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Results for “Bayesian analysis”

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PubMed1997

A critical pathway for management of patients with acute chest pain who are at low risk for myocardial ischemia: recommendations and potential impact.

BACKGROUND: Use of resources for patients with acute chest pain may be improved with clinical strategies that integrate research, Bayesian analysis, and expert opinion. OBJECTIVES: To 1) develop a critical pathway for management of patients with acute chest pain who are at low risk for complications of ischemic heart disease and 2) assess the potential effects of implementation of the pathway on patient safety and resource use. DESIGN: Evidence-based consensus and prospective cohort study. SETTING: Urban teaching hospital. PATIENTS: Patients at least 30 years of age who were seen in the emergency department for chest pain and who did not have a history of trauma or abnormalities on radiologic study. INTERVENTION: Physician-opinion leaders defined criteria for patient inclusion in the pathway and for remaining on the pathway after 6 or 12 hours of observation. Criteria were defined for appropriateness of direct admission, direct discharge, or 6 hours of observation followed by exercise treadmill testing. MEASUREMENTS: Number of patients admitted to the hospital, number of days that patients were hospitalized, and clinical outcome. RESULTS: 2898 of 4585 patients (63%) were admitted to the hospital; of the 2898, 1152 (40%) were classified as potentially eligible for the pathway and 1068 (93%) had a benign clinical course during the initial observation period. The 1068 patients had a mean length of stay of 2.8 +/- 4.8 days. If 47% of these patients had been discharged after observation and exercise testing, implementation of the pathway would have reduced the number of admissions by 505 (17%) and days of hospitalization by 1407 (11%). CONCLUSIONS: Retrospective analysis suggests that a critical pathway for patients with acute chest pain may substantially reduce resource use. Prospective study is needed to ensure increased efficiency without increased adverse outcomes.

Acute Disease↗

PubMedDate not supplied

Detection of undiagnosed coagulopathies using routine rapid heparin neutralization.

OBJECTIVE: To determine the most frequent clinical causes of a prolonged activated partial thromboplastin time (APTT) result, and to determine whether a new heparin-removal device (the Hepchek, Pall Biomedical, Glen Cove, NY 11542) is capable of efficiently detecting the causes of these values. DESIGN: A combination of chart review and laboratory testing comparing the criterion standard--the heparin chromogenic substrate assay--with the Hepchek. Laboratory investigations were blinded and controlled. SETTING: Inpatient, acute-care hospital. PATIENTS: A total of 1,000 hospital patients with a variety of hemostatic disorders. MAIN OUTCOME MEASURE: The extent to which the Hepchek accurately identified the etiology of a prolonged APTT result. RESULTS: The APTT was prolonged in 25.2% of samples. The presence of heparin in the sample was confirmed by chromogenic assay or by using the Hepchek heparin-removal filter. The presence of heparin was confirmed in 12.8% of all samples and in more than 50% of all abnormal samples. The cause of the abnormal APTT was often unappreciated by the clinician. Bayesian analysis of the Hepchek's ability to diagnose heparin correctly as the cause of the abnormal APTT showed a sensitivity of 100% and specificity of 99.9%. CONCLUSION: Use of the Hepchek in the routine clinical laboratory is an efficient and rapid method of detecting heparin as a cause of isolated prolonged APTT results, and should reduce demands for unwarranted coagulation analyses and inappropriate treatment with blood products.

Bayes Theorem↗

PubMed1998

Etiology and clinical implications of eosinophilic pleural effusions.

