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The purpose of this paper was to introduce the methods of the "layered person-time data" rate ratio analysis and the SAS implementation. The specific contents included the following four aspects： ① the point estimation and the confidence interval estimation of the layer i rate ratio in the stratified person-time data； ② the homogeneity test of the rate ratios among the different layers； ③ the point estimation and the confidence interval estimation of the common rate ratio； ④ the linear trend test of the incidence density in the stratified person-time data. Through two examples， it showed the statistical calculation process based on the SAS software to realize the aforementioned four kinds of the analysis contents， including providing the SAS program code， the explanation of the SAS output results， and giving the statistical and professional conclusions.
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En este manuscrito se revisan algunos aspectos básicos de la utilización de regresiones en los estudios epidemiológicos, haciendo énfasis en aquellas aplicadas al estudio de eventos discretos. De esta manera se hace una introducción a los modelos lineales generalizados, cuya estructura es una extensión de una ecuación lineal para analizar desenlaces discretos. De este modo podemos estimar medidas de asociación como la razón de tasas usando la regresión de Poisson, o bien, el riesgo relativo (o la razón de prevalencias) usando la regresión log-binomial. En cada caso es esencial conocer la naturaleza de la variable dependiente, su distribución y reconocer las limitaciones de cada una de las herramientas de análisis.
Some basic aspects about using regressions in epidemiological studies are reviewed. Particularly, this manuscript focused on those applied to the study of discrete events. Generalized lineal models, such as Poisson and log-binomial, have a structure that is an extension of a lineal equation to analyze discrete outcomes. Thus, we can estimate association measures as the incidence rate ratio, using the Poisson regression, or the relative risk (or prevalence ratio), using log-binomial regression. In each case it is essential to know the nature of the dependent variable, as well as, its distribution and recognize the limitations of each analysis tool.
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Humans , Linear Models , Binomial Distribution , Poisson Distribution , Risk , Prevalence RatioABSTRACT
Objective To investigate the diagnostic value of strain rate ratio in the diagnosis of benign and malignant breast masses.Methods 80 patients with suspicious nodules(104 lesions) were selected as the research subjects.The ultrasonic diagnostic apparatus equipped with ultrasonic elastography was used for conventional ultrasound examination and comprehensive elastography.The tumor location,lesion number,lesion size,shape,smooth edge or boundary,internal lesions and peripheral echo characteristics,calcification and blood supply were recorded, and two dimensional ultrasound imaging and elastography images on the tumor area were measured,took the average value;start the elastic imaging mode, strain rate automatic generation of strain rate lesions and surrounding normal glandular tissue system,and the two strain ratio ( SR) .To determine the best diagnostic value of SR in judging the nature of the lesions.Finally,the result was evaluated by accuracy,sensitivity,specificity,positive predictive value and negative predictive value.Results In 104 breast lesions,58 lesions were benign and 46 malignant lesions were malignant.The pathological diagnosis as the final standard,using ultrasonic elastic strain rate ratio and area ratio to determine the nature of the lesion,the ratio of the strain rate(t=8.342) and the area ratio of benign and malignant lesions(t=7.541),the difference was statistically significant(all P<0.05).The results showed that the sensitivity, specificity,accuracy,positive predictive value and negative predictive value of two-dimensional ultrasound in diagnosis of breast cancer were 73.91%,86.20%,80.76%,80.95%,80.61%,respectively.The sensitivity,specificity, accuracy,positive predictive value and negative predictive value of SR in the diagnosis of breast cancer were 91.30%,89.65%,90.38%,87.50%,92.85%,respectively.The results showed that the sensitivity(χ2 =9.641), accuracy(χ2 =8.332) and negative predictive accuracy(χ2 =8.950) of two dimensional ultrasound and ultrasonic (χ2 =8.743)image were significantly higher than those of the two-dimensional ultrasound(all P<0.01),and the specificity was higher than that of the two-dimensional ultrasound(χ2 =2.421,P<0.05).Conclusion The strain rate ratio of ultrasonic elasticity imaging has important diagnostic value in breast benign and malignant tumors.Its accuracy is higher than conventional two-dimensional ultrasound.This method is not only cheap,safe,real-time, non radioactive,but also can be used in the diagnosis of the lesions,so it is worthy of clinical application.
