Carlos Eduardo Melo Martínez | Universidad Distrital Francisco Jose de Caldas, Bogota, Colombia (original) (raw)
Papers by Carlos Eduardo Melo Martínez
Journal of Agricultural, Biological and Environmental Statistics
A new method based on distances for modeling continuous random data in Gaussian random fields is ... more A new method based on distances for modeling continuous random data in Gaussian random fields is presented. In non-stationary cases in which a trend or drift is present, dealing with information in regionalized mixed variables (including categorical, discrete and continuous variables) is common in geosciences and environmental sciences. The proposed distance-based method is used in a geostatistical model to estimate the trend and the covariance structure, which are key features in interpolation and monitoring problems. This strategy takes full advantage of the information at hand due to the relationship between observations, by using a spectral decomposition of a selected distance and the corresponding principal coordinates. Unconditional simulations are performed to validate the efficiency of the proposed method under a variety of scenarios, and the results show a statistical gain when compared with a more traditional detrending method. Finally, our method is illustrated with two applications: earth’s average daily temperatures in Croatia, and calcium concentration measured at a depth of 0–20 cm in Brazil. Supplementary materials accompanying this paper appear online.
AStA Advances in Statistical Analysis
In the context of local interpolators, radial basis functions (RBFs) are known to reduce the comp... more In the context of local interpolators, radial basis functions (RBFs) are known to reduce the computational time by using a subset of the data for prediction purposes. In this paper, we propose a new distance-based spatial RBFs method which allows modeling spatial continuous random variables. The trend is incorporated into a RBF according to a detrending procedure with mixed variables, among which we may have categorical variables. In order to evaluate the efficiency of the proposed method, a simulation study is carried out for a variety of practical scenarios for five distinct RBFs, incorporating principal coordinates. Finally, the proposed method is illustrated with an application of prediction of calcium concentration measured at a depth of 0–20 cm in Brazil, selecting the smoothing parameter by cross-validation.
Journal of Applied Statistics, 2015
We present a solution to problems where the response variable is a count, a rate or binary using ... more We present a solution to problems where the response variable is a count, a rate or binary using a generalised linear space–time autoregressive model with space–time autoregressive disturbances (GLSTARAR). The possibility to test the fixed effect specification against the random effect specification of the panel data model is extended to include space–time error autocorrelation or a space–time lagged dependent variable. Space-time generalised estimating equations are used to estimate the spatio-temporal parameters in the model. We also present a measure of goodness of fit, and show the pseudo-best linear unbiased predictor for prediction purposes. Additionally, we propose a joint space–time modelling of mean and dispersion to give a solution when the variance is not constant. In the application, we use social, economic, geographic and state presence variables for 32 Colombian departments in order to analyse the relationship between the number of armed actions (AAs) per 1000 km committed by the guerrillas of the FARC-EP and ELN during the years 2003–2009, and a set of covariates given by attention rate to victims of violence, forced displacement-households expelled, forced displacement-households received, total armed confrontations per year, number of AAs by military forces and percentage of people living in urban area.
Revista Tecnura, Jun 15, 2009
Statistica Neerlandica, 2015
We propose a beta spatial linear mixed model with variable dispersion using Monte Carlo maximum l... more We propose a beta spatial linear mixed model with variable dispersion using Monte Carlo maximum likelihood. The proposed method is useful for those situations where the response variable is a rate or a proportion. An approach to the spatial generalized linear mixed models using the Box–Cox transformation in the precision model is presented. Thus, the parameter optimization process is developed for both the spatial mean model and the spatial variable dispersion model. All the parameters are estimated using Markov chain Monte Carlo maximum likelihood. Statistical inference over the parameters is performed using approximations obtained from the asymptotic normality of the maximum likelihood estimator. Diagnosis and prediction of a new observation are also developed. The method is illustrated with the analysis of one simulated case and two studies: clay and magnesium contents. In the clay study, 147 soil profile observations were taken from the research area of the Tropenbos Cameroon Programme, with explanatory variables: elevation in metres above sea level, agro-ecological zone, reference soil group and land cover type. In the magnesium content, the soil samples were taken from 0- to 20-cm-depth layer at each of the 178 locations, and the response variable is related to the spatial locations, altitude and sub-region.
