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Biomedical subjects

J Lau

Publications and source records attributed to J Lau.

At least 19 recordsLinked to original sources
PubMed1992

Cumulative meta-analysis of therapeutic trials for myocardial infarction.

BACKGROUND: The large volume of published randomized, controlled trials has led to a need for meta-analyses to track therapeutic advances. Performing a new meta-analysis whenever the results of a new trial of a particular therapy are published permits the study of trends in efficacy and makes it possible to determine when a new treatment appears to be significantly effective or deleterious. We describe the use of such a procedure, cumulative meta-analysis, to assess therapeutic trials among patients with myocardial infarction. METHODS: We performed cumulative meta-analyses of clinical trials that evaluated 15 treatments and preventive measures for acute myocardial infarction. RESULTS: An example of this method is its application to the use of intravenous streptokinase as thrombolytic therapy for acute infarction. Thirty-three trials evaluating this therapy were performed between 1959 and 1988. We found that a consistent, statistically significant reduction in total mortality (odds ratios, 0.74; 95 percent confidence interval, 0.59 to 0.92) was achieved in 1973, after only eight trials involving 2432 patients had been completed. The results of the 25 subsequent trials, which enrolled an additional 34,542 patients through 1988, had little or no effect on the odds ratio establishing efficacy, but simply narrowed the 95 percent confidence interval. In particular, two very large trials, the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico trial in 1986 (11,712 patients) and the Second International Study of Infarct Survival trial in 1988 (17,187 patients) did not modify the already established evidence of efficacy. We used a similar approach to study the accumulating evidence of efficacy (or lack of efficacy) of 14 other therapies and preventive measures for myocardial infarction. CONCLUSIONS: Cumulative meta-analysis of therapeutic trials facilitates the determination of clinical efficacy and harm and may be helpful in tracking trials, planning future trials, and making clinical recommendations for therapy.

Confidence Intervals↗
PubMed1992

A clinical trials database as a research tool in health care.

OBJECTIVE: The rapid, efficient, and accurate communication of clinical research findings to both clinicians and researchers is essential to the process of improving medical care. This information should be conveyed in a form that facilitates the interpretation of the complete body of research on a specific condition. Unfortunately, the prevailing system for dissemination of clinical research fails to meet these criteria. This paper proposes a system for cataloging clinical trials and communicating their results in a comprehensive and comprehensible format. METHOD: The system involves the use of a hierarchical matrix structure that allows for the selection and evaluation of related groups of clinical trials. The format of the data is tailored to the requirements of metaanalysis. RESULTS: An example is presented using the treatment of acute Crohn's disease and including a sample metaanalysis of immunosuppressive therapy for this condition. CONCLUSIONS: The hierarchical matrix structure in conjunction with a comprehensive database of clinical trials holds the potential to facilitate access to and interpretation of clinical research.

Acute Disease↗
PubMed1992

A comparison of results of meta-analyses of randomized control trials and recommendations of clinical experts. Treatments for myocardial infarction.

OBJECTIVE: To examine the temporal relationship between accumulating data from randomized control trials of treatments for myocardial infarction and the recommendations of clinical experts writing review articles and textbook chapters. DATA SOURCES: (1) MEDLINE search from 1966 to present; search terms used were myocardial infarction, clinical trials, multicenter studies, double-blind method, meta-analysis, and the text word "random:"; (2) references from pertinent articles and books; and (3) all editions of English-language general medical texts and manuals and review articles on treatment of myocardial infarction. STUDY SELECTION: Randomized control trials of therapies for reducing the risk of total mortality in myocardial infarction (acute and secondary prevention). Review articles and textbook chapters dealing with the general clinical management of patients with myocardial infarction. DATA EXTRACTION: Two authors read the material and recorded the results; disagreements were resolved by conference. DATA SYNTHESIS: We used the technique of cumulative meta-analysis (performing a new meta-analysis when the results of a new clinical trial are published) and compared the results with the recommendations of the experts for various treatments for myocardial infarction. Discrepancies were detected between the meta-analytic patterns of effectiveness in the randomized trials and the recommendations of reviewers. Review articles often failed to mention important advances or exhibited delays in recommending effective preventive measures. In some cases, treatments that have no effect on mortality or are potentially harmful continued to be recommended by several clinical experts. CONCLUSIONS: Finding and analyzing all therapeutic trials in a given field has become such a difficult and specialized task that the clinical experts called on to summarize the evidence in a timely fashion need access to better databases and new statistical techniques to assist them in this important task.