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OBJECTIVES: Effects of aging and leisure time physical activity (LPA) might influence the effect of occupational physical activity (OPA) on risk for cardiovascular disease (CVD). This study was conducted to determine whether OPA affects CVD after controlling the effects of LPA and other risk factors for CVD such as job stress. METHODS: Participants were 131 male Korean manual workers. Tests for heart rate variability (HRV) were conducted for five minutes in the morning at work. We defined OPA as the combined concept of relative heart rate ratio (RHR), evaluated using a heart rate monitor. RESULTS: Whereas high OPA was not related to any HRV items in the younger age group, high OPA was associated with an increased number of low-value cases among all HRV items in older workers. Exercise had beneficial effects only in the younger group. After controlling for exercise and other risk factors, the odds ratios of the root-mean square of the difference of successive normal R-R intervals (rMSSD) and high frequency band power (HF) among the older age and high OPA group compared with the younger age and low OPA group were 64.0 and 18.5, respectively. Social support and shift work were independent risk factors in HRV. CONCLUSIONS: OPA in aging workers increases CVD risks. This study provides support for the need for protection of aging workers from physical work overload, and indicates the need for further study of optimal limits of OPA.
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Humans , Male , Aging , Cardiovascular Diseases , Heart Rate , Heart , Leisure Activities , Motor Activity , Odds Ratio , Risk FactorsABSTRACT
Background: Human Herpes Virus 2 (HSV-2) infection has been shown to be significantly associated with several obstetric complications, especially if the infection occurred during the pregnancy. Advocacy for policy formulation and the design of interventions requires local data on the risk factors for incident HSV-2 infection. The aim of this study is to assess HSV-2 sero-incidence among pregnant women in Benin and the effect of socio-demographic factors, HIV status, and HSV-1 status. Study Location, Design and Duration: Pregnant women attending ante-natal clinic in University of Benin Teaching Hospital and Central Hospital, Benin were prospectively recruited. A cross-sectional study was done and baseline data, obtained. The HSV-2 seronegative participants were followed up till the last clinic appointments [the closest appointment to their expected delivery dates (EDD)]. The study took place between November 2011 and December 2012. Methods: On recruitment a structured self-administered questionnaire was used to capture their socio-demographic data. Obstetric data was obtained from the patients’ case notes. Their HSV-1 and HSV-2 serostatuses were determined using an HSV glycoprotein G-based type-specific ELISA technique. Their HIV statuses were also determined. All those who were seronegative for HSV-2 were retested for HSV-2 six months later and/or on their last clinic appointment before the EDD. Incidence rates were calculated per person-years. Data analysis utilized SPSS version 16 software. Results: Out of the 674 participants, 315(46.8%) were HSV-2 seropositive while 359 (53.2%) were seronegative. 15.9% (57) of the HSV-2 sero-negative ones were lost to follow-up, giving a response rate of 84.1%. Seroincidence rate was found to be 17.9 per 100 person-years. There was significant association of seroincidence with younger reproductive age groups, unmarried status, and education below secondary level. Relative Risk (RR) and Incidence rate ratio (IRR) of HSV-2 infection among the HIV-infected cohort were 55.15 [95%CI:17.0-179.1] and 72.37 [95% CI:71.11-73.63] respectively. The RR and IRR among the HSV-1-seronegative cohort were 1.43 [95%CI:0.64-3.17] and 11.62 [95%CI:9.60-13.64] respectively. Conclusion: Seroincidence rate of HSV-2 infection among pregnant women in Benin was found to be 17.9 per 100 person-years. Positive HIV status, young age, unmarried status, and low education level were indicators of increased risk of incident HSV-2 infection.
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Objective To explore the value of elastography score and strain rate ratio in the diagnosis of small breast malignant focus. Methods We retrospectively analyzed 22 patients with breast small malignant foci less than 10 mm. Ultrasound characteristics were summed up in breast small cancer. Results On elastogram, 2 patients scored 3, 14 scored 4 and 6 scored 5.The average strain rate ratio of all foci was 4.76, and there was correlation between it and elastography scores. Conclusion Ultrasonic elastography has important value in the diagnosis of breast small cancer.