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Biomedical subjects

S S Cross

Publications and source records attributed to S S Cross.

At least 55 records · Page 3Linked to original sources
PubMed2000

What levels of agreement can be expected between histopathologists assigning cases to discrete nominal categories? A study of the diagnosis of hyperplastic and adenomatous colorectal polyps.

AIMS: To assess the levels of agreement between histopathologists for a two-class nominal categorization process--the discrimination between hyperplastic and adenomatous colorectal polyps. METHODS: Fifty hyperplastic and 50 adenomatous polyps received consecutively in the laboratory were categorized by nine histopathologists, and the level of agreement between all observers and the original diagnosis was assessed using kappa statistics. RESULTS: For the eight observers with 11 months or more experience in histopathology, there was a high level of agreement with kappa statistics ranging from 0.84 to 0.98. This process was performed rapidly with an average of 13 to 22 seconds spent on each case. One observer with only 6-weeks' experience of histopathology had a lower overall level of agreement with kappa statistics ranging from 0.46 to 0.54, but the performance on the later cases was much higher. CONCLUSIONS: The level of agreement in the distinction between hyperplastic and adenomatous colorectal polyps is high among histopathologists with at least moderate amounts of experience in histopathology. The one virtually naïve observer showed a marked learning response during the study without feedback on case outcome. This suggests that histopathologists are very reliable in assigning cases to distinct nominal categories and that learning of these processes occurs early in a histopathologist's career.

Adenomatous Polyps↗
PubMed2000

Validation of a decision support system for the cytodiagnosis of fine needle aspirates of the breast using a prospectively collected dataset from multiple observers in a working clinical environment.

We have used a 692 case dataset, collected retrospectively by a single observer, to develop decision support systems for the cytodiagnosis of fine needle aspirates of breast lesions. In this study, we use a 322 case dataset that was prospectively collected by multiple observers in a working clinical environment to test two predictive systems, using logistic regression and the multilayer perceptron (MLP) type of neural network. Ten observed features and the patient age were used as input features. The systems were developed using a training set and test set from the single observer dataset and then applied to the multiple observer dataset. For the independent test cases from the single observer dataset, with a threshold set for no false positives on the training set, logistic regression produced a sensitivity of 82% (95% confidence interval 73-91) and a predictive value of a positive result (PV +) of 98% (95-99), the values for the MLP were 79% (69-89) and 100%, respectively. However the performance on the prospective multiple observer dataset was much worse, with a sensitivity of 72% (65-80), and PV + of 97% (94-99) for logistic regression and 67% (60-75) and 91% (85-97) for the MLP. These results suggest that there is considerable interobserver variability for the defined features and that this system is unsuitable for further development in the clinical environment unless this problem can be overcome.

Adolescent↗
PubMed1999

Visualisation of biomedical datasets by use of growing cell structure networks: a novel diagnostic classification technique.

BACKGROUND: Medical research produces large multivariable datasets that are difficult to visualise and interpret intuitively. We describe a novel growing cell structure (GCS) technique that compresses multidimensional datasets into two dimensional maps with colour overlays that can be visually interpreted. METHODS: The two-dimensional map is self-discovered from the training set by distribution of cases to different nodes according to similarity between the cases at each node. Nodes are added to the map until there is no further significant reduction in error. The Parzen window method is used to estimate the probability distribution of the training cases, and this probability is converted to posterior class probabilities by use of Bayes' theorem. Classification performance can be assessed by means of receiver operating characteristic (ROC) curves. Colour maps of the values of each input variable at each node are constructed, which illustrate the relation between each input variable and the overall distribution of cases in the network map. FINDINGS: From a dataset of 11 input variables from 692 fine-needle aspirate samples from breast lesions, a 32-node network produced an area under the ROC curve of 0.96, which was not significantly different from that for logistic regression (0.98, z=1.09, p>0.05). Colour maps of the input variables showed that some variables had discrete distributions over exclusively benign or malignant areas of the network, and were thus discriminant, whereas others, such as foamy macrophages, covered both benign and malignant regions. INTERPRETATION: This technique produces dimensional compression that allows multidimensional data to be displayed as two-dimensional colour images. This envisioning of information allows the highly developed visuospatial abilities of human observers to perceive subtle inter-relations in the dataset.

