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  1. Rapid typing of dengue viruses by the microprecipitin agar gel diffusion technique
    Chan YC
    Med J Malaya, 1965 Sep;20(1):83.
    PMID: 4221437
  2. Lo, the ever confounding nipple shadow!
    Boo WH, Chan YC
    Malays Fam Physician, 2020;15(3):79-82.
    PMID: 33329866
    The discovery of a solitary pulmonary nodule (SPN) on chest imaging can be alarming for both the clinician and the patient. In the absence of a uniform guideline, managing SPN is nothing short of challenging for primary care physicians (PCPs). We present a case here of a patient presenting with prolonged cough who also displayed unilateral SPN on her chest radiograph. Through further examination, this presence was later shown to be a nipple shadow simulating SPN, and the patient was spared unnecessary testing and psychological distress.
  3. Comparative analysis of NS3 sequences of temporally separated dengue 3 virus strains isolated from southeast Asia
    Chow VT, Seah CL, Chan YC
    Intervirology, 1994;37(5):252-8.
    PMID: 7698880
    By a combination of PCR and direct-cycle sequencing using consensus primers, we analyzed approximately 400-bp fragments within the NS3 genes of twenty-one dengue virus type 3 strains isolated from five neighboring Southeast Asian countries at different time intervals from 1956 to 1992. The majority of base disparities were silent mutations, with few predicted amino acid substitutions, thus emphasizing the strict conservation of the NS3 gene. Phylogenetic trees constructed on the basis of these nucleotide differences revealed distinct but related clusters of strains from the Philippines, Indonesia, and strains from Singapore and Malaysia of the 1970s and early 1980s, while the Thai cluster was relatively more distant. This genetic relationship was compatible with that proposed by other workers who have studied other dengue 3 virus genes such as E, M and prM. However, we observed that the more recent, epidemic-associated dengue 3 strains from Singapore and Malaysia of the late 1980s and early 1990s were more closely related to the Thai cluster, implying their evolution from the latter, and emphasizing the importance of viral spread via increasing travel within the Southeast Asian area and elsewhere. Nucleotide sequence analysis of the NS3 genes of dengue viruses can serve to advance the understanding of the epidemiology and evolution of these viruses.
  4. Haemorrhagic fever with renal syndrome: clinical, virological and epidemiological perspectives
    Chan YC, Wong TW, Yap EH
    Ann Acad Med Singap, 1987 Oct;16(4):696-701.
    PMID: 2895603
    Haemorrhagic fever with renal syndrome (HFRS) is caused by a group of RNA viruses within the family of Bunyaviridae known as hantaviruses. The classical, severe form of HFRS is characterized by fever, headache, abdominal and lumbar pain, proteinuria, haemorrhagic phenomena, shock and renal failure. The disease is associated with the prototype Hantaan virus and occurs in rural areas of Korea and China with Apodemus mice as reservoir hosts. A clinically less severe form of HFRS, which is caused by Seoul virus, occurs in urban areas with the house rat Rattus novegicus as the main reservoir host. The disease in nonendemic areas may be atypical and patients with symptoms the hepatitis and minimal renal involvement have been observed in Malaysia. Outbreaks of HFRS in humans involving infected laboratory rat colonies have occurred in several medical centres in various countries. Hantaviruses cause a chronic, asymptomatic infection in rodents which excrete the virus in their lungs, saliva and urine. Man becomes infected mainly by inhalation of infected droplets from healthy rodent carriers. Seroepidemiological studies using mainly the indirect immunoflourescent antibody test of sera from humans and rats showed that hantaviruses have a worldwide distribution.
  5. Fulltext Clinical profile, morbidity and outcome of adult patients with psoriasis at a district hospital in Northern Malaysia
    Loo CH, Chan YC, Lee KQ, Tharmalingam P, Tan WC
    Med J Malaysia, 2015 Jun;70(3):177-81.
    PMID: 26248781 MyJurnal
    INTRODUCTION: Psoriasis is a common, chronic, relapsing, immune-mediated inflammatory disease. Our objective is to review the clinical profile, co-morbidities, and outcome of patients with psoriasis.
    METHODS: This is a cross-sectional study of outpatient psoriasis patients attending the dermatology clinic, Hospital Sultan Abdul Halim (HSAH) between January 2012 and June 2014. Data collection was based on Malaysian Psoriasis Registry.
    RESULTS: Among 296 patients with psoriasis, Malays were the most common 175 (59.1%), followed by Indians 82 (27.7%), Chinese 37 (12.5%) and others 2 (0.6%). Male to female ratio was 1.2:1. More than half (54.7%) of the patients had early onset disease (age 40 or less). Only 26 patients (8.8%) have positive family history. The most common clinical presentation was chronic plaque psoriasis (89.9%), followed by erythrodermic psoriasis (4.7%), guttate psoriasis (3.0%) and pustular psoriasis (1.7%). Twenty eight percent had nail involvement while arthropathy was seen only in 14.7%. Common triggers were sunlight (46.0%), stress (31.1%), trauma (5.4%), food (4.0%), pregnancy (4.0%), and upper respiratory tract infections (2.7%). Co-morbidities observed include ischaemic heart disease (7.1%), hypertension (26.7%), dyslipidemia (17.6%), and diabetes mellitus (22.0%). All patients were on topical medications. About 6.8% of the patients were treated with phototherapy. One third of patients (35.5%) were given systemic therapy. Out of these, 84 patients (80.0%) were on methotrexate while only 16 (15.2%) on acitretin. None was on cyclosporine or biologic. In term of disease severity, 41.7% of patients had BSA >10% and 31.4% patients had DLQI > 10.
    CONCLUSION: Our patients show a similar clinical profile and outcome as our Malaysian psoriasis population. However they tend to have a more severe disease. There is a need for a more effective targeted therapy for a better outcome.
    Study site: Dermatology clinic, Hospital Sultan Abdul Halim (HSAH), Sungai Petani, Kedah, Malaysia
  6. Fulltext Stigmatizing attitudes toward people living with HIV/AIDS (PLWHA) among primary health care providers in Kinta District, Perak
    Chan YC, Binti Mawardi M, Ismail Daud AH
    Malays Fam Physician, 2021 Mar 25;16(1):31-38.
    PMID: 33948140 DOI: 10.51866/oa0001
    Background: Stigmatizing attitudes expressed by health care providers prevent some members of at-risk populations from accessing human immunodeficiency virus (HIV) screening and care. This attitude contributes to the continuity of the infection dissemination within our community, which gives an impact on the healthcare service and the curtailment of the global HIV/acquired immunodeficiency syndrome (AIDS) pandemic.

