Differential cancer predisposition in Lynch syndrome: insights from molecular analysis of brain and urinary tract tumors.

Hereditary non-polyposis colorectal carcinoma (Lynch syndrome) is among the most common hereditary cancers in man and a model of cancers arising through deficient DNA mismatch repair (MMR). Lynch syndrome patients are predisposed to different cancers in a non-random fashion, the basis of which is poorly understood. We addressed this issue by determining the molecular profiles for different tumors from a nationwide cohort of Lynch syndrome families (approximately 150 tumors in total). We focused on some less prevalent cancers, affecting the brain (n = 7) and urinary tract (five bladder and five ureter uroepithelial cancers and four kidney adenocarcinomas), and compared their molecular characteristics to those of the most common cancers, colorectal, gastric and endometrial adenocarcinomas, from the same families. Despite origin from verified MMR gene mutation carriers, the frequency of high-level microsatellite instability in tumors varied between high (100-96% for ureter, stomach and colon), intermediate (63-60% for endometrium and bladder) and low (25-0% for kidney and brain). In contrast to gastrointestinal and endometrial carcinomas, active (nuclear) beta-catenin was rare and KRAS mutations were absent in brain and urological tumors. Compared with other tumors, frequent stabilization of p53 protein characterized urinary tract cancers. Promoter methylation of tumor suppressor genes discriminated the tumors in an organ-specific manner. Our findings suggest that different Lynch syndrome tumors develop along different routes. Uroepithelial cancers of the ureter (and bladder to lesser extent) share many characteristics of MMR deficiency-driven tumorigenesis, whereas brain tumors and kidney adenocarcinomas follow separate pathways.

CD44 expression and its relationship with MMP-9, clinicopathological factors and survival in oral squamous cell carcinoma.

We investigated the expression of CD44 and MMP-9 in primary oral squamous cell carcinoma (OSCC) and evaluated their association with each other and clinicopathological factors as well as their prognostic value during long term follow up. Histological samples from 138 OSCC patients were immunohistochemically stained for the expression of CD44 and MMP-9. The staining results were compared with conventional prognostic factors and their impacts to patients' prognosis were also studied with survival analyses. Irregular staining of CD44 in tumour cells was associated with poor tumour differentiation (p=0.003), higher clinical stage (III-IV) (p=0.049), and the presence of T3-4 tumour stage (p=0.03). Strong stromal MMP-9 staining intensity was correlated with poor tumour differentiation (p=0.03). In univariate survival analysis irregular staining of CD44 in tumour cells was related to poor disease free and overall survival (p=0.001 and p<0.001, respectively). In multivariate analysis CD44 staining was a significant independent predictor for overall (p=0.03) and disease free survival (p=0.003). MMP-9 expression showed no statistical significance in survival analyses. Strong stromal staining intensity of MMP-9 correlated with irregular staining of CD44 in tumour cells, but had no prognostic significance in the present cohort. However, irregular staining of CD44 predicted more advanced disease and shortened survival of the patients.

Systematic segregation to mutant mitochondrial DNA and accompanying loss of mitochondrial DNA in human NT2 teratocarcinoma Cybrids.

In this study a well-characterized pathological mutation at nucleotide position 3243 of human mitochondrial DNA was introduced into human rho(0) teratocarcinoma (NT2) cells. In cloned and mixed populations of NT2 cells heteroplasmic for the mutation, mitotic segregation toward increasing levels of mutant mitochondrial DNA always occurred. Rapid segregation was frequently followed by complete loss of mitochondrial DNA. These findings support the idea that pathological mitochondrial DNA mutations are particularly deleterious in specific cell types, which can explain some of the tissue-specific aspects of mitochondrial DNA diseases. Moreover, these findings suggest that mitochondrial DNA depletion may be an important and widespread feature of mitochondrial DNA disease.

Prognostic significance of E-cadherin-catenin complex in epithelial ovarian cancer.