Artificial Intelligence↗
PubMed1999

Matrix metalloproteinase levels are elevated in inflammatory bowel disease.

BACKGROUND & AIMS: The expression of matrix metalloproteinases 1, 2, 3, and 9 was examined in biopsy specimens removed from adult and pediatric patients with ulcerative colitis and Crohn's disease. The aim of this study was to determine if the expression of these enzymes was altered between areas of actively inflamed vs. noninvolved mucosa in the same patient and between patients with diseased bowel vs. a control group of patients. METHODS: Proteolytic activity was quantified by zymography using image analysis. The identity of the matrix metalloproteinases was confirmed by using inhibitors, by comparison with purified standards, and by Western immunoblotting with specific antibodies. RESULTS: In patients with ulcerative colitis (n = 21), a significant increase (P = 0.0051) in metalloproteinase activity was found in inflamed areas of mucosa compared with noninvolved regions. The levels of activity also were significantly greater (P < 0.001) in noninvolved areas of the bowel (n = 21) compared with levels in control patients (n = 9). In Crohn's disease (n = 8), differences between ulcerated and nonulcerated sites were not significantly different but levels of protease activity at both of these sites were significantly elevated compared with levels in control patients (P < 0.03). Of the proteases detected, matrix metalloproteinase 9 was the most abundantly expressed in the inflamed bowel; neutrophils were confirmed as the likely origin of this protease. CONCLUSIONS: The abundance and activation of matrix metalloproteinases significantly increases in ulcerative colitis and Crohn's mucosa. Inhibitors of these proteolytic enzymes may therefore be of therapeutic value in the treatment of inflammatory bowel disease.

Adolescent↗
PubMed1999

Acp. Best practice no 155. Pathological investigation of deaths following surgery, anaesthesia, and medical procedures.

The pathological investigation of deaths following surgery, anaesthesia, and medical procedures is discussed. The definition of "postoperative death" is examined and the classification of deaths following procedures detailed. The review of individual cases is described and the overall approach to necropsy and interpretation considered. There are specific sections dealing with the cardiovascular system (including air embolism, perioperative myocardial infarction, cardiac pacemakers, central venous catheters, cardiac surgery, heart valve replacement, angioplasty, and vascular surgery); respiratory system (postoperative pneumonia, pulmonary embolism, pneumothorax); central nervous system (dissection of cervical spinal cord), hepatobiliary and gastrointestinal system; musculoskeletal system; and head and neck region. Deaths associated with anaesthesia are classified and the specific problems of epidural anaesthesia and malignant hyperthermia discussed. The article concludes with a section on the recording of necropsy findings and their communication to clinicians and medicolegal authorities.

Anesthesia↗
PubMed1998

Evaluation of a statistically derived decision tree for the cytodiagnosis of fine needle aspirates of the breast (FNAB).

A decision tree for the diagnosis of FNAB was derived from defined human observations using a rule induction method, C4.5 (a derivative of the ID3 algorithm). This algorithm is an implementation of the top-down induction method where the tree is determined iteratively by adding those nodes and branches which maximize the information gain at each step. The tree was derived from a training set of 200 FNAB with known outcome using 10 defined features (from one observer) and patient age. The tree contained a total of seven nodes (six observable features and patient age) with eight endpoints (four benign, four malignant). The tree was applied to a test set of 400 further FNAB with observations from the training observer and produced a sensitivity of 95%, specificity of 93% and a positive predictive value (PPV) of a malignant result of 89%. Four trainee pathologists were given a training session on the observable features and then used the tree to determine outcome in a further 50 FNAB. The observers were blind to clinical details apart from age and the endpoints were coded with letters and not labelled benign or malignant. The results from these observers produced ranges of sensitivity 80-96%, specificity 64-92%, PPV 73-92% and kappa statistics (with known outcome) 0.6-0.8. Reported difficulties in using the tree included estimation of nuclear size. These results were worse than the performance of the observers on a further 50 cases without using the decision tree (sensitivity 80-100%, specificity 72-100%, PPV 78-100%, kappa 0.72-0.92). The original 50 case test set was rerandomized and the four trainee observers made all 10 defined observations on each specimen without using the decision tree; these observations were then used to derive decisions from the tree. The performance from this method was similar to that using selected features from the tree, suggesting that observation of all features together does not improve the reliability of each specific observation. The poor performance of this tree suggests that this methodology may be unsuitable for producing decision support aids for diagnostic or training purposes in this domain.

