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Biomedical subjects

D W Chan

Publications and source records attributed to D W Chan.

159 records · Page 9Linked to original sources
PubMed1983

Clinical assessment of a radioimmunoassay for free thyroxine using a modified tracer.

A radioimmunoassay for measuring free thyroxine in plasma was introduced by Amersham using a I-125-labeled T4 derivative that does not bind significantly to the thyroxine-binding proteins. We evaluated this RIA for its clinical utility in assessing 278 patients with thyroid and nonthyroidal diseases. The precision of the Amerlex free T4 assay, expressed as coefficient of variation, was 20% at 0.16 ng/dl, 6.9% at 0.55 ng/dl, 4.2% at 1.08 ng/dl, 5.3% at 2.29 ng/dl, and 6.3% at 3.18 ng/dl. A reference range for free T4 was established as 0.68-1.8 ng/dl, n = 171. The correlation coefficients (r) of a dialysis method and a free thyroxine index were 0.871 and 0.911, respectively. Free T4 correctly classified 98% euthyroid, 92% hypothyroid, 100% hyperthyroid, 100% euthyroid with elevated TBG, and 87% of phenytoin patients. In addition, 80 patients with acute nonthyroidal illness were studied. Most of these patients have normal to low free T4, very low T3, and elevated rT3. We found this free T4 assay to be precise, easy to perform, and reliable in classifying thyroid status in most patients.

Evaluation Studies as Topic↗
PubMed1981

Specific binding proteins for human chorionic gonadotrophin in a patient with trophoblastic disease.

Human chorionic gonadotrophin (hCG) is present in high concentration in patients with trophoblastic disease. The hCG concentration parallels tumor activity. The first known case of an endogenous binder for hCG in the serum of a patient with trophoblastic disease is reported. The patient's hCG concentration was not detectable when analyzed by a radioimmunoassay using a double antibody method; however, it was positive by a radioimmunoassay using polyethylene glycol precipitation. A high serum blank was also observed in this patient. This led the authors to suspect the presence of an endogenous binder for hCG. Scatchard analysis of the patient's serum revealed a high affinity binder with Ka = 1 x 10(10) M(-1), concentration of binding site = 2 x 10(-11) M. This investigation strongly suggested a specific binder(s) for hCG in the serum of this patient.

Adolescent↗
PubMed1980

An assessment of Stat Tek: a reagent-strip method for glucose determination.

Stat Tek, a reagent--strip method for glucose determination, has been evaluated. Aqueous solution of glucose standard is not recommended. The linearity of serum glucose is between 630 to 3,450 mg/l. The within run precision is between 0.7% to 3.0%. The day-to-day precision is between 2.8% to 5.6%. The recovery of glucose added to serum is between 95 to 101%. The correlation of glucose by Stat-Tek and SMA 6/60 show small proportional and constant errors. Stat-Tek is simple and easy to use; however, proper quality control and training of the user are essential for the correct measurement of glucose.

Blood Glucose↗
PubMed1977

The binding of a synthetic progestin, R5020 to transcortin and serum albumin.

R5020 (17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione), a synthetic progestin, was tested for its binding to purified human transcortin, albumin and human serum. Scatchard analysis showed that R5020 bound relatively weakly to transcortin (Kass = 8 X 10(6)M-1); in 20% human serum or albumin greater than 90% was bound with low Kass and an indeterminate number of binding sites.

Humans↗
PubMedDate not supplied

Depressive symptoms and depressed mood among Chinese medical students in Hong Kong.

The depressive symptoms and symptom dimensions of 335 undergraduate Chinese medical students were assessed and described using the Beck Depression Inventory (BDI). Although there were subtle sex differences in the endorsement of specific symptoms, male and female medical students did not differ in the degree of depressed mood as reflected in the BDI scores. Using the cutoff scores of 9/10 and 29/30, respectively, close to half of the Chinese medical students would be in the depressed range, and 2% would be in the severely depressed range. While Chinese medical students appeared to have higher mean BDI score than US medical students, their mean score was not higher than that derived from a separate sample of 213 Chinese nonmedical undergraduates.