OBJECTIVE: To clarify the prognostic role of E-cadherin and beta- and gamma-catenins, and their relation to CD44 in epithelial ovarian carcinoma. METHODS: The expression of E-cadherin and beta- and gamma-catenins was analysed immunohistochemically in 305 primary epithelial ovarian cancers and 44 metastases, and related to CD44 expression, clinicopathological factors, and the patients' survival. RESULTS: Reduced cell surface expression of E-cadherin, beta-catenin, and gamma-catenin was particularly frequent in serous and endometrioid histological types. Reduced cell surface expression of E-cadherin and beta-catenin was also associated with poor differentiation. Nuclear positivity of beta-catenin was associated with high CD44 expression, endometrioid histology, and local stage of the tumour, whereas nuclear gamma-catenin expression was associated with serous histology and poor differentiation. In the univariate analysis, preserved cell surface beta-catenin expression in the whole study material and nuclear expression of beta- and gamma-catenins in the subgroup of endometrioid ovarian cancers were predictors of better 10 year disease related survival. Preserved cell surface expression of E-cadherin and beta-catenin predicted favourable recurrence-free survival. These statistical significances were not retained in multivariate analysis. CONCLUSIONS: The correlation between nuclear beta-catenin and CD44 indicates that beta-catenin may regulate the transcription of CD44 in epithelial ovarian cancer. E-cadherin-catenin complex members are associated with the prognosis of patients with epithelial ovarian cancer, but these univariate associations were not strong enough to compete for significance with the traditional clinicopathological factors.

Replication errors in benign and malignant tumors from hereditary nonpolyposis colorectal cancer patients.

A replication error (RER) phenotype has been documented both in sporadic colorectal tumors and in tumors from patients with hereditary nonpolyposis colorectal cancer (HNPCC). In the current study 8 of 49 (16%) sporadic colorectal cancers (CRCs) and 25 of 29 (86%) CRCs from HNPCC patients were found to be RER+. All 9 (100%) CRCs from HNPCC patients with germline mutations of the mismatch repair gene MSH2 were found to be RER+, while 16 of 20 CRCs from HNPCC kindreds unlinked or not studied for linkage to MSH2 were RER+. Corresponding analysis in colorectal adenomas revealed that only 1 of 33 (3%) sporadic tumors but 8 of 14 (57%) HNPCC tumors were RER+. Moreover, RER was found in all 6 extracolonic cancers (endometrium, 2; kidney, 1; stomach, 1; duodenum, 1; and ovary, 1) derived from members of HNPCC families. These data suggest the involvement of mismatch repair deficiency in the premalignant stage of tumorigenesis in HNPCC cases, and suggest that mismatch repair genes (MSH2 or others) are defective in the germline of nearly all these patients.

Clinical significance of alpha-catenin, collagen IV, and Ki-67 expression in epithelial ovarian cancer.

PURPOSE: To analyze alpha-catenin and collagen IV expression in epithelial ovarian cancer with special reference to their prognostic significance and correlations with clinical and pathologic characteristics, as well as cell proliferation marker Ki-67. PATIENTS AND METHODS: Alpha-catenin, collagen IV, and Ki-67 expression was immunohistochemically analyzed in paraffin-embedded specimens of 316 patients with epithelial ovarian cancer. RESULTS: Alpha-catenin and collagen IV expression was not interrelated or related to International Federation of Gynecology and Obstetrics (FIGO) stage or proliferation marker Ki-67. Alpha-catenin expression was reduced (< 100%) in 50% of primary tumors. Reduced alpha-catenin and collagen IV expression was directly related to high histologic grade (P < .001). In both univariate and multivariate analyses, Ki-67 proliferation significantly predicted overall survival. In the subset of 86 patients with stage I tumor, a reduced (< 100%) alpha-catenin expression approached statistical significance as a negative prognostic factor (P = .035) and retained its statistical significance in the multivariate analysis (P = .025). The low (< 30%) expression of alpha-catenin (n = 10) was a sign of inferior survival as compared with normal expression in both the univariate (P = .0107) and multivariate analyses (P = .0105). CONCLUSION: Alpha-catenin expression seems to be a useful marker of those FIGO stage I tumors likely to run a less favorable course. The high cell proliferative activity was associated with poor survival. In the future, alpha-catenin and Ki-67 expression should be studied in a large prospective cohort that includes early-stage cancers to select the more aggressive tumors for intense early chemotherapy.

Genotypic stability, segregation and selection in heteroplasmic human cell lines containing np 3243 mutant mtDNA.