Humans↗
PubMed1992

Prediction of mortality in patients in acute medical wards using basic laboratory and anthropometric data.

The value of anthropometric and biochemical indices in predicting short-term mortality among patients in general medical wards was assessed in 294 patients admitted consecutively to a district hospital over a one month period. Using a stepwise logistic regression model and supported by the linear discriminant analysis method, mortality within 3 months could be predicted with sensitivity of 83% and specificity of 84% using the following variables: sex, functional ability, urea, total protein, alkaline phosphatase and albumin-adjusted calcium. Addition of anthropometric values and biochemical nutritional indices did little to improve the accuracy of the prediction, contrary to previous findings among surgical patients and elderly residents of long-term care institutions.

Activities of Daily Living↗
PubMed1992

Combined chemotherapy and radiotherapy versus best supportive care in the treatment of inoperable non-small-cell lung cancer.

Between October 1984 and July 1988, 119 patients with limited-stage inoperable non-small-cell lung cancer (NSCLC) were randomized to receive either active treatment (arm 1) or best supportive treatment (arm 2). Arm 1 patients received 3 courses of chemotherapy with cisplatin (100 mg/m2, day 1) and etoposide (125 mg/m2 i.v., day 1; 250 mg/m2 p.o., day 2-3), followed by radiotherapy (4,000 cGy/20 fractions/4 weeks). Arm 2 patients only received best supportive care. Fifty-three and 66 patients were randomized to arms 1 and 2, respectively. Thirty-eight patients in arm 1 and 57 in arm 2 were evaluable for survival. Median survivals of arms 1 and 2 were 12.4 and 8.7 months, respectively (p = 0.047). In the multivariate analysis, only age and histology were independent prognostic variables in predicting survival. The overall response rate after chemotherapy was 20.6% (complete remission 5.9%, partial remission 14.7%). Toxicities were mainly anemia, leukopenia, vomiting and alopecia. This study suggests that active treatment has marginal survival benefit in NSCLC though with considerable toxicities.

Actuarial Analysis↗
PubMed1992

Prevalence of tardive dyskinesia, tardive dystonia, and respiratory dyskinesia among Chinese psychiatric patients in Hong Kong.

OBJECTIVE: Only scanty information on the prevalence of tardive dyskinesia in Chinese patients has been available. This study was undertaken to examine the prevalence of tardive dyskinesia, tardive dystonia, and respiratory dyskinesia in Chinese psychiatric patients in Hong Kong. METHOD: All inpatients of a mental hospital in Hong Kong, except those in the admission and children's wards, were surveyed with the Abnormal Involuntary Movement Scale, and standard research criteria were used to establish the diagnosis of tardive dyskinesia. In addition, patients were screened for tardive dystonia, according to published criteria, and for respiratory dyskinesia by physical examination and laboratory tests. RESULTS: Among the 917 patients surveyed, the prevalence rates were 9.3% for tardive dyskinesia, 0.4% for tardive dystonia, and 1.2% for respiratory dyskinesia. With multivariate analysis, greater age and a lower current dose of antipsychotic, but not the presence of mood disorder, were factors found to be significantly associated with tardive dyskinesia. CONCLUSIONS: The prevalence rates were much lower than those found in Western studies. This may indicate that there is an ethnic difference in the prevalence of these conditions. Prospective cross-cultural studies are necessary to explore this possibility.

Adolescent↗
PubMed1991

Synthesis of 3'-amino-2',3'-dideoxy-hexofuranose nucleosides with potential anti-viral activity.

