CT Quantitative Analysis and Its Relationship with Clinical Features for Assessing the Severity of Patients with COVID-19

Objective

To investigate the value of initial CT quantitative analysis of ground-glass opacity (GGO), consolidation, and total lesion volume and its relationship with clinical features for assessing the severity of coronavirus disease 2019 (COVID-19).

Materials and Methods

A total of 84 patients with COVID-19 were retrospectively reviewed from January 23, 2020 to February 19, 2020. Patients were divided into two groups: severe group (n = 23) and non-severe group (n = 61). Clinical symptoms, laboratory data, and CT findings on admission were analyzed. CT quantitative parameters, including GGO, consolidation, total lesion score, percentage GGO, and percentage consolidation (both relative to total lesion volume) were calculated. Relationships between the CT findings and laboratory data were estimated. Finally, a discrimination model was established to assess the severity of COVID-19.

Results

Patients in the severe group had higher baseline neutrophil percentage, increased high-sensitivity C-reactive protein (hs-CRP) and procalcitonin levels, and lower baseline lymphocyte count and lymphocyte percentage (p < 0.001). The severe group also had higher GGO score (p < 0.001), consolidation score (p < 0.001), total lesion score (p < 0.001), and percentage consolidation (p = 0.002), but had a lower percentage GGO (p = 0.008). These CT quantitative parameters were significantly correlated with laboratory inflammatory marker levels, including neutrophil percentage, lymphocyte count, lymphocyte percentage, hs-CRP level, and procalcitonin level (p < 0.05). The total lesion score demonstrated the best performance when the data cut-off was 8.2%. Furthermore, the area under the curve, sensitivity, and specificity were 93.8% (confidence interval [CI]: 86.8–100%), 91.3% (CI: 69.6–100%), and 91.8% (CI: 23.0–98.4%), respectively.

Conclusion

CT quantitative parameters showed strong correlations with laboratory inflammatory markers, suggesting that CT quantitative analysis might be an effective and important method for assessing the severity of COVID-19, and may provide additional guidance for planning clinical treatment strategies.

CT imaging changes of corona virus disease 2019(COVID-19): a multi-center study in Southwest China

BACKGROUND

Since the first case of a coronavirus disease 2019 (COVID-19) infection pneumonia was detected in Wuhan, China, a series of confirmed cases of the COVID-19 were found in Southwest China. The aim of this study was to describe the imaging manifestations of hospitalized patients with confirmed COVID-19 infection in southwest China.

METHODS

In this retrospective study, data were collected from 131 patients with confirmed coronavirus disease 2019 (COVID-19) from 3 Chinese hospitals. Their common clinical manifestations, as well as characteristics and evolvement features of chest CT images, were analyzed.

RESULTS

A total of 100 (76%) patients had a history of close contact with people living in Wuhan, Hubei. The clinical manifestations of COVID-19 included cough, fever. Most of the lesions identified in chest CT images were multiple lesions of bilateral lungs, lesions were more localized in the peripheral lung, 109 (83%) patients had more than two lobes involved, 20 (15%) patients presented with patchy ground glass opacities, patchy ground glass opacities and consolidation of lesions co-existing in 61 (47%) cases. Complications such as pleural thickening, hydrothorax, pericardial effusion, and enlarged mediastinal lymph nodes were detected but only in rare cases. For the follow-up chest CT examinations (91 cases), We found 66 (73%) cases changed very quickly, with an average of 3.5 days, 25 cases (27%) presented absorbed lesions, progression was observed in 41 cases (46%), 25 (27%) cases showed no significant changes.

CONCLUSION

Chest CT plays an important role in diagnosing COVID-19. The imaging pattern of multifocal peripheral ground glass or mixed consolidation is highly suspicious of COVID-19, that can quickly change over a short period of time.