The mitochondrial genotype of heteroplasmic human cell lines containing the pathological np 3243 mtDNA mutation, plus or minus its suppressor at np 12300, has been followed over long periods in culture. Cell lines containing various different proportions of mutant mtDNA remained generally at a consistent, average heteroplasmy value over at least 30 wk of culture in nonselective media and exhibited minimal mitotic segregation, with a segregation number comparable with mtDNA copy number (>/=1000). Growth in selective medium of cells at 99% np 3243 mutant mtDNA did, however, allow the isolation of clones with lower levels of the mutation, against a background of massive cell death. As a rare event, cell lines exhibited a sudden and dramatic diversification of heteroplasmy levels, accompanied by a shift in the average heteroplasmy level over a short period (<8 wk), indicating selection. One such episode was associated with a gain of chromosome 9. Analysis of respiratory phenotype and mitochondrial genotype of cell clones from such cultures revealed that stable heteroplasmy values were generally reestablished within a few weeks, in a reproducible but clone-specific fashion. This occurred independently of any straightforward phenotypic selection at the individual cell-clone level. Our findings are consistent with several alternate views of mtDNA organization in mammalian cells. One model that is supported by our data is that mtDNA is found in nucleoids containing many copies of the genome, which can themselves be heteroplasmic, and which are faithfully replicated. We interpret diversification and shifts of heteroplasmy level as resulting from a reorganization of such nucleoids, under nuclear genetic control. Abrupt remodeling of nucleoids in vivo would have major implications for understanding the developmental consequences of heteroplasmy, including mitochondrial disease phenotype and progression.

Is it possible to reduce endoscopy workload using age, alarm symptoms and H. pylori as predictors of peptic ulcer and oesophagogastric cancers?

OBJECTIVES: We examined referrals to oesophagogastroduodenoscopy and the impact of demographic and clinical variables to predict major findings (peptic ulcer, cancer) on oesophagogastroduodenoscopy. METHODS: We collected data on 3669 consecutive patients referred for oesophagogastroduodenoscopy. RESULTS: Dyspeptic and reflux symptoms constituted 80% of oesophagogastroduodenoscopy referrals. A major finding was observed in 419 patients (11.4%). The mean age of cancer patients was 72.7 years (95% confidence interval (CI) 70.0-76.5 years) and that of peptic ulcer patients 62.0 years (95% CI 60.5-63.5 years). Independent risk factors for a major finding were age >50 years (odds ratio (OR) 1.62, 95% CI 1.24-2.10), male sex (OR 1.38, 95% CI 1.11-1.72), ulcer-type pain (OR 2.33, 95% CI 1.80-3.02), weight loss (OR 1.70, 95% CI 1.14-2.53), anaemia (OR 1.82, 95% CI 1.38-2.40), bleeding symptoms (OR 3.27, 95% CI 2.26-4.75) and Helicobacter pylori (OR 2.49, 95% CI 2.00-3.11), whereas reflux symptoms were protective (OR 0.73, 95% CI 0.53-1.00). The area under receiver operating characteristic curve of age over 50 years with alarm symptoms to predict major finding was 0.68 (95% CI 0.65-0.71), which positive H. pylori status increased to 0.71 (95% CI 0.69-0.74). Of the major findings, 87.2% were detected in patients with risk factors. Major findings were detected in 15.1% patients with and 8.1% (p < 0.001) without alarm symptoms. CONCLUSIONS: Dyspeptic and reflux symptoms constitute the majority of oesophagogastroduodenoscopy workload. Discriminative power of alarm symptoms even with positive H. pylori status to detect peptic ulcer or cancer was low. Because of their low cancer risk, reflux and dyspeptic patients younger than 50 years can be treated without oesophagogastroduodenoscopy.

Expression of cyclooxygenase-2 in dysplasia of the stomach and in intestinal-type gastric adenocarcinoma.

PURPOSE: Cyclooxygenase (Cox) is the key enzyme in conversion of arachidonic acid to prostanoids. Two Cox genes have been cloned, and expression of Cox-2 mRNA and protein has been shown to be elevated in several human malignancies and in animal models of carcinogenesis. The purpose of this study was to investigate Cox-2 protein expression in human gastric dysplasias and adenocarcinomas. EXPERIMENTAL DESIGN: Performance of several Cox-2 antibodies was evaluated, after which Cox-2 protein expression was studied in 67 gastric cancer specimens and in eight definitive dysplasias by using immunohistochemistry. RESULTS: Cox-2 positivity was detected in 58% (25/43) of the intestinal-type (well-differentiated) tumors and 6% (1/18) of diffuse-type (poorly differentiated) tumors. Consistent with these data, we detected higher expression of Cox-2 mRNA, protein, and enzymatic activity in well-differentiated gastric cancer cell lines (MKN-28 and MKN-74) when compared with poorly differentiated cell lines (HSC-39 and KATO III). Cox-2 immunoreactivity was localized to the carcinoma cells, but the stroma of the tumors was negative. However, strong Cox-2 positivity was consistently detected in stromal cells at sites of erosions and ulcerations. Furthermore, four of nine (44%) definitive dysplasias of the stomach that showed no evidence of invasion were positive for Cox-2. CONCLUSIONS: Cox-2 is expressed by the neoplastic cells in the intestinal-type gastric adenocarcinoma and by precarcinogenic (dysplastic) lesions leading to this disease.

