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PubMed1990

Incidence, risk, and prognosis factors of nosocomial pneumonia in mechanically ventilated patients.

Seventy-eight (24%) episodes of nosocomial pneumonia (NP) were detected in 322 consecutive mechanically ventilated patients admitted to a 1,000-bed teaching hospital from April 1987 through May 1988 to assess the incidence, risk, and prognosis factors of NP acquired during mechanical ventilation (MV). The risk and prognosis factors for developing NP during MV were studied using both univariate and multivariate statistical techniques. Multivariate analysis selected the following variables significantly associated with a higher risk for developing ventilator-associated pneumonia: more than one intubation during MV (p = 0.000012), a prior episode of aspiration of gastric content (p = 0.00018), a MV period longer than 3 days (p = 0.015), the presence of chronic obstructive pulmonary disease (COPD) (p = 0.048), and the use of positive end-expiratory pressure (PEEP) during MV (p = 0.092). The presence of an ultimately or rapidly fatal underlying disease (p = 0.0018), worsening of acute respiratory failure caused by pneumonia (p = 0.0096), the presence of septic shock (p = 0.016), an inappropriate antibiotic treatment (p = 0.02), and the type of intensive care unit (ICU) hospitalization (noncardiac surgery and nonsurgical ICU compared with post-cardiac surgery ICU) (p = 0.08) were those factors selected by a stepwise logistic regression analysis as independently worsening the prognosis. The overall fatality rate was 23% (73 of 322). The mortality of patients with NP was higher (33%; 26 of 78; p less than 0.01) when compared with fatality rates of patients without NP (19%; 47 of 244).(ABSTRACT TRUNCATED AT 250 WORDS)

Cross Infection↗
PubMed1984

Methodological guidelines for reading drug-evaluation research.

The present paper discusses methodological issues in psychopharmacological research. The intention is to provide readers of drug-evaluation research with a set of basic guidelines that will assist them to critically evaluate the investigations they encounter in the psychiatric literature. This paper describes the underlying rationale and basic principles associated with applying statistical analyses to drug-evaluation research data, and also addresses 11 additional methodological issues: specification of the research sample with respect to descriptive variables, diagnostic criteria, reliability of the diagnosis, the control group, random assignment of subjects to treatment conditions, blindness, subject attrition, treatment complications and side effects, the power of statistical tests, multivariate statistical analysis, and the reliability of the dependent variable. Evidence is presented to support the premise that there is a need to read drug-evaluation research critically.

Double-Blind Method↗
PubMed1993

Multivariate assessment of computer-analyzed corneal topographers.

Methodological aspects of multivariate statistical models to describe and to assess data from computer-analyzed corneal topographers (CACT) are considered. The data generated by repeated curvature mappings of calibrated steel balls are discussed in detail with the objective of formulating the basic questions and suggesting directions to assess data from clinical applications of CACT. The interpretation of seemingly straightforward concepts such as accuracy and precision is revisited with the objective of understanding its meaning in future clinical and experimental applications of CACT. Some of the statistical problems related to the analysis of corneal astigmatism based on CACT data are also discussed.

Astigmatism↗
PubMed2001

Application of factorial design to the study of xylitol production from eucalyptus hemicellulosic hydrolysate.

This study deals with the bioconversion of xylose into xylitol by Candida guilliermondii FTI 20037 using eucalyptus hemicellulosic hydrolysate obtained by acid hydrolysis. The influence of various parameters (ammonium sulfate, rice bran, pH, and xylose concentration) on the production of xylitol was evaluated. The experiments were based on multivariate statistical concepts, with the application of factorial design techniques to identify the most important variables in the process. The levels of these variables were quantified by the response surface methodology, which permitted the establishment of a significant mathematical model with a coefficient determination of R2 = 0.92. The best results (xylitol = 10.0 g/L, yield factor = 0.2 g/g, and productivity = 0.1 g/[L x h]) were attained with hydrolysate containing ammonium sulfate (1.1 g/L), rice bran (5.0 g/L), and xylose (initial concentration of 60.0 g/L), after 72 h of fermentation. The pH of fermentation was adjusted to 8.0 and the inoculum level utilized was 3 g/L.

Ammonium Sulfate↗
PubMed2003

A helping computer system prognosing the survival of patients with Hodgkin's disease.