Knowledge, Attitude and Preventive Practice on Dementia Care among Primary Health Professionals in Macao

The Macao Dementia Policy was recognized by Alzheimer Disease International as the 27th globally and one of the highest stage 5 to develop dementia friendly community and primary health professionals are in a pivotal position to enhance community-based dementia prevention and care quality. This study aimed to investigate the knowledge, attitude and preventive practice on dementia care among primary health professionals in Macao. A specially designed 30-item questionnaire was developed and validated for the study. The Content Validity Index (CVI) and Cronbach's α of the questionnaire were 0.973 and 0.808. The questionnaires were distributed to all 375 primary health professionals from 8 Health Centers throughout Macao and 234 valid questionnaires (62.4%) were returned. The score for dementia care knowledge was 87.02±14.01; attitude was 69.52±5.83; preventive practice was 77.88±13.18, of which doctors (79.89±13.77) was significantly higher (t=2.29, p=0.023) than nurses (75.91±12.33). There were positive relationships between preventive practice and attitude (r=0.163, p=0.014), and age (r=0.212, p=0.002), and a negative relationship between knowledge and age (r=-0.139, p=0.040). These findings have significant implications that most primary health professionals in Macao had sufficient knowledge, a positive attitude and appropriate preventive practice on dementia care. However, enhanced dementia education to improve knowledge and preventive practice was a strong agenda for the training for senior staff and nurses.

Chest CT Severity Score: An Imaging Tool for Assessing Severe COVID-19

PURPOSE

To evaluate the value of chest CT severity score (CT-SS) in differentiating clinical forms of coronavirus disease 2019 (COVID-19).

MATERIALS AND METHODS

A total of 102 patients with COVID-19 confirmed by a positive result from real-time reverse transcription polymerase chain reaction on throat swabs who underwent chest CT (53 men and 49 women, 15-79 years old, 84 cases with mild and 18 cases with severe disease) were included in the study. The CT-SS was defined by summing up individual scores from 20 lung regions; scores of 0, 1, and 2 were respectively assigned for each region if parenchymal opacification involved 0%, less than 50%, or equal to or more than 50% of each region (theoretic range of CT-SS from 0 to 40). The clinical and laboratory data were collected, and patients were clinically subdivided according to disease severity according to the Chinese National Health Commission guidelines.

RESULTS

The posterior segment of upper lobe (left, 68 of 102; right, 68 of 102), superior segment of lower lobe (left, 79 of 102; right, 79 of 102), lateral basal segment (left, 79 of 102; right, 70 of 102), and posterior basal segment of lower lobe (left, 81 of 102; right, 83 of 102) were the most frequently involved sites in COVID-19. Lung opacification mainly involved the lower lobes, in comparison with middle-upper lobes. No significant differences in distribution of the disease were seen between right and left lungs. The individual scores in each lung and the total CT-SS were higher in severe COVID-19 when compared with mild cases (P < .05). The optimal CT-SS threshold for identifying severe COVID-19 was 19.5 (area under curve = 0.892), with 83.3% sensitivity and 94% specificity.

CONCLUSION

The CT-SS could be used to evaluate the severity of pulmonary involvement quickly and objectively in patients with COVID-19.© RSNA, 2020.

Coronavirus disease 2019: initial chest CT findings

OBJECTIVES

To systematically analyze CT findings during the early and progressive stages of natural course of coronavirus disease 2019 and also to explore possible changes in pulmonary parenchymal abnormalities during these two stages.

METHODS

We retrospectively reviewed the initial chest CT data of 62 confirmed coronavirus disease 2019 patients (34 men, 28 women; age range 20-91 years old) who did not receive any antiviral treatment between January 21 and February 4, 2020, in Chongqing, China. Patients were assigned to the early-stage group (onset of symptoms within 4 days) or progressive-stage group (onset of symptoms within 4-7 days) for analysis. CT characteristics and the distribution, size, and CT score of pulmonary parenchymal abnormalities were assessed.

RESULTS

In our study, the major characteristic of coronavirus disease 2019 was ground-glass opacity (61.3%), followed by ground-glass opacity with consolidation (35.5%), rounded opacities (25.8%), a crazy-paving pattern (25.8%), and an air bronchogram (22.6%). No patient presented cavitation, a reticular pattern, or bronchial wall thickening. The CT scores of the progressive-stage group were significantly greater than those of the early-stage group (p = 0.004).

CONCLUSIONS

Multiple ground-glass opacities with consolidations in the periphery of the lungs were the primary CT characteristic of coronavirus disease 2019. CT score can be used to evaluate the severity of the disease. If these typical alterations are found, then the differential diagnosis of coronavirus disease 2019 must be considered.