The mitochondrial inner membrane AAA metalloprotease family in metazoans.

Three metalloproteases belonging to the AAA superfamily (Yme1p, Afg3p and Rca1p) are involved in protein turnover and respiratory chain complex assembly in the yeast inner mitochondrial membrane. Analysis of the completed genome sequences of Caenorhabditis elegans and Drosophila melanogaster indicates that this gene family typically comprises 3-4 members in metazoans. Phylogenetic analysis reveals three main branches represented, respectively, by Saccharomyces cerevisiae YME1, human SPG7 (paraplegin) and S. cerevisiae AFG3 and RCA1. mt-AAA metalloproteases are weak candidates for several previously studied Drosophila mutants. A full elucidation of the cellular and physiological roles of mt-AAA metalloproteases in metazoans will require the creation of targeted mutations.

Foveolar hyperplasia at the gastric cardia: prevalence and associations.

AIMS: In the gastric antrum and body, foveolar hyperplasia is a feature of reactive gastritis resulting from--for example, duodenogastric bile reflux and the use of non-steroidal anti-inflammatory drugs (NSAIDs). The aim of this study was to examine the occurrence and clinical relevance of gastric cardiac foveolar hyperplasia. METHODS: The study population was drawn from a consecutive series of 1698 patients sent for upper gastrointestinal endoscopy. Only cases without chronic gastritis or Barrett's oesophagus were included. The final study population consisted of 307 patients. RESULTS: Foveolar hyperplasia was seen in the gastric cardiac mucosa in 31 (10%) patients with histologically normal stomach mucosa, but none had endoscopically noticeable hyperplastic polyps. Compared with patients without gastric cardiac hyperplasia, those with hyperplasia more often had chronic inflammation and complete intestinal metaplasia in the junctional biopsies (48% v 77% and 9% v 26%, respectively). Logistic regression analysis revealed that chronic cardiac inflammation (odds ratio (OR), 3.2; 95% confidence interval (CI), 1.3 to 7.8) and intestinal metaplasia of the complete type (OR, 2.8; 95% CI, 1.1 to 7.1) were independent risk factors for cardiac foveolar hyperplasia. In univariate analysis, endoscopic erosive oesophagitis (endoscopy positive gastro-oesophageal reflux disease) and the use of NSAIDs were not related to the presence of foveolar hyperplasia. CONCLUSIONS: Foveolar hyperplasia in the gastric cardiac mucosa occurs in patients with histologically normal non-gastritic stomachs and may develop as a consequence of chronic inflammation limited to the gastro-oesophageal junction ("junctitis"). It is not associated directly with endoscopy positive gastro-oesophageal reflux disease or the use of NSAIDs.

Immunohistochemical study of neuroendocrine cells at the gastric cardia mucosa.

BACKGROUND/AIMS: The gastric cardia mucosa is a narrow band of tissue between the oesophagus and the stomach. The physiological role of this tissue is unknown. This study examined the presence and characteristics of neuroendocrine cells at this site. METHODS: Biopsy samples were obtained from across normal appearing squamocolumnar junctions. The cardiac mucosa was defined as the presence of special type mucosa composed of mucous secreting glands in the immediate vicinity of oesophageal squamous epithelium. Biopsy specimens were stained with haematoxylin and eosin, alcian blue (pH 2.5) periodic acid Schiff, and modified Giemsa. The chromogranin A and Fontana-Masson stains were used to identify neuroendocrine cells, which were also stained immunohistochemically for gastrin, serotonin, glucagon, pancreatic polypeptide, somatostatin, and vasoactive intestinal peptide. RESULTS: Chromogranin positive cells were seen in 18 cases with adequate biopsy specimens from the gastric cardia mucosa. These cells were all serotonin positive, but stains for other peptide hormones remained negative. Serotonin positive cells were detected only at the base of foveolae at the periphery of mucous secreting cardiac glands, giving a microscopic appearance resembling that of endocrine cells at the gastric antrum. The presence and numbers of serotonin positive cells did not correlate with chronic inflammation or intestinal metaplasia of the cardiac mucosa. These cells were seen both in Helicobacter pylori positive and negative patients. CONCLUSIONS: Serotonin positive cells appear to be the sole neuroendocrine cell type at the gastric cardia mucosa. These cells may have a role in regulating the physiology of the gastric cardia mucosa and the lower oesophageal sphincter.