Adolescent↗
PubMedDate not supplied

Antepartum and postpartum thrombomodulin levels in preeclamptic and normotensive pregnancies.

OBJECTIVE: To determine whether changes in plasma levels of thrombomodulin from antepartum to postpartum reflect the postpartum regression of preeclampsia. METHODS: Twenty-four preeclamptic women and 34 healthy, normotensive women with singleton pregnancies were studied in the third trimester. Plasma levels of thrombomodulin in the antepartum and postpartum periods were measured by a two-site immunoenzymatic assay. Two-tailed Student t test and paired-comparison t test were used for statistical analyses. The results were expressed as mean +/- standard error. RESULTS: Antepartum plasma thrombomodulin levels in preeclampsia were significantly higher than postpartum levels (71.3 +/- 8.5 versus 55.5 +/- 5.4 ng/mL; P = .006), which was not seen in the normotensive controls (49.9 +/- 3.1 versus 44.2 +/- 3.8 ng/mL; P > .05). Antepartum plasma levels of thrombomodulin in preeclamptic women were significantly higher than those in the normotensive controls (P = .01). However, postpartum plasma levels of thrombomodulin in preeclamptic women were not significantly higher than those in the normotensive controls (P > .05). CONCLUSION: Significantly decreased postpartum plasma thrombomodulin levels in preeclamptic pregnancies strongly correspond to clinical postpartum regression of preeclampsia.

Adult↗
PubMedDate not supplied

Multicenter evaluation of the performance and clinical utility in longitudinal monitoring of the Bayer Immuno 1 complexed PSA assay.

We conducted a multicenter evaluation of the analytical and clinical performance of the automated Bayer Immuno 1 complexed PSA (cPSA) assay, and compared assay performance to the Bayer Immuno 1 PSA assay. We sought to determine whether measurements of cPSA could be of clinical utility in the management of patients with prostate cancer. Results of the 10-day imprecision across three evaluation sites produced total CV < 2.50% and an analytical sensitivity of 0.02 microgram/L. There was an increased trend in clinical sensitivity for prostate cancer with increasing stage of disease (71-86%). Clinical specificity for patients with benign urogenital disease was 74.8%, and for other nonprostate diseases ranged from 91.1-100%. Retrospective serial monitoring of 155 patients with prostate cancer demonstrated concordance of cPSA measurements to clinical status for 97% of the patients analyzed. Results from the clinical studies using the Bayer Immuno 1 cPSA assay were comparable to results obtained with the Bayer Immuno 1 PSA assay. The Bayer Immuno 1 cPSA assay demonstrates analytical performance and clinical effectiveness in the management of prostate cancer patients during the course of disease and therapy.

Adolescent↗
PubMedDate not supplied

Multicenter evaluation of the Elecsys CA 125 II assay.

The technical performance and clinical usefulness of the newly developed Elecsys CA 125 II assay (Boehringer Mannheim) was evaluated in a multicenter study. Imprecision studies were carried out using control sera and human pool sera with CA 125 concentrations from 11 to 1026 U/ml. Within-run CVs between 0.7 to 4.8% (median 1.7%) and between-day CVs between 2.4 to 10.9% (median 5.7%) were found. Method comparison studies with Enzymun-Test CA 125 II carried out in four laboratories yielded slopes between 0.94 to 1.07 and intercepts < 3 U/ml. A good comparability of the Elecsys CA 125 II assay was also found with one MEIA and the Centocor" IRMA. For a second MEIA and a second IRMA the slopes were 1.23 and 1.42, and the corresponding correlation coefficients were 0.987 and 0.977, respectively. The Elecys CA 125 II concentrations are clearly related to the tumor stage of ovarian carcinoma patients. The maximum of diagnostic efficiency of ovarian carcinoma patients compared with patients of benign gynecological diseases is reached at 150 U/ml with a specificity of 93% and a sensitivity of 69%. Follow-up studies of ovarian carcinoma patients reflect the status of the disease and the effect of various therapeutic applications. The technical and clinical evaluation of the Elecsys CA 125 II assay show a superior analytical performance with a broad measuring range up to 5000 U/ml and a short measuring time of 18 minutes.