INTRODUCTION AND AIMS: Hodgkin's disease is an uncommon form of lymphoma occurring mainly at 15-35 years of age. Prognostic evaluation plays an important role by supplying a rational working linkage between the wide complexity of disease presentations and available therapeutic resources. Improved prognostic evaluation able to identify the likely outcome of a given patient would be of considerable clinical importance. The aim of this study was to develop and present a computer system and tools that will allow physicians to make more precise prognosis of the survival in such patients. MATERIAL AND METHODS: Several mathematical models were developed using multivariate statistical survival analyses. Data on 116 patients with Hodgkin's disease treated in the Clinic of Hematology (Plovdiv, Bulgaria) between 1974 and 2001, were collected. The patients' database consisted of general information for each patient (name initials, age, sex, date of diagnosis, etc.) as well as of specialized clinical information. RESULTS: The present system has provided different options for calculation of survival probabilities and prognosis using deterministic models for each patient. CONCLUSIONS: The use of the present system in routine practice has allowed physicians to facilitate the process of making more precise prognosis of survival. In this way, they have been able to optimize the treatment scheme and improve the quality of life of their patients.

Adolescent↗
PubMed2002

Metabolic trajectory characterisation of xenobiotic-induced hepatotoxic lesions using statistical batch processing of NMR data.

Multivariate statistical batch processing (BP) analysis of 1H NMR urine spectra was employed to establish time-dependent metabolic variations in animals treated with the model hepatotoxin, alpha-naphthylisothiocyanate (ANIT). ANIT (100 mg kg(-1)) was administered orally to rats (n = 5) and urine samples were collected from dosed and matching control rats at time-points up to 168 h post-dose. Urine samples were measured via 1H NMR spectroscopy and partial least squares (PLS) based batch processing analysis was used to interpret the spectral data, treating each rat as an individual batch comprising a series of timed urine samples. A model defining the mean urine profile over the 7 day study period was established, together with model confidence limits (+/-3 standard deviation), for the control group. Samples obtained from ANIT treated animals were evaluated using the control model. Time-dependent deviations from the control model were evident in all ANIT treated animals consisting of glycosuria, bile aciduria, an initial decrease in taurine levels followed by taurinuria and a reduction of tricarboxylic acid cycle intermediate excretion. BP provided an efficient means of visualising the biochemical response to ANIT in terms of both inter-animal variation and net variation in metabolite excretion profiles. BP also allowed multivariate statistical limits for normality to be established and provided a template for defining the sequence of time-dependent metabolic consequences of toxicity in NMR based metabonomic studies.

1-Naphthylisothiocyanate↗
PubMed1998

Diagnostic classification of autoantibody repertoires in endocrine ophthalmopathy using an artificial neural network.

PURPOSE: The aim of this study was to classify the human IgG autoantibody repertoire of sera from patients suffering from endocrine ophthalmopathy (EOP) and healthy subjects (CTRL) for diagnostic purposes using the recently developed Megablot technique. This technique allows for the simultaneous and quantitative screening of a large set of antigens and uses multivariate statistical techniques and an artificial neural network. METHODS: Sera were tested against Western blots (WBs) of SDS-PAGE preparations of proteins from human extraorbital eye muscle (EOP: n = 16; CTRL: n = 11). Digital image analysis was performed. The blots were subsequently analyzed by multivariate statistical techniques (analysis of discriminance) and an artificial neural network (probalistic neural network). RESULTS: The sera of both the EOP and CTRL groups showed a complex staining pattern against WBs of SDS-PAGEs from human eye muscle. Using the multivariate statistical technique for classification, all of the known samples and 85% of the unknown samples (not presented during calculation) were assigned to their correct clinical group. Using the artificial neural network as classifier, all of the samples presented during training and 96.3% of the unknown samples (not trained) were assigned correctly. CONCLUSIONS: The artificial neural network exceeds the ability of multivariate statistical techniques such as analysis of discriminance to assign unknown samples to their correct predefined group. Thus, the neural network exceeds other methods in generalizing some similarities of blots used for classification. This study reveals that our new technique and its evaluation using a neural network can be used as a helpful diagnostic tool in autoimmune diseases such as endocrine ophthalmopathy.

Adult↗
PubMed1994

The menopausal transition: a dynamic approach to the pathogenesis of neurovegetative complaints.

In our cross-sectional study we investigated the separate influence of three main factors, namely menopausal and estrogen status, and chronological age, on ten neurovegetative climacteric complaints reported in the scale of Kupperman et al. A multivariate statistical analysis was performed by a multivariate statistical approach on 1161 untreated women seen at the Menopause Center of the Ferrara University Hospital. Ninety women (age range, 41-54 years) were premenopausal; 492 women (age range, 38-55 years) were perimenopausal with irregular periods or amenorrhea for less than 12 months; 468 women (age range, 41-69 years) had a spontaneous menopause (age range, 37-66 years); 111 had had hysterectomy with bilateral ovariectomy while still regularly menstruating. Serum estrone was used as the indicator of the patients' estrogen status. A clear positive trend was demonstrated between menopausal status and the prevalence of depression, hot flushes, insomnia and joint pain. However, only the prevalence of hot flushes amongst these four symptoms was significantly related with the climacteric estrogen decline (beta = -0.006, P = 0.001). Moreover, menopausal status appeared to influence the intensity of fatigue, hot flushes, insomnia and paresthesia. Age was found to significantly (P = 0.053) co-vary only with the intensity of the hot flushes, with a positive relation (beta = 0.092, r = 0.104, P = 0.003), whereas estrone values did not significantly co-vary with any symptom. Furthermore, while neurovegetative symptoms are largely present also in the absence of hot flushes, when these latter are present, they exacerbate both the intensity and the prevalence of all the other symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Ensembles of radial basis function networks for spectroscopic detection of cervical precancer.

The mortality related to cervical cancer can be substantially reduced through early detection and treatment. However, current detection techniques, such as Pap smear and colposcopy, fail to achieve a concurrently high sensitivity and specificity. In vivo fluorescence spectroscopy is a technique which quickly, noninvasively and quantitatively probes the biochemical and morphological changes that occur in precancerous tissue. A multivariate statistical algorithm was used to extract clinically useful information from tissue spectra acquired from 361 cervical sites from 95 patients at 337-, 380-, and 460-nm excitation wavelengths. The multivariate statistical analysis was also employed to reduce the number of fluorescence excitation-emission wavelength pairs required to discriminate healthy tissue samples from precancerous tissue samples. The use of connectionist methods such as multilayered perceptrons, radial basis function (RBF) networks, and ensembles of such networks was investigated. RBF ensemble algorithms based on fluorescence spectra potentially provide automated and near real-time implementation of precancer detection in the hands of nonexperts. The results are more reliable, direct, and accurate than those achieved by either human experts or multivariate statistical algorithms.

Algorithms↗
PubMed1976

A new statistical evaluation of the dominant-lethal mutation test.

A multivariate statistical method for evaluation of the dominant-lethal mutation test is outlined which takes into consideration the dependence among the dimensions of the test. It can also be fitted into a computer programme as is necessary with dominant-lethal tests which often give a large number of data. This article describes a multivariate statistical method and gives an example of an experiment evaluated with the method.

Genes, Dominant↗
PubMed1999

[A causal model of blood enzyme data and visualization of tissue conditions].

Quantitative diagnostics is an important field in which clinical data are converted into medical information. A variety of approaches to obtain medical diagnoses have been developed and multivariate statistical analysis supports the diagnostic process. Although many clinical data are affected by body conditions such as disease and functional failure, only a few models take this phenomenon into consideration. The correlation between laboratory test results can be understood as a causal relationship between body conditions and clinical test data variations. A multivariate statistical method, factor analysis, expresses a causal relationship between latent variables and observed variables. We developed a causal model for blood enzyme data using factor analysis. The latent variables were assumed to be organ specific regarding 9 enzyme data. This causal model expressed clinical knowledge within blood enzymes and allowed visualization of organ conditions. The visualization of laboratory data is useful to screen patient's pathological states.

Data Interpretation, Statistical↗
PubMed1993

The risk of determining risk with multivariable models.

PURPOSE: To review the principles of multivariable analysis and to examine the application of multivariable statistical methods in general medical literature. DATA SOURCES: A computer-assisted search of articles in The Lancet and The New England Journal of Medicine identified 451 publications containing multivariable methods from 1985 through 1989. A random sample of 60 articles that used the two most common methods--logistic regression or proportional hazards analysis--was selected for more intensive review. DATA EXTRACTION: During review of the 60 randomly selected articles, the focus was on generally accepted methodologic guidelines that can prevent problems affecting the accuracy and interpretation of multivariable analytic results. RESULTS: From 1985 to 1989, the relative frequency of multivariable statistical methods increased annually from about 10% to 18% among all articles in the two journals. In 44 (73%) of 60 articles using logistic or proportional hazards regression, risk estimates were quantified for individual variables ("risk factors"). Violations and omissions of methodologic guidelines in these 44 articles included overfitting of data; no test of conformity of variables to a linear gradient; no mention of pertinent checks for proportional hazards; no report of testing for interactions between independent variables; and unspecified coding or selection of independent variables. These problems would make the reported results potentially inaccurate, misleading, or difficult to interpret. CONCLUSIONS: The findings suggest a need for improvement in the reporting and perhaps conducting of multivariable analyses in medical research.

Humans↗
PubMed2003

Principal components analysis as an evaluation and classification tool for lower torso sEMG data.

The use of univariate statistical techniques on multivariate electromyography data can fail to uncover important relationships between variables. Principal components analysis (PCA) is a multivariate statistical technique that can be used as a data exploration tool, both by classifying participants and simplifying data structures. Past research using this technique has focused on discriminating between "patients" and "normals". This investigation explored the use of PCA on electromyography data from healthy participants, with the objective of elucidating any between-participant differences in the multivariate patterns of muscle coactivation. Results indicated that, even between healthy participants, quantitative and qualitative differences in muscle coactivation patterns exist and that, in the context of the lower torso, a large portion (>70%) of the empirically determined muscle activation could be synthesized in a theoretical three-parameter control model.

Abdominal Muscles↗
PubMed2001

A review of analytical techniques for gait data. Part 1: Fuzzy, statistical and fractal methods.

In recent years, several new approaches to gait data analysis have been explored, including fuzzy systems, multivariate statistical techniques and fractal dynamics. Through a critical survey of recent gait studies, this paper reviews the potential of these methods to strengthen the gait laboratory's analytical arsenal. It is found that time-honoured multivariate statistical methods are the most widely applied and understood. Although initially promising, fuzzy and fractal analyses of gait data remain largely unknown and their full potential is yet to be realized. The trend towards fusing multiple techniques in a given analysis means that additional research into the application of these two methods will benefit gait data analysis.

Electromyography↗
PubMed2003

Prospective randomized comparative study of the effectiveness and safety of electrohydraulic and electromagnetic extracorporeal shock wave lithotriptors.

PURPOSE: We compared the efficacy of 2 shock wave energy sources, electrohydraulic (Dornier MFL 5000, Dornier MedTech, Wessling, Germany) and electromagnetic (DLS, Dornier Lithotriptor S, Dornier MedTech), for the treatment of urinary calculi. MATERIALS AND METHODS: A prospective randomized study of 694 patients with urinary stones was conducted during 12 months to compare the efficacy of the 2 machines. Entrance criteria were radiopaque single or multiple stones at any location within the kidney or the ureter, 25 mm or smaller that had not previously been treated by any means. Patients with congenital anomalies were excluded from this study with all other contraindications for extracorporeal shock wave lithotripsy. Following lithotripsy a plain abdominal film and tomograms were done 1 week after each session to determine if there were residual stones and assess the need for re-treatment. Patients were evaluated 4 weeks after lithotripsy by plane abdominal x-ray and spiral computerized tomography. Success was defined as no residual stones. Univariate and multivariate statistical analyses were performed for different variables that may have an impact on the success rate, including the type of lithotriptor. Comparisons of treatment parameters, complications and success rate for both lithotriptors were done. RESULTS: Of 9 variables examined with univariate analysis 6 had a significant impact on the success rate. Of these 4 maintained their statistical impact on multivariate analysis. These were side, site of the stones, renal morphology and type of lithotriptor. Treatment time was significantly shortened for DLS (54 +/- 32.9 minutes compared to 65.7 +/- 44.7 for MFL, p <0.001). The re-treatment rate was lower for DLS at 34% versus 51.6% for the MFL (p <0.001). The overall success rate was 85.4%. It was 88.5% for DLS compared to 82.4% for MFL (p = 0.03). No statistically significant difference between the lithotriptors was noted for ureteral calculi (p >0.05). The success rate was higher in the DLS group for renal stones especially lower caliceal and pyelic stones (p <0.05). The success rate was higher in DLS group for stones 10 mm or smaller, 92.8% versus 85.3% for MFL (p = 0.03). The success rate was comparable in both groups for stones larger than 10 mm (81.8% for DLS versus 77.9% for MFL, p >0.05). No statistically significant difference was found in the complication rate for the groups. Steinstrasse were noted in 4% of patients treated with MFL and 3% of those treated with DLS. Subcapsular hematomas were noted in 2 patients in each group. No procedures after extracorporeal shock wave lithotripsy were needed in either group. CONCLUSIONS: The electromagnetic lithotriptor (Dornier lithotriptor S) has significant clinical advantages over the electrohydraulic lithotriptor (Dornier MFL 5000) in terms of treatment time, re-treatment rate and success rate, although there is no difference in the complication rate.