Biopsy, Needle↗
PubMed1998

Grading and scoring in histopathology.

In many areas of histopathology a nominal category, such as a diagnosis of breast carcinoma, does not give enough information for the referring clinician to make decisions about patient prognosis and treatment. Therefore scoring and grading systems have been developed which provide additional information. This article reviews the principles behind these systems with particular reference to the relationships between the natural clustering (or nonclustering) of cases and the imposition of arbitrary class boundaries on such distributions. The difference between real numbers and the ordinal categorical numeric labels, which are often produced by histopathology scoring systems, is discussed. The reproducibility of scoring and grading systems is reviewed and generic suggestions are given for developing new systems and for their validation.

Disease Management↗
PubMed1998

Audit of the histopathological diagnosis of non-neoplastic colorectal biopsies: achievable standards for the diagnosis of inflammatory bowel disease.

AIM: To assess the performance of a histopathology department in diagnosing inflammatory bowel diseases with comparison of reports from other centres. STUDY POPULATION: 1067 sets of endoscopic biopsies received in the department of histopathology, Royal Hallamshire Hospital, 1990-1995. METHODS: The histopathological diagnosis of non-neoplastic endoscopic colorectal biopsies was audited using data from histopathology reports. The biopsy diagnosis by the initial reporting pathologist and final diagnosis after additional investigations (endoscopy, radiology, microbiology) or surgery were used to derive sensitivity, specificity, and positive predictive values for categories of disease. RESULTS: Diagnosis was validated for 1067 biopsy sets (43% of those initially assessed). For all biopsies (with or without active inflammation) reports highly suggestive or suggestive of Crohn's disease had a sensitivity of 50%; for ulcerative colitis the comparable figure was 62%. Sensitivity was the same for both diagnoses (74%) in those biopsies with active inflammation. Positive predictive values for highly suggestive diagnoses of ulcerative colitis or Crohn's disease were 100%. In all biopsies the specificity of a histopathological diagnosis of normality was 96%. CONCLUSIONS: These results compare favourably with the other published audits and present an achievable level of performance for non-specialist hospitals with non-specialist histopathology services.

Adolescent↗
PubMed1998

The effect of four interventions on the informational content of histopathology reports of resected colorectal carcinomas.

AIM: To investigate the effect of different interventions on the inclusion of data items in the histopathology reports of resected colorectal carcinomas. STUDY POPULATION: 272 routine histopathology reports on colorectal carcinomas from the department of histopathology, Royal Hallamshire Hospital, Sheffield. METHODS: The presence or absence of 10 specific data items was recorded for each report. The reports were divided into five audit periods. In the initial period reports were generated using free text with no agreed guidelines. In period 2, text guidelines had been issued; in period 3, flow diagram guidelines had been issued; and in periods 4 and 5, template proformas were attached to each specimen request form. RESULTS: All interventions produced some increase in inclusion rate for some features, but only with the introduction of template proformas did these rates approach 100% for all data items. Inclusion rates were 100% for all items in all cases reported using a proforma. In the final audit period 96% of specimens were reported using proformas. CONCLUSIONS: Template proformas produce a high rate of inclusion of data items in reports of colorectal carcinoma resection specimens.

Colorectal Neoplasms↗
PubMed1997

Fractals in pathology.

Many natural objects, including most objects studied in pathology, have complex structural characteristics and the complexity of their structures, for example the degree of branching of vessels or the irregularity of a tumour boundary, remains at a constant level over a wide range of magnifications. These structures also have patterns that repeat themselves at different magnifications, a property known as scaling self-similarity. This has important implications for measurement of parameters such as length and area, since Euclidean measurements of these may be invalid. The fractal system of geometry overcomes the limitations of the Euclidean geometry for such objects and measurement of the fractal dimension gives an index of their space-filling properties. The fractal dimension may be measured using image analysis systems and the box-counting, divider (perimeter-stepping) and pixel dilation methods have all been described in the published literature. Fractal analysis has found applications in the detection of coding of coding regions in DNA and measurement of the space-filling properties of tumours, blood vessels and neurones. Fractal concepts have also been usefully incorporated into models of biological processes, including epithelial cell growth, blood vessel growth, periodontal disease and viral infections.

