Drop-outs and a random regression model

The implications of drop-outs for power of random regression model (RRM) tests of significance for differences in the rate of change produced by two treatments in a randomized parallel-groups design were investigated by Monte Carlo simulation methods. The two-stage RRM fitted a least squares linear regression equation to all of the available data for each individual, and then ANOVA or ANCOVA tests of significance were applied to the resulting slope coefficients. The tests of significance were adequately protected against type I error, but power was seriously eroded by the presence of drop-outs. Simple endpoint analyses with baseline and time-in-treatment covaried proved more robust against the power degradations.     

ESTIMATION FOLLOWING EXTENSION OF A STUDY ON THE BASIS OF CONDITIONAL POWER

Proschan and Hunsberger [1] Proschan, M A and Hunsberger, S A. 1995. Designed Extension of Studies Based on Conditional Power. Biometrics, 51: 1315–1324. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar] propose a method based on conditional power for designed extension of a study beyond its originally intended sample size. Their data-dependent sampling method can be viewed as a two-stage procedure in which the target total sample size is dependent upon the data observed at the first stage. We demonstrate that the maximum likelihood estimate of the parameter of interest upon completion may be biased, and that this bias is similar in direction and magnitude to that commonly associated with estimation following a group sequential test with predetermined target total sample size. Furthermore, we show how a bias adjusted estimate may be formed.     

不同检测系统白细胞计数结果的偏倚评价

目的了解不同检测系统白细胞(WBC)计数结果的偏倚评价。方法分别在7个检测系统(Bayer120,3台CD1700,Coulter,CD3500,Bayer60)检测质控物和55例临床标本的WBC并对数据进行相关的统计学分析。结果不同水平的质控物和不同浓度的患者全血的WBC测定结果在各检测系统间差异均有显著性(P<0.01);各检测系统间的相关系数均大于0.975;可靠性分析除Bayer60外可靠性系数α均接近1;以Bayer120作标准检测系统对其他检测系统作临床可接受性能评价,Coulter临床接受,CD3500,Bayer60临床部分可接受,3台CD1700临床都不接受。结论7个检测系统测定WBC结果精密度符合临床要求,但临床可接受性能评价存在不可比性,需要采取整改措施。     

Attributions, deception, and event related potentials: an investigation of the self-serving bias

Self-serving attributions occur when negative personal outcomes are ascribed to external circumstances and when positive outcomes are ascribed to internal factors. Individuals strategically employ the self-serving bias to maintain and protect positive self-views. The current study investigated the neural correlates of the self-serving bias using dense array EEG, giving 20 participants false (success or failure) feedback during a facial working memory task. Participants made self-serving attributions during the task, primarily following failure feedback. Voltage and source analyses in response to attribution stimuli revealed that, compared to self-serving responses, non-self-serving attributions were preceded by enhanced dorsomedial frontal cortex activity. This finding suggests that unbiased attributions require greater self-control, overriding the automatic tendency for self-enhancement.     

Anodal tDCS of dorsolateral prefontal cortex during an Implicit Association Test

Anodal stimulation of dorsolateral prefrontal cortex by transcranial Direct Current Stimulation (tDCS) has been shown to enhance performance on working memory tasks. However, it is not yet known precisely which aspects of working memory – a broad theoretical concept including short-term memory and various executive functions – are involved in such effects. In the current study, we aimed to determine whether tDCS would reduce bias effects on an Implicit Association Test, in which subjects must respond either congruently or incongruently to pre-existing evaluative associations. Such biases reflect a conflict between automatic associations and executive function, and tDCS was hypothesized to cause a shift in this balance in favor of executive function. The results clearly contradicted this hypothesis: tDCS did improve reaction times, but in the congruent rather than incongruent mapping condition. We conclude that DLPFC tDCS does not directly improve the ability to overcome bias; previous findings concerning working memory enhancement appear to reflect effects on a different component of executive function.     

两种血凝分析仪检测系统性能验证及结果比对

目的 评价新投入使用的一台全自动血凝分析仪性能,并与临床上现用的凝血仪进行结果一致性的比较.方法根据审核标准对新投入使用的一台血凝分析仪进行精密度、线性、携带污染率、正确度评价;参照美国国家临床实验室标准化协会(NCCLS)的EP-5和EP-9文件,对新投入使用的血凝分析仪与临床正在使用并且性能稳定的血凝分析仪进行结果比对以及偏倚分析.结果 新投入使用的血凝分析仪的批内精密度(低值、中值、高值)在检测凝血酶原时间(PT)时分别为0.93%、1.32%、1.27%,活化部分凝血酶时间(APTT)为1.42%、0.84%、1.17%,纤维蛋白原(FIB)为1.82%、3.13%、3.19%,凝血酶时间(TT)为1.78%、1.76%、1.38%;FIB的实际检测值与理论值的线性回归方程为y=1.012x+0.0219(P＞0.05),截距与0之间差异无统计学意义(t=0.2287,P＞0.05),直线斜率与1之间差异无统计学意义(t=0.3221,P＞0.05),FIB线性回归方程与y=x直线方程差异无统计学意义;携带污染率为-2.33%;两台仪器PT、FIB的检测结果在医学决定水平处偏倚95%CI小于美国临床实验室修正法规1988(CLIA'88)规定的可接受偏倚.结论 新投入使用的一台血凝分析仪性能符合仪器说明书的要求;两台血凝分析仪结果一致.