Adolescent↗
PubMed1993

Malignancy-associated changes in monocytes and lymphocytes in acute leukemias measured by high-resolution image processing.

A number of methods are available for classifying lymphoid and myeloid leukemias in peripheral blood and bone marrow. However, in clinical diagnosis an initial and particularly important step is morphologic analysis. All the cells in this investigation were classified by two hematologic experts. In most cases, immunophenotyping and immunocytochemical analyses were performed. Routinely prepared Romanowsky-Giemsa-stained peripheral blood smears (approximately 23,000 cells) were scanned by a high-resolution color TV/microscope system and analyzed by color and texture algorithms. In addition to blast cells, lymphocytes and monocytes exhibited a leukemia-associated change in morphology. The calculated texture and color features were most significant for the subtyping performed by the statistical program. With multivariate statistical analysis, seven mathematical subtypes of lymphocytes and five of monocytes could be found over all the specimens. Acute myeloblastic leukemia (AML, M1-M2), acute myelomonocytic leukemia (AMMOL, M4) and acute monocytic leukemia (AMOL, M5) could be differentiated by their distributions of monocyte subtypes. However, this was impossible for the lymphocyte subtypes. Acute lymphoblastic leukemias (B-ALL and T-ALL) were discernible with the aid of lymphocyte subtypes and acute myeloid conditions from viral infections, such as with the Epstein-Barr virus. The method increased the relevance of image processing in clinical diagnosis of acute leukemias and showed that the "normal" cell populations were not really normal in malignant leukemias.

Burkitt Lymphoma↗
PubMed1990

Lack of useful clinical predictors of response to splenectomy in patients with chronic idiopathic thrombocytopenic purpura.

We set out to identify clinical or analytical variables that might predict the response to splenectomy in patients with chronic idiopathic thrombocytopenic purpura (ITP). We retrospectively examined 138 mostly adult patients with chronic ITP, treated with splenectomy. Information was compiled from five Public Health Hospitals from a questionnaire and chart review. Sixty-one potentially prognostic variables were analysed by univariate and multivariate statistical methods. After multivariate analysis, age (relative risk = 1.02; CI 1-1.03) and a severity of the bleeding diathesis (relative risk = 1.6; CI 1.13-2.22) were independent prognostic factors for a sustained response to splenectomy. An independent analysis of the postsplenectomy counts showed that an early (days 1-3) thrombocyte count exceeding 156 x 10(9)/l cells increases the likelihood of a permanent unmaintained response. Our data indicate that the response to splenectomy in patients with chronic ITP cannot be adequately predicted on the basis of pre-splenectomy clinical or analytical variables.

Adult↗
PubMed2003

Hepatology and the Canadian gastroenterologist: interest, attitudes and patterns of practice: results of a national survey from the Canadian Association of Gastroenterology.

BACKGROUND: Hepatology has emerged as a subspecialty distinct from gastroenterology. Despite this, there is no formal certification examination or accredited training program, and training remains combined with gastroenterology. AIM: To determine attitudes, perceptions and patterns of practice with respect to liver disease among Canadian gastroenterologists. METHODS: A survey questionnaire was distributed to clinician gastroenterologists who are members of the Canadian Association of Gastroenterology. The responses of subgroups of respondents were compared by univariate and multivariate statistical techniques. RESULTS: Hepatologists constituted 20 of 201 respondents, the rest identifying themselves as gastroenterologists. Among gastroenterologists, liver disease constituted 10% of in- and out-patient practice. Despite this, 85% of gastroenterologists maintain an interest in hepatology, 49% perform liver biopsies, 60% treat hepatitis C, and 54% treat hepatitis B. In all of these areas, university-based gastroenterologists were consistently less likely than community-based gastroenterologists to maintain an interest and practice in hepatology, a finding that remained statistically significant on multivariate analysis. With regard to hepatology training, 90% of hepatologists and 94% of gastroenterologists felt that hepatology training should remain combined with gastroenterology, although 55% of hepatologists felt that current training was adequate compared with 79% of gastroenterologists, who were satisfied with the status quo. CONCLUSIONS: Hepatology remains relevant and important to Canadian gastroenterologists, especially those who have community-based practices. Canadian gastroenterologists and hepatologists are not in favour of separating hepatology training from existing gastroenterology training programs, although hepatologists feel that the current level of training is suboptimal.

Attitude of Health Personnel↗