Biomarkers, Tumor↗
PubMedDate not supplied

Clinical utility of serum HER-2/neu testing on the Bayer Immuno 1 automated system in breast cancer.

UNLABELLED: The clinical utility of automated serum HER-2/neu measurements in breast cancer run on the Bayer random analyzer Immuno 1 was analyzed in several steps: [a] The reference interval was determined for 242 normal healthy pre- and postmenopausal females. [b] The clinical specificity of serum HER-2/neu to separate healthy controls from 210 patients with non-malignant breast--and non-breast diseases was calculated. [c] The clinical sensitivity of cross-sectional serum HER-2/neu values for 204 patients (pts) with stage I-IV breast cancer was established. [d] Specimens from 103 stage IV breast cancer pts were tested for their parallel between serial serum HER-2/neu results and disease course. RESULTS: [a] The value of 13.03 ng/ml exceeded 95% of the results from the healthy female population. Based on the mean +2 standard deviations value of 14.7 ng/dl, the upper limit of normal was established at 15 ng/ml. [b] The specificity for benign breast diseases and other benign non-breast diseases was 98.0% and 94.6%, respectively. [c] The correlation of increased serum HER-2/neu levels and stage of breast cancer revealed the best sensitivity of 40% for stage IV disease. [4] Thirty-eight (36.9%) of 103 stage IV patients had initial HER-2/neu values > 15 ng/ml, 33 of whom showed longitudinal HER-2/neu concentrations which paralleled the clinical course of the disease giving a sensitivity of 86.8%.

Automation↗
PubMedDate not supplied

Longitudinal evaluation of prostate-specific antigen levels in men with and without prostate disease.

OBJECTIVE: To evaluate longitudinal changes in prostate-specific antigen (PSA) levels in men with and without prostate disease. DESIGN: Case-control study of men with and without prostate disease who were participants in a prospective aging study. SETTING: Gerontology Research Center of the National Institute on Aging; the Baltimore (Md) Longitudinal Study of Aging. PATIENTS: Sixteen men with no prostate disease (control group), 20 men with a histologic diagnosis of benign prostatic hyperplasia (BPH), and 18 men with a histologic diagnosis of prostate cancer. OUTCOME MEASURES: Multiple PSA and androgen determinations on serum samples obtained from 7 to 25 years prior to histologic diagnosis or exclusion of prostate disease. RESULTS: Changes in androgen levels with age did not differ between groups. Control subjects did not show a significant change in PSA levels with age. There was a significant difference in the age-adjusted rate of change in PSA levels between groups (prostate cancer greater than BPH greater than control; P less than .01). At 5 years before diagnosis when PSA levels did not differ between subjects with BPH and prostate cancer, rate of change in PSA levels (0.75 micrograms/L per year) was significantly greater in subjects with prostate cancer compared with control subjects and subjects with BPH. Also, rate of change in PSA levels distinguished subjects with prostate cancer from subjects with BPH and control subjects with a specificity of 90% and 100%, respectively. CONCLUSIONS: The most significant factor affecting serum PSA levels with age is the development of prostate disease. Rate of change in PSA levels may be a sensitive and specific early clinical marker for the development of prostate cancer.

Aged↗
PubMedDate not supplied

CA-549: immunohistochemistry and serum levels in breast carcinoma and other neoplasms.

CA-549 is a high molecular weight acidic glycoprotein found in the serum of breast cancer patients. Detection of CA-549 in serum using an immunoradiometric assay has [1] correlated with disease course in breast cancer patients and [2] aided in establishing the diagnosis of breast cancer in patients with metastatