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Biomedical subjects

W H Ng

Publications and source records attributed to W H Ng.

At least 19 recordsLinked to original sources
PubMed2005

A case-control study of SARS versus community acquired pneumonia.

The clinical, laboratory, and radiological features at presentation of 16 children (<12 years) with severe acute respiratory syndrome (SARS) and pneumonia were compared with 32 age matched patients with community acquired pneumonia for determination of predictive factors that could allow early differentiation of the two conditions. A definitive contact history was the most important predictor for SARS. Raised serum lactate dehydrogenase concentration in the presence of low neutrophil count and serum creatine phosphokinase level at presentation also indicated an increased likelihood of SARS-coronavirus infection in young children.

Biomarkers↗
PubMed2005

Role of imaging in management of hemophilic patients.

OBJECTIVE: The purpose of this study was to evaluate the role of symptomatology and conventional radiographic scoring in predicting synovial hypertrophy, which could affect the clinical management of hemophilic patients. MATERIALS AND METHODS: Twenty males (mean age, 14.3 years old) with hemophilic arthropathy, including 34 symptomatic joints and 26 asymptomatic joints (16 knees, 20 ankles, and 24 elbows) had conventional radiographs of individual joints obtained that were rated according to the Arnold-Hilgartner stage and the Pettersson score. The patients also underwent MRI for the detection of synovial hypertrophy. The association of synovial hypertrophy and symptomatology was evaluated using the chi-square or Fisher's exact test. The best sensitivity, specificity, and positive and negative predictive values in detection of synovial hypertrophy using symptomatology and radiographic scoring were calculated. RESULTS: A significant association was seen between symptomatology and synovial hypertrophy of the knee and ankle joints (p < 0.05). The sensitivity, specificity, and positive and negative predictive values of symptomatology in detection of synovial hypertrophy of the knee were 100%, 78%, 78%, and 100%, respectively, and for the ankle were 83%, 75%, 83%, and 75%, respectively. The Arnold-Hilgartner stage and Pettersson score of the radiograph had a significant association with synovial hypertrophy of the knee and ankle joints (p < 0.05). Arnold-Hilgartner staging provided a better prediction of synovial hypertrophy, with sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 100%, 100%, and 100% for knees and 82%, 100%, 100%, and 82% for ankles. CONCLUSION: In hemophilic patients, the presence of symptomatology in the knee and ankle joints is associated with synovial hypertrophy, and scoring of the conventional radiographs using Arnold-Hilgartner staging is useful for the prediction of synovial hypertrophy.

Adolescent↗
PubMed2005

An active surveillance study of vancomycin-resistant Enterococcus in Queen Elizabeth Hospital, Hong Kong.

OBJECTIVE: To assess the rate of faecal vancomycin-resistant Enterococcus colonisation in high-risk patients in a regional hospital. DESIGN: Prospective observational surveillance study. SETTING: Queen Elizabeth Hospital, Hong Kong. PATIENTS: From September 2001 to December 2002, stool samples from patients in the intensive care unit and patients in whom Clostridium difficile testing was requested were used for study using a broth enrichment method. MAIN OUTCOME MEASURES: Number of faecal vancomycin-resistant Enterococcus colonisation. RESULTS: A total of 2414 cultures from 1792 patients were tested for vancomycin-resistant Enterococcus using a broth enrichment method. Only one (0.06%) patient was found to harbour a vancomycin-resistant Enterococcus faecalis in the gastro-intestinal tract. Surveillance cultures from contacts of the case revealed another six with vancomycin-resistant Enterococcus faecalis. Vancomycin-resistant Enterococcus faecalis was also later reported from a clinical specimen (catheterized urine) of another patient. They were all epidemiologically linked to the index case. Mean inhibitory concentrations of vancomycin and teicoplanin were determined to be higher than 256 and 0.5 microgram/mL, respectively by E-test for all the vancomycin-resistant Enterococcus isolates. Polymerase chain reaction analysis confirmed the presence of vanB genes and the result was in line with the phenotype. Pulsed-field gel electrophoresis confirmed a monoclonal vancomycin-resistant Enterococcus outbreak. Strict infection control measures recommended by the Centers for Disease Control and Prevention were followed and the outbreak was successfully controlled. CONCLUSION: Vancomycin-resistant Enterococcus colonisation is rare, but present among high-risk patients in our hospital. A routine surveillance programme should be implemented that will enable early case detection and prompt initiation of infection control measures to prevent the emergence of an endemic situation.

Enterococcus faecalis↗
PubMed2004

Comparison of breath-hold 2D phase-contrast with non breath-hold cine phase-contrast MRA in the assessment of azygos venous blood flow in portal hypertension.

