Constructing a cut-off point for a quantitative diagnostic test

This paper is concerned with the problem of constructing a suitable cut-off point for a quantitative diagnostic test from a sample of diseased and non-diseased individuals, when the specificity and/or sensitivity required for the resulting diagnostic classification rule are specified. Statistical procedures are discussed which yield an explicit cut-off point, together with the necessary confidence limits on the true specificity and sensitivity of the test operating at this point (by contrast to confidence limits referring to an unknown optimal choice of the cut-off point). Sample size formulae are derived, showing a relative efficiency of up to 1.5 for a new procedure introduced in this paper over the usual procedure based on tolerance limits.     

Estimation of prevalence on the basis of screening tests

Estimates of disease prevalence based on screening tests can be severely biased unless adjusted for the sensitivity and specificity of the screening test. One such adjusted estimate, the maximum likelihood estimator proposed by Levy and Kass, can yield an extreme estimate of zero or one that has undesirable characteristics such as a standard error of zero. We develop here a Bayesian estimator which always falls between zero and one. Users without specialized software can use the maximum likelihood estimate for most circumstances and, in special cases, such as a zero estimate of prevalence, turn to the Bayesian estimate. Others can use software to carry out a complete Bayesian solution. We have provided a method to obtain numerical values for the Bayesian estimate for those ranges of sample size (20-100), sensitivity (0.7-0.9) and specificity (0.7-0.9) for which the use of this estimator seems most practical.     

The Autonomic Differentiation of Emotions Revisited: Convergent and Discriminant Validation

The convergent and discriminant validity of three models of physiological emotion specificity were compared. Forty-two female students served as subjects in a 2 (Context of emotional inductions: real-life, imagery) X 3 (Emotion: fear, anger, control) +1 (Happiness induced in real-life context) repeated measures design. The dependent measures included self-reports of emotion, Gottschalk-Gleser affect scores, back and forearm extensor EMG activity, body movements, heart period, respiration period, skin conductance, skin temperatures, pulse transit time, pulse volume amplitude, and blood volumes. Self-report data confirmed the generation of affective states in both contexts, as intended. Planned multivariate comparisons between physiological profiles established discriminant validity for fear and anger in the real-life context, whereas under imagery, emotion profiles were essentially equal. Convergent validity could not be substantiated. Implications for models of physiological specificity of emotion were discussed.     

Sensitivity and Specificity of Lung Cancer Screening in Osaka, Japan

Sensitivity and specificity were evaluated for lung cancer screening conducted at 8 municipalities in Osaka Prefecture during 1981–1985. As a screening policy, all attendants were examined by miniature chest X-ray, and the high-risk group, defined as those who smoked cigarettes or had bloody sputum, were also examined by 3-day pooled sputum cytology. A total of 33,599 screening tests for 19,028 people who were 40 years old or more at the time of screening were conducted, resulting in 33,490 miniature chest X-ray examinations for 18,992 people and 11,420 sputum cytologies for 7,070 people. As a result, 43 lung cancer cases were detected. All test-negatives were followed by means of record linkage with the files of the Osaka Cancer Registry up to the end of 1986. There were 24 cases who were diagnosed as having lung cancer without having given a positive screening result in 1981-1986. Assuming the preclinical detectable phase of lung cancer to be one year uniformly, the sensitivity and specificity for the lung cancer screening were estimated to be 71.6% and 95.3%, respectively. The feasibility of increasing the sensitivity is discussed.     

Syphilis and blood donors: Comparison of two different diagnostic strategies

In this study the validity of the methods provided for by Italian law (VDRL or RPR tests) were compared with the diagnostic strategy suggested by WHO (the use of VDRL and TPHA tests in parallel). Sensitivity, specificity and posterior probability of infection after a positive or a negative result were estimated. The application of two tests in parallel produces a statistically significant increase of sensitivity from 47% to 98% while the increase of proportion of false positives is not significant (from 15% to 16%). Probability of infection when the result is negative to the RPR is 0.07%o while a negative result to the RPR and the TPHA tests has a probability to be really infected of 0.003%o. The use of the two tests (RPR and TPHA) in parallel is able to give the highest degree of sensitivity, indispensable to select possible blood donors, while maintaining a good degree of specificity. The authors concluded that the use of VDRL alone does not exclude infectivity of a blood sample, and in accordance with WHO and international recommendations, the VDRL or RPR and TPHA tests should be used in parallel for syphilis screening.     

