Fuzzy theory approach for temporal model-based diagnosis: An application to medical domains

OBJECTIVE

The aim of this work is to provide a theoretical framework which is sufficiently expressive to describe temporal evolution of diseases, and also to propose a diagnostic process for building explanations of patient's observed temporal evolution based on these disease descriptions.

BACKGROUND

Model-based diagnosis (MBD) tackles the problem of troubleshooting systems by starting from a description of their structure and function (or behaviour). It is in this area where the use of deep causal models, as part of MBD systems, has shown its greater efficiency over classical rule based systems. From its beginnings, the temporal dimension was considered as an important component in MBD, since it makes it possible to define the dynamic behaviour. Several approaches have been proposed to represent time in MBD, enabling the representation of temporal concepts and relations, as well as the use of temporal reasoning mechanisms.

METHODOLOGY

We first propose a temporal behavioural model (TBM), which allows us to capture the dynamics underlying temporal evolution of diseases and to include contextual information. Contextual information is required to model how contextual factors change the temporal evolution of diseases. The temporal component is modelled by fuzzy temporal constraints networks (FTCN), which makes the representation of quantitative and qualitative imprecise temporal information possible. We also provide a diagnostic process, which is based on a temporal adaptation of classical cover and differentiate method.

RESULTS

The TBM and diagnostic process proposed provides a unique framework which addresses three problems not dealt with together so far: (a) the inclusion of contextual information, (b) the expressivity of the solution provided, and (c) the evaluation of the diagnostic hypotheses. This proposal demonstrates that the FTCN formalism provides mechanisms sufficiently expressive to cope with the intrinsic imprecision in the description of diseases' temporal evolution. The explanation generated provides the user with a complete picture of the temporal evolution of diseases and its causal links, thus allowing the appearance of repeated instances of the same disease through time. Mechanisms are provided which evaluate the credibility of alternative hypotheses, based on possibility theory. A prototype is presented along with a knowledge acquisition tool that guides medical experts in the model building process.

CONCLUSIONS

In this paper, we propose a model that tightly couples methods from MBD area with constraint-based temporal reasoning techniques. The proposed model allows us to model complex contextual relationships in a compact way as well as providing solutions expressive enough to be used for decision support purposes. The solution provided conforms a causal network entailing the abnormal observations, including pathophysiological and etiological states. Furthermore, different instances of the same diagnostic hypotheses, located at different time instants, are also possible in the final solution. Finally, we provide an analysis of related and future works.

Persistence of circulating tumour cells after treatment predicts clinical outcome in breast cancer patients

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Background: The hematogenous distant metastasis is the leading cause of cancer death. This process involves the passage through the blood and lymphatic circulation of circulating tumor cells (CTC) with metastatic properties. Thus, the early detection of such cells has important implication for cancer prognosis, monitoring of treatment and to predict clinical outcome. We present the results that showed that CTC are prognostic factor after chemotherapy independently of treatment. Methods: A total of 59 patients with breast cancer were enrolled in this study between April 2000 and December 2002. The median follow-up was 50 months. All patients received chemotherapy as first line treatment. Results of this work included CTC detection one month after of the end of chemotherapy. After informed consent, 10ml of heparinized peripheral blood was collected from patients. For enrichment of CTC we use the Carcinoma Cell Enrichment and Detection kit using MACS technology (Miltenyi Biotec). After enrichment of epithelial tumor cells immunomagnetic labeled with a multi- cytokeratin-specific antibody, the positive cells were detected by immunocytochemical staining with alkaline phosphatase substrate. Results: Analysis of CTC after chemotherapy: Circulating tumor cells were detected in 32 patients (54.23%). A mean number of cells were detected 3.7 (SD 13.9; range 1–105).The number of CTC was correlationed with progression free of disease (PFS) and overall survival (OS). In the univariate Cox proportional hazard regression analysis number cells were significantly associated with OS (p = 0.020) and PFS (p = 0.008). In the multivariate Cox proportional hazard regression analysis, number cells admit borderline statically significance with PFS (p = 0.052) and OS (p = 0.071). Conclusions: Our results suggest that the persistence of CTC after the treatment predicts clinical outcome and therefore the detection of CTC in breast cancer patients might allow monitoring of chemotherapy response.

No significant financial relationships to disclose.

Evaluation of the triangular fibrocartilage in cadaveric wrists by means of arthrography, magnetic resonance (MR) imaging, and MR arthrography

PURPOSE

To evaluate the diagnostic accuracy of arthrography, magnetic resonance (MR) imaging, and MR arthrography in the detection and localization of defects of the triangular fibrocartilage (TFC) in cadaveric wrists, using arthroscopy as a reference standard.

