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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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Department: search.filters.department.Department of MathematicsSubject: search.filters.subject.Medicine

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    Segregation indices for disease clustering
    (Wiley-Blackwell, 2014) Department of Mathematics; Department of Mathematics; Ceyhan, Elvan; Faculty Member; College of Sciences; N/A
    Spatial clustering has important implications in various fields. In particular, disease clustering is of major public concern in epidemiology. In this article, we propose the use of two distance-based segregation indices to test the significance of disease clustering among subjects whose locations are from a homogeneous or an inhomogeneous population. We derive the asymptotic distributions of the segregation indices and compare them with other distance-based disease clustering tests in terms of empirical size and power by extensive Monte Carlo simulations. The null pattern we consider is the random labeling (RL) of cases and controls to the given locations. Along this line, we investigate the sensitivity of the size of these tests to the underlying background pattern (e.g., clustered or homogenous) on which the RL is applied, the level of clustering and number of clusters, or to differences in relative abundances of the classes. We demonstrate that differences in relative abundances have the highest influence on the empirical sizes of the tests. We also propose various non-RL patterns as alternatives to the RL pattern and assess the empirical power performances of the tests under these alternatives. We observe that the empirical size of one of the indices is more robust to the differences in relative abundances, and this index performs comparable with the best performers in literature in terms of power. We illustrate the methods on two real-life examples from epidemiology. Copyright (c) 2013 John Wiley & Sons, Ltd.
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    Frequency of nerve root sleeve cysts in autosomal dominant polycystic kidney disease
    (Galenos Publ House, 2016) Asik, Murat; Tufan, Fatih; Akpinar, Timur Selcuk; Akalin, Nilgul; Tunc, Necmeddin; Hasiloglu, Zehra Isik; Altiparmak, Mehmet Riza; Ecder, Tevfik; Albayram, Sait; Department of Mathematics; Department of Mathematics; Ceyhan, Elvan; Faculty Member; College of Sciences; N/A
    Background: There is sporadic data about the occurrence of spinal meningeal cysts in patients with autosomal dominant polycystic kidney disease ( ADPKD). We suggest that there is a relationship with the frequency and size of spinal meningeal cysts and headache, intracranial aneurysms, and cerebrospinal fluid leakage in patients with ADPKD. Aim: To investigate the relationship with spinal meningeal cyst, cerebrospinal fluid leakage, and headache in patients with ADPKD. Study Design: Cross-sectional study. Methods: We enrolled 50 patients with ADPKD and 37 healthy volunteers. This cross-sectional study included patients with ADPKD and matched healthy volunteers. Magnetic resonance imaging myelography was performed using the 3D-T2 HASTE technique in an MRI scanner. We questioned our subjects regarding presence of headache and evaluated headache severity using a visual analog scale. The relationship between the number and size of spinal men-ingeal cysts with headache, intracranial aneurysms, and liver cysts was also investigated. Results: Spinal meningeal cysts were more numerous and larger in patients than in controls (14.8 +/- 11.6 vs. 6.4 +/- 4.6 cysts respectively, p<0.001, 68.3 +/- 49.3 vs. 25.4 +/- 20.1 mm, p<0.001, respectively). Spinal cyst number and size were similar in APDKD patients with or without intracranial aneurysms. Headache score was correlated with the size and number of spinal meningeal cysts. This was valid only in patients with ADPKD. Conclusion: Abnormality involving the vessel wall in ADPKD may explain the increased number of spinal meningeal cysts in ADPKD. Moreover, leakage of cerebrospinal fluid secondary to spinal meningeal cyst may be responsible for recurrent severe headache by causing spontaneous intracranial hypotension in these patients.