Journal of the Royal Statistical Society Series A (Statistics in Society)
Soil Carbon, 2014
ABSTRACT
Statistical Methods in Medical Research, 2013
Risk models derived from environmental data have been widely shown to be effective in delineating... more Risk models derived from environmental data have been widely shown to be effective in delineating geographical areas of risk because they are intuitively easy to understand. We present a new method based on distances, which allows the modelling of continuous and non-continuous random variables through distance-based spatial generalised linear mixed models. The parameters are estimated using Markov chain Monte Carlo maximum likelihood, which is a feasible and a useful technique. The proposed method depends on a detrending step built from continuous or categorical explanatory variables, or a mixture among them, by using an appropriate Euclidean distance. The method is illustrated through the analysis of the variation in the prevalence of Loa loa among a sample of village residents in Cameroon, where the explanatory variables included elevation, together with maximum normalised-difference vegetation index and the standard deviation of normalised-difference vegetation index calculated f...
AStA Advances in Statistical Analysis, 2014
ABSTRACT In the context of regression with a beta-type response variable, we propose a new method... more ABSTRACT In the context of regression with a beta-type response variable, we propose a new method that links two methodologies: a distance-based model, and a beta regression with variable dispersion. The proposed model is useful for those situations where the response variable is a rate, a proportion or parts per million, and this variable is related to a mixture of continuous and categorical explanatory variables. We present the main statistical properties and several measures for selection of the most predictive dimensions for the model. In our proposal we only need to choose a suitable distance for both the mean model and the variable dispersion model depending on the type of explanatory variables. The mean and precision predictions for a new individual, and the problem of missing data are also developed. Rather than removing variables or observations with missing data, we use the distance-based method to work with all data without the need to fill in or impute missing values. Finally, an application of mutual funds is presented using the Gower distance for both the mean model and the variable dispersion model. This methodology is applicable to any problem where estimation of distance-based beta regression coefficients for correlated explanatory variables is of interest.
Archivos De Bronconeumologia, 2003
ABSTRACT Introducción: A pesar de que se ha demostrado el papel de la broncoscopia flexible en pe... more ABSTRACT Introducción: A pesar de que se ha demostrado el papel de la broncoscopia flexible en pediatría como una importante herramienta diagnóstica y terapéutica, el procedimiento puede ocasionar complicaciones que el broncoscopista debe prever antes de su realización; sin embargo, no se conocen con precisión los factores que se asocian a la presencia de estas complicaciones. Objetivo: Determinar la incidencia y los factores que se asocian a la presencia de complicaciones debidas a la realización de broncoscopias en pacientes pediátricos. Material y método: Se realizó un estudio de cohorte retrospectivo, en el que se revisaron los registros de los pacientes de entre 1 mes y 18 años de edad a los que se les realizó broncoscopia entre el 1 de enero y el 31 de diciembre de 2002. Se registró para cada paciente la presencia o no de varias variables predictoras y de complicaciones posbroncoscopia. Resultados: Después de ajustar por el tipo de acceso a la vía aérea, la edad menor o igual a 3 meses fue el único factor independiente que se asoció a la presencia de alguna complicación (odds ratio = 8,19; intervalo de confianza del 95%, 1,61-41,55; p = 0,01). Conclusiones: Concluimos que los pacientes con una edad menor o igual a 3 meses tienen mayor riesgo de presentar complicaciones tras la realización de broncoscopias con anestesia general, por lo que debe establecerse un balance riesgo-beneficio en pacientes de esta edad y considerar la realización del procedimiento bajo sedación.