胸水ADA、CEA检测在结核性与癌性胸膜炎鉴别诊断中的价值

[目的]探讨胸水腺苷脱氨酶(ADA)和癌胚抗原(CEA)检测在结核性胸膜炎与癌性胸膜炎鉴别诊断中的价值.[方法]选择38例结核性胸膜炎和42例癌性胸膜炎住院患者,用速率法检测胸水ADA活性,电化学发光免疫法检测胸水CEA,评价二者诊断的真实性、预测值和似然比.[结果]结核性胸膜炎组ADA阳性率86.8%高于癌性胸膜炎组的2.4%(P＜0.01);癌性胸膜炎组CEA阳性率71.4%高于结核性胸膜炎组的2.6%(P＜0.01).ADA诊断结核性胸膜炎的敏感性为86.8%、特异性97.6%、正确诊断(约登)指数(Yoden's index)0.84、阳性预测值97.1%、阴性预测值89.1%、阳性似然比36.49、阴性似然比0.14;CEA诊断癌性胸膜炎的敏感性71.4%、特异性97.4%、约登指数0.84、阳性预测值96.8%、阴性预测值75.51%、阳性似然比27.16、阴性似然比为0.29.[结论]检测胸水ADA、CEA在结核性胸膜炎与癌性胸膜炎鉴别诊断中有重要的临床意义.     

经穴特异性研究的思考

经穴特异性研究引起了国内外学者的密切关注,但缺乏利用现代科学技术进行深入、系统的研究。对于回答经穴特异性和影响效应产生的关键因素等科学问题,尚缺乏有说服力的结论性研究成果。经穴特异性研究,应围绕针灸有效病症的经穴展开,采用多种现代科学技术,解决“针灸有效病症经穴的生物物理特性、病理反应、效应及其配伍规律”的关键科学问题,创立经穴特异性理论模型,以丰富和发展经穴特异性理论。     

立氏立克次体实时荧光定量聚合酶链反应检测方法的建立

目的采用TaqMan-MGB探针建立立氏立克次体实时荧光定量聚合酶链反应（PCR）检测方法.方法依据立氏立克次体外膜蛋白B基因序列设计引物和探针,以克隆的ompB基因片段为DNA模板,在ABI 7900型荧光定量PCR检测仪上建立实时荧光定量PCR检测方法.结果建立的定量标准曲线Ct值与模板拷贝数呈线性关系（R2=0.996）,最低检测浓度为5拷贝/μl;用荧光定量PCR方法检测其他相关立克次体和常见非立克次体病原菌,检出结果均为阴性.用该方法检测立氏立克次体感染的豚鼠血液标本、小鼠脾脏标本及细胞培养标本,检测的结果与立氏立克次体感染相关.结论研究建立的检测立氏立克次体实时荧光定量PCR方法具有高特异性和高敏感性,适用于快速检测各种样本中的立氏立克次体和立氏立克次体感染早期的实验室诊断.     

Tropheryma whippelii DNA in Saliva of Patients Without Whipple's Disease

Summary Tropheryma whippelii is the causative agent of Whipple's disease, a difficult to diagnose systemic illness. Amplification of part of its 16S ribosomal RNA gene(s) has become a standard diagnostic method because of increased sensitivity as compared to classical histopathological analysis. Recently, we demonstrated the presence of T. whippelii DNA by PCR in duodenal biopsies and/or gastric juice of a considerable fraction of individuals without clinical signs of Whipple's disease. In this follow-up study, saliva and dental plaques of the same patients were screened for the presence of T. whippelii DNA. Six out of the 14 previously PCR-positive persons but none of the 17 controls had T. whippelii DNA in their saliva. Our results suggest that Whipple bacteria are ubiquitous environmental or commensal organisms causing Whipple's disease only in a particular subset of individuals, possibly those with an as yet uncharacterized immunological defect. Received: January 1, 2000 · Revision accepted: April 20, 2000     

对性传播疾病特殊性的理性思考

感染性微生物通过性接触在人与人之间传播性病。性病流行与政策、经济、文化价值观相关。社会对性病患者歧视，性病患者有羞耻、负罪、悲观、放纵心理和行为以及疑病症、神经症的表现。我国性病医疗市场存在混乱及过度医疗问题。防治性病要社会综合力量，整顿医疗市场和提高医务人员业务和道德水平。