Fook Tim Chew

Seasonal trends of viral respiratory tract infections in the tropics.

To evaluate the seasonal trends of viral respiratory tract infections in a tropical environment, a retrospective survey of laboratory virus isolation, serology and immunofluorescence microscopy in two large general hospitals in Singapore between September 1990 and September 1994 was carried out. Respiratory tract viral outbreaks, particularly among infants who required hospitalization, were found to be associated mainly with respiratory syncytial (RSV) infections (72%), influenza (11%) and parainfluenza viruses (11%). Consistent seasonal variations in viral infections were observed only with RSV (March-August) and influenza A virus (peaks in June, December-January). The RSV trends were associated with higher environmental temperature, lower relative humidity and higher maximal day-to-day temperature variation. Although the influenza A outbreaks were not associated with meteorological factors, influenza B isolates were positively associated with rainfall. These data support the existence of seasonal trends of viral respiratory tract infections in the tropics.

Prevalence and severity of asthma, rhinitis, and eczema in Singapore schoolchildren.

This study was part of an international effort to evaluate the epidemiology of asthma and allergic diseases around the world. The aim was to assess the prevalence and severity of these disorders in Singapore schoolchildren. The international study of asthma and allergies in childhood (ISAAC) written questionnaire was administered to 6238 schoolchildren. The respondents were parents of a 6-7 year cohort (n = 2030), and schoolchildren aged 12-15 years (n = 4208). The overall cumulative and 12 month prevalence of wheezing were 22% and 12%, respectively. The prevalence of doctor diagnosed asthma was 20%. Rhinitis was reported by 44% and chronic rashes by 12%. Multiple logistic regression analysis showed that a higher prevalence of wheezing and rhinitis was associated with males, and subjects of higher socioeconomic status (based on type of housing and total family income). More severe asthma related symptoms were present in Malays and Indians than in the Chinese. Allergic disorders are common in Singapore and prevalence is comparable to some populations in the West. Demographic and socioeconomic factors appear to influence the prevalence and severity of these disorders.

Sensitization to local dust-mite fauna in Singapore.

Background: Recent studies showed the presence of a unique dust‐mite fauna in the indoor environment of Singapore. Immediate hypersensitivity to these dust mites, along with other known indoor allergens, may play a role in the pathogenesis of allergic respiratory diseases. This study evaluated the sensitization rates of the local atopic population to these allergens.

A rule-based approach for robust clump splitting

This paper presents a robust rule-based approach for the splitting of binary clumps that are formed by objects of diverse shapes and sizes. First, the deepest boundary pixels, i.e., the concavity pixels in a clump, are detected using a fast and accurate scheme. Next, concavity-based rules are applied to generate the candidate split lines that join pairs of concavity pixels. A figure of merit is used to determine the best split line from the set of candidate lines. Experimental results show that the proposed approach is robust and accurate.

Age- and Sex-Related Changes in Lymphocyte Subpopulations of Healthy Asian Subjects: From Birth to Adulthood

Flow cytometric analysis of lymphocyte subsets were evaluated in 391 healthy Asian subjects ranging in age from birth to 40 years. Lymphocyte subsets were analysed using specific monoclonal antibodies: CD20 (B cells), CD3 and CD2 (T cells), CD16 and CD56+ (NK cells), CD4/CD3+ (helper-inducer T cells), CD8/ CD3+ (suppressor/cytotoxic T cells), HLA-DR expression on CD3 and CD25 (Tac) on CD3. The total white cell count, absolute lymphocyte counts, and B cell percentages peaked in infancy and declined steadily with age. Absolute counts of each subset, which were derived from absolute lymphocyte counts, also followed this trend. Increases with age were seen in the NK, T cell (CD2, CD3), and CD8 percentages. Males tended to have higher NK and CD8 percentages than females, and, conversely, females had higher CD3 and CD4 percentages than males. Comparison of our results with studies involving Caucasian subjects indicated higher NK percentages in our Asian population and lower CD4 absolute counts in the males of our population. These results indicate the presence of age, sex, and probable racial differences in lymphocyte subset expression. Our results may serve as reference standards for the Asian population.

PATTERN OF FOOD-INDUCED ANAPHYLAXIS IN CHILDREN OF AN ASIAN COMMUNITY

a tricyclic antidepressant. In week 4 of the treatment with phenytoin, the patient developed in 24±48 h fever of 398C combined with generalized erythematous skin rash. The other systemic and neurologic probes were normal. The blood cell count showed leukocytosis with eosinophilia (16 500 leukocytes/mm, 12% eosinophils), and the coagulation study, biochemical and hepatic pro®le, hemocultures, coprocultures, and urocultures then done, as well as the chest radiography, were normal. Computed tomography of the skull described the continuity to a parietal level without any other important alteration. With the clinical suspicion that there was an adverse reaction to medication, the phenytoin and the tricyclic antidepressant were stopped. During the following week, the patient continued to show fever and eosinophilia, and the skin rash became desquamative. The clinical situation worsened gradually and between days 8 and 10 after stopping the phenytoin, she showed acute hepatic failure with high cytolysis and cholestasis (glucose 57 mg/dl, SGOT 1535 U/l, SGPT 497 U/l, gamma GT 1055 U/l, alkaline phosphatase 662 U/l, cholesterol 110 mg/dl, total bilirubin 17.5 mg/dl, LDH 2862 U/l, albumin 1.7 g/dl), linked to severe coagulopathy (prothrombin Ac. 21%, APTT 53/29). The analysis then done did not reveal any indication of a possible cause, and the abdominal echography showed only a spleen slightly increased in size. In the following days, the patient developed acute renal failure and pancytopenia with severe neutropenia (2400 leukocytes/mm with 190 neutrophils, 10 000 blood platelets/mm, hemoglobin 8.9 g/dl). The patient died 15 days after stopping the phenytoin. The autopsy showed submassive hepatic necrosis linked to splenomegaly, and moderate in ̄ammatory in®ltrated vascular congestion of the skin. The anatomopathologic diagnosis was phenytoin hypersensitivity syndrome. Phenytoin is an anticonvulsant affecting hepatic metabolism. Among its more frequent side-effects are gastric intolerance, skin rash, and gingival hyperplasia. Less frequently, cases of hypersensitivity syndrome to DFH have been described. This syndrome with anticonvulsants was ®rst described in 1950 by Chaiken et al. (1); they called it dilantin hypersensitivity syndrome. Later, cases involving carbamacepine, primidone, and phenobarbital were described. The hypersensitivity syndrome to phenytoin is of low incidence (1/1000±10 000 treated with DFH), and it usually appears between weeks 1 and 4 of treatment. Risk factors have not been clearly identi®ed when they appeared and their origin is not dose dependent. Skin signs were the most common in the syndrome in the study by Silverman (2). Fever, lymphadenopathies, and megalies are common, as well as leukocytosis and eosinophilia. Aplastic marrow and hepatic affectation are less common. Those rare signs appear late during the development of the syndrome, and most of the patients who develop them have previous skin alterations. The pathogenic mechanism of this syndrome has not been established. Most of the facts suggest a hypersensitivity phenomenon, although idiosyncratic and toxic mechanisms with enzymatic induction of Cp 450 and the production of intermediary metabolites have also been involved. These metabolites are potentially cytotoxic, and they can alter the lymphocytic function, increasing the hepatocellular necrosis and lymphadenopathies, as described by Haword et al. (3). The diagnosis of this syndrome is clinical and analytic. Studies of lymphocytic stimulation and the patch test can indicate the therapeutic option of withdrawal of DFH, although the patients condition can alter. This emphasizes the danger of a premature diagnosis. Steroids are usually used during the treatment, although their indexing is not well established and does not alter the mortality rate. However, they are effective in the skin symptoms and can shorten their course. Excessive medication taken with DFH can worsen the prognosis. Dreifuss et al. (4) have shown cross-reactivity with other anticonvulsants and interaction with antidepressants. The mortality rate in this syndrome rises to 30±40% if hepatic damage occurs. Mullick (5), in a clinical pathologic study, has reported 20 cases of hepatic injury associated with diphenylhydantoin; the mortality rate without hepatic affectation was 10%. Our patient showed hypersensitivity syndrome to DFH after 4 weeks of treatment. She developed fever, desquamative erythema, and eosinophilia linked to aplastic marrow and severe hepatic failure, which caused her death.