Journal of Asthma, 2008
There is evidence that prevalence and severity of asthma in children has risen. Risk factors for ... more There is evidence that prevalence and severity of asthma in children has risen. Risk factors for severe asthma have been studied extensively in children living in developed countries, but little is known about factors determining the severity of asthma in Latin American countries. The aim of this study was to investigate the role of suspected, potential risk factors for asthma severity in a population of children living in urban Bogota. We studied 175 children, 2 to 16 years old, with asthma attending an asthma clinic. Severe cases and nonsevere asthmatic subjects were compared regarding suspected, potential pre-, peri-, and postnatal risk factors. After controlling for asthma duration, we found that children never breast fed (OR, 11.53; 95% CI, 2.35-56.50; p = 0.003), mothers 30 years or younger at the child's birth (OR, 3.44; 95% CI, 1.23-9.63; p = 0.019), usual use of acetaminophen for fever in the child in the 12 months previous to the survey application (OR, 3.13; 95% CI, 1.14-8.56; p = 0.026), older siblings at birth (OR, 3.81; 95% CI, 1.28-11.32; p = 0.016), and primary or secondary school as the highest level of education attained by mother (OR, 3.20; 95% CI, 1.01-10.07; p = 0.046) were all independent predictors of severe asthma. No breastfeeding, maternal age at child's birth of less than 30 years, routine use of acetaminophen for fever in the child in the 12 months previous to the survey application, older siblings at birth, and primary or secondary school as the highest level of education attained by mother were independent predictors of severe asthma. Some of these risk factors are clearly modifiable. Further prospective, population-based studies with a bigger sample size and a more representative sample of the general population residing in the city are needed to retest and clarify these associations.
Introduction: Surgical wait times have been shown to be of significance in other malignancies, bu... more Introduction: Surgical wait times have been shown to be of significance in other malignancies, but limited studies exist in renal cell cancer (RCC). We analyzed surgical waiting time for RCC patients to see if there was an adverse impact on pathological characteristics. Methods: Our centre triages RCC patients on the basis of perceived tumour risk. The waiting time for surgery is adjusted stage for stage: clinical T1 at 90 days, T2 at 40 days, T3 and T4 at 30 days. We retrospectively reviewed the charts of 354 patients who underwent surgery for RCC. Patients were assessed for pathological upstaging, positive lymph nodes, tumour recurrence and tumour size within each stage. Analysis was performed, using surgical waiting time as a categorical variable, to test for associations with disease recurrence or adverse pathological characteristics. Results: The median time from the first consultation to surgery was 41 days and the mean follow-up was 26.6 months. Waiting time stage for stage was: clinical T1 at 57.12 days, clinical T2 at 36.8 days, clinical T3 and T4 at 30.32 days. On multivariate analysis, pathological tumour size was associated with progression, whereas no significant association was found between waiting time and upstaging. Higher stage tumours, sarcomatoid pathology and clinical evidence of progression were associated with shorter waiting times for early interventions. Conclusions: There was no statistically significant evidence for upstaging or progression during the waiting period for our group of patients. The data reinforce previous studies reporting a "safe" period of active surveillance in T1 RCC without affecting their final pathological outcome.
Journal of …, 2010
Widespread introduction of robot-assisted laparoscopic radical prostatectomy (RALRP) has led to m... more Widespread introduction of robot-assisted laparoscopic radical prostatectomy (RALRP) has led to multiple surgeons going through the learning curve (LC). One of the recommendations for surgeons on the LC for RALRP is to choose patients with smaller glands. We evaluated our LCs to determine whether prostate size influenced intraoperative outcomes and positive surgical margin rates. Data were obtained from a prospective database for the first 154 cases of RALRP performed by a single surgeon. Patients were divided into three groups based on prostate volume (PV): <40 cc (group 1), 40 to 60 cc (group 2), or >60 cc (group 3). PV was estimated by preoperative transrectal ultrasonography (TRUS) and correlated with pathologic weight (PW). Perioperative and immediate postoperative outcomes were evaluated. A statistically significant difference in total operative times between the groups (206 minutes vs 201 minutes vs 233 minutes for groups 1, 2, and 3, respectively) was noted. With regard to individual intraoperative steps, the bladder neck reconstruction and anastomosis time was longer in group 3. No other statistically significant differences were noted. The Pearson correlation coefficient between PV estimation by TRUS and PW was r = 0.785, and an additional analysis based on PW supports the results of our study. Prostate size influenced total operative times and the bladder neck reconstruction and anastomosis time. Our data support the use of preoperative TRUS to estimate PV and recommendations for surgeons starting on their LC to choose glands less than 60 cc.