Michael type addition of DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) phthalimide salt to 4,6-di-O-acetyl-2,3-dideoxy-aldehydo-D-erythro-trans-hex-2-enos e 2 and concomitant acetyl shift give an anomeric mixture of arabino and ribo isomers of 5,6-di-O-acetyl-2,3-dideoxy-3-phthalimido-D-hexofuranose 3 which after acetylation at the anomeric hydroxy group is separated to give 4 and 5. Subsequent reaction with 5'-substituted silylated uracil in the presence of TMS-triflate results in three different 5',6'-di-O-acetyl-2',3'-dideoxy-3'-phthalimido-D-hexofuranose nucleosides 7, 9, and 10 which were deprotected to give the corresponding 3'-amino nucleosides 8, 11, and 12. The compounds 7-12 were investigated for their activity against HSV-1 and HIV-1.

Animals↗
PubMed1991

Free-radical synthesis of 3-(2-cyanoethyl)- and 3-(2-methoxycarbonylethyl)-2,3-dideoxy-alpha-D-erythro-pentofu ranoside and their application in the synthesis of potential antiviral nucleosides.

Free-radical reaction of different carbohydrate educts 2, 5, and 7 with acrylonitrile in the presence of tributyltin hydride and a radical initiator (AIBN) gave the methyl 3-(2-cyanoethyl)-2,3-dideoxypentofuranosides 3a and 6. Similar reaction of 2 with methyl acrylate gave 3-(2-methoxycarbonylethyl)-2,3-dideoxypentofuranose 3b. Nucleoside coupling of 3a with silylated uracil gave an anomeric mixture of beta- and alpha-nucleoside 8 and 9 which were deprotected to give 10 and 11, respectively. Similar reaction of 3b with silylated N4-isobutyrylcytosine gave 12 and 13 which were deprotected to give the final nucleosides 16 and 17, respectively. None of the compounds 10a, 11, 14-17 showed significant activity against HIV.

Antiviral Agents↗
PubMed1991

Increased production of tumour necrosis factor alpha in chronic hepatitis B virus infection.

Plasma tumour necrosis factor alpha (TNF) and in-vitro TNF production by peripheral blood mononuclear cells (PBMC) were studied in 22 HBsAg seropositive patients and compared with 23 normal and 10 disease controls. Plasma TNF and unstimulated TNF production correlated (Rs = 0.55, p = 0.012) and were significantly elevated in HBsAg and HBeAg seropositive patients (p less than 0.001, p = 0.006) compared with normal controls. TNF production was also elevated in these patients when PBMC were stimulated with interferon-gamma (p less than 0.05) or LPS (p = 0.035). Plasma TNF and TNF production in HBsAg anti-HBe seropositive subjects were not elevated. TNF production in unstimulated cells correlated with serum HBV DNA level (R = 0.53, p = 0.02) but not with serum aspartate transaminase (AST) or histological activity. It is concluded that PBMC are activated to produce TNF both spontaneously and in response to second stimuli in chronic hepatitis B virus infection and that this activity is related to the presence of viral replication.

Chronic Disease↗
PubMed1991

Synthesis and evaluation of antiviral activity of L-acosamine and L-ristosamine nucleosides of furanose configuration.

Mercuric-catalyzed hydrolysis of acetylated L-rhamnal 1 gives an alpha,beta-unsaturated aldehyde 2. 1,4-Addition of DBU-phthalimide salt with concomitant acetyl shift resulted in L-ribo and L-arabino isomers of 5-O-acetyl-2,3,6-trideoxy-3-phthalimido-hexofuranose 3 and 4. After acetylation at the anomeric center, coupling with silylated thymine resulted in three new nucleosides, with L-acosamine and L-ristosamine of furanose configuration as the carbohydrate moiety. The target compounds have been evaluated for their antiviral activity against HIV and HSV-1.

Antiviral Agents↗
PubMed1990

Factors of prognostic significance in Chinese children with tuberculous meningitis.

A study was undertaken to identify factors of prognostic importance for 199 Chinese children with tuberculous meningitis treated in Hong Kong between 1961 and 1984 inclusive. During the period under study rifampicin and then pyrazinamide were introduced into treatment regimens and intrathecal therapy was abandoned. An analysis of pretreatment characteristics and details of chemotherapy by multivariate logistic regression identified two independent variables that predicted prognosis, namely clinical stage at the time of diagnosis, and age. Changes in treatment policies and the introduction of new anti-tuberculosis drugs did not appear to influence prognosis.

Adolescent↗
PubMed1990

Incidence of ABO haemolytic disease of the newborn in a group of Hong Kong babies with severe neonatal jaundice.