MATERIAL AND METHODS

Twenty-four specimen wrists were evaluated. The different imaging modalities were blinded to reviewers and were interpreted independently. A classification of TFC defects was used for the evaluation of images in the different imaging modalities, thus permitting a more uniform correlation. Two cases were excluded from the MR imaging study because of poor image quality. Contingency tables with the chi-square test and Fisher's exact test were used for statistical analysis.

RESULTS

Defects of the TFC were identified in 17 of the 24 specimen wrists by means of arthroscopy, and 16 defects were observed when arthrography was carried out. With MR imaging 14 defects of the TFC were detected in the 22 specimen wrists evaluated, and with MR arthrography 16 defects were observed. Most defects were central or combined (two or more defects). In comparison to arthroscopy, the accepted diagnostic gold standard, the following results were found for arthrography in the detection of TFC defects: sensitivity 95%, specificity 100%, and accuracy 95% (P<0.0005); for MR imaging: sensitivity 86%, specificity 85%, and accuracy 70% (P<0.002); and for MR arthrography: sensitivity 100%, specificity 85%, and accuracy 95% (P<0.0005).

CONCLUSION

The results of the study seem to indicate that both arthrography and MR arthrography have high accuracy, and either would be useful for evaluation of the TFC. The combined approach using both techniques would have a very high accuracy equivalent to that resulting from arthroscopy.

Burow's grafts in the facial region

BACKGROUND

Full-thickness skin grafts are an important tissue source for reconstructive surgery. Burow's grafts are full-thickness skin grafts that use adjacent lax skin as the donor site. This technique has also been referred to as island grafts, dog-ear grafts or adjacent-tissue skin grafts.

OBJECTIVE

The objective was to describe the technique of Burow's grafts for reconstruction of facial defects taking account of its benefits and limitations.

METHODS

The operative technique is simple: after a circular excision of the cutaneous lesion, we enlarged the excision line (towards one or both sides of the defect) following the relaxed tension lines. We created a secondary triangular defect by excising skin that is then used for the graft (as donor site). After adequate undermining, we proceeded to direct linear closure of this secondary defect. Finally, the graft was placed and sutured in the remaining defect.

RESULTS

The proximity of the donor site provides an excellent tissue match because colour, hair density, texture, sebaceous features and thickness are similar to the recipient site. A good cosmetic result is therefore ensured.

CONCLUSION

Burow's grafts can be a good choice for reconstruction of extensive facial surgical defects because of aesthetic results. In addition, it is a simple technique that can be performed in one sole surgical act, with local anaesthesia and without changing the operative site.

The spectrum of mutations and molecular pathogenesis of hemophilia A in 181 Portuguese patients

Disease-causing alterations within the F8 gene were identified in 177 hemophilia A families of Portuguese origin. The spectrum of non-inversion F8 mutations in 101 families included 67 different alterations, namely: 36 missense, 8 nonsense and 4 splice site mutations, as well as 19 insertions/deletions. Thirty-four of these mutations are novel. Molecular modeling allowed prediction of the conformational changes introduced by selected amino acid substitutions and their correlation with the patients' phenotypes. The relatively frequent, population-specific, missense mutations together with de novo alterations can lead to significant differences in the spectrum of F8 mutations among different populations.

Epidermolysis bullosa acquisita: diagnosis by fluorescence overlay antigen mapping and clinical response to high-dose intravenous immunoglobulin

Epidermolysis bullosa acquisita (EBA) is a chronic, subepidermal blistering disease characterized by the presence of autoantibodies to type VII collagen, located below the lamina densa of the basement membrane zone (BMZ). There is a large clinical and histological overlap between EBA and other subepidermal autoimmune bullous diseases, therefore, complex immunological techniques are required to make an accurate diagnosis. Therapy of EBA is also a difficult issue. Most patients do not respond to several common immunosuppressive agents. We describe a patient who has shown a good response to high-dose intravenous immunoglobulin therapy.

Supplementary Motor Area Encodes Reward Expectancy in Eye-Movement Tasks

Neural activity signifying the expectation of reward has been found recently in many parts of the brain, including midbrain and cortical structures. These signals can facilitate goal-directed behavior or the learning of new skills based on reinforcements. Here we show that neurons in the supplementary motor area (SMA), an area concerned with movements of the body and limbs, also carry a reward expectancy signal in the postsaccadic period of oculomotor tasks. While the monkeys performed blocks of memory-guided and object-based saccades, the neurons discharged a burst after a ∼200-ms delay following the target-acquiring saccade in the memory task but often fired concurrently with the target-acquiring saccade in the object task. The hypothesis that this postsaccadic bursting activity reflects the expectation of a reward was tested with a series of manipulations to the memory-guided saccade task. It was found that although the timing of the bursting activity corresponds to a visual feedback stimulus, the visual feedback is not required for the neurons to discharge a burst. Second, blocks of no-reward trials reveal an extinction of the bursting activity as the monkeys come to understand that they would not be rewarded for properly generated saccades. Finally, the delivery of unexpected rewards confirmed that in many of the neurons, the activity is not related to a motor plan to acquire the reward (e.g., licking). Thus we conclude that reward expectancy is represented by the activity of SMA neurons, even in the context of an oculomotor task. These results suggest that the reward expectancy signal is broadcast over a large extent of motor cortex, and may facilitate the learning of new, coordinated behavior between different body parts.

