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Biomedical subjects

K F Lam

Publications and source records attributed to K F Lam.

32 records · Page 2Linked to original sources
PubMed2003

What are the non-biomedical reasons which make family doctors over-prescribe antibiotics for upper respiratory tract infection in a mixed private/public Asian setting?

OBJECTIVES: To examine the non-biomedical reasons which make family doctors over-prescribe antibiotics for upper respiratory tract infection (URTI) in a mixed private/public Asian setting. METHODS: The questionnaire was sent to the members of the Hong Kong College of Family Physicians between August and December 2001. RESULTS: A total of 801 family doctors completed a postal questionnaire with an overall response rate of 65.0. A significant number of respondents (21.8) felt they might be prescribing antibiotics too often for URTI but the majority of them felt they were using antibiotics just a bit too often. Doctors who were older, more senior or in private practice were more likely to feel that they might be prescribing antibiotics too often. More than 50 of respondents thought that to satisfy the patient or his/her carer and fear of medicolegal problem if the patient deteriorates would make them very likely or likely to over-prescribe antibiotics for patients with URTIs. Public doctors might over-prescribe in order to save time, whereas private doctors might do so in order to keep patients in their practice. CONCLUSION: The results showed that doctors with certain characteristics are more likely to over-prescribe antibiotics. Factors, other than biomedical ones, may play important roles in doctor's prescription of antibiotics for URTI.

Anti-Bacterial Agents↗
PubMed2003

Why do family doctors prescribe antibiotics for upper respiratory tract infection?

The prescribing behaviour of family doctors in Hong Kong towards upper respiratory tract infections (URTIs), and the major clinical factors that might affect such behaviour, were studied. Members of the Hong Kong College of Family Physicians were surveyed; 801 completed the questionnaire with an overall response rate of 65%. Purulent nasal discharge, purulent sputum, persistent fever over three days, patients looking unwell, exudates on throat, inflamed eardrums and cervical lymphadenopathy made more than half the respondents 'likely' or 'very likely' to prescribe antibiotics. Those in private practice and those who graduated in Hong Kong were more likely to prescribe antibiotics, while fellows of the College were less likely to do so. Vocational training and higher qualifications in family medicine/general practice, however, revealed minimal effect. Our results showed that many doctors are still prescribing antibiotics when they encounter URTI patients presenting with clinical factors that have been proven to have no or little benefit from antibiotics.

Adult↗
PubMed2002

Generalized supremum tests for the equality of cause specific hazard rates.

In this paper we propose two new classes of asymptotically distribution-free Renyi-type tests for testing the equality of two risks in a competing risk model with possible censoring. This work extends the work of Aly, Kochar and McKeague [1994, Journal of American Statistical Association, 89, 994-999] and many of the existing tests for this problem belong to these newly proposed classes. The asymptotic properties of the proposed tests are investigated. Simulation studies are done to compare the performance with existing tests. A competing risks data set is analyzed to demonstrate the usefulness of the procedure.

Animals↗
PubMed2002

Anxiety but not depression determines health care-seeking behaviour in Chinese patients with dyspepsia and irritable bowel syndrome: a population-based study.

AIMS: To study the prevalence of dyspepsia and irritable bowel syndrome and the effects of co-existing anxiety and depression on health care utilization by a population survey in Chinese. METHODS: Ethnic Chinese households were invited to participate in a telephone survey using a validated bowel symptom questionnaire and the hospital anxiety and depression scale. Gastrointestinal symptoms were classified as dyspepsia and irritable bowel syndrome according to the Rome I criteria and gastro-oesophageal reflux disease by the presence of weekly heartburn or acid regurgitation. The anxiety and depression scores were compared between patients who sought medical attention and those who did not, using multiple logistic regression analysis. RESULTS: One thousand, six hundred and forty-nine subjects completed the interview (response rate, 62%). The population prevalences of dyspepsia, irritable bowel syndrome and gastro-oesophageal reflux disease were 18.4%, 4.1% and 4.8%, respectively. Dyspepsia and irritable bowel syndrome were associated with anxiety, depression, medical consultation, sick leave and adverse effects on social life. The degree of anxiety was an independent factor associated with health care-seeking behaviour in both dyspeptics (P = 0.003) and irritable bowel syndrome patients (P = 0.036). CONCLUSIONS: Irritable bowel syndrome and dyspepsia are associated with anxiety, depression, significant social morbidity, health care utilization and days off work. Anxiety is an independent factor in determining health care utilization in patients with dyspepsia and irritable bowel syndrome.

Adult↗
PubMed2002

Modeling multivariate survival data by a semiparametric random effects proportional odds model.

