727 research outputs found
Testing for Serial Correlation, Spatial Autocorrelation and Random Effects
This paper considers a spatial panel data regression model with serial correlation on each spatial unit over time as well as spatial dependence between the spatial units at each point in time. In addition, the model allows for heterogeneity across the spatial units using random effects. The paper then derives several Lagrange Multiplier tests for this panel data regression model including a joint test for serial correlation, spatial autocorrelation and random effects. These tests draw upon two strands of earlier work. The first is the LM tests for the spatial error correlation model discussed in Anselin and Bera (1998) and in the panel data context by Baltagi, Song and Koh (2003). The second is the LM tests for the error component panel data model with serial correlation derived by Baltagi and Li (1995). Hence the joint LM test derived in this paper encompasses those derived in both strands of earlier works. In fact, in the context of our general model, the earlier LM tests become marginal LM tests that ignore either serial correlation over time or spatial error correlation. The paper then derives conditional LM and LR tests that do not ignore these correlations and contrast them with their marginal LM and LR counterparts. The small sample performance of these tests is investigated using Monte Carlo experiments. As expected, ignoring any correlation when it is significant can lead to misleading inferencepanel data, spatial correlation
Clinical Characteristics and Treatment Outcomes of Mycobacterium kansasii Lung Disease in Korea
*These authors contributed equally to this work. ∙The authors have no financial conflicts of interest. Purpose: While Mycobacterium kansasii is a common cause of nontuberculous mycobacterial (NTM) lung disease in many developed countries, M. kansasii is infrequently isolated in Korea. We investigated the clinical and radiological features and treatment outcomes of M. kansasii lung disease in Korea retrospectively. Materials and Methods: We identified 41 patients with M. kansasii lung disease who met the diagnostic criteria for NTM lung disease in two tertiary referral hospitals in Seoul, Korea, between January 1998 and December 2007. Results: Their median age was 63 years [interquartile range (IQR) 51-75 years] and 33 (81%) were men. Twenty-three patients (56%) were smokers and 13 patients (32%) had previous pulmonary tuberculosis. The most common radiographic findings were nodules (n = 22, 54%) and consolidation (n = 22, 54%). Cavitation was present in 13 patients (32%). Thirty-one patients (76%) were treated with isoniazid, rifampin, and ethambutol. The median treatment duration was 16 months (IQR 9-18 months). The negative conversion rate after 12 months of treatment was 95%. Conclusion: Clinicians should be aware of the various radiographic manifestations of M. kansasii lung disease. With appropriate treatment, these patients have a good prognosis
Report of a Korean Patient with Cystic Fibrosis, Carrying Q98R and Q220X Mutations in the CFTR Gene
Although cystic fibrosis (CF) is one of the most frequently seen autosomal-recessive disorders in Caucasians, it is extremely rare in the Korean population. Recently, a 15-yr-old Korean boy was admitted to our hospital complaining of coughing, sputum, and exertional dyspnea. Chest radiographs and computed tomographic chest and paranasal sinus scans revealed diffuse bronchiectasis and pansinusitis. Pulmonary function tests revealed severe obstructive impairment. The average sweat chloride concentrations on both of the patients' forearms were 63.0 mM/L (reference limit: <40 mM/L). Upon mutation analysis, two different mutations (Q98R and Q220X) were identified in the cystic fibrosis transmembrane conductance regulator gene, both of which had been previously detected in CF patients, one from France and the other from England. As CF is quite rare in Korea, the diagnosis of CF in this patient might be delayed. Therefore, we recommend that a diagnosis of CF should be suspected in patients exhibiting unexplained chronic respiratory symptoms
Successful Treatment of Mycobacterium celatum Pulmonary Disease in an Immunocompetent Patient Using Antimicobacterial Chemotherapy and Combined Pulmonary Resection
Mycobacterium celatum is a nontuberculous mycobacterium that rarely causes pulmonary disease in immunocompetent subjects. We describe the successful treatment of M. celatum lung disease with antimicobacterial chemotherapy and combined pulmonary resection. A 33-year-old woman was referred to our hospital with a 3-month history of a productive cough. Her medical history included pulmonary tuberculosis 14 years earlier. Her chest X-ray revealed a large cavitary lesion in the left upper lobe. The sputum smear was positive for acid-fast bacilli, and M. celatum was subsequently identified in more than three sputum cultures, using molecular methods. After 1 year of therapy with clarithromycin, ethambutol, and ciprofloxacin, the patient underwent a pulmonary resection for a persistent cavitary lesion. The patient was considered cured after receiving 12 months of postoperative antimycobacterial chemotherapy. There has been no recurrence of disease for 18 months after treatment completion. In summary, M. celatum is an infrequent cause of potentially treatable pulmonary disease in immunocompetent subjects. Patients with M. celatum pulmonary disease who can tolerate resectional surgery might be considered for surgery, especially in cases of persistent cavitary lesions despite antimycobacterial chemotherapy
Nontuberculous mycobacterial lung disease: ecology, microbiology, pathogenesis, and antibiotic resistance mechanisms
The incidence and prevalence of lung disease caused by nontuberculous mycobacteria (NTM) are increasing worldwide. Environmental sources of NTM include water, soil, and dust, and the acquisition of NTM infection depends on sufficient environmental exposure, host susceptibility factors such as immunocompromised status or cystic fibrosis, and mycobacterial virulence factors. The development of molecular methods has allowed the characterization of new species and the identification of NTM to the precise species and subspecies levels. Mycobacterium avium complex, M. abscessus complex, and M. kansasii are the most frequently identified organisms causing lung disease. Susceptibility to disease is incompletely understood, and thus, it is unclear what preventative measures may be effective. Additionally, NTM have natural and acquired resistance mechanisms to several antibiotics. Better understanding of the ecology, pathogenesis, and mycobacterial genetics and antibiotic resistance mechanisms is essential for preventing NTM infections and developing new regimens for effective treatment
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