This prospective study examined the etiology of eosinophilic pleural effusions investigated at a Thai thoracic center from January 1996 to February 1998. Among the 405 eligible pleural effusions, 31 were eosinophilic (EoPF) and 374 were noneosinophilic (NEoPF). Malignant effusions were established in 159 of the 405 patients, yielding a prevalence of 0.39. Malignant effusions were responsible in 24 of the 31 EoPF (77.4%), and 135 of the 374 NEoPF (36%)(p = 0.01). Bayesian analysis showed the post-test probability of malignancy in eosinophilic pleural effusions among our patient population to be 0.76. Tuberculous pleuritis was the etiology in 155 patients with NEoPF (41.4%) but in none of the patients with EoPF (p <0.001). There was no significant difference between EoPF and NEoPF in miscellaneous causes including paragonimiasis, amebiasis, lupus pleuritis, chylothorax, and yellow nail syndrome. It is concluded that eosinophilic pleural effusions are at least as likely to be malignant as noneosinophilic effusions. The finding of eosinophilic pleural effusions should not be regarded as suggestive of benign conditions.

Bayes Theorem↗

PubMedDate not supplied

Accuracy of combined clinical findings and fine needle aspiration cytology for the diagnosis in palpable breast tumors.

OBJECTIVE: A prospective study to evaluate the confidence level and predictive value of the fine needle aspiration biopsy was performed in the Oncology Service, "Hospital 20 de Noviembre, ISSSTE", Mexico City. MATERIAL AND METHODS: The cases with a palpable breast tumor, histologically confirmed who presented from 1992 to 1994 were included. One aspirate was done in each patient and these were reviewed by the same pathologist. We determined sensitivity, specificity and predictive value of the test. Age, border characteristics, size and mobility of the tumor were evaluated by Bayesian analysis. RESULTS: From 213 aspirates, 199 were elegible for diagnosis, 98 (46%) had a diagnosis of carcinoma, 13 were acellular and one suggestive. The acellular diagnoses were considered negative and suggestive positive, for analysis purposes. Mean age and tumor size were: 46.6 years (range 14-90) and 3.7 cm. (range 1-13) respectively. Sensitivity (0.932), specificity (0.973) and positive predictive value (96.9%) were estimated. We observed a high probability of true positive [P(D+/T+)] > 0.8 results in patients between 40 and 60 years of age, irregular borders, size > 2 cm and fixed lesions. CONCLUSIONS: The test has a high confidence level and in presence of two or more of the clinical factors mentioned, definitive decisions regarding treatment could be taken, without need of histologic confirmation.

Adolescent↗

PubMed2000

[Usefulness of the IUATLD respiratory symptoms questionnaire for the differential diagnosis of bronchial asthma and chronic bronchitis].

Our objective was to determine the diagnostic value of the questionnaire devised by the International Union against Tuberculosis and Lung Disease (IUATLD) for distinguishing between bronchial asthma and chronic bronchitis. We therefore compared clinical diagnoses established independently by two pneumologists for 211 patients to the patients' responses to the IUATLD questionnaire. The questions were analyzed for their ability to discriminate using the responses as independent variables and the diagnosis as the dependent variable. The individual predictive capacity of each question and the discriminating functions that identified the best clusters of questions were calculated using bayesian analysis. Finally, we compared IUATLD results to tests that assessed lung function (spirometry), obstruction variability (bronchodilator test, peak flow, bronchial challenge test), atopy (prick test, serum IgE), and clinical and biological markers (eosinophilia). The questionnaire correctly diagnosed 91% of the patients and a cluster of five questions registered a sensitivity of 85.6%, specificity of 91.4%, a positive predictive value of 93.1% and a negative predictive value of 82.2%, thus proving superior to the other tests. These results, along with the ease of administering the questionnaire allows us to consider the IUATLD instrument to be a good tool for the differential diagnosis of bronchial asthma and chronic bronchitis.

Adolescent↗

PubMed2000

[Pharmacokinetics and individual dose adjustment of carboplatin].