Pulmonary adiaspiromycosis in a two year old girl.

A case of disseminated bilateral pulmonary adiaspiromycosis is reported in a two year old Finnish girl. She recovered from this rare infection after treatment with amphotericin B. She is the first human case of adiaspiromycosis in Scandinavia and she is the youngest child with this disease reported so far. Electron microscopy showed that the three layers of the spore wall were not typical; rather, there seemed to be a gradual transition between the main wall zones, which may be split into an indefinite number of thin layers. Varying numbers and thicknesses were seen with different staining methods, and in different spores. Diagnosis relies on recognition of the fungus in a pulmonary biopsy specimen, because there are no reliable serological tests and culture of the fungus is time consuming and not always successful. It was thought that this patient had become infected as a result of contact with soil dust containing the spores in the yard surrounding her home, and as a result of her mother's work in a large garden shop.

Nuclear beta catenin expression is related to unfavourable outcome in oropharyngeal and hypopharyngeal squamous cell carcinoma.

AIMS: To investigate the expression of alpha, beta, and gamma catenins in oropharyngeal and hypopharyngeal squamous cell carcinoma and their relations to each other, as well as to clinical data, tumour differentiation, and prognosis. METHODS: Primary tumours for analysis were obtained from 138 patients diagnosed with squamous cell carcinoma of the oropharynx or hypopharynx between 1975 and 1998 in eastern Finland. Immunohistochemistry was used to evaluate the expression of alpha, beta, and gamma catenins. The expression patterns of all catenins were related to clinical data and survival. RESULTS: The expression patterns of all three catenins were significantly interrelated. Reduced gamma catenin expression was significantly associated with poor histological differentiation. No association was found between alpha or beta catenin expression and clinicopathological characteristics. In univariate analysis, patients whose tumours had nuclear beta catenin expression had shorter overall survival than patients with no nuclear expression. In Cox multivariate analysis, nuclear beta catenin expression, tumour status (T class), and Karnofsky performance index were independent prognostic factors of overall survival. CONCLUSIONS: Reduced expression of gamma catenin is associated with dedifferentiation in primary squamous cell carcinoma of the oropharynx and hypopharynx. The fact that nuclear beta catenin expression independently predicts short overall survival suggests that it might be a valuable prognostic marker in pharyngeal squamous cell carcinoma.

Interpretation guidelines of DNA histograms from tissue sections of breast cancer.

BACKGROUND: Evaluation of nuclear DNA staining intensity from histological breast cancer sections has not always been accepted, because of the difficulties in interpreting the histograms. One reason for this is the lack of evidence based interpretation guidelines. MATERIALS AND METHODS: The DNA staining intensity of 140 breast cancer samples was measured with flow cytometry (FCM) and image cytometry (ICM). The methods were compared by using grading efficiency (GE). RESULT: First, the ICM histograms were evaluated with a computer assisted image cytometry system using different cut off points for aneuploidy. The GE results varied from 67.9-76.4%. Subjective interpretation and evaluation according two previously published interpretation methods did not improve the GE. Secondly, we excluded histograms which showed clearly different cell clones in FCM and ICM. The GE of remaining histograms was 77.9%. Comparison of these histograms allowed formulation of interpretation guidelines which improved the GE to 85.3%. CONCLUSIONS: This study suggests that efficient interpretation guidelines of section-based DNA histograms can be created.

Gastric metaplasia and chronic inflammation at the duodenal bulb mucosa.

