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Biomedical subjects

C Y Chan

Publications and source records attributed to C Y Chan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Immunization of HIV-infected children with varicella vaccine.

OBJECTIVE: To determine the safety and immunogenicity of varicella vaccine in children with human immunodeficiency virus (HIV) infection. Children (n = 41) who were mildly affected by HIV (Centers for Disease Control and Prevention stage N1 or A1) and had no history or serum antibody indicative of prior varicella infection were immunized with two doses of live attenuated varicella vaccine. RESULTS: A minority of the vaccine recipients had mild local or systemic reactions. Vaccination had no effect on the clinical stage of HIV or the HIV RNA plasma load. CD4 cell percentage and CD4 cell count were marginally decreased at week 4 after the first vaccination; this effect was no longer present at week 8 after vaccination. Two months after the second dose of vaccine, 60% of vaccine recipients had anti-varicella antibody in their serum, and 83% had a positive lymphocyte proliferation assay response to varicella antigen. CONCLUSION: On the basis of its safety and immunogenicity, varicella vaccine should be considered in the childhood vaccines given to mildly affected HIV-infected children.

Antibodies, Viral↗
PubMed2001

Childhood vaccination against varicella: persistence of antibody, duration of protection, and vaccine efficacy.

OBJECTIVE: To document the duration of protection afforded by Oka/Merck varicella vaccine over a 7-year period. STUDY DESIGN: The subjects were healthy children 1 to 12 years of age originally enrolled in clinical studies to evaluate the primary immune response to varicella vaccine 6 weeks after vaccination. Each was monitored for antibody persistence, breakthrough infection, and household exposure to varicella to produce estimates of vaccine efficacy. RESULTS: The 6-year cumulative varicella antibody persistence rate was 99.5% (95% CI: 98.9%, 100.0%). The annual breakthrough rate through 7 years ranged from 0.2% to 2.3% per year; the estimated cumulative event rate was 6.5%. Comparison of the observed average annual breakthrough rate with the age-adjusted expected annual incidence rate of varicella in unvaccinated children corresponded to an estimated vaccine efficacy of 93.8% to 94.6%. Eighty vaccinated children were exposed to varicella in the household, resulting in 8 (10%) cases of infection. When compared with the historical attack rate of 86.8% in unvaccinated susceptible persons exposed to varicella in the household, this yields an estimated vaccine efficacy of 88.5% (95% CI: 80.9%, 96.1%). Varicella cases in vaccinated children generally were mild. CONCLUSION: The live attenuated varicella vaccine is highly effective in inducing persistent immunity and long-term protection against breakthrough varicella infection.

Age Distribution↗
PubMed2001

Postantibiotic effects of antituberculosis agents alone and in combination.

The postantibiotic effects (PAEs) of seven antimycobacterial agents, tested at their respective peak concentrations in serum alone and in different combinations, against Mycobacterium tuberculosis ATCC 27294 were studied with a radiometric culture system in parallel with the viable count method. Rifampin gave the longest PAE (67.8 h) among the drugs used alone, and combinations of first-line drugs generally gave PAEs longer than 120 h. The data obtained might help provide a better understanding of the scientific basis of intermittently administered antituberculosis chemotherapy.

Antitubercular Agents↗
PubMed2001

Rapid identification of mycobacterium tuberculosis complex from Bactec 12B broth cultures originating from non-respiratory secretion specimens: comparison between Accuprobe and in-house polymerase chain reaction.

The rapid identification of Mycobacterium tuberculosis complex from 161 consecutive positive Bactec 12B cultures originated from non-respiratory secretion specimens was evaluated by comparing Accuprobe and an in-house polymerase chain reaction method. Using conventional biochemical method as the gold standard, 85.7% of the isolates (n = 138) were identified as Mycobacterium tuberculosis. The sensitivities of Accuprobe and the in-house-polymerase chain reaction method in identifying Mycobacterium tuberculosis complex were 92.0% (127/138) and 93.5% (129/138), respectively. Specificities of both methods being 87.0% (20/23 for both tests). Using a batch system of performing identification once weekly, the average turnaround time for Accuprobe, from the time of primary inoculation, was 27 days, which was comparable with that of in-house polymerase chain reaction, which was 29 days. The average time required for a confirmatory result based on conventional biochemical identification method was 84 days. The estimated reagent cost of in-house polymerase chain reaction was only one-fifth of that of Accuprobe. Therefore, the choice of methodology will depend on the individual laboratory's availability of resources and clinical demand. In the event of discrepant results between rapid identification methods and conventional methods, histological examination and clinical assessment can provide guidance as to the nature of the infection.

Bacteriological Techniques↗
PubMed2001

Ruptured abdominal aortic aneurysms: a personal experience.

Despite advances in surgical technique and peri-operative care, mortality from ruptured abdominal aortic aneurysm presenting to a hospital remains around 50%. This is in contrast to the mortality rate of < 5% for elective repair. In a two and a half year period,the principal surgeon operated on 10 patients with ruptured AAA, with a peri-operative and overall mortality of 30%. One of the ten patients had a ruptured mycotic aneurysm. We present our experience with these patients and also correlate this with recent publications.

Abdominal Pain↗
PubMed2001

An unusual cutaneous metastasis from hepatocellular carcinoma.

Cutaneous metastases from hepatocellular carcinoma are rare. In this report we detail a case of hepatocellular carcinoma with the unusual manifestations of multiple skin metastases. A 49-year-old male, who had received surgical resection of hepatocellular carcinoma one year prior, presented with multiple reddish-blue, firm, painless and nonulcerative cutaneous papules and nodules over the fingers, palms, toes, soles and back. Pathology of the cutaneous nodules showed characteristic hepatocellular carcinoma with trabecular gland formation. These lesions grew very rapidly and developed to cauliflower appearances which had not been described previously in the literature. The patient died of respiratory failure secondary to lung metastasis two months after the first appearance of the skin lesions.

Carcinoma, Hepatocellular↗
PubMed2001

Laparoscopic fenestration of a simple hepatic cyst.

Hepatic cysts are usually asymptomatic, most being detected incidentally during imaging. Distinction has to be made between a simple hepatic cyst from more sinister types such as a parasitic cyst and a cyst occurring as part of a neoplastic process. Intervention in a simple hepatic cyst is only indicated when they become symptomatic or when they grow at a rapid rate. Surgery is the mainstay of treatment, with laparoscopic intervention becoming more and more widely accepted. We present here the first case of laparoscopic fenestration of liver cyst performed in our hospital and also review the literature on this modality of treatment.

Cysts↗
PubMed2000

The prognostic significance of p16(INK4a)/p14(ARF) locus deletion and MDM-2 protein expression in adult acute myelogenous leukemia.

BACKGROUND: The p16(INK4a) locus encodes two distinct proteins, p16(INK4a) and p14(ARF). Although p16(INK4a) and p15(INK4b) are involved in the phosphorylation of the retinoblastoma (Rb) protein, p14(ARF) interacts with the MDM-2 oncoprotein antagonizing its function as a suppressor of p53. The role of deletions of p16(INK4a)/p14(ARF) and p15(INK4b) and expressions of MDM-2 in myeloid leukemias and its influence on prognosis remain unclear. METHODS: The authors analyzed deletions of p16(INK4)/p14(ARF) and p15(INK4b) in 74 adults with acute myeloid leukemia (AML) by Southern blotting. Western blotting was used to determine Rb protein phosphorylation in patients with deletions of p16(INK4)/p14(ARF) and p15(INK4b). Then, they analyzed the levels of MDM-2 protein expression and correlated it with prognosis in an expanded population of 79 adults with AML by immunoblot analysis and solid-phase radioimmunoassay. RESULTS: Deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) occurred in 4 of 74 patients (5%) (hemizygous in 3, homozygous in 1 patient). Although the complete remission (CR) rate was similar (79% vs. 50%; P = 0.187), CR duration (10 vs. 46 weeks; P < 0.001), event free survival rate (EFS; 6 vs. 85 weeks; P < 0.004) and overall survival rate (11 vs. 86 weeks; P = 0.001) were significantly shorter in patients with deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b). Thirty-seven (47%) of 79 patients studied for MDM-2 showed increased MDM-2 expression. These patients had a significantly shorter EFS rate (50 vs. 64 weeks; P = 0.023) and a trend for shorter CR duration (24 vs. 53 weeks; P = 0.07). Overall survival rate was not significantly different (50 vs. 84 weeks; P = 0.136). CONCLUSIONS: The authors concluded that 1) deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) occur with low incidence in patients with AML; 2) patients with deletions of p16(INK4a)/p14(ARF) and/or p15(INK4b) have a significantly shorter CR duration, EFS rate, and overall survival rate than do patients without deletions; (3) overexpression of MDM-2 is common in AML and is associated with shorter CR duration and EFS rate. Mechanisms other than p14(ARF) deletion are responsible for MDM-2 overexpression, and this overexpression may play a role in the biology of the disease.

Adult↗
PubMed2000

Human exposure to respirable suspended particulate and airborne lead in different roadside microenvironments.

The aim of this study is to evaluate the particulate air pollution in selected roadside microenvironments of Hong Kong through an intensive field study dated from January 1997 to February 1997. The study employed the microenvironment monitoring technique to access the exposure of pedestrians to respirable suspended particulate and airborne lead (Pb) at heavily trafficked roadsides. A total of 62 roadside sites in 14 districts covering the most urbanized and densely populated areas were selected. It was found that pedestrians were exposed to a 24 h average of respirable suspended particulate, PM10, and airborne Pb (APb), typically ranged from 25.56 to 337.40 microg/m3 and 70.71 to 285.71 ng/m3, respectively. The average PM10 concentrations at different roadside microenvironments corresponding to urban residential, urban commercial, urban industrial and new town areas were 91.84, 129.08, 83.83, and 118.89 microg/m3 respectively. The corresponding values for APb were 130.01, 143.40, 127.40 and 173.17 ng/m3, respectively. It was found that measurement at EPD nearby rooftop monitoring stations might not reflect the actual roadside PM10 exposure. Most APb field study data was significantly higher than the nearby fixed station data.

Air Pollutants↗
PubMed2000

Aminoglycoside resistance in Mycobacterium kansasii, Mycobacterium avium-M. intracellulare, and Mycobacterium fortuitum: are aminoglycoside-modifying enzymes responsible?

Aminoglycoside acetyltransferase was detected in Mycobacterium kansasii and M. fortuitum but not in M. avium-M. intracellulare when they were screened by a radioassay. Aminoglycoside phosphotransferase and nucleotidyltransferase activities were absent from all three species tested. Acetyltransferases from both M. kansasii and M. fortuitum displayed relatively high K(m)s, all at the millimolar level, for substrates including tobramycin, neomycin, and kanamycin A. The K(m) of each substrate was well above the corresponding maximum achievable level in serum. The low affinities of these enzymes for their substrates suggested that drug modification in vivo was very unlikely. Among the various substrates tested, no apparent positive correlation was found between substrate affinity and resistance level. The presence of aminoglycoside-modifying enzymes in these mycobacterial species was therefore not shown to confer resistance to aminoglycosides.

Acetyltransferases↗
PubMed2000

Clinics in diagnostic imaging (45). Osmotic myelinolysis ( central potine myelinolysis).

A 65-year-old woman developed progressive neurological deterioration following rapid correction of hyponatremia. Magnetic resonance imaging showed T2 hyperintense areas in the central pons, basal ganglia and deep white matter, typical of osmotic myelinolysis (OM). Previously thought to be uniformly fatal, there are increasing reports of non-fatal cases of OM. The recognition and understanding of this entity is important to prevent or reduce the incidence of its occurrence, as there is no specific treatment once it develops. The clinical and radiological features of OM are reviewed.

Aged↗
PubMed2000

Stereotactic brain biopsies in AIDS patients--early local experience.

AIM: To assess the usefulness of stereotactic brain biopsies in AIDS patients with cerebral lesions in Singapore. METHODS: A total of 10 patients with AIDS and cerebral lesions underwent stereotactic brain biopsies in the Department of Neurosurgery, Tan Tock Seng Hospital (TTSH) between September 1997 and September 1998. The patients were referred from the Communicable Diseases Centre (CDC), TTSH. These patients either failed a trial of therapy for toxoplasmosis encephalitis (TE) or had CT/MRI scans which did not suggest TE. Four were CT-guided and six were MRI-guided stereotactic biopsies. The Radionics Cosman-Robert-Wells (CRW) stereotactic apparatus was used for all cases. RESULTS: The male to female ratio was 9:1. Histological diagnosis from biopsy was lymphoma (5), metastatic adenocarcinoma (1), TE (1), abscess (1), encephalitis (1) and granulomatous tissue (1-presumed tuberculosis). CONCLUSION: The early experience is that stereotactic brain biopsy is useful in patients with AIDS and cerebral lesions. The etiology is confirmed in the majority of cases and impacts on management decisions and prognostication.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Need for vaccination of susceptible food handlers against hepatitis A in Taiwan.

BACKGROUND: With the improvement in the socioeconomic situation and general hygiene standards in Taiwan, the prevalence of antibodies to the hepatitis A virus (anti-HAV) in the general population has declined markedly in recent years. To avoid food-borne outbreaks of HAV infection caused by susceptible food handlers in Taiwan, we investigated the seroprevalence of anti-HAV among the target population and also evaluated the immunogenicity and reactogenicity of the inactivated hepatitis A vaccine in this study group. METHODS: Two hundred and forty-four food handlers employed in four restaurants at Taipei Veterans General Hospital participated in the anti-HAV serologic screening program in July 1997. Of them, 48 susceptible food handlers received three doses of 720 enzyme-linked immunosorbent units of inactivated hepatitis A vaccine at 0, 1 and 6 months. RESULTS: Of the 244 food handlers who underwent anti-HAV serologic screening, 169 (69.3%) were anti-HAV positive. The seroprevalence of anti-HAV was related to age: 91.5% of food handlers over 30 years of age were positive for anti-HAV but only 22.8% of food handlers younger than 30 were anti-HAV positive. Anti-HAV response was observed in all vaccinees after a booster vaccination at month 6. The response persisted to 1 year. The side-effects of the vaccinations were minimal. CONCLUSIONS: Susceptible food handlers should receive hepatitis A vaccination. Hepatitis A vaccine is safe and immunogenic in this target population.

Adolescent↗
PubMed1999

Long-term follow-up of hepatitis A vaccination in children.

We conducted this follow-up study to evaluate the long-term immunogenicity of an inactivated hepatitis A vaccine in children. Ninety-six children who had seroconversion to antibody to HAV (anti-HAV) after receiving a three-dose schedule of inactivated hepatitis A vaccine were enrolled into this study. Sixty months after the initial vaccination, all vaccinees who received annual follow-up still had protective levels of anti-HAV. The geometric mean titer (GMT) of anti-HAV, peaking at month 7 (4133 mIU/mL), kept declining throughout the follow-up period. The GMTs in months 12, 24, 36, 48 and 60 were 1722, 896, 896, 645 and 403 mIU/mL, respectively. Nine of the vaccinees were hepatitis B virus carriers. Their anti-HAV titers tended to be lower than those of the remaining vaccinees at all time-points, but the difference was not significant (p > 0.05). Natural booster was noted in one vaccinee during the follow-up period. In conclusion, inactivated hepatitis A vaccine is safe and immunogenic in children, the duration of protection against HAV infection is longer than five years.

Child↗
PubMed1999

Radiation dose reduction in paediatric cranial CT.

BACKGROUND: There is no consensus about the optimal milliamperage-second (mAs) settings for computed tomography (CT). Most operators follow the recommended settings of the manufacturers, but these may not be the most appropriate settings. OBJECTIVE: To determine whether a lower radiation dose technique could be used in CT of the paediatric brain without jeopardising the diagnostic accuracy of the images. MATERIALS AND METHODS: A randomised prospective trial. A group of 53 children underwent CT using manufacturer's default levels of 200 or 250 mAs; 47 underwent scanning at 125 or 150 mAs. Anatomical details and the confidence level in reaching a diagnosis were evaluated by two radiologists in a double-blinded manner using a 4-point scoring system. RESULTS: For both readers there was no statistically significant difference in the confidence level for reaching a diagnosis between the two groups. The 95 % confidence intervals and P values were -0.9-1.1 and 0.13 (reader 1) and -1.29-1.37 and 0.70 (reader 2), respectively. Reliability tests showed the results were consistent. CONCLUSIONS: The recommended level may not be the optimum setting. Dose reduction of 40 % is possible on our system in paediatric brain CT without affecting the diagnostic quality of the images.

Brain↗
PubMed1999

Improved recovery of Mycobacterium tuberculosis from pleural aspirates: bedside inoculation, heparinized containers and liquid culture media.

The effects of bedside inoculation, heparinized containers and liquid culture media on the recovery of Mycobacterium tuberculosis from pleural aspirates were evaluated in this study. Of 155 patients, 63 were diagnosed to have pleural effusion tuberculous in origin. The overall recovery of M. tuberculosis was 57.1%. Bedside inoculation of the specimens produced a significantly higher yield than laboratory inoculation using non-heparinized specimens. When the pleural aspirates were transported in heparinized containers, the recovery rate was comparable to that from bedside inoculation, but lower when non-heparinized containers were used. No significant difference was found in recovery rate between the two liquid media, but the rate was significantly higher with the use of liquid media than conventional solid media. Thus, bedside inoculation of pleural aspirates, use of heparinized containers for transport for delayed inoculation in the laboratory and use of liquid culture media are recommended.

Anticoagulants↗