KEY POINTS

• Multiple GGOs with consolidations in the periphery of the lungs were the primary CT characteristic of COVID-19. • The halo sign may be a special CT feature in the early-stage COVID-19 patients. • Significantly increased CT score may indicate the aggravation of COVID-19 in the progressive stage.

The Value of Whole-Brain Perfusion Parameters Combined with Multiphase Computed Tomography Angiography in Predicting Hemorrhagic Transformation in Ischemic Stroke

OBJECTIVE

To explore the value of whole-brain perfusion parameters combined with multiphase computed tomography angiography (MP-CTA) in predicting the hemorrhagic transformation (HT) of ischemic stroke.

METHODS

A total of 64 patients with ischemic stroke who underwent noncontrast computed tomography, computed tomography perfusion imaging, and computed tomography angiography before treatment from August 2017 to June 2019 were included retrospectively. The perfusion parameters cerebral blood volume (CBV), cerebral blood flow (CBF), time to peak (TTP), mean transit time (MTT), time to maximum (Tmax), and permeability surface (PS) were measured by postprocessing software (Advantage Workstation 4.7 (Revolution, GE Healthcare, USA)), and their ratios between the healthy and affect side relative CBV, relative CBF, relative time to peak (rTTP), relative mean transit time (rMTT), relative Tmax, and relative permeability surface (rPS) were calculated. The differences in perfusion parameters between the HT group and the non-HT group were evaluated. The collateral circulation scores and HT rates were assessed by MP-CTA. Receiver operating characteristic curves were drawn to analyze the diagnostic efficiency of valuable parameters and their correlations with HT. The rate of HT in different treatments were compared.

RESULTS

The CBV values in the HT group were lower than those in the non-HT group (P < .05), while the TTP, MTT, Tmax, PS, rTTP, rMTT, and rPS values in the HT group were higher than those in the non-HT group (P < .05). PS (r = .63, area under curve = .881) and rPS (r = .52, area under curve = .814) were significantly correlated with HT. The combination of perfusion parameters and the MP-CTA scores can improve the diagnostic efficiency (area under curve = .891). The HT rate in the group with poor collateral (64.29%) was higher than that in the group with good collateral (11.11%).

CONCLUSIONS

Whole-brain perfusion parameters and MP-CTA scores have important application value in assessing the HT risk of ischemic stroke patients before treatment.

IKKε aggravates inflammatory response via activation of NF-κB in rheumatoid arthritis

OBJECTIVE

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease, whereas its cause still remains elusive. Typical pathological manifestations of RA include persistent synovitis and bone degeneration in the surrounding joints. Although the incidence of RA is high in population, currently there have been no effective cures for it. The purpose of this study is to investigate the therapeutic effects and main mechanism of IKKε (inhibitor of nuclear factor kappa-B kinase ε) in collagen II induced- Rheumatoid Arthritis (CIA) mice model.

MATERIALS AND METHODS

IKKε-/- and wild-type (WT) littermate control mice were intraperitoneally injected with 5 mg/kg collagen II monoclonal antibody cocktail (Cab) for 5 days. After that, the nociception threshold and clinical rheumatoid arthritis articular damage score of mice were evaluated. After 5 days-CAb treatment, serum levels of a series of inflammatory cytokines including interleukin-6 (IL-6), IL-1β, tumor necrosis factor-α (TNF-α) and interferon (IFN) were detected with enzyme-linked immunosorbent assay (ELISA) in both groups. Besides, Real-time reverse transcription polymerase chain reaction (Real-time RT-PCR) was used to evaluate the expression of these inflammatory cytokines in plantar tissues. In addition, Western blot was performed to investigate the protein levels of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B) signaling pathway. Moreover, WT mice receiving CAb were further applied with or without IKK inhibitor amlexanox (25 mg/kg) to investigate the expression of the above-mentioned inflammatory cytokines.

RESULTS

Our work showed that IKKε-/- mice with CIA displayed less nociception and suppressed inflammatory response than WT mice. Meanwhile, the clinical rheumatoid arthritis articular damage scores were significantly decreased in IKKε-/- mice. The levels of TNF-α, IL-1β, IL-6 in serum and plantar tissues in IKKε-/- mice were significantly lower than those in WT mice. Besides, NF-κB expression in IKKε-/- mice was significantly decreased. Similarly, the same phenotype was observed in WT mice administrated with IKKε inhibitor amlexanox as that of IKKε-/- mice, indicating that inflammatory and nociception responses were remarkably decreased than those of the negative controls.