Two methods were used to determine the incidence of ABO haemolytic disease of the newborn (ABO-HDN) among Hong Kong Chinese infants. The first method employed the Lui elution technique to elute anti-A,B from cord blood of Group A and B babies with a Group O mother, and set out to correlate the titration score of the eluate with the serum bilirubin of the neonates. This method proved to be a failure because of the poor correlation. The second method was mathematical. By comparing the 'expected' frequency of various mother-infant ABO combinations (based on the ABO distribution of our local population) with the 'observed' frequency of a cohort of infants with severe neonatal jaundice, it was found that only two combinations (O-A and O-B mother-infant pairs) were responsible for ABO-HDN, for which the incidence was 1 in 5 among infants with a serum bilirubin level of 300 mumols/L or more.

ABO Blood-Group System↗
PubMed1990

Controlled ovarian hyperstimulation for in vitro fertilization using buserelin and gonadotropin in patients with previous failed cycles.

Fifteen patients who had had previous unsuccessful in vitro fertilization and embryo transfer (IVF) cycles were treated with intranasal buserelin, a gonadotropin releasing hormone agonist (GnRH-a), commencing in the mid-luteal phase prior to ovarian stimulation in the next cycle. The use of buserelin was associated with the suppression of spontaneous luteinizing hormone (LH) surges (nil versus 6), an increase in gonadotropin requirements (27.3 versus 13.7 ampoules), higher serum estradiol peak levels (8, 154 versus 4,446 pmol/l), more oocytes retrieved (87 versus 20) as well as more embryos being transferred (28 versus 7). In buserelin-treated cycles, 2 pregnancies resulted but no oocyte was recovered in 2 of the 3 poor responders.

Adult↗
PubMed1990

Topical prostaglandin E2 gel for cervical ripening and closure of the ductus arteriosus in the newborn.

The closure time of the ductus arteriosus was investigated in 29 full term babies born vaginally after induction with prostaglandin E2 and in 22 controls. Serial Doppler echocardiography studies showed a significantly prolonged closure time in babies induced by prostaglandin E2. Whether the difference is related to changes in fetal prostaglandin E2 concentration remains to be established.

Administration, Topical↗
PubMed1987

Decision analysis: a progress report.

Since its introduction into medicine 15 years ago, decision analysis has been applied to difficult clinical problems. Several important advances have made the process more practical and acceptable: computer programs that eliminate the need for burdensome calculations, improved techniques for designing analytic models, the ability to carry out sensitivity analyses over several dimensions simultaneously, and the elaboration of clinically relevant measures of utility. Using these techniques, analysts have addressed many important clinical issues including screening for and prevention of disease, tradeoffs among tests and treatments, and the interpretation of clinical data under conditions of uncertainty. Problems with the approach remain and applications have not been extensive, but decision analysis is evolving as a powerful clinical tool and gradually is gaining acceptance in medical practice.

Bayes Theorem↗
PubMed1987

Idiopathic nephrotic syndrome. Puncturing the biopsy myth.

We used decision analysis to compare the conventional strategy of biopsy-tailored therapy with alternative strategies not using renal biopsy in treating adults with idiopathic nephrotic syndrome. We evaluated data on steroid and platelet-inhibitor therapies and a new clinical strategy, empiric sequential therapy. This sequential approach involves use of short-term alternate-day steroid agents, followed by long-term platelet inhibitors for persistent nephrotic syndrome. Our results indicate that, contrary to usual practice, use of renal biopsy is not necessary in caring for adult patients with idiopathic nephrotic syndrome; empiric short-term alternate-day steroid therapy is equally efficacious. If the benefits of platelet-inhibitor therapy for treating membranoproliferative glomerulonephritis are confirmed, empiric sequential therapy also will be equally efficacious. Our study shows how decision analysis can be used to identify superfluous diagnostic procedures.

Adult↗
PubMed1979

Mycotic aneurysm of the inferior mesenteric artery.

This is the first reported case of successful management of a mycotic aneurysm of the inferior mesenteric artery. The only helpful clinical manifestations were episodes of previous abdominal pain and a history of bacterial endocarditis. The surgical management involved simple excision without revascularization of the inferior mesenteric artery.

Adult↗