Azygos venous blood flow as an index of blood flow through the gastroesophageal collaterals and varices is of value in the prediction of gastrointestinal bleeding. Measurement of azygos venous blood flow has been achieved by non breath-hold (NBH) cine phase-contrast magnetic resonance imaging. The objective of this study was to compare the faster breath-hold (BH) phase-contrast technique with the standard (NBH) cine phase-contrast technique in the measurement of azygos blood flow. Thirty-two cirrhotic patients with esophageal varices were examined by magnetic resonance imaging using a BH technique and a NBH cine phase-contrast technique to measure the flow velocity, flow volume and calibre of the azygos vein at the mid-right atrial level. The flow values were obtained on the velocity image of the phase-contrast study. Values obtained from the two methods were evaluated statistically for the strength and significance of correlation by the Pearson test. Measurement by the BH method performed at full-inspiration as well as end-expiration was also obtained in 15 healthy volunteers. The breath-hold phase-contrast method has significant but weak correlation with non BH cine phase-contrast method in the measurement of azygos venous blood flow volume (r = 0.55, p < 0.01) and flow velocity (r = 0.43, p = 0.01). However, the calibre of the azygos vein gave a strong correlation in these two methods (0.82). In the subgroup of patients whose azygos blood flow velocity was greater than 7.4 cm/s, the correlation of azygos blood flow volume is strong (r = 0.80, p < 0.01). The azygos vein calibre remains highly correlated between the BH and NBH method, in both high flow velocity (r = 0.73) and low flow velocity (r = 0.83) groups. Breath-hold sequence leads to higher values for flow velocity and flow volume in the cirrhotic patients and also the control group. In patients with portal hypertension, BH 2D phase-contrast (PC) magnetic resonance angiography (MRA) could give a comparable estimation of the calibre of the azygos vein as the NBH 2D cine PC MRA but not for azygos flow volume. In patients with high azygos flow velocity, the strong correlation in flow volume between the BH and NBH method suggests that the BH method may be a time-saving alternative to the NBH method.

Azygos Vein↗
PubMed2004

Non-traumatic spontaneous acute epidural haematoma -- report of two cases and review of the literature.

Epidural haematomas are usually associated with preceding head trauma. The entity of non-traumatic spontaneous acute epidural haematoma is rare and most commonly occurs in the presence of infectious disease. It can also occur in the presence of coagulopathy, vascular malformations of the dura mater and haemorrhagic tumours. Sickle cell disease, systemic lupus erythematosus, open heart surgery and haemodialysis have also been implicated as causative factors. The authors report two cases of spontaneous epidural haematomas (one of unknown aetiology and one from a coagulation disorder) and discuss the aetiological agents involved in this rarely described condition.

Adult↗
PubMed2003

Correlation between annual change in health status and computer tomography derived lung density in subjects with alpha1-antitrypsin deficiency.

BACKGROUND: There is increasing recognition that questionnaires of health status and lung density measurements are more sensitive tools for assessing progression of emphysema than forced expiratory volume in 1 second (FEV(1)) and transfer coefficient (KCO). A study was undertaken to investigate prospectively the correlation between annual change in health status and computer tomography (CT) derived lung density in subjects with alpha(1)-antitrypsin deficiency. METHODS: Twenty two patients of mean (SD) age 40.7 (9.2) years with ZZ type alpha(1)-antitrypsin deficiency were investigated at baseline and 30 months later by FEV(1) and KCO, St George Respiratory Questionnaire (SGRQ), and by a spiral CT scan of the chest. CT data of chest images were analysed using software designed for automated lung contour detection and lung density measurements. The density data were corrected for changes in inspiration levels. RESULTS: Changes in lung density, expressed as 15th percentile point or relative area below -950 HU, correlated well with changes in health status (SGRQ total score): R = -0.56, p = 0.007 or R = 0.6, p = 0.003. Neither changes in health status nor changes in lung density correlated significantly with changes in FEV(1) or changes in KCO. CONCLUSIONS: The SGRQ total score (which is a global measure in COPD) and lung density (a specific measure of emphysema) are sensitive to deterioration in patients with alpha(1)-antitrypsin deficiency. This finding may facilitate future studies with new drugs specific for emphysema, a frequently occurring component of COPD.

Adult↗
PubMed2003

Clinics in diagnostic imaging (89). Infantile hepatosplenic haemangioendotheliomas.

The ultrasonographical and computed tomography findings of a six-month-old female infant with haemangioendotheliomas of the liver and spleen are described. The splenic lesion had an unusual ultrasonographical appearance of a well-defined isoechoic mass with a hypoechoic rim. Diagnosis was confirmed by histological examination of the hepatic biopsy specimen. Hepatosplenic lesions in the first year of life may be due to a variety of pathological processes. It is important to include haemangioendotheliomas in the differential diagnosis of hepatosplenic masses in an infant.

Female↗
PubMed2001

Tethered cord syndrome preceding syrinx formation--serial radiological documentation.

The authors report a case of tethered cord syndrome preceding the development of a syrinx, which subsequently resolved with detethering. This was shown conclusively with serial radiological imaging, although the patient did not improve clinically. The lack of clinical improvement is likely to be due to the delay in surgery caused by infections in this patient, and early detethering should therefore be the aim in patients with tethered cord syndrome.

Decompression, Surgical↗
PubMed2001

Giant aneurysm treated by bilateral cervical carotid artery to proximal middle cerebral artery bypass and balloon embolisation: a case report.

The authors describe a case of a 59 year-old Chinese lady with a history of spontaneous left caroticocavernous fistula in 1988 treated by left internal carotid artery clipping and muscle embolisation. She subsequently presented with a subarachnoid haemorrhage in November 1997 secondary to rupture of an unclippable giant right internal carotid artery aneurysm. This was treated satisfactorily with bilateral cervical carotid artery to proximal middle cerebral artery bypass followed by balloon occlusion. Postoperatively, the patient has no neurological deficit and CT angiogram shows good patency of both grafts 6 months after surgery.

Balloon Occlusion↗
PubMed2001

Nitric oxide and subarachnoid hemorrhage: elevated level in cerebrospinal fluid and their implications.

OBJECTIVE: Nitric oxide (NO) plays an important role in the pathogenesis of neuronal injury after brain ischemia, and decreased levels of NO have been implicated in the pathogenesis of vasospasm after subarachnoid hemorrhage (SAH). In this study, we measured the ventricular cerebrospinal fluid (CSF) NO levels in patients with SAH and correlated the levels with clinical grade and middle cerebral artery velocities measured with transcranial Doppler ultrasound. METHODS: All patients with spontaneous SAH documented on computed tomography and with an external ventricular drain inserted within 24 hours of hemorrhage were included in the study. A total of 16 patients were studied between August 1999 and August 2000. CSF was collected serially at the time of surgery and subsequently at daily intervals. It was collected during the time that the external ventricular drain remained patent and in situ. NO levels were measured by photometric analysis by using a nitrite/nitrate assay kit (Cayman Chemical, Ann Arbor, MI). RESULTS: The peak NO level in patients with SAH ranged from 9.96 to 168.16 micromol, with a median of 36.93 micromol. The levels were significantly elevated as compared with the control group (5.16 micromol, P < 0.05). The median NO level in patients with poor-grade SAH was 67.14 micromol as compared with 27.42 micromol in patients with good-grade hemorrhage (P < 0.05). No correlation was seen between CSF NO levels and middle cerebral artery velocities. The median NO level was 33.2 micromol in patients with a poor outcome as compared with 30.25 micromol in patients with a good outcome (P > 0.05). CONCLUSION: This study showed that NO levels are elevated after spontaneous SAH, and the degree of elevation is higher in patients with poor-grade SAH.

Adult↗
PubMed1997

Desmoid tumor (fibromatosis) of the breast. A clinician's dilemma--a case report and review.

Desmoid tumor of the breast is a clinician's dilemma as it is difficult to differentiate it from carcinoma clinically, mammographically, and cytologically. Histologically, it must be distinguished from fibrosarcoma. Current management favors wide excision with clear margins. Recurrence is relatively common and usually occurs within 3 years of excision. Adjuvant hormonal therapy does not reduce local recurrence rates; evidence indicates that postoperative radiotherapy can improve the 10-year recurrence-free survival rate.

Adult↗
PubMed1995

Release of mast-cell-derived mediators after endobronchial adenosine challenge in asthma.

Preformed and newly generated mediators released from airway mast cells may play a role in adenosine-induced bronchoconstriction. To investigate the possible role of mast-cell-derived mediator release in mediating bronchoconstriction induced by adenosine 5'-monophosphate (AMP), we have examined the fluid obtained by bronchoalveolar lavage for inflammatory mediators and markers of airway permeability immediately after instillation of AMP directly into an airway segment of 10 asthmatic subjects. Eight subjects completed the protocol. When compared with the saline-challenged segment, the response to endobronchial stimulation with AMP was characterized by a prompt reduction in airway caliber paralleled by a significant rise in PGD2, histamine, and tryptase levels in the lavage fluid. After AMP challenge, the median (range) concentration for PGD2 increased from 36 to 205 pg/ml (p = 0.006), for histamine from 184 to 433 pg/ml (p = 0.018), and for tryptase from 0.30 to 0.54 ng/ml (p = 0.013). In addition, a small but significant rise in albumin levels (from 27.8 to 36.1 micrograms/ml; p = 0.031) was detected after endobronchial challenge with AMP. These findings indicate that adenosine-induced responses may be initiated by the acute release of mast-cell-derived mediators, including PGD2, histamine, and tryptase.

Adenosine Monophosphate↗
PubMed1990

Adenosine bronchoconstriction in asthma: investigations into its possible mechanism of action.

1. Inhaled adenosine and its parent nucleotide, adenosine 5'-monophosphate (AMP) provoke bronchoconstriction in atopic and asthmatic individuals but not in normal subjects. 2. In clinical studies, histamine H1-receptor antagonists, cyclo-oxygenase inhibitors and the mast cell 'stabilising' drugs, sodium cromoglycate and nedocromil, protect against the effects of adenosine bronchoprovocation suggesting the involvement of secondary mast cell mediator release. 3. Adenosine and its analogues potentiate histamine and leukotriene release from mast cells activated by other stimuli in vitro, and may also increase net mediator release from mast cells by counteracting the inhibitory effect of circulating adrenaline. 4. Although adenosine fulfils many of the criteria required for a mediator in asthma, its importance is not fully understood, and the mechanisms by which it provokes bronchoconstriction in asthmatic subjects is far from concluded. 5. Two possibilities are that either adenosine acts directly on luminal mast cells to upregulate histamine secretion, or it acts to initiate neuronal reflexes which stimulate histamine release indirectly and possibly activate peptidergic and/or cholinergic pathways.

Adenosine↗
PubMed1990

The response of plasma histamine to bronchoprovocation with methacholine, adenosine 5'-monophosphate, and allergen in atopic nonasthmatic subjects.

To investigate the possible role of mast cell histamine release in mediating adenosine 5'-monophosphate (AMP)-induced bronchoconstriction, we have measured the histamine concentration in peripheral venous plasma following inhalation of methacholine, AMP, and allergen in concentrations sufficient to provoke mean maximum decreases in FEV1 of 42.8 +/- 2.2%, 46.5 +/- 3.9%, and 40.9 +/- 4.6%, respectively, in 10 atopic, nonasthmatic subjects. Mean baseline plasma concentrations of histamine were 0.25 +/- 0.02, 0.22 +/- 0.03, and 0.29 +/- 0.03 ng/ml on the methacholine, AMP, and allergen study days, respectively. Plasma histamine did not change following methacholine-induced bronchoconstriction, but increased in 9 out of 10 subjects to a mean maximum value of 0.78 +/- 0.15 ng/ml following inhalation of allergen (p less than 0.005). Following bronchial challenge with AMP, there was a significant elevation in plasma histamine in 9 out of 10 subjects to a mean maximum value of 0.39 +/- 0.03 ng/ml (p less than 0.005). We conclude that AMP-induced bronchoconstriction is associated with the enhanced release of histamine in the airways, probably from airway mast cells. However, the rise in plasma histamine, in being smaller than that occurring with a dose of allergen that provoked a similar degree of bronchoconstriction, suggests that additional mechanisms are operative in mediating the airways response to this nucleotide.

Adenosine Monophosphate↗
PubMed1989

The inhibitory actions of azelastine hydrochloride on the early and late bronchoconstrictor responses to inhaled allergen in atopic asthma.

We have examined the effect of azelastine hydrochloride, 8.8 mg, on the early and late responses to inhaled allergen in a group of 12 atopic subjects with asthma. On two separate days, 3 weeks apart, patients were administered either oral azelastine, 8.8 mg, or matched placebo. Four hours later they inhaled via nebulizer, a dose of allergen (grass pollen or Dermatophagoides pteronyssinus) that had previously been demonstrated to produce a 25% fall in FEV1. Plasma-histamine concentrations and FEV1 levels were measured at intervals during the subsequent 8 hours. After placebo, allergen inhalation produced rapid bronchoconstriction in all subjects with a maximum mean fall in FEV1 at 30 minutes of 22.8 +/- 3.4% from the postsaline baseline value. Five subjects also developed a late bronchoconstriction response with a fall in FEV1 of greater than 15% from postsaline baseline value between 2 and 8 hours after challenge. Azelastine reduced the bronchoconstrictor response during the first 10 minutes and produced a maximum mean fall at 30 minutes of 21.2 +/- 4.4% from the postsaline baseline value. Azelastine had a marked inhibitory effect, reducing the maximum mean fall from 23.9 +/- 6.3% to 9.6 +/- 3.9% from the postsaline baseline value. Analysis of the area under the FEV1 response time-course curves revealed that azelastine reduced the early response (first 2 hours) by 32.5% (p less than 0.05) (all subjects) and reduced the late response (2 to 8 hours) by 70.2% (p less than 0.05) (n = 5). Azelastine had no significant inhibitory effect on the early increase in plasma histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