CONCLUSIONS

IKKε plays an important role in promoting nociception and inflammatory response in CIA. Our research demonstrated that knockout of IKKε may serve as a new direction for clinical prevention and treatment of rheumatoid arthritis. IKKε inhibitor amlexanox may become a new drug for the treatment of rheumatoid arthritis.

[Pilot study of the relationship between clinical classification of gallbladder cancer and prognosis: a retrospective multicenter clinical study]

Objectives: To propose a novel clinical classification system of gallbladder cancer, and to investigate the differences of clinicopathological characteristics and prognosis based on patients who underwent radical resection with different types of gallbladder cancer. Methods: The clinical data of 1 059 patients with gallbladder cancer underwent radical resection in 12 institutions in China from January 2013 to December 2017 were retrospectively collected and analyzed.There were 389 males and 670 females, aged (62.0±10.5)years(range:22-88 years).According to the location of tumor and the mode of invasion,the tumors were divided into peritoneal type, hepatic type, hepatic hilum type and mixed type, the surgical procedures were divided into regional radical resection and extended radical resection.The correlation between different types and T stage, N stage, vascular invasion, neural invasion, median survival time and surgical procedures were analyzed.Rates were compared by χ(2) test, survival analysis was carried by Kaplan-Meier and Log-rank test. Results: Regional radical resection was performed in 940 cases,including 81 cases in T1 stage,859 cases in T2-T4 stage,119 cases underwent extended radical resection;R0 resection was achieved in 990 cases(93.5%).The overall median survival time was 28 months.There were 81 patients in Tis-T1 stage and 978 patients in T2-T4 stage.The classification of gallbladder cancer in patients with T2-T4 stage: 345 cases(35.3%)of peritoneal type, 331 cases(33.8%) of hepatic type, 122 cases(12.5%) of hepatic hilum type and 180 cases(18.4%) of mixed type.T stage(χ(2)=288.60,P<0.01),N stage(χ(2)=68.10, P<0.01), vascular invasion(χ(2)=128.70, P<0.01)and neural invasion(χ(2)=54.30, P<0.01)were significantly correlated with the classification.The median survival time of peritoneal type,hepatic type,hepatic hilum type and mixed type was 48 months,21 months,16 months and 11 months,respectively(χ(2)=80.60,P<0.01).There was no significant difference in median survival time between regional radical resection and extended radical resection in the peritoneal type,hepatic type,hepatic hilum type and mixed type(all P>0.05). Conclusion: With application of new clinical classification, different types of gallbladder cancer are proved to be correlated with TNM stage, malignant biological behavior and prognosis, which will facilitate us in preoperative evaluation,surgical planning and prognosis evaluation.

The effect of primer cap material on ballistic toolmark evidence

There has recently been an increase in the research and implementation of advanced measurement techniques to ballistic toolmark identification. This has led to a shift from greyscale imaging to the acquisition of dense areal datasets. With the addition of mathematical correlation algorithms, these advanced techniques will be advantageous in criminal investigation. However, with the use of areal topography comes the addition of height point data which may differ in primer caps of varying material composition. This study discusses the differences in the overall topography of firing pin impressions in different primer cap materials, and the effect it has on the successful correlation of ballistic toolmark evidence.

Increased intrinsic connectivity for structural atrophy and functional maintenance after acute ischaemic stroke

BACKGROUND AND PURPOSE

Significant clinical recovery has commonly been observed in ischaemic stroke patients with irreversible brain structural damage. However, brain mechanisms that help to maintain clinical function remain unclear.

METHODS

Sixty-two patients with acute ischaemic stroke underwent longitudinal clinical assessments and magnetic resonance scanning. The clinical recovery trajectory was evaluated using a hierarchical linear model and intrinsic connectivity was analysed with a seed-based approach to examine its changing pattern based on the regional volume changes calculated using voxel-wise analysis.

RESULTS

It was observed that clinical outcome measures improved mainly in the short-term period (baseline versus 3 weeks) and then remained stable. Grey matter volume was reduced significantly in the bilateral caudate over the entire 3-year long-term period. Significant intrinsic connectivity increases were observed in the caudate-middle cingulum over the short-term period and in the caudate-precuneus and caudate-calcarine over the long-term period. Finally, it was found that increased caudate-calcarine connectivity was associated with reduced right caudate volume, and a positive correlation was found between increased caudate-middle cingulum connectivity and the amount of modified Rankin score changes.