Iron Deficiency—An Underrecognized Problem in Nonanemic and Erythrocytic Kidney Transplant Recipients: Risks and Effects of ACEI and of Iron Treatment

The state of iron deposits in long-term kidney graft recipients is not well-known. Angiotensin enzyme inhibitors (ACEIs) reduce hematocrit levels in patients with posttransplant erythrocytosis (PTE), but their action on iron deposits has not been sufficiently evaluated. We designed this study to investigate the prevalence of iron deficiency among patients without anemia, the efficacy of ACEI treatment and its influence on iron deposits, and the risks of iron treatment in patients with symptomatic iron deficiency but no anemia. One hundred thirty eight patients were included if they had a kidney transplant for more than a year, with good renal function, with no anemia, and with neither iron nor rHuEpo, ARA, or ACEI treatment. One hundred seventeen had a normal Ht (group 1) and 21 had PTE (group 2). Iron deficiency was found in 73 (62.4%) group 1 patients and in 10 (47%) group 2 patients. Two group 1 patients with symptoms of iron deficiency were treated with oral iron. Their symptoms disappeared, but one developed PTE. Enalapril treatment decreased Ht levels in PTE but not in control patients. Furthermore, this drug increased iron deposits in PTE and controls with a baseline iron deficiency. We conclude that there is a high prevalence of iron deficiency in long-term transplanted patients without anemia. Furthermore, iron treatment must be carefully administered because of the risk of PTE. Enalapril treatment decreased Ht levels in PTE but not in control patients and increased iron deposits in patients with baseline iron deficiency.

Influence of Angiotensin-Converting Enzyme Polymorphism Gene, IGF-1, and Other Factors in the Response Rate of Hematocrit to Enalapril Treatment in Patients With Posttransplant Erythrocytosis

A significant relationship between hematocrit values and serum parameters such as the insulin like growth factor (IGF-1) and calcium was observed in patients with posttransplant erythrocytosis (PTE). Since angiotensin-converting enzyme inhibitors (ACEI) decrease hematocrit (Ht) levels in these patients, ACE genotype should play an important role. We designed this study to investigate whether ACE genotype or baseline concentrations of IGF-1, IGF-blood binding protein 3 (BP3), growth hormone (GH), or Ca influenced the response of Ht to ACEI treatment. Twenty-one kidney graft recipients with PTE were treated with enalapril (2.5 to 5 mg/d) for 1 year. IGF-1, BP3, GH, Ca, and Ht were determined before as well as 15, 30, 90, 180, and 365 days after enalapril treatment. ACE polymorphism was also determined. Enalapril treatment significantly decreased Ht levels. Only IGF-1 baseline levels showed a positive correlation to the decreased Ht (P < .025). ACE genotype as determined in 18 patients, showed no correlation with the response to enalapril. Patients with ACE genotype II showed a tendency to an earlier display of PTE. We conclude that low doses of enalapril decrease Ht levels in PTE patients; that PTE begins earlier in patients with II ACE genotype; and that only IGF-1 baseline levels influence the Ht decrease after treatment. These observations suggest that ACEI decrease the Ht via an inhibitory effect on IGF-1, which has a stimulary effect on erythropoiesis.

Effects of ornithine on neutrophil (PMN) free amino acid and ?-keto acid profiles and immune functions in vitro

The objective of this study was to determine the effects of ornithine on polymorphonuclear leucocyte (PMN) free amino- and alpha-keto acid profiles, superoxide anion (O2-) generation, hydrogen peroxide (H2O2) formation and released myeloperoxidase activity (MPO). Exogenous ornithine significantly increased PMN asparagine, glutamine, aspartate, glutamate, arginine, citrulline, alanine, alpha-ketoglutarate and pyruvate as intracellular ornithine increased. Concerning PMN immune function markers ornithine increased H2O2-generation and MPO activity while O2- -formation was decreased. We believe therefore that ornithine is important for affecting PMN "susceptible free amino- and alpha-keto acid pool" although the mechanisms are not yet clear. This may be one of the determinants in PMN nutrition considerably influencing and modulating PMN host defense capability.