BACKGROUND: Chronic inflammation and gastric metaplasia are often observed in biopsy specimens from the duodenal bulb of Heliobacter pylori positive patients with duodenal ulcer disease (DU). AIMS: We set out to investigate the prevalence of these lesions and their associations with other gastric and duodenal histopathological lesions. PATIENTS: A total of 1255 consecutive patients who underwent upper gastrointestinal endoscopy were recruited into the present study. METHODS: Two biopsy specimens were obtained from each of the following sites: duodenal bulb, gastric antrum, gastric body, and distal to the superior duodenal angle. These specimens were stained with hematoxylin-eosin, alcian blue periodic acid Schiff (pH 2.5) and modified Giemsa (Heliobacter pylori infection was determined only by histology). RESULTS: The mean age of the study population was 57 years, and male:female ratio 1:1.6. Overall, 235 (19%) had gastric metaplasia and/or chronic inflammation in the duodenal bulb mucosa, and H. pylori organisms could be found in 17 (1%). In univariate analyses, gastric metaplasia and/or chronic duodenal bulb inflammation positively associated with male sex (p = 0.046), Heliobacter pylori-positive chronic gastritis (p = 0.033), villous atrophy of distal duodenal mucosa, i.e., coeliac disease (p < 0.001), duodenal ulcer (p < 0.001), and duodenal bulb deformity and scarring in endoscopy (p < 0.001), but not with age (p = 0.7) nor use of nonsteroidal anti-inflammatory drugs (p = 0.055). Multivariate analysis revealed that independent risk factors for gastric metaplasia and chronic inflammation in duodenal bulb were duodenal Heliobacter pylori infection (odds ratio 1.6, 95% confidence interval CI 1.1-2.1), and villous atrophy of the distal duodenal mucosa (odds ratio 12.7, 95% CI 4.4-36.5), while chronic atrophic gastritis was protective against them (odds ratio 0.5, 95% CI 0.3-0.8). CONCLUSIONS: In addition to Heliobacter pylori infection, duodenal bulb gastric metaplasia and chronic inflammation may result from predisposition to toxic dietary components in gluten-sensitive subjects.

Segmentation of digital signals based on estimated compression ratio.

We have studied the problem of approximating a digital signal with a suitable continuous broken line. We use the approximative broken line for further analysis of the signal as detection of peaks, waves, and other structural features. We can also save considerable amount of storage space with an approximation that does not lose too much significant information about the original signal. Our work is based on examining different distance metrics and different segmentation methods with respect to the remaining residual error in the resulting approximation. The aim of the work has been to develop a method that can perform segmentation with an acceptable amount of residual error without a need to define a large set of parameters that control the segmentation process. Our contribution is to examine the effect of the estimated compression ratio of the resulting approximation and finding an estimate of this compression ratio. We first define a target in the form of a compression ratio of the resulting approximation and then by applying our method, try to find a suitable threshold parameter to achieve this target. We have tested our method with electrocardiogram (ECG) signals and the compression ratio of the approximation has been found to be a suitable target to control the segmentation process.

Modifying an expert system construction to pattern recognition solution.

Medical expert systems are a successful field of applied artificial intelligence. We constructed an otoneurological expert system in our previous research, and in this study we consider its reasoning method. The reasoning process can be described as a modified nearest neighbour solution derived from pattern recognition. The expert system was tested and functions reliably.

Latency estimation of auditory brainstem response by neural networks.

In the clinical application of auditory brainstem responses (ABRs), the latencies of five to seven main peaks are extremely important parameters for diagnosis. In practice, the latencies have mainly been done by manual measurement so far. In recent years, some new techniques have been developed involving automatic computer recognition. Computer recognition is difficult, however, since some peaks are complicated and vary a lot individually. In this paper, we introduce an artificial neural network method for ABR research. The detection of ABR is performed by using artificial neural networks. A proper bandpass filter is designed for peak extraction. Moreover, a new approach to estimate the latencies of the peaks by artificial neural networks is presented. The neural networks are studied in relation to the selection of model, number of layers and number of neurons in each hidden layer. Experimental results are described showing that artificial neural networks are a promising method in the study of ABR.

Treatment of missing data values in a neural network based decision support system for acute abdominal pain.

In this study different substitution methods for the replacement of missing data values were inspected for the use of these cases in a neural network based decision support system for acute appendicitis. The leucocyte count had the greatest number of missing values and was used in the analyses. Four different methods were compared: substituting means, random values, nearest neighbour and a neural network. There were great differences in the substituted leucocyte count values between different methods and only nearest neighbour and neural network agreed about most of the cases. The importance of the substitution method for the final diagnostic classification of the patients by the neural network based decision support system was found to be small.