In this article, the focus is on the analysis of multivariate survival time data with various types of dependence structures. Examples of multivariate survival data include clustered data and repeated measurements from the same subject, such as the interrecurrence times of cancer tumors. A random effect semiparametric proportional odds model is proposed as an alternative to the proportional hazards model. The distribution of the random effects is assumed to be multivariate normal and the random effect is assumed to act additively to the baseline log-odds function. This class of models, which includes the usual shared random effects model, the additive variance components model, and the dynamic random effects model as special cases, is highly flexible and is capable of modeling a wide range of multivariate survival data. A unified estimation procedure is proposed to estimate the regression and dependence parameters simultaneously by means of a marginal-likelihood approach. Unlike the fully parametric case, the regression parameter estimate is not sensitive to the choice of correlation structure of the random effects. The marginal likelihood is approximated by the Monte Carlo method. Simulation studies are carried out to investigate the performance of the proposed method. The proposed method is applied to two well-known data sets, including clustered data and recurrent event times data.

Animals↗
PubMed2002

Normal 24-hour ambulatory proximal and distal gastroesophageal reflux parameters in Chinese.

OBJECTIVE: To quantify normal proximal and distal oesophageal acid parameters in healthy Chinese. DESIGN: Observational study. SETTING: University teaching hospital, Hong Kong. SUBJECTS AND METHODS: Twenty healthy adults who were not on medication and were free from gastrointestinal symptoms were recruited by advertisement. Ambulatory oesophageal acid (pH<4) exposure parameters were recorded at distal and proximal sites, 5 and 20 cm, respectively above the lower oesophageal sphincter. RESULTS: The 95th percentile for reflux parameters assessed in the distal/proximal oesophagus were: percent total time pH<4, 4.6/0.7%; percent upright time pH<4, 7.0/1.1%; percent supine time pH<4, 4.5/0.5%; number of reflux episodes, 73/12; number of reflux episodes with pH<4 for >5 minutes, 4/0; and the longest single acid exposure episode, 11.2/3.0 minutes. CONCLUSION: Physiological gastroesophageal reflux occurs in healthy Chinese. These initial data provide a preliminary reference range that could be utilised by laboratories studying Chinese subjects.

Adult↗
PubMed2001

Marginal likelihood estimation for proportional odds models with right censored data.

One major aspect in medical research is to relate the survival times of patients with the relevant covariates or explanatory variables. The proportional hazards model has been used extensively in the past decades with the assumption that the covariate effects act multiplicatively on the hazard function, independent of time. If the patients become more homogeneous over time, say the treatment effects decrease with time or fade out eventually, then a proportional odds model may be more appropriate. In the proportional odds model, the odds ratio between patients can be expressed as a function of their corresponding covariate vectors, in which, the hazard ratio between individuals converges to unity in the long run. In this paper, we consider the estimation of the regression parameter for a semiparametric proportional odds model at which the baseline odds function is an arbitrary, non-decreasing function but is left unspecified. Instead of using the exact survival times, only the rank order information among patients is used. A Monte Carlo method is used to approximate the marginal likelihood function of the rank invariant transformation of the survival times which preserves the information about the regression parameter. The method can be applied to other transformation models with censored data such as the proportional hazards model, the generalized probit model or others. The proposed method is applied to the Veteran's Administration lung cancer trial data.

Antineoplastic Agents↗
PubMed2001

Dynamic random effects models for times between repeated events.

We consider recurrent event data when the duration or gap times between successive event occurrences are of intrinsic interest. Subject heterogeneity not attributed to observed covariates is usually handled by random effects which result in an exchangeable correlation structure for the gap times of a subject. Recently, efforts have been put into relaxing this restriction to allow non-exchangeable correlation. Here we consider dynamic models where random effects can vary stochastically over the gap times. We extend the traditional Gaussian variance components models and evaluate a previously proposed proportional hazards model through a simulation study and some examples. Besides, semiparametric estimation of the proportional hazards models is considered. Both models are easily used. The Gaussian models are easily interpreted in terms of the variance structure. On the other hand, the proportional hazards models would be more appropriate in the context of survival analysis, particularly in the interpretation of the regression parameters. They can be sensitive to the choice of model for random effects but not to the choice of the baseline hazard function.

Animals↗
PubMed2001

Family doctors' attitudes towards patient self-management of upper respiratory tract infections.

OBJECTIVES: To determine the clinical attitudes and behaviour of family doctors in Hong Kong towards patient self-management of upper respiratory tract infections, and factors which may influence this practice. DESIGN: Questionnaire survey conducted between February 1999 and April 1999. SETTING: Hong Kong College of Family Physicians. PARTICIPANTS: Members of the Hong Kong College of Family Physicians. RESULTS: A total of 730 family doctors completed a postal questionnaire on self-management of upper respiratory tract infection, giving an overall response rate of 71.9%. The majority (95.2%) of respondents agreed that patients should be advised on self-management. More than two thirds (69.7%) of respondents also considered patients should be advised on self-medications for upper respiratory tract infection. Nearly two thirds and one third of respondents stated they would advise more than 60% of patients on self-management and self-medication, respectively. A close association was noted between the doctor's view on the usefulness of antibiotics for upper respiratory tract infection and patient advice regarding self-management and self-medication strategies. CONCLUSION: Doctors with certain characteristics are more likely to advise patients with upper respiratory tract infection on self-management and self-medication for upper respiratory tract infection.

Adult↗
PubMed1983

Assignment of the alpha and beta chains of human propionyl-CoA carboxylase to genetic complementation groups.

Propionicacidemia is a metabolic disorder resulting from a deficiency of propionyl-CoA carboxylase activity. The enzyme is composed of two polypeptides: a 72,000-dalton alpha chain which contains the biotin ligand and a 56,000-dalton beta chain. It has been suggested that the two major complementation groups in this disorder, pccA and pccBC (with subgroups pccB and pccC), correspond to the genes encoding these two chains. To correlate gene product with complementation groups, 15 mutant and four normal human fibroblast strains were analyzed by [35S]methionine and [3H]biotin labeling. Immunoprecipitation and gel electrophoresis of the polypeptides revealed that alpha chains are synthesized by mutants of pccBC and both subgroups but not in four out of five pccA mutants. On the other hand, beta chains were detected only in pccB mutants. We suggest that pccA encodes the alpha chain of PCC while pccBC encodes the beta chain, and furthermore predict that the beta chain is unstable in the absence of the alpha chain.

Amino Acid Metabolism, Inborn Errors↗
PubMed1977

A kinetic analysis of the processive enzyme Lactobacillus plantarum exoribonuclease.

Oligonucleotide chains consisting of adenosine residues and ranging from 1 to 70 residues in length have been tested as substrates or inhibitors with Lactobacillus plantarum exoribonuclease (EC3.1.4.20). The kinetic constants V, Km, and Ki are all chain-length dependent. Ki decreases with increasing chain length to a minimum for oligonucleotides seven residues in length and then begins to increase slightly. Kinetic plots indicate that the oligonucleotides are almost all competitive inhibitors of poly A hydrolysis. However, the oligonucleotide (Ap)3A greater than p probably leads to mixed inhibition. The enzyme is unable to retain its processivity when it hydrolyzes short oligonucleotides such as (Ap)2A and (Ap)3A. It is proposed that L. plantarum exoribonuclease possesses seven binding sites for the polynucleotide. When the enzyme is bound to a long-chain-length substrate the complex is stabilized by a binding energy of about 8 Kcal/mol. After cleavage of the terminal nucleotide the remaining binding energy is still sufficient to maintain an enzyme-substrate complex. The shortened nucleotide chain is moved relative to the enzyme to re-form the seven-bond association by a gradient of energy of about 1.7 Kcal/mol for the change from six to seven bonds.

Adenosine↗
PubMed1977

Genetic complementation of propionyl-CoA carboxylase deficiency in cultured human fibroblasts.

Propionyl-CoA carboxylase (PCC) deficiency is an inherited metabolic disorder showing considerable variability of expression. We have investigated the possibility that there is a genetic basis for the clinical heterogeneity in this disorder by examining complementation in Sendai virus mediated heterokaryons of mutant fibroblast strains. Restoration of PCC activity was monitored in individual multinucleate cells in situ using a radioautographic procedure which detects the incorporation of 14C-propionate into trichloracetic acid precipitable material. Each mutant strain incorporated negligible amounts of radioactivity compared to control strains. Activity was not restored when different mutants were mixed without virus or when homokaryons were produced by self-fusion. Seven mutant strains were fused in all pairwise combinations and examined for increased 14C-propionate incorporation in heterokaryons. Two main complementation groups were revealed. One group was composed of three mutants. The other was a complex group composed of four mutants in which intragroup complementation was demonstrated. Two mutants showing excellent complementation by radioautography were examined for complementation by the direct assay of PCC ACTIVITY. The enzyme activity of virus-treated preparations with 23% multinucleate cells was 183 U (pmol/min/mg protein) compared to 16 U for the untreated mixture (normal range 450-850 u). We conclude that PCC deficiency resulted from mutations of heterogeneous origin, although the classification of mutants into complementation groups did not correlate with patterns of clinical heterogeneity.

Amino Acid Metabolism, Inborn Errors↗
PubMedDate not supplied

Management of upper respiratory tract infection by family doctors.

The prescribing behaviour of family doctors in Hong Kong towards upper respiratory tract infections (URTIs) and the factors that might affect such behaviour were studied. All 1016 members of the Hong Kong College of Family Physicians were sent a postal questionnaire. A total of 730 family doctors completed the questionnaire, with an overall response rate of 71.8%. Doctors who were older, more senior, or in private practice were more likely to think antibiotics were useful for URTIs and to prescribe them. These doctors were also more likely to think their patients would expect antibiotics from them. Postgraduate vocational training in general practice/family medicine helped make family doctors think fewer patients would expect antibiotics from them but did not affect their perception of the usefulness of antibiotics for URTIs. Our results showed that doctors with certain characteristics were more likely to prescribe antibiotics for URTIs and these doctors may be targeted for continued medical education.

Adult↗