Bone Diseases↗
PubMed1997

Image analysis of low magnification images of fine needle aspirates of the breast produces useful discrimination between benign and malignant cases.

Fine needle aspirates of the breast (FNAB) (n = 362; 204 malignant, 158 benign), prepared by cytocentrifuge methods and stained by the Papanicolaou technique, were analysed using a semi-automated image analysis system at a low magnification which precluded resolution of nuclear detail. The measured parameters were integrated optical density, fractal textural dimension, number of cellular objects (single cells and contiguous groups of cells), distance between cellular objects (mean, s.d., skewness and kurtosis), area of cellular objects (mean, s.d., skewness, kurtosis) and the nearest neighbour statistic. The cases were divided into a 200-case training set and a 162-case test set. Analysis was performed by logistic regression and the multi-layer Perceptron type of artificial neural network. Logistic regression and the neural network produced similar performances with a sensitivity of 82-83%, specificity 85% and a positive predictive value for a malignant result of 85%. A non-parametric analysis of all the predictor variables showed that all except the mean area of cellular objects and the s.d. of this measurement were significant discriminants (P < 0.05), but most were highly interrelated and this was reflected in the selection of only three predictor variables by forward and backward conditional logistic regression. This study shows that much diagnostic information is present in low power views of FNAB, and that image analysis could form the basis of a semi-automated decision-support aid.

Biopsy, Needle↗
PubMed1997

Does funeral preference influence clinical necropsy request outcome?

Attitudes towards necropsy have been shown to be more favourable amongst those relatives preferring cremation as a method of disposal compared to those with a preference for burial. In a two-year retrospective study, no significant relationship was found between funeral preferences (burial or cremation) and clinical necropsy request outcome when age, sex and religion were taken into account. Potential religious objections to necropsy were infrequent and cremation was found to have become the most popular method of disposing of the dead during a period when local clinical necropsy rates have continued to decline. Funeral preference is unlikely to have been a significant factor in the decline in clinical necropsy rates.

Attitude to Health↗
PubMed1996

Ownership and uses of human tissue: does the Nuffield bioethics report accord with opinion of surgical inpatients?

OBJECTIVE: To compare opinion of surgical inpatients with the conclusions of the report of the Nuffield Council on Bioethics regarding the ownership and uses of human tissue. DESIGN: Survey of results of questionnaires completed by patients. SETTING: Large teaching hospital. SUBJECTS: 384 postoperative adult surgical patients. RESULTS: There was strong support among patients for the use of tissues in medical education, research, and science with the exception of those tissues which may transmit disease to others. Few patients (39; 10%) believed that they retained ownership of tissue removed at surgery. Most believed that the tissue belonged to the hospital (103; 27%), to nobody (103; 27%), or to the laboratory (77; 20%). Most patients had not been given any information about the possible uses of their tissues after removal. CONCLUSIONS: Surgical inpatients seem to endorse the conclusions of the Nuffield report regarding the ownership and uses of human tissue. The recommendations regarding patient information and consent procedures should be implemented at the earliest opportunity.

Adult↗
PubMed1996

Application of the fuzzy ARTMAP neural network model to medical pattern classification tasks.

This paper presents research into the application of the fuzzy ARTMAP neural network model to medical pattern classification tasks. A number of domains, both diagnostic and prognostic, are considered. Each such domain highlights a particularly useful aspect of the model. The first coronary care patient prognosis, demonstrates the ARTMAP voting strategy involving 'pooled' decision-making using a number of networks, each of which has learned a slightly different mapping of input features to pattern classes. The second domain, breast cancer diagnosis, demonstrates the model's symbolic rule extraction capabilities which support the validation and explanation of a network's predictions. The final domain, diagnosis of acute myocardial infarction, demonstrates a novel category pruning technique allowing the performance of a trained network to be altered so as to favour predictions of one class over another (e.g. trading sensitivity for specificity or vice versa). It also introduces a 'cascaded' variant of the voting strategy intended to allow identification of a subset of cases which the network has a very high certainty of classifying correctly.

Artificial Intelligence↗