Thorax, 1994
Bordetella bronchiseptica is recognised as a respiratory tract pathogen in many mammalian species... more Bordetella bronchiseptica is recognised as a respiratory tract pathogen in many mammalian species, but has rarely been implicated in human infection. A case is reported of pneumonia caused by B bronchiseptica in a patient suffering from acquired immunodeficiency syndrome (AIDS).
The Journal of …, 2005
Hypertension is a risk factor for mild cognitive deterioration and vascular dementia. Cognitive d... more Hypertension is a risk factor for mild cognitive deterioration and vascular dementia. Cognitive deterioration attributable to normal aging was distinguished from cognitive deterioration related to hypertension by means of neuropsychologic tests. Sixty hypertensive patients, aged 65-80 years, were compared with 30 normotensive individuals. Patients with a history of stroke and/or transient ischemic attacks, diabetes, atrial fibrillation, hypercholesterolemia, or bypass surgery, and those diagnosed with dementia, depression, or anxiety, were excluded. Neither gender differences, duration of hypertension (10.2±8.2 years), nor prescribed antihypertensive drug treatment had an influence on study results. Immediate recall was impaired in both groups. The hypertensive patients evinced impairment in all tests vs. the normotensive subjects. Mean deferred recall scores ± SD were 5.68±2.6 vs. 7.13±2.4; p<0.01. Deficits in attention speed and executive function, as measured by nonperformance on the Trail Making Test Part B, were present in 46% of hypertensive patients vs. 13% of normotensive patients (p<0.005), with more errors made by the hypertensive patients (1.15±1.54 vs. 0.46±0.9; p<0.02). Scores on the Stroop Color and Word Test also revealed deficits in the hypertensive patients (24.7±7.6 vs. 32±10.7; p<0.005). Compared with the control group, the hypertensive participants revealed more deficits in skills involving delayed recall and prefrontal-region skills. The relevant neuropsychologic tests were sufficiently sensitive and proved easy to use in clinical practice. (J Clin Hypertens. 2005;7:598-604)
Arquivos de gastroenterologia
Context -The serum carcinoembryonic antigen (CEA) is an important prognostic factor in colorectal... more Context -The serum carcinoembryonic antigen (CEA) is an important prognostic factor in colorectal cancer, however the rectum presents different routes of venous drainage, stating that the level of CEA in peripheral and mesenteric rectal tumors may be different, depending on the location of the tumor in the rectal segment. Objective -The goal of this study was to evaluate the relationship between the peripheral and mesenteric venous levels of CEA and the association between these levels and the tumour location in the rectums of patients successfully operated on for rectal carcinoma. Methods -Thirty-two patients who were surgically treated for rectal carcinoma were divided into patients with tumours located in the upper rectum (n = 11) or lower rectum (n = 21).
Journal of plastic, reconstructive & aesthetic surgery : JPRAS, 2014
Desmoid tumors are neoplasms of the conjunctive tissue that are characterized by exclusive locore... more Desmoid tumors are neoplasms of the conjunctive tissue that are characterized by exclusive locoregional growth, frequent recurrence and minimal metastatic potential. They mainly affect individuals with familial adenomatous polyposis of the colon, and rarely occur isolated. The single form of this neoplasm most frequently appears in women of reproductive age, and during pregnancy. A case of a desmoid tumor of large proportions located in the abdominal wall is described. It appeared at the 17th week of pregnancy in a woman without any history of familial adenomatous polyposis. The neoplasm was totally extirpated, with the use of a polypropylene prosthesis for reconstitution of the abdominal wall. One year after the surgery, the patient continues to be well, while using non-steroidal anti-inflammatory drugs for the prevention of relapses.
