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Biomedical subjects

D W Chan

Publications and source records attributed to D W Chan.

At least 145 records · Page 8Linked to original sources
PubMed1987

Automated quantification of choriogonadotropin: analytical correlation between serum and urine with creatinine correction.

We evaluated the Boehringer Mannheim Diagnostics ES 600 automated immunoassay system for measuring choriogonadotropin (hCG) in human serum, plasma, and urine. The ES 600, an automated sample-selective, multibatch analyzer, is based on immunoenzymometric coated-tube technology. Interassay CVs for assay of both serum and urine ranged from 2% to 16%. The analytical sensitivity was 0.5 int. unit/L. Results for serum correlated well with qualitative "Icon" and quantitative "Tandem" assays (Hybritech). In addition, results for serum and urinary hCG correlated well when the latter was expressed in terms of creatinine excretion. These results suggest that determination of hCG in urine can be correlated with those in serum for use as a marker for chorionic tumors or for screening abnormal pregnancies, where the rate of hCG production may be important.

Autoanalysis↗
PubMed1986

Maturational changes in Canadian adolescents' cognitive attitudinal structure concerning marijuana.

Thirty-four items concerning marijuana use were administered three times to a cohort of Canadian high school students between Grades 11 and 13, in 1977 (n = 439), 1978 (n = 419), and 1979 (n = 167). These items were designed to measure four distinct constructs: attitude, perceived peer approval or disapproval, concern about risks, and symbolic protest against conventional society. A cross-sectional factor analysis of the Grade 13 data supported the hypothesized factor structure, as had earlier work with college students. However, analogous analyses on the Grade 11 and Grade 12 data contradicted the hypothesized factor structure. Most notably, separate factors for positive and negative attitude appeared in the Grade 11 and 12 analyses. The data were interpreted primarily in terms of maturational changes, largely through elimination of alternative interpretations by internal analyses and previous findings. Implications were discussed for adolescent cognitive-attitudinal development, attitude theory, and analysis of panel data.

Adolescent↗
PubMed1986

Sex misinformation and misconceptions among Chinese medical students in Hong Kong.

Sex knowledge and attitudes of 97 Chinese undergraduate medical students were assessed by ratings on a set of belief statements. The results of their responses indicated two salient dimensions of health concern and sex as unclean, reflecting areas of gaps in sex knowledge as well as misconceptions traceable to traditional Chinese beliefs on the association between health and semen. Respondents also reported relying more on the public media than health professionals as a source of sex information. Implications for sex education in general and for medical students in particular are discussed.

Attitude of Health Personnel↗
PubMed1986

Evaluation of a monoclonal immunoenzymometric assay for alpha-fetoprotein.

A monoclonal immunoenzymometric assay for alpha-fetoprotein was evaluated for detection and monitoring of hepatocellular carcinoma (HCC). We studied 1343 serum specimens from 759 patients with various neoplastic and non-neoplastic diseases. The interassay CV for this assay (M-AFP) ranged from 3.5 to 5.5%, with a minimum detectable concentration of 2.2 micrograms/L, as compared with 10 micrograms/L for a polyclonal (P-AFP) RIA for AFP. The calibration curve (0-300 micrograms/L) was linear, and serum dilutions paralleled it. The reference interval (0-9 micrograms/L) was established from data on 111 healthy subjects. Regression analysis of the AFP concentration (0-300 micrograms/L) of HCC patients obtained with the M-AFP assay (y) and the P-AFP RIA (x) yielded the equation y = (1.125)x - 0.52 (r = 0.9395, n = 165), with a considerable number of discrepant results for AFP less than 100 micrograms/L. By M-AFP immunoassay, AFP was above-normal (greater than 9 micrograms/L) in most HCC patients (80%), and to a lesser extent in other liver tumors (48%). AFP was within the normal reference interval for most patients with germ-cell tumors or benign liver disease and for other disease groups. For maximum diagnostic efficiency (90%) for HCC the decision level was increased to 100 micrograms of AFP per liter. Changes in serum AFP were correlated with changes in tumor volume in most HCC patients.

Antibodies, Monoclonal↗
PubMed1986

Affinity chromatographic separation of alpha-fetoprotein variants: development of a mini-column procedure, and application to cancer patients.

This is an affinity chromatographic procedure for separating variants of alpha-fetoprotein in 0.1 mL of serum on a disposable mini-column containing 0.9 mL of concanavalin A-Sepharose, at pH 6.4 and with a flow rate of 5 mL/h. The binding capacity of the column is 52 micrograms. Analytical recovery was 90%. Between-run CVs varied from 2.0% for samples with a high percentage of concanavalin A nonreactive fraction to 13% for samples with a low percentage. The mean proportion of nonreactive alpha-fetoprotein was 13.4% for patients with hepatocellular carcinoma, 62.2% for testicular carcinoma, and 8.9% for nonmalignant liver diseases. This suggests that the alpha-fetoprotein variants could be used to distinguish hepatocellular carcinoma from other carcinomas. Serial determination of the concanavalin A nonreactive fraction in such patients showed a relatively constant percentage. This indicates that monitoring variants in patients with hepatocellular carcinoma throughout their clinical course may not provide useful information additional to that provided by the values for total serum alpha-fetoprotein.

Adenoma, Bile Duct↗
PubMed1986

Performance of solid-state 48 detector gamma counter using solid phase total thyroxin and free thyroxin assays.

We evaluated the performance of an automated 48 detector KinetiCount gamma counter using solid phase reagents for total thyroxin (TT4) and free thyroxin (FT4). Interassay coefficients of variations (CV) for both total T4 and free T4 ranged from 5.4% to 13%. Between-method correlation coefficients were 0.9798 for TT4 and 0.8844 for FT4. Detection limits for TT4 and FT4 were 3 micrograms/l and 3 ng/l, respectively. TT4 was linear up to 200 micrograms/l. The recovery of TT4 was between 99 to 101%. A computer-stored standard curve for total T4 was stable over a 6-day period. The 48 counting chambers demonstrated stability over a 45-day period with no significant changes in counting efficiency (p greater than 0.5). Precision between the 48 chambers gave a CV of 1.6%. Crosstalk between chambers was less than 0.3% with count rates up to 80,000 cpm. We conclude that the KinetiCount immunoassay system using solid phase separation technology performs well and is suitable for routine clinical use.

Evaluation Studies as Topic↗
PubMed1985

The Chinese version of the General Health Questionnaire: does language make a difference?

The English and Chinese versions of the General Health Questionnaire (GHQ) were administered to a sample of 72 bilingual respondents for the evaluation of version equivalence by a series of item analyses, reliability analyses and factor analyses. Although certain notable discrepancies were observed at the item level, the two versions were found to be comparable at the scale level. In addition, cogent evidence was provided for the relative robustness of the symptom dimensions as assessed by the two versions of the GHQ.

Adolescent↗
PubMed1985

Immunoenzymetric assay for creatine kinase MB with subunit-specific monoclonal antibodies compared with an immunochemical method and electrophoresis.

Results of an immunoenzymetric assay (TANDEM-E CKMB) for creatine kinase (CK; EC 2.7.3.2) MB isoenzyme, in which subunit-specific monoclonal antibodies are used, were compared with those by an immunochemical method (Isomune-CK) and electrophoresis (Corning agarose gel). The study involved 200 patients; greater than 500 samples were analyzed by all three methods. The analytical performances were acceptable. Between-method correlation coefficients ranged from 0.881 to 0.975. Two reference intervals were established for the immunoassays: 0-4 micrograms/L (TANDEM) and 0-4 U/L (Isomune) for "normal" patients; 0-9 micrograms/L (TANDEM) and 0-14 U/L (Isomune) for noninfarct patients. Agreement with respect to increased CK-MB as defined by the reference intervals for the noninfarct patient was 96% between TANDEM and electrophoresis, 90% between Isomune and electrophoresis. All three methods are acceptable for use in determining CK-MB, but the overall diagnostic efficiencies for the mass or activity concentration of the isoenzyme and for its proportion of total CK activity, based on the predictive value model, are 92% (electrophoresis, 0-7 U/L), 90% (electrophoresis, 0-4%), 92% (TANDEM, 0-9 micrograms/L), 88% (TANDEM, 0-3% index), 88% (Isomune, 0-14 U/L), and 83% (Isomune, 0-4%). All three methods can detect CK-MB in serum, but its presence is not necessarily diagnostic of acute infarct. We recommend using the actual concentration of CK-MB to evaluate patients with suspected acute myocardial infarct, and the percentage of CK-MB when total CK is very high.

Antibodies, Monoclonal↗
PubMed1984

Life event scaling: the Chinese experience.

Two hundred and sixty-one staff and student members in a university community responded to a questionnaire to rate 69 life events on a scale of 'upsettingness'. There were relatively great consensus in their ratings as a group and relatively great consistency in their ratings across diverse status groups differing in age, sex, marital status and staff-student membership. An examination of specific events however revealed subtle differences among groups. In general, the perception of life events could be meaningfully conceptualized in dimensions interpretable as personal loss and failure, gain and achievement, environmental and role change, personal catastrophe, minor interpersonal problems, and legal and court-related problems. It was suggested that adjustment, control and desirability are event attributes which capture different aspects of the perception of life events.

Adolescent↗
PubMed1984

Dimensions of psychopathology among alcoholic patients, college students, prison inmates and general psychiatric patients.

The Differential Personality Inventory was administered to four samples of subjects: 404 alcoholic patients, 292 college students, 720 prison inmates, and 181 general psychiatric patients. Exploratory factor analysis on the self-report data yielded seven factors in each sample. The six factors, interpreted as common across samples, were: hypochondriacal complaining, blunted affect versus emotional reactivity, interpersonal conflict, depressed withdrawal, cognitive disorganization, and dysfunctional coping. Implications for the empirical development of a multiaxial diagnostic system and the construction of a case-identifying instrument in psychiatric epidemiological research were discussed.

Alcoholism↗
PubMed1984

Medication compliance in a Chinese psychiatric out-patient setting.

The knowledge and attitudes of 36 psychiatric out-patients regarding medication were investigated by personal interview. Over 80 per cent of the variance of self-report medication compliance was predictable from an array of socio-economic variables and cognitive variables. Compliers and non-compliers differed in their expectancy and prior experience of beneficial effects of the medication, and in their fear of undesirable side-effects and the problem of addiction. Using causal modeling procedures, self-report compliant behaviour was causally linked to favourable attitudes and fear, which in turn were linked to knowledge of name, dose, purpose, and side-effects of the medication and the perceived stigma of the illness. Implications for patient education aimed at improving patient compliance are discussed.

Adolescent↗
PubMed1983

Reliability, validity and the structure of the General Health Questionnaire in a Chinese context.

The 30-item General Health Questionnaire (GHQ), the 24-item Self-Reporting Questionnaire (SRQ), and a Chinese version of the Minnesota Multiphasic Personality Inventory (MMPI) were administered to 225 English-speaking Chinese. The GHQ was found to have high internal consistency as a scale and to assess 5 dimensions of psychopathology: anxiety, inadequate coping, depression, insomnia, and social dysfunctioning. As a brief screening instrument, it correlated 0.49 with the SRQ. In the 'case-non-case' classification, it yielded a concordance rate of above 75% with the SRQ. Using the MMPI modal profiles derived from classification research as criterion measures, sensitivity, specificity and correct classification rates were above 70%. Implications for future research with the GHQ are discussed.

Adolescent↗
PubMed1983

Clinical evaluation of two direct procedures for free thyroxin, and of free thyroxin index determined nonisotopically and by measuring thyroxin-binding globulin.

We have investigated the clinical utility of two direct radioimmunoassays for free thyroxin, an enzyme-inhibition immunoassay, and a direct measurement of thyroxin-binding globulin (TBG) by radioassay. All assay methods correctly identified greater than or equal to 90% of euthyroid, hyperthyroid, and hypothyroid patients who had normal TBG concentrations. In patients with altered TBG concentrations, none of the assays correctly classified all categories of patients. However, the direct assays of free thyroxin concentrations were able to classify correctly more patients with altered TBG concentrations than did the free thyroxin index methods. The free thyroxin index methods evaluated may be acceptable for routine use, if the concentration of thyroxin and the measurement of TBG capacity are reported along with the index value. Patients with altered TBG concentrations included a group of euthyroid pregnant patients. Significant decreases in free thyroxin in the third trimester were detected by all the assays studied. For patients in the first and second trimester, the mean free thyroxin concentration measured varied with the assay method.

Evaluation Studies as Topic↗
PubMed1983

Meaning of serum free-thyroxin values in nonthyroidal illnesses: seven methods compared.

Serum free thyroxin (FT4) was determined in 40 patients with various nonthyroidal illnesses. We studied seven methods: (1) a free thyroxin index calculated from total T4 and triiodothyronine resin uptake; (2) a free T4 index determined by enzyme inhibitor assays (Abbott's "Tetrazyme" and "Thyrozyme"); (3) a free T4 index calculated from total T4 and thyroxin-binding globulin; (4) free T4 by equilibrium dialysis; (5) Amersham's free T4 RIA; (6) Clinical Assays' one-step free T4 RIA; and (7) Clinical Assays' two-step free T4 RIA. Approximately half of the free T4 results were in the euthyroid range and the other half in the hypothyroid range by methods 1, 2, 5, and 6. Results for free T4 by methods 3 and 7 were similar to those by equilibrium dialysis (method 4), the percentages of patients with results in the euthyroid range being 68%, 65%, and 76%, respectively.

Dialysis↗