CONCLUSIONS

The increased intrinsic connectivity found in this study tends to be a compensatory mechanism for post-stroke structural damage, associated with clinical recovery. The study helps in understanding the significance of enhanced intrinsic connectivity in post-stroke long-term assessment and rehabilitation.

[Primary small cell neuroendocrine carcinoma of the tonsil: a case report]

Neuroendocrine carcinoma(NEC) of the tonsil is extremely rare that exhibits highly malignant and poorly prognosis. Only a few of case reports and the optial treatment is still uncertain. Here, the current study presents a case of 60-year-old male with neck mass rapidly growing for four months. It was diagnosed a primary tonsil neuroendocrine carcinoma. And he was treated by one cycle of cisplatin and etoposide. It had no effect and the tumor was rapidly progressed. With review of the literatures, the nomenclature, clinicopathological characteristics and treatment modalities of this rare tumor are discussed.

[Screening for hotspot mutations associated with genetic hearing impairment in pregnant women and subsequent prenatal diagnosis in high risk pregnancies]

Objective: To screen for hotspot gene mutations associated with genetic deafness in Chinese pregnant women, and to perform risk assessment and prenatal diagnosis in high-risk families. Methods: Between November 2012 and October 2017, 26 117 pregnant women were screened by molecular hybridization microarray for 9 hot-spot mutations in 4 hereditary deafness related genes (GJB2 c. 35 del G, c. 176_191 del 16 bp, c. 235 del G, c. 299_300 del AT, GJB3 c. 538 C>T, SLC26A4 c. 2168 A>G, IVS 7-2 A>G, mitochondrial DNA 12S rRNA m. 1494 C>T, m. 1555 A>G). Genotype analysis was carried out in husbands of women carrying mutations, and prenatal diagnosis was carried out in the fetuses with high risk of deafness. Results: Among all women tested, 1 208(4.63%) were carriers of genetic deafness mutations, 7 with hearing impairment were affected by homozygous or compound heterozygous mutations, 51 were mitochondrial gene mutation carriers, 103 were carriers of GJB3 c. 538 C>T heterozygous mutation, 1 026 were carriers of GJB2 or SLC26A4 heterozygous mutations, and 21 carried heterozygous mutations in two genes simultaneously. In 394 families, the husbands accepted gene sequence testing, and 27 in which were determined as carriers of mutations in identical genes as their wives. Among which, 18 families received prenatal diagnosis, and 5 fetuses were diagnosed as hereditary deafness. In 9 families who did not receive prenatal diagnosis, 1 neonate was diagnosed as compound heterozygote after delivery. Conclusion: In order to prevent birth defects with congenital hearing problems, it is effective to provide screening for hotspot mutations in pregnant women and to perform prenatal diagnosis on high risk pregnancies.

Clinical analysis of Hashimoto thyroiditis coexistent with papillary thyroid cancer in 1392 patients

Papillary thyroid carcinoma (PTC) is the most common malignant tumour of the thyroid. The effect of the concurrent presence of Hashimoto's thyroiditis (HT) and PTC is still under debate. The aim of this study is to investigate the influence of coexistent HT on prognostic outcomes and the association of coexistent HT with clinicopathological features. The demographic and clinicopathological data of 1,392 patients who underwent surgery in our hospital from 2007 to 2016 was collected and analysed. Among 1,392 PTC patients, the rate of HT was 25.6%. There were significant differences in the mean levels of thyroid stimulating hormone (3.27 vs. 2.41 μIU/L, p < 0.01), thyroperoxidase antibodies (110.31 vs. 131.2 U/ml, p < 0.01) and thyroglobulin antibodies (131.90 vs. 113.53 ng/ml, p < 0.01) between the two groups. PTC patients with HT had the following characteristics compared to patients without HT: smaller tumour size (p < 0.01), female predominance (p < 0.01) and higher rate of multifocality (p = 0.024). In addition, patients with HT had a significantly lower rate of lymph node metastasis (LNM) and advanced TNM stage than patients without HT (all p < 0.01). Multivariate analysis found that both age and multifocality were significantly associated with central LNM in HT patients (p < 0.01, p = 0.019, respectively). Extrathyroidal invasion and TSH level were also significant independent factors for lateral LNM in HT patients (p < 0.008, p = 0.04, respectively). HT is associated with a significantly higher risk of PTC. The coexistence of HT in PTC patients is associated with favourable clinical outcomes compared to PTC without HT. Total thyroidectomy and prophylactic central compartment lymphadenectomy should be a choice for PTC patients with HT.

Improvements of interfacial friction and heat transfer models for rectangular narrow channel reflood simulation based on RELAP5

Plate fuel assembly is widely used in reactor cores due to benefits of the narrow rectangular channels. Compared with rod assembly, the heat transfer area and power density can be increased in narrow rectangular channel, where little researches on post-CHF thermal-hydraulic characteristics have been done. Once the loss of coolant accident happens, post-CHF thermal-hydraulic characteristics are important for accident mitigation. This paper mainly evaluates the corresponding reflood models in RELAP5/MOD3 code. Combined with the post-CHF thermal-hydraulic characteristics in the narrow channel, interfacial friction model and post-CHF heat transfer models are modified. According to the comparison results with Saxena reflood experiments, conclusions can be obtained that the original RELAP5/MOD3 code overestimates quench front velocity and heat transfer in the film boiling region. The results from the code with new models agree better with the experimental data.

Racial disparities in vaccination for seasonal influenza in early childhood

OBJECTIVES

Influenza vaccination is the best protection against infection and severe complications of disease, such as hospitalization and death. Therefore, it is important to accurately estimate vaccination coverage and to evaluate the role of race/ethnicity. This study examines racial disparities in influenza vaccination among children using a nationally representative sample.

STUDY DESIGN

This study used cross-sectional data from the 2009-2014 National Immunization Survey for children aged 19-35 months (n = 98,186) in the United States.

METHODS

The outcome variable was receipt of influenza vaccination (yes/no) and exposure variable was race/ethnicity. Weighted multivariate logistic regression was used to estimate the odds ratio and 95% confidence intervals (CIs) for the effect of race/ethnicity on receipt of the influenza vaccine.

RESULTS

The overall vaccination rates were 81.6% for non-Hispanic whites, 79.2% for Hispanics, 80.5% for non-Hispanic blacks, and 80.7% for non-Hispanic mixed/other. In the adjusted model, compared with non-Hispanic white children, Hispanic children were 13% less likely to receive influenza vaccination within the last 12 months (adjusted odds ratio [aOR] = 0.87; 95% CI: 0.80-0.94). In addition, children aged 24-29 months (aOR = 0.48; 95% CI: 0.44-0.52) and 30-35 months (aOR = 0.33; 95% CI: 0.30-0.36) were significantly less likely to receive influenza vaccination within the last 12 months compared with those who were 19-23 months old.

CONCLUSIONS

There were differences in influenza vaccination rates among different racial groups. Hispanic children had the lowest vaccination rates. Findings from our study have significant implications for targeted interventions to increase the overall vaccination rate for children in the United States.

Establishment and characterization of a new cell line from koi brain (Cyprinus carpio L.)

A novel permanently growing brain cell line from koi (Cyprinus carpio L.) (KB cell line) was established, and its suitability for detection of koi herpesvirus (KHV) was demonstrated in this study. The KB cell line was optimally maintained at 27°C in Leibovitz's L-15 medium supplemented with 10% foetal bovine serum (FBS). It was subcultured more than 100 times, and chromosome analysis revealed that 51.54% of KB cells at passage 80 maintained the abnormal diploid chromosome number 2n = 96 while the modal chromosome number was 2n = 100. The cell line was cryopreserved in liquid nitrogen at -196°C and was recovered from storage after 1 year with good cell viability and vitality. The results of virus isolation demonstrated that KB cells were susceptible to KHV, which was shown by the presence of an obvious cytopathic effect and abundant virus particles. The viral titres of KHV in KB reached 10^5.73 TCID₅₀ /0.1 ml within 7 days. Immunofluorescence and Western blot assays confirmed that KB replicated KHV. The newly established KB cell line will serve as a useful tool to elucidate KHV disease (KHVD) pathogenesis.