Abstract：

Objective To evaluate the performance of a newly installed fully automatic coagulation analyzer and compare the consistency of its testing results with the confirmed clinical automatic coagulation analyzer at our department MethodsPrecision,linearity,carryover and accuracy of the newly installed coagulation analyzer were evaluated according to the national required standards.Then the testing results were analyzed between the newly installed and confirmed coagulation analyzers according to the EP-5 and EP-9 documents of national committee for clinical laboratory standards(NCCLS).Results For the newly installed coagulation analyzer,the low,median and high values of relative intra-precision were:0.93%,1.32% and 1.27% for prothrombin time(PT);1.42%,0.84% and 1.17% for activated partial thromboplastin time(APTT);1.82%,3.13% and 3.19% for fibrinogen(FIB);1.78%,1.76% and 1.38% for thrombin time(TT)respectively.The linear regression equation of FIB actual and theoretical values was y=1.012x + 0.0219(P＞0.05).There was no significant statistical difference between the intercept and 0(t=0.2287,P＞0.05)and between linear slope and 1(t=0.3221,P＞0.05).The carryover was-2.33%.The testing results of defined acceptable bias of PT and FIB in CLIA'88 for two analyzers were within the acceptable 95%confidence interval of bias. ConclusionThe precision,linearity,carryover and accuracy of the newly installed coagulation analyzer meet the requirements of instrument user manual.The performance and the testing results of the same sample from two coagulation analyzers are consistent.     

两种检测方法测定C反应蛋白的比较

目的评估速率散射比浊法和免疫透射比浊法检测C反应蛋白(CRP)的分析性能。方法分别采用速率散射比浊法(美国Siemens Healthcare Diagnostica公司BN-Ⅱ特定蛋白仪)和免疫透射比浊法(芬兰OrionDiagnostica公司CRP快速检测仪)对CRP进行测定,方法学评价指标为精密度、线性范围、抗干扰性、相关性及偏倚。结果 CRP浓度为2.0～80.0 mg/L时,BN-Ⅱ特定蛋白仪总变异系数(CV)<6%;CRP浓度为8.0～80.0 mg/L时,CRP快速检测仪总CV<7%;检测线性范围为8.0～70.0 mg/L。血红蛋白(Hb)<10 g/L、胆红素(Bil)<300 mg/L对2种方法检测干扰<10%,在可接受范围内。甘油三酯(TG)<20 mmoL/L时BN-Ⅱ特定蛋白仪不受影响(干扰<10%)。CRP快速检测仪在TG>15 mmol/L时低值血清干扰>10%,高值血清不受干扰。50份血样相关分析的结果显示2台仪器测定结果的相关性良好(r=0.98,P<0.01)。线性回归分析经Cusum检验显示2台仪器间偏倚差异无统计学意义(P>0.05),BN-Ⅱ特定蛋白仪测定结果较CRP快速检测仪结果偏低,Bland-Altman曲线显示2种方法的平均偏倚为-2.1。结论速率散射比浊法和免疫透射比浊法的精密度、抗干扰性、线性范围符合要求。虽然系统间测定结果存在一定偏倚,但也符合临床检测要求。     

两种不同检测系统测定血清总蛋白的结果比对与偏倚评估

目的 探讨本实验室内待测系统与参比系统测定血清总蛋白(TP)的可比性.方法 参照临床和实验室标准化协会(CLSI)颁发的EP9-A2文件,每天取患者样本8份,分别用待测系统与参比系统测定TP,并且每次均进行平行管测定,共测定5天;记录试验数据,经离群点检验后,计算相关系数和回归方程,进行偏倚评估.结果 测定结果无方法内离群点及方法间离群点;两种检测系统TP测定结果的相关系数和回归方程分别为r=0.999(P=0.000),Y=1.035X-1.211(X、Y分别为参比系统、待测系统的TP测定结果);两种检测系统在TP医学决定水平(Xc)处的预期偏倚(Bc)小于可接受偏倚(P＜0.05).结论 上述两种检测系统测定血清TP的结果基本一致,在本实验室内可以使用两种系统检测血清TP.     

Administrative database research infrequently used validated diagnostic or procedural codes

Objective

Administrative database research (ADR) frequently uses codes to identify diagnoses or procedures. The association of these codes with the condition it represents must be measured to gauge misclassification in the study. Measure the proportion of ADR studies using diagnostic or procedural codes that measured or referenced code accuracy.

Study Design and Setting

Random sample of 150 MEDLINE-cited ADR studies stratified by year of publication. The proportion of ADR studies using codes to define patient cohorts, exposures, or outcomes that measured or referenced code accuracy and Bayesian estimates for probability of disease given code operating characteristics were measured.

Results

One hundred fifteen ADR studies (76.7% [95% confidence interval (CI), 69.3-82.8]) used codes. Of these studies, only 14 (12.1% [7.3-19.5]) measured or referenced the association of the code with the entity it supposedly represented. This proportion did not vary by year of publication but was significantly higher in journals with greater impact factors. Of five studies reporting code sensitivity and specificity, the estimated probability of code-related condition in code-positive patients was less than 50% in two.

Conclusion

In ADR, diagnostic and procedural codes are commonly used but infrequently validated. People with a code frequently do not have the condition it represents.