Carboplatin differs from cisplatin by its pharmacokinetics and toxicity profile. Carboplatin is mainly eliminated by the kidneys and its dose-limiting toxicity is the bone marrow suppression. Myelosuppression of carboplatin is more closely correlated with the area under the curve (AUC) of ultrafiltrable plasma concentration versus time to which a patient is exposed, than it is with the administered dose. Similar relationships have been shown between AUC and antitumour effect, although they are in a smaller number and less close. Several methods of dosage individualisation a priori (before carboplatin administration) have been proposed. Since carboplatin is often prescribed to patients with altered renal functions, this dose optimisation is particularly justified. Dose individualisation is based on both equations allowing to predict the patient carboplatin clearance and the choice of target AUC. The different equations proposed are based on direct measurement of the renal filtration glomerular rate or on patient demographic and biological characteristics such as weight and serum creatinine. The respective advantages and limits of these equations are now well known. However, the values of optimal AUC that depend on cytotoxic drugs combined to carboplatin and the patient hematopoietic status, are not precisely determined for each protocol of chemotherapy. When carboplatin is given by reiterated administrations within each course, it is possible to adjust the last doses according to a limited number of blood samples following the first infusion and a Bayesian analysis of the observed plasma concentrations. These methodologies are more complex, but they may be useful for the intensification protocols. Carboplatin is still the only cytotoxic drug for which dose is individualised not according to the body surface area but according to pharmacokinetic parameters.

Age Factors↗

PubMed2001

[The best in 2000 on thrombosis].

It is nearly impossible to follow and integrate all the new information in each subspeciality of cardiology. In the last months, important data has been published which may change clinical practice. In this domain, over half the cases of suspected coronary chest pain would only require a very short stay in a chest pain unit. The history, an accurate evaluation of symptoms, the application of Bayesian analysis, ECG interpretation and serum troponine measurement, associated with a degree of clinical experience, will allow orientation of the patient to a coronary care unit or hospital discharge (with possible out-patient referral). Patients with true unstable angina will no longer be treated by continuous intravenous injection of non-fractionated heparin because, in theory and in practice, this has been replaced with subcutaneous LMW heparin.... On the other hand, the electric syringe will continue to be required for the integration of the anti-GPIIB-IIIA for the treatment of unstable angina after the recommendations published concomitantly in the United States and Europe. This type of patient, especially with a "positive" troponine, will probably not be kept waiting long before referral to the catheter laboratory for coronary angiography and revascularisation. The long-term results of the FRISC II trial are confirmed by an even earlier invasive approach (Tactics-Timi 18) using anti-GPIIb-IIIa. In the first hours, and independently of other older prognostic factors, it will be possible to "predict or compare" the risk of coronary recurrence based on the results of certain biological "markers". In many centres, cases with ST elevation on the ECG could well be included in a phase III "medical protocol", associating a half-dose thrombolytic and an anti-GPIIb-IIIa. Finally, patients who will have been admitted to the chest pain unit with a suspected pulmonary embolism, for example because they had not been treated prophylactically with aspirin before hip surgery, will probably have the choice, after d-dimer measurement, between pulmonary scintigraphy and helicoidal CT scan. If the diagnosis of pulmonary embolism is confirmed, a single subcutaneous injection of LMW heparin could replace the conventional continuous intravenous injection of heparin. The earliest possible oral anticancer ... pardon me I anticoagulant treatment should be prescribed and explained.

Fibrinolytic Agents↗

PubMed2001

Evaluation of limited blood sampling in a preceding 99mTc-labeled diagnostic study to predict the pharmacokinetics and myelotoxicity of 186Re-cMAb U36 radioimmunotherapy.