Detection of two orchid viruses using quartz crystal microbalance (QCM) immunosensors.

Quartz crystal microbalance (QCM) immunosensors are based on the principle that adsorption of substances on the surface of a quartz crystal changes its resonance oscillation frequency. A QCM immunosensor was developed for the detection of both cymbidium mosaic potexvirus (CymMV) and odontoglossum ringspot tobamovirus (ORSV) by pre-coating the QCMs with virus-specific antibodies. Upon binding of virions in either purified form or crude sap of infected orchids with the immobilised virus antibodies, the increase in mass at the QCM surface resulted in a reduction in the frequency of resonance oscillation in a manner dependent upon the amount of virus bound. The QCM was able to detect as low as 1 ng each of the two orchid viruses. This detection sensitivity is comparable to enzyme linked immunosorbent assay (ELISA) but the assay is faster. This immunoassay was shown to be specific, sensitive, rapid and economical, thus providing a viable alternative to virus detection methods. This is the first report using QCM immunosensors to detect plant viruses.

Multiple wheat flour allergens and cross-reactive carbohydrate determinants bind IgE in baker’s asthma

To cite this article: Sander I, Rozynek P, Rihs H‐P, van Kampen V, Chew FT, Lee WS, Kotschy‐Lang N, Merget R, Brüning T, Raulf‐Heimsoth M. Multiple wheat flour allergens and cross‐reactive carbohydrate determinants bind IgE in baker’s asthma. Allergy 2011; 66: 1208–1215.

House dust mite fauna of tropical Singapore.

Sensitization to house dust mites is very common in the tropics. This study evaluated the dust mite fauna in Singaporean homes.

Associations between home dampness and presence of molds with asthma and allergic symptoms among young children in the tropics.

Existing literature has shown that home dampness increases indoor mold burden and is associated with increased allergic symptoms among young children in temperate environments. There is no report of any studies of similar nature in the tropics where conditions are characterized typically by high temperatures and humidity with rainfall throughout the year. To evaluate if there are associations between the prevalence of current asthma and allergic symptoms in young children (age 1.5–6 yr) with dampness and indoor mold in childrens bedrooms in a tropical environment. A cross‐sectional study adopting an expanded and modified ISAAC –International Study on Asthma and Allergies in Children– questionnaire for the evaluation of asthma and allergies was conducted on 6794 children (4759 responded – 70%) attending 120 randomly selected daycare centers. Specific information on demographics, home dampness, and the visible presence of indoor molds were obtained. The prevalence ratios (PR) and 95% confidence interval (CI) were determined by Cox proportional hazard regression model with assumption of a constant risk period as recommended for cross‐sectional studies. The calculated PRs were controlled for age, gender, ethnicity, socio‐economic status, type of housing, maternal and paternal atopy, respiratory infections, environmental tobacco smoke (ETS) exposure, and food allergy. After adjusting for potential confounding effects, home dampness was observed to be significantly associated with current symptoms of rhinoconjunctivitis (adjusted PR 1.53, 95% CI: 1.00–2.33). The visible presence of mold was significantly associated with current symptoms of rhinitis (PR 1.55, 95% CI: 1.16–2.07) and rhinoconjunctivitis (PR 2.38, 95% CI: 1.51–3.75). Indoor dampness and mold in childrens bedroom are important risk factors associated with allergic symptoms in young children in Singapore.