatments (three dates of sowing as main, three tillage systems as subplot and two irrigation regimes as the sub-subplot) were conducted for two years (2004–2006) and simulations were made for 15 years using CropSyst model. Field and simulated results showed that grain yields of maize and wheat crops were more in early July planted maize and early November planted wheat on silt loam soil. Different statistical parameters (root mean square error, coefficient of residual mass, model efficiency, coefficient of correlation and paired t-test) indicated that CropSyst model did fair job to simulate biomass production and grain yield for maize–wheat cropping system under varying soil texture, date of planting and irrigation regimes.     

作物生长模型PGROWTH微气象模块的实验验证

以生长在中国科学院禹城综合实验站的蒸散计里的小麦和玉米为材料,测定和收集了运行生长模型ＰＧＲＯＷＴＨ所需的参数,对小麦和玉米分别进行了四天和两天运算,将从北京时间６：００到１８：００每两小时观察一次的蒸散,气温和各种辐射与相应的计算结果做了对比,结果表明上述各测定的模拟结果与实验结果吻合良好。