UNLABELLED: 186Re-labeled chimeric monoclonal antibody U36 (cMAb U36) was recently evaluated in a phase I dose escalation study in head and neck cancer patients. All 13 patients received 99mTc-labeled cMAb U36 before 186Re-cMAb U36 radioimmunotherapy. The aim of this study was to evaluate the suitability of multiple or limited blood sampling to predict clearance, red marrow absorbed dose, and myelotoxicity of 186Re-cMAb U36. METHODS: Population pharmacokinetics of 186Re-cMAb U36 were analyzed with a nonparametric expectation algorithm (NPEM 2) and used for Bayesian analysis of individual patient data to predict cMAb U36 clearance. RESULTS: 186Re-cMAb U36 clearance was most accurately predicted (r = 0.91, P < 0.001) with limited sampling for sample points 4 and 72 h after administration of 186Re-cMAb U36. These predictions were less accurate with 99mTc-cMAb U36 (r = 0.51, P = 0.078 for multiple sampling; r = 0.47, P = 0.104 for sampling at 4 and 21 h after administration). Thrombocytopenia was found to be correlated with the red marrow absorbed dose and was equally well predicted by limited blood sampling after administration of 99mTc-cMAb U36 (r = 0.81, P < 0.01) or 186Re-cMAb U36 (r = 0.79, P < 0.01). CONCLUSION: Limited sampling seems useful to predict pharmacokinetics and myelotoxicity of 186Re-cMAb U36.

Aged↗

PubMed2003

How the probability of a false positive affects the value of DNA evidence.

Errors in sample handling or test interpretation may cause false positives in forensic DNA testing. This article uses a Bayesian model to show how the potential for a false positive affects the evidentiary value of DNA evidence and the sufficiency of DNA evidence to meet traditional legal standards for conviction. The Bayesian analysis is contrasted with the "false positive fallacy," an intuitively appealing but erroneous alternative interpretation. The findings show the importance of having accurate information about both the random match probability and the false positive probability when evaluating DNA evidence. It is argued that ignoring or underestimating the potential for a false positive can lead to serious errors of interpretation, particularly when the suspect is identified through a "DNA dragnet" or database search, and that ignorance of the true rate of error creates an important element of uncertainty about the value of DNA evidence.

Bayes Theorem↗

PubMed2002

Biomarkers and proof of concept.

Starting with an overview over the early human phase of drug development, the Pearson index, a normalized measure for the financial net present value of a drug development project, is introduced and it is shown how the value of obtaining critical information early can be quantified. Biomarkers used in this phase can be a means to obtain such information. Biomarkers can be classified as mechanistic, empirical or model based. Proof of concept trials are used to obtain the information. These trials can be proof of mechanism if they use a biomarker to investigate their mode of action, proof of viability if they investigate tolerability of putatively therapeutic doses or proof of efficacy if they use a clinical endpoint in a selected, homogenous population. If these trials are to decide on further development of a candidate drug, traditional statistical methods are not adequate. In the framework of decision analysis. Bayesian statistics offer an alternative. The basic techniques of this concept are introduced. The role of clinical electrophysiology is discussed in this framework.

Bayes Theorem↗

PubMed2003

[Dyspareunia in women is common, particularly in younger women. Pain history and the women's age provide valuable clues for diagnosis].

Very little is known about the causes of dyspareunia. The aim of this study was to investigate the diagnoses in a non-patient population of women after a short interview and a careful pelvic examination, and to analyze the predictive value of age and different pain characteristics according to Bayesian analysis and Bayes' Theorem. Sixty-four women with severe and prolonged dyspareunia were recruited from the Swedish national screening program for cervical cancer. It was shown that the diagnoses varied with age, and that age and various pain characteristics were very good predictors of the different diagnoses. The study concludes that diagnosing the most common types of severe dyspareunia is fairly easy and that extensive examinations are not generally required.

Adult↗

PubMed1992

The course of autonomic neural function in chronic uraemic patients during haemodialysis treatment.

Autonomic function was followed in 19 patients with uraemia on chronic haemodialysis treatment over a period of 18 months. A smaller group of 12 patients were studied over 56 months. The battery of cardiovascular reflex tests included R-R interval variation test, deep breathing, Valsalva manoeuvre, heart rate, and blood pressure responses to standing and sustained handgrip. Two indices of autonomic function were measured: the autonomic score, and the confidence level on Bayesian analysis. There was great variability in the course of autonomic function over the period studied, with improvement occurring in some subjects and deterioration in others. In addition some patients did not develop any abnormality. Among those patients with uraemia and normal autonomic function at the start of the study, a deterioration occurred in 33-36% in the 18-month follow-up but in 62.5% in the 56-month follow-up. As a group there was no significant change in autonomic function during follow-up, although a clear trend to deterioration was found despite chronic haemodialysis treatment.