    Objective: This study was conducted to identify stigmatizing attitudes toward people living with HIV/AIDS (PLWHA) and their determinants among primary health care providers in Kinta District, Perak.

    Methodology: A cross-sectional study was conducted in 36 primary care clinics in Kinta District, Perak. Using stratified random sampling, 365 primary health care providers were recruited into the study. A validated self-administered questionnaire was used to obtain sociodemographic data as well as information on the healthcare experiences of healthcare providers, their knowledge of HIV/AIDS, and attitudes toward PLWHA. Determinants were identified using multiple linear regression.

    Results: More than half of the respondents (54.1%) had never provided care to HIV/AIDS patients. A minority (29.9%) had received training on HIV/AIDS. This study shows that doctors (Coef.= -9.50, 95% CI: -18.93, -0.07, p= 0.048), respondents with HIV-positive relatives, (Coef.= -5.61, 95% CI: -10.57, -0.65, p= 0.027), those who had provided care to HIV/AIDS patients (Coef.= -2.38, 95% CI: -4.31, -0.45, p= 0.016), and those with a higher knowledge score on HIV/AIDS (Coef.= -0.86, 95% CI: -1.59, -0.13, p= 0.021) were less likely to show stigmatizing attitudes toward PLWHA.

    Conclusion: The issue of stigmatizing attitudes toward PLWHA among primary health care providers needs to be addressed. This study finds that knowledge, profession, experiences with caring for PLWHA, gender, and having HIV-positive relatives are significant predictors of stigmatizing attitudes toward PLWHA among primary health care providers in Kinta District, Perak. Interventional programs to improve knowledge and awareness, as well as decrease stigma toward PLWHA, should be implemented among all health care providers, especially those who have no opportunity to provide direct care.