Journal of Agricultural, Biological and Environmental Statistics
A new method based on distances for modeling continuous random data in Gaussian random fields is ... more A new method based on distances for modeling continuous random data in Gaussian random fields is presented. In non-stationary cases in which a trend or drift is present, dealing with information in regionalized mixed variables (including categorical, discrete and continuous variables) is common in geosciences and environmental sciences. The proposed distance-based method is used in a geostatistical model to estimate the trend and the covariance structure, which are key features in interpolation and monitoring problems. This strategy takes full advantage of the information at hand due to the relationship between observations, by using a spectral decomposition of a selected distance and the corresponding principal coordinates. Unconditional simulations are performed to validate the efficiency of the proposed method under a variety of scenarios, and the results show a statistical gain when compared with a more traditional detrending method. Finally, our method is illustrated with two applications: earth’s average daily temperatures in Croatia, and calcium concentration measured at a depth of 0–20 cm in Brazil. Supplementary materials accompanying this paper appear online.
AStA Advances in Statistical Analysis
In the context of local interpolators, radial basis functions (RBFs) are known to reduce the comp... more In the context of local interpolators, radial basis functions (RBFs) are known to reduce the computational time by using a subset of the data for prediction purposes. In this paper, we propose a new distance-based spatial RBFs method which allows modeling spatial continuous random variables. The trend is incorporated into a RBF according to a detrending procedure with mixed variables, among which we may have categorical variables. In order to evaluate the efficiency of the proposed method, a simulation study is carried out for a variety of practical scenarios for five distinct RBFs, incorporating principal coordinates. Finally, the proposed method is illustrated with an application of prediction of calcium concentration measured at a depth of 0–20 cm in Brazil, selecting the smoothing parameter by cross-validation.
Journal of Applied Statistics, 2015
We present a solution to problems where the response variable is a count, a rate or binary using ... more We present a solution to problems where the response variable is a count, a rate or binary using a generalised linear space–time autoregressive model with space–time autoregressive disturbances (GLSTARAR). The possibility to test the fixed effect specification against the random effect specification of the panel data model is extended to include space–time error autocorrelation or a space–time lagged dependent variable. Space-time generalised estimating equations are used to estimate the spatio-temporal parameters in the model. We also present a measure of goodness of fit, and show the pseudo-best linear unbiased predictor for prediction purposes. Additionally, we propose a joint space–time modelling of mean and dispersion to give a solution when the variance is not constant. In the application, we use social, economic, geographic and state presence variables for 32 Colombian departments in order to analyse the relationship between the number of armed actions (AAs) per 1000 km committed by the guerrillas of the FARC-EP and ELN during the years 2003–2009, and a set of covariates given by attention rate to victims of violence, forced displacement-households expelled, forced displacement-households received, total armed confrontations per year, number of AAs by military forces and percentage of people living in urban area.
Revista Tecnura, Jun 15, 2009
Statistica Neerlandica, 2015
We propose a beta spatial linear mixed model with variable dispersion using Monte Carlo maximum l... more We propose a beta spatial linear mixed model with variable dispersion using Monte Carlo maximum likelihood. The proposed method is useful for those situations where the response variable is a rate or a proportion. An approach to the spatial generalized linear mixed models using the Box–Cox transformation in the precision model is presented. Thus, the parameter optimization process is developed for both the spatial mean model and the spatial variable dispersion model. All the parameters are estimated using Markov chain Monte Carlo maximum likelihood. Statistical inference over the parameters is performed using approximations obtained from the asymptotic normality of the maximum likelihood estimator. Diagnosis and prediction of a new observation are also developed. The method is illustrated with the analysis of one simulated case and two studies: clay and magnesium contents. In the clay study, 147 soil profile observations were taken from the research area of the Tropenbos Cameroon Programme, with explanatory variables: elevation in metres above sea level, agro-ecological zone, reference soil group and land cover type. In the magnesium content, the soil samples were taken from 0- to 20-cm-depth layer at each of the 178 locations, and the response variable is related to the spatial locations, altitude and sub-region.
Journal of the Royal Statistical Society Series A (Statistics in Society)
Soil Carbon, 2014
ABSTRACT
Statistical Methods in Medical Research, 2013
Risk models derived from environmental data have been widely shown to be effective in delineating... more Risk models derived from environmental data have been widely shown to be effective in delineating geographical areas of risk because they are intuitively easy to understand. We present a new method based on distances, which allows the modelling of continuous and non-continuous random variables through distance-based spatial generalised linear mixed models. The parameters are estimated using Markov chain Monte Carlo maximum likelihood, which is a feasible and a useful technique. The proposed method depends on a detrending step built from continuous or categorical explanatory variables, or a mixture among them, by using an appropriate Euclidean distance. The method is illustrated through the analysis of the variation in the prevalence of Loa loa among a sample of village residents in Cameroon, where the explanatory variables included elevation, together with maximum normalised-difference vegetation index and the standard deviation of normalised-difference vegetation index calculated f...
AStA Advances in Statistical Analysis, 2014
ABSTRACT In the context of regression with a beta-type response variable, we propose a new method... more ABSTRACT In the context of regression with a beta-type response variable, we propose a new method that links two methodologies: a distance-based model, and a beta regression with variable dispersion. The proposed model is useful for those situations where the response variable is a rate, a proportion or parts per million, and this variable is related to a mixture of continuous and categorical explanatory variables. We present the main statistical properties and several measures for selection of the most predictive dimensions for the model. In our proposal we only need to choose a suitable distance for both the mean model and the variable dispersion model depending on the type of explanatory variables. The mean and precision predictions for a new individual, and the problem of missing data are also developed. Rather than removing variables or observations with missing data, we use the distance-based method to work with all data without the need to fill in or impute missing values. Finally, an application of mutual funds is presented using the Gower distance for both the mean model and the variable dispersion model. This methodology is applicable to any problem where estimation of distance-based beta regression coefficients for correlated explanatory variables is of interest.
Archivos De Bronconeumologia, 2003
ABSTRACT Introducción: A pesar de que se ha demostrado el papel de la broncoscopia flexible en pe... more ABSTRACT Introducción: A pesar de que se ha demostrado el papel de la broncoscopia flexible en pediatría como una importante herramienta diagnóstica y terapéutica, el procedimiento puede ocasionar complicaciones que el broncoscopista debe prever antes de su realización; sin embargo, no se conocen con precisión los factores que se asocian a la presencia de estas complicaciones. Objetivo: Determinar la incidencia y los factores que se asocian a la presencia de complicaciones debidas a la realización de broncoscopias en pacientes pediátricos. Material y método: Se realizó un estudio de cohorte retrospectivo, en el que se revisaron los registros de los pacientes de entre 1 mes y 18 años de edad a los que se les realizó broncoscopia entre el 1 de enero y el 31 de diciembre de 2002. Se registró para cada paciente la presencia o no de varias variables predictoras y de complicaciones posbroncoscopia. Resultados: Después de ajustar por el tipo de acceso a la vía aérea, la edad menor o igual a 3 meses fue el único factor independiente que se asoció a la presencia de alguna complicación (odds ratio = 8,19; intervalo de confianza del 95%, 1,61-41,55; p = 0,01). Conclusiones: Concluimos que los pacientes con una edad menor o igual a 3 meses tienen mayor riesgo de presentar complicaciones tras la realización de broncoscopias con anestesia general, por lo que debe establecerse un balance riesgo-beneficio en pacientes de esta edad y considerar la realización del procedimiento bajo sedación.
Journal of Asthma, 2008
There is evidence that prevalence and severity of asthma in children has risen. Risk factors for ... more There is evidence that prevalence and severity of asthma in children has risen. Risk factors for severe asthma have been studied extensively in children living in developed countries, but little is known about factors determining the severity of asthma in Latin American countries. The aim of this study was to investigate the role of suspected, potential risk factors for asthma severity in a population of children living in urban Bogota. We studied 175 children, 2 to 16 years old, with asthma attending an asthma clinic. Severe cases and nonsevere asthmatic subjects were compared regarding suspected, potential pre-, peri-, and postnatal risk factors. After controlling for asthma duration, we found that children never breast fed (OR, 11.53; 95% CI, 2.35-56.50; p = 0.003), mothers 30 years or younger at the child&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s birth (OR, 3.44; 95% CI, 1.23-9.63; p = 0.019), usual use of acetaminophen for fever in the child in the 12 months previous to the survey application (OR, 3.13; 95% CI, 1.14-8.56; p = 0.026), older siblings at birth (OR, 3.81; 95% CI, 1.28-11.32; p = 0.016), and primary or secondary school as the highest level of education attained by mother (OR, 3.20; 95% CI, 1.01-10.07; p = 0.046) were all independent predictors of severe asthma. No breastfeeding, maternal age at child&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s birth of less than 30 years, routine use of acetaminophen for fever in the child in the 12 months previous to the survey application, older siblings at birth, and primary or secondary school as the highest level of education attained by mother were independent predictors of severe asthma. Some of these risk factors are clearly modifiable. Further prospective, population-based studies with a bigger sample size and a more representative sample of the general population residing in the city are needed to retest and clarify these associations.
Introduction: Surgical wait times have been shown to be of significance in other malignancies, bu... more Introduction: Surgical wait times have been shown to be of significance in other malignancies, but limited studies exist in renal cell cancer (RCC). We analyzed surgical waiting time for RCC patients to see if there was an adverse impact on pathological characteristics. Methods: Our centre triages RCC patients on the basis of perceived tumour risk. The waiting time for surgery is adjusted stage for stage: clinical T1 at 90 days, T2 at 40 days, T3 and T4 at 30 days. We retrospectively reviewed the charts of 354 patients who underwent surgery for RCC. Patients were assessed for pathological upstaging, positive lymph nodes, tumour recurrence and tumour size within each stage. Analysis was performed, using surgical waiting time as a categorical variable, to test for associations with disease recurrence or adverse pathological characteristics. Results: The median time from the first consultation to surgery was 41 days and the mean follow-up was 26.6 months. Waiting time stage for stage was: clinical T1 at 57.12 days, clinical T2 at 36.8 days, clinical T3 and T4 at 30.32 days. On multivariate analysis, pathological tumour size was associated with progression, whereas no significant association was found between waiting time and upstaging. Higher stage tumours, sarcomatoid pathology and clinical evidence of progression were associated with shorter waiting times for early interventions. Conclusions: There was no statistically significant evidence for upstaging or progression during the waiting period for our group of patients. The data reinforce previous studies reporting a "safe" period of active surveillance in T1 RCC without affecting their final pathological outcome.
Journal of …, 2010
Widespread introduction of robot-assisted laparoscopic radical prostatectomy (RALRP) has led to m... more Widespread introduction of robot-assisted laparoscopic radical prostatectomy (RALRP) has led to multiple surgeons going through the learning curve (LC). One of the recommendations for surgeons on the LC for RALRP is to choose patients with smaller glands. We evaluated our LCs to determine whether prostate size influenced intraoperative outcomes and positive surgical margin rates. Data were obtained from a prospective database for the first 154 cases of RALRP performed by a single surgeon. Patients were divided into three groups based on prostate volume (PV): &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;40 cc (group 1), 40 to 60 cc (group 2), or &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;60 cc (group 3). PV was estimated by preoperative transrectal ultrasonography (TRUS) and correlated with pathologic weight (PW). Perioperative and immediate postoperative outcomes were evaluated. A statistically significant difference in total operative times between the groups (206 minutes vs 201 minutes vs 233 minutes for groups 1, 2, and 3, respectively) was noted. With regard to individual intraoperative steps, the bladder neck reconstruction and anastomosis time was longer in group 3. No other statistically significant differences were noted. The Pearson correlation coefficient between PV estimation by TRUS and PW was r = 0.785, and an additional analysis based on PW supports the results of our study. Prostate size influenced total operative times and the bladder neck reconstruction and anastomosis time. Our data support the use of preoperative TRUS to estimate PV and recommendations for surgeons starting on their LC to choose glands less than 60 cc.
Thorax, 1994
Bordetella bronchiseptica is recognised as a respiratory tract pathogen in many mammalian species... more Bordetella bronchiseptica is recognised as a respiratory tract pathogen in many mammalian species, but has rarely been implicated in human infection. A case is reported of pneumonia caused by B bronchiseptica in a patient suffering from acquired immunodeficiency syndrome (AIDS).
The Journal of …, 2005
Hypertension is a risk factor for mild cognitive deterioration and vascular dementia. Cognitive d... more Hypertension is a risk factor for mild cognitive deterioration and vascular dementia. Cognitive deterioration attributable to normal aging was distinguished from cognitive deterioration related to hypertension by means of neuropsychologic tests. Sixty hypertensive patients, aged 65-80 years, were compared with 30 normotensive individuals. Patients with a history of stroke and/or transient ischemic attacks, diabetes, atrial fibrillation, hypercholesterolemia, or bypass surgery, and those diagnosed with dementia, depression, or anxiety, were excluded. Neither gender differences, duration of hypertension (10.2±8.2 years), nor prescribed antihypertensive drug treatment had an influence on study results. Immediate recall was impaired in both groups. The hypertensive patients evinced impairment in all tests vs. the normotensive subjects. Mean deferred recall scores ± SD were 5.68±2.6 vs. 7.13±2.4; p<0.01. Deficits in attention speed and executive function, as measured by nonperformance on the Trail Making Test Part B, were present in 46% of hypertensive patients vs. 13% of normotensive patients (p<0.005), with more errors made by the hypertensive patients (1.15±1.54 vs. 0.46±0.9; p<0.02). Scores on the Stroop Color and Word Test also revealed deficits in the hypertensive patients (24.7±7.6 vs. 32±10.7; p<0.005). Compared with the control group, the hypertensive participants revealed more deficits in skills involving delayed recall and prefrontal-region skills. The relevant neuropsychologic tests were sufficiently sensitive and proved easy to use in clinical practice. (J Clin Hypertens. 2005;7:598-604)
Arquivos de gastroenterologia
Context -The serum carcinoembryonic antigen (CEA) is an important prognostic factor in colorectal... more Context -The serum carcinoembryonic antigen (CEA) is an important prognostic factor in colorectal cancer, however the rectum presents different routes of venous drainage, stating that the level of CEA in peripheral and mesenteric rectal tumors may be different, depending on the location of the tumor in the rectal segment. Objective -The goal of this study was to evaluate the relationship between the peripheral and mesenteric venous levels of CEA and the association between these levels and the tumour location in the rectums of patients successfully operated on for rectal carcinoma. Methods -Thirty-two patients who were surgically treated for rectal carcinoma were divided into patients with tumours located in the upper rectum (n = 11) or lower rectum (n = 21).
Journal of plastic, reconstructive & aesthetic surgery : JPRAS, 2014
Desmoid tumors are neoplasms of the conjunctive tissue that are characterized by exclusive locore... more Desmoid tumors are neoplasms of the conjunctive tissue that are characterized by exclusive locoregional growth, frequent recurrence and minimal metastatic potential. They mainly affect individuals with familial adenomatous polyposis of the colon, and rarely occur isolated. The single form of this neoplasm most frequently appears in women of reproductive age, and during pregnancy. A case of a desmoid tumor of large proportions located in the abdominal wall is described. It appeared at the 17th week of pregnancy in a woman without any history of familial adenomatous polyposis. The neoplasm was totally extirpated, with the use of a polypropylene prosthesis for reconstitution of the abdominal wall. One year after the surgery, the patient continues to be well, while using non-steroidal anti-inflammatory drugs for the prevention of relapses.