Adult↗

PubMed2004

Surgeon-directed ultrasound for trauma is a predictor of intra-abdominal injury in children.

This study investigated the efficacy of surgeon-directed focused assessment with sonography for trauma (FAST) in conjunction with physical exam (PEx) as a predictor of intra-abdominal injury in children. Injured children (ages < or = 17) presenting to a level I trauma center with abdominal trauma were evaluated in the emergency department (ED) by the trauma team of surgical attendings and residents. PEx and FAST were performed immediately upon arrival to the ED and results compared to CT, the standard exam for presence of intra-abdominal injury. Data was collected prospectively from July 1, 2000, until April 30, 2002. One hundred and twenty injured children underwent evaluation of abdominal trauma with PEx, FAST, and abdominal CT. Two patients had false-negative CT scans. Bayesian analysis was applied to the results of the remaining 118 patients. FAST compared with CT findings revealed sensitivity 70 per cent, specificity 100 per cent, positive predictive value 100 per cent, and negative predictive value 92 per cent. FAST results were combined with PEx findings such that either suggestive of intra-abdominal injury was regarded as a "positive exam." Sensitivity was 100 per cent, specificity 74 per cent, positive predictive value 53 per cent, and negative predictive value 100 per cent. Surgeon-directed FAST with consideration of PEx is a predictor of intra-abdominal injury in children.

Abdominal Injuries↗

PubMedDate not supplied

[Long-term follow-up cytogenetic survey and biological dosimetry in persons evacuated from 30-km Chernobyl NPP zone].

The paper presents the results of the follow-up cytogenetic survey and biological dosimetry carried out in inhabitants of Pripiat' town and nearby villages, who were departured from the Chernobyl NPP 30-km exclusive zone during first days after the Chernobyl catastrophe. The unstable chromosome aberration level in inhabitants were significantly increased above control in terms up to 1 year after evacuation and declined gardually during next 14 years. In early period the cytogenetic damage frequency in evacuees showed no dependence on gender. The chromosome type aberration level appeared to be lower in young persons comparing with adults. The dicentrics plus centric rings yield had a positive correlation with duration of staying at Chernobyl zone. The average doses of protracted exposure were calculated from the dicentrics and centric rings yields; the dose estimations appeared to be 1.4 times higher in persons evacuated 3-11 days after the accident than that of in persons with shorter departure time. Uing the Bayesian analysis the probabilistic distribution of biological doses was constructed for the studied evacuees group. This distribution was characterized by a mean dose of 360 mGy, the modal doses of 200-450 mGy and 80% of probability density within the dose range 0-1000 mGy, that seems to be sufficient for considering the increased risk of late somatic radiation effects for this cohort.

Adolescent↗

PubMed2005

[Phylogeny of chinese catfishes inferred from mitochondrial cytochrome b sequences].

The mitochondrial DNA cytochrome b gene was sequenced from 27 catfish species representing 11 families and 24 genera catfishes in China. Aligning with cytochrome b sequences of eight catfish species from North America and Africa retrieved from GenBank, and selecting Astyanax mexicanu, Cyprinus carpio, and Sardinops melanostictus as outgroups, we constructed a matrix of 38 DNA sequences. The phylogenetic trees were constructed by using Bayesian method and Maximum Parsimony (MP) method. The results showed that (1) there are three base pair deletions of mitochondrial cytochrome b gene compared with Characiformes, Cypriniformes, and Clupeiformes; (2) the representatives of Chinese catfish species form a monophyletic group; and (3) the molecular phylogenetic trees constructed with both methods suggest that the families Sisoridae, Akysidae and Amblycipitidae form a monophyletic group, and the families Clariidae, Schilbidae, Ariidae, Ictaluridae, Cranoglanididae, Pangasiidae, Siluridae, Claroteidae, and Bagridae also form a monophyletic group. The families Cranoglanididae from China and Ictaluridae from North America form a sister-group relationship, and the families Clariidae, Ictaluridae, Siluridae, and Sisoridae are obviously monophyletic groups. But the position of the family Plotosidae was not resolved by Bayesian analysis and maximum parsimony inference.

Animals↗

PubMed2005

Molecular phylogeny of penaeid shrimps inferred from two mitochondrial markers.

Penaeid shrimps are an important resource in crustacean fisheries, representing more than the half of the gross production of shrimp worldwide. In the present study, we used a sample of wide-ranging diversity (41 shrimp species) and two mitochondrial markers (758 bp) to clarify the evolutionary relationships among Penaeidae genera. Three different methodologies of tree reconstruction were employed in the study: maximum likelihood, neighbor joining and Bayesian analysis. Our results suggest that the old Penaeus genus is monophyletic and that the inclusion of the Solenocera genus within the Penaeidae family remains uncertain. With respect to Metapenaeopsis monophyly, species of this genus appeared clustered, but with a nonsignificant bootstrap value. These results elucidate some features of the unclear evolution of Penaeidae and may contribute to the taxonomic characterization of this family.

Algorithms↗

PubMed2006

Disease mapping using mixture distribution.

BACKGROUND & OBJECTIVES: Data on infectious diseases like tuberculosis (TB) have been analyzed in the past without giving adequate attention to spatial variations. Earlier studies also attempted to display disease status of sub regions, usually census tracts, by categorizing them into quartiles, that helps the authorities to identify high- or low-risk areas. This approach is based mainly on binomial and Poisson models for disease data, and the recent attempts focus on using mixture models of Poisson distribution. We carried out this study to find wards of Madurai Corporation having high risks for TB disease, to develop a model of mixture of Poisson distributions for the number of cases and to classify each ward to one of many risk groups for TB disease, and to represent spatial distribution of TB incidence in Madurai city. METHODS: produced the observed counts of TB patients in 72 wards of Madurai Corporation. The number of risk groups and the Poisson parameters of each group were found by maximum likelihood approach using the computer package C.A.MAN (Computer Assisted Mixture ANalysis). Bayesian methods were used to associate each ward to a particular risk group. The results were geographically presented in maps by using ArcView mapping software. RESULTS: Using binomial model, 26 wards were categorized as high risk wards, and with mixture model approach 15 wards showed standardized morbility ratio (SMR) >1. The wards along river Vaigai and densely populated wards had high risk. INTERPRETATION & CONCLUSION: Our findings demonstrate the usefulness of the mixture models for disease data with geographical variations.

Bayes Theorem↗

PubMed1991

The role of imaging in prostate cancer.

For patients with prostate cancer, diagnostic imaging can play three roles: screening, staging, and monitoring. Bayesian analysis dictates that if the prior probability of cancer is relatively low or if the consequences of a false-positive result are unacceptable, the test must be optimally specific. If the prior probability of cancer is high or if the consequences of missing it are unacceptable, the test must be optimally sensitive. For screening, the consequences of a miss are slight, and the consequences of labeling an insignificant cancer significant are serious. Thus, a very specific test is required. No current imaging modality fulfills this criterion. For staging, the prior probability of significant disease is relatively high, and the consequences of a miss serious, so a very sensitive test is required. Transrectal sonography, plus biopsy under sonographic control, fulfills this criterion for local disease, as does a bone scan for bone metastases. For monitoring, the prior probability is high, and the consequences of a miss serious, so a very sensitive test is needed. The bone scan is sensitive for bone metastases. Although CT is not sensitive for detecting lymph node metastases, it has practical clinical advantages over other imaging modalities for monitoring purposes in that it can detect disease in multiple structures at once. It is the only test that can monitor prostate size, the size of the lymph nodes, and whether hydronephrosis or liver metastases are present all in the scope of one examination.

Diagnostic Imaging↗