  7. Fulltext Poor tolerance of motor cortex rTMS in chronic migraine
    Teo WP, Kannan A, Loh PK, Chew E, Sharma VK, Chan YC
    J Clin Diagn Res, 2014 Sep;8(9):MM01-2.
    PMID: 25386478 DOI: 10.7860/JCDR/2014/9377.4886
    BACKGROUND: Two small studies had evaluated the efficacy of rTMS in migraine. One tested high frequency rTMS over the dorsolateral prefrontal cortex while the other evaluated 1 Hz rTMS over the vertex.
    AIM: To test the feasibility of 10 Hz rTMS of motor cortex as an adjunctive therapy in patients with chronic migraine
    Materials and Methods: We randomized (2:1 ratio) chronic migraine patients on medical preventive treatment to receive either rTMS or sham therapy for 10 sessions. rTMS (80% resting motor threshold, 10Hz, 20 trains, 5 secs/train, inter-train interval 1 min, total 1000 stimuli/session) was applied over the right motor cortex.
    RESULT: Nine patients were randomized. Six received rTMS and three had sham therapy. Three patients in the rTMS arm withdrew from the study due to increased headache frequency and discomfort from the treatment. The remaining six cases (3 rTMS, 3 sham) completed the study. The study was prematurely stopped due to the significant worsening of headache from rTMS. No significant differences in outcome measures were found between real and sham rTMS.
    CONCLUSION: Although the study was terminated prematurely, the high dropout rate (50%) due to worsening headaches suggested that rTMS over the motor cortex is poorly tolerated in chronic migraine.
    KEYWORDS: Adverse effect; Central sensitization; Chronic migraine; Cortical excitability; Headache; rTMS
    Study site: Neuroscience clinic of National University Hospital, Singapore
  8. Are ERM (ezrin/radixin/moesin) proteins targets for autoantibodies in demyelinating neuropathies?
    Miyaji K, Shahrizaila N, Umapathi T, Chan YC, Hirata K, Yuki N
    Hum Immunol, 2014 Nov;75(11):1089-91.
    PMID: 25286001 DOI: 10.1016/j.humimm.2014.09.010
    Ezrin, radixin and moesin, which are strongly expressed in the Schwann cell microvilli, are putative targets for autoantibodies in acute or chronic inflammatory demyelinating polyneuropathy (AIDP or CIDP). An association between anti-moesin IgG antibodies and cytomegalovirus-related AIDP has been postulated. None of 41 AIDP patients, including 8 cytomegalovirus-related AIDP patients, and 23 CIDP had IgG or IgM antibodies to ezrin, radixin and moesin; whereas, one patient with cytomegalovirus-related AIDP had anti-ezrin IgM antibodies. Ezrin, radixin and moesin are unlikely targets for autoantibodies in AIDP and CIDP, and the association of anti-moesin antibodies with cytomegalovirus-related AIDP was not confirmed.
  9. The value of comparing mortality of Guillain-Barré syndrome across different regions
    Wong AH, Umapathi T, Shahrizaila N, Chan YC, Kokubun N, Fong MK, et al.
    J Neurol Sci, 2014 Sep 15;344(1-2):60-2.
    PMID: 24993467 DOI: 10.1016/j.jns.2014.06.021
    To study the clinical profile of Guillain-Barré syndrome (GBS) patients who died in 4 Asian countries in order to understand factors underlying any variation in mortality.
  10. Fulltext Antibodies to single glycolipids and glycolipid complexes in Guillain-Barré syndrome subtypes
    Shahrizaila N, Kokubun N, Sawai S, Umapathi T, Chan YC, Kuwabara S, et al.
    Neurology, 2014 Jul 8;83(2):118-24.
    PMID: 24920848 DOI: 10.1212/WNL.0000000000000577
    To comprehensively investigate the relationship between antibodies to single glycolipids and their complexes and Guillain-Barré syndrome subtypes and clinical features.
  11. Fulltext Comparison of PCR-based genotyping methods for hepatitis B virus
    Lim CK, Tan JT, Ravichandran A, Chan YC, Ton SH
    Malays J Pathol, 2007 Dec;29(2):79-90.
    PMID: 19108399 MyJurnal
    Hepatitis B virus (HBV) is classified into eight genotypes (A to H). In this study, three genotyping methods were compared for their sensitivity and accuracy, namely PCR-RFLP on the S region, PCR-RFLP on the pre-S region and nested PCR with type specific primers. Sixty HBV samples from infected sera were genotyped. The nested PCR with type specific primers was found to be the most sensitive and produced substantial numbers of co-infections by genotypes B and C. The sensitivities for both PCR-RFLP methods were lower and did not reveal co-infections. Generally, the three methods produced consistent genotyping results in samples infected by single genotypes but for co-infections by genotypes B and C, the two PCR-RFLP methods yielded only single genotypic results. For the cases of single genotypic infections, genotypes ascertained by sequencing were in concordance across all three methods. However, when co-infections occurred, PCR analysis on clones revealed only single genotypic infections.
  12. Epidemiological aspects of an outbreak of dengue fever/dengue haemorrhagic fever in Singapore
    Goh KT, Ng SK, Chan YC, Lim SJ, Chua EC
    Southeast Asian J. Trop. Med. Public Health, 1987 Sep;18(3):295-302.
    PMID: 3433161
    A nation-wide outbreak of 260 cases of DF/DHF with 1 death occurred in Singapore from Apr-Sept 1986. The outbreak originated from 3 separate foci of transmission at the western, south-eastern and north-eastern parts of the island and then spread to other dengue receptive urban and suburban areas. The morbidity rate was highest in young male Chinese adults between 15 and 24 years of age. The outbreak was rapidly brought under control through destruction of adult Aedes mosquitoes, surveys and source reduction of larval breeding habitats, health education and to a certain extent law enforcement. The Aedes population was high in the main foci of transmission although the overall house index was only 1.1. Other factors which could have precipitated the outbreak included waning herd immunity of the human population and continuous introduction of dengue virus into the country.
  13. Haemorrhagic fever with renal syndrome involving the liver
    Chan YC, Wong TW, Yap EH, Tan HC, Lee HW, Chu YK, et al.
    Med J Aust, 1987 Sep 07;147(5):248-9.
    PMID: 2890086
    A case of haemorrhagic fever with renal syndrome that originated in Malaysia is reported. The patient presented with clinical symptoms which were not typical of the disease as seen in endemic regions. Renal involvement, which is characteristic of haemorrhagic fever with renal syndrome, was mild, and the predominant symptom was a persistently marked elevation of serum transaminase levels that was suggestive of hepatitis. Liver involvement has not been described in the Asian form of haemorrhagic fever with renal syndrome. The patient developed a petechial skin rash and had severe thrombocytopenia. Serological confirmation of the diagnosis of haemorrhagic fever with renal syndrome was obtained by the demonstration of significant antibody rises to hantaviruses in the patient's acute- and convalescent-phase sera.
  14. Correlations of HBV genotypes, mutations affecting HBeAg expression and HBeAg/ anti-HBe status in HBV carriers
    Lim CK, Tan JT, Khoo JB, Ravichandran A, Low HM, Chan YC, et al.
    Int J Med Sci, 2006;3(1):14-20.
    PMID: 16421626
    This study was carried out to determine the effects of hepatitis B virus genotypes, core promoter mutations (A1762G1764-->T1762A1764) as well as precore stop codon mutations (TGG-->TAG) on HBeAg expression and HBeAg/ anti-HBe status. Study was also performed on the effects of codon 15 variants (C1858/ T1858) on the predisposition of precore stop codon mutations (TGG-->TAG). A total of 77 sera samples were analyzed. Fifty one samples were successfully genotyped of which the predominant genotype was genotype B (29/ 51, 56.9 %), followed by genotype C (16/ 51, 31.4 %). Co-infections by genotypes B and C were observed in four samples (7.8 %). To a lesser degree, genotypes D and E (2.0 % each) were also observed. For core promoter mutations, the prevalence was 68.8 % (53/ 77) for A1762G1764 wild-type and 14.3 % (11/ 77) for T1762A1764 mutant while 9.1 % (7/ 77) was co-infected by both strains. The prevalence of codon 15 variants was found to be 42.9 % (33/ 77) for T1858 variant and 16.9 % (13/ 77) for C1858 variant. No TAG mutation was found. In our study, no associations were found between genotypes (B and C) and core promoter mutations as well as codon 15 variants. Also no correlation was observed between HBeAg/ anti-HBe status with genotypes (B and C) and core promoter mutations.
  15. Electrodiagnosis of reversible conduction failure in Guillain-Barré syndrome
    Chan YC, Punzalan-Sotelo AM, Kannan TA, Shahrizaila N, Umapathi T, Goh EJH, et al.
    Muscle Nerve, 2017 Nov;56(5):919-924.
    PMID: 28093784 DOI: 10.1002/mus.25577
    INTRODUCTION: In this study we propose electrodiagnostic criteria for early reversible conduction failure (ERCF) in axonal Guillain-Barré syndrome (GBS) and apply them to a cohort of GBS patients.

    METHODS: Serial nerve conduction studies (NCS) were retrospectively analyzed in 82 GBS patients from 3 centers. The criteria for the presence of ERCF in a nerve were: (i) a 50% increase in amplitude of distal compound muscle action potentials or sensory nerve action potentials; or (ii) resolution of proximal motor conduction block with an accompanying decrease in distal latencies or compound muscle action potential duration or increase in conduction velocities.

    RESULTS: Of 82 patients from 3 centers, 37 (45%) had ERCF, 21 (26%) had a contrasting evolution pattern, and 8 (10%) had both. Sixteen patients did not show an amplitude increase of at least 50%.

    CONCLUSION: Our proposed criteria identified a group of patients with a characteristic evolution of NCS abnormality that is consistent with ERCF. Muscle Nerve 56: 919-924, 2017.

  16. A study on the knowledge, attitudes and practices of Southeast Asian dermatologists in the management of atopic dermatitis
    Chan YC, Tay YK, Sugito TL, Boediardja SA, Chau DD, Nguyen KV, et al.
    Ann Acad Med Singap, 2006 Nov;35(11):794-803.
    PMID: 17160196
    INTRODUCTION: This study evaluated the knowledge, attitudes and practices of Southeast Asian dermatologists in the management of atopic dermatitis (AD).

    MATERIALS AND METHODS: A questionnaire survey of 255 dermatologists in Indonesia, Malaysia, the Philippines, Singapore, Thailand and Vietnam.

    RESULTS: Familiarity with diagnostic criteria varied considerably. The usage of moisturisers by the respondents from Vietnam and Indonesia was significantly less frequent than the other countries. Most respondents (91% to 100%) used topical corticosteroids in children with mild-to-moderately severe dermatitis. Some respondents in the Philippines (17% to 19%) and Vietnam (11% to 25%) only used topical corticosteroids for severe disease. For infected eczema, most respondents would prescribe systemic antibiotics for mild-to-moderate infection. A minority in the Philippines (14%) and Vietnam (11%) did so only for severe infection. The top 4 systemic antibiotics prescribed most frequently were: erythromycin, cloxacillin, cephalosporin and amoxicillin/clavulanic acid. In Indonesia, a large proportion of the respondents (47%) prescribed amoxicillin most frequently. The majority of respondents (60% to 100%) prescribed both sedating and non-sedating oral antihistamines. Most respondents used oral corticosteroids to treat severe AD. Some in Malaysia, Singapore and Vietnam used cyclosporin (7% to 58%), azathioprine (5% to 31%) and methotrexate (5% to 14%). With the exception of those in Singapore, the majority of respondents (71% to 97%) did not use phototherapy.

    CONCLUSION: Familiarity with diagnostic criteria, the early and judicious use of moisturisers and topical corticosteroids, as well as the treatment of Staphylococcus aureus superinfection with penicillinase-stable antibiotics should be emphasised in this region.

  17. FDG-PET predicted unfavorable tumor histology in living donor liver transplant recipients; a retrospective cohort study
    Ling LL, Hsu CC, Yong CC, Elsarawy AM, Chan YC, Wang CC, et al.
    Int J Surg, 2019 Sep;69:124-131.
    PMID: 31386913 DOI: 10.1016/j.ijsu.2019.07.035
    BACKGROUND: Tumor histology affects outcome after liver transplantation (LT) for hepatocellular carcinoma (HCC). This study explores the association between F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and tumor histology in living donor liver transplantation (LDLT) recipients and their outcome.

    MATERIALS AND METHODS: Two hundred fifty-eight patients with primary liver tumors who underwent FDG-PET before LDLT were enrolled in this retrospective study. Unfavorable tumor histology was defined as primary liver tumor other than a well- or moderately differentiated HCC. Thirteen patients had unfavorable tumor histology, including 2 poorly differentiated HCC, 2 sarcomatoid HCC, 5 combined hepatocellular cholangiocarcinoma, 3 intrahepatic cholangiocarcinoma, and 1 hilar cholangiocarcinoma.

    RESULTS: FDG-PET positivity was significantly associated with unfavorable tumor histology (P < 0.001). Both FDG-PET positivity and unfavorable tumor histology were significant independent predictors of tumor recurrence and overall survival. In a subgroup analysis of patients with FDG-PET-positive tumors, unfavorable tumor histology was a significant independent predictor of tumor recurrence and overall survival. High FDG uptake (tumor to non-tumor uptake ratio ≥ 2) was a significant predictor of unfavorable tumor histology. Patients with high FDG uptake and/or unfavorable tumors had significantly higher 3-year cumulative recurrence rate (70.8% versus 26.2%, P = 0.004) and worse 3-year overall survival (34.1% versus 70.8%, P = 0.012) compared to those with low FDG uptake favorable tumors.

    CONCLUSIONS: The expression of FDG-PET is highly associated with histology of explanted HCC and predicts the recurrence. FDG-PET-positive tumors with high FDG uptake may be considered contraindication for LDLT due to high recurrence rate except when pathology proves favorable histology.

  18. Fulltext Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: A 1-Year Follow-up
    Nguyen TN, Qureshi MM, Klein P, Yamagami H, Mikulik R, Czlonkowska A, et al.
    Neurology, 2023 Jan 24;100(4):e408-e421.
    PMID: 36257718 DOI: 10.1212/WNL.0000000000201426
    BACKGROUND AND OBJECTIVES: Declines in stroke admission, IV thrombolysis (IVT), and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the effect of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), IVT, and mechanical thrombectomy over a 1-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020).

    METHODS: We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, IVT treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases.

    RESULTS: There were 148,895 stroke admissions in the 1 year immediately before compared with 138,453 admissions during the 1-year pandemic, representing a 7% decline (95% CI [95% CI 7.1-6.9]; p < 0.0001). ICH volumes declined from 29,585 to 28,156 (4.8% [5.1-4.6]; p < 0.0001) and IVT volume from 24,584 to 23,077 (6.1% [6.4-5.8]; p < 0.0001). Larger declines were observed at high-volume compared with low-volume centers (all p < 0.0001). There was no significant change in mechanical thrombectomy volumes (0.7% [0.6-0.9]; p = 0.49). Stroke was diagnosed in 1.3% [1.31-1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82-2.97], 5,656/195,539) of all stroke hospitalizations.

    DISCUSSION: There was a global decline and shift to lower-volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared with the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year.

    TRIAL REGISTRATION INFORMATION: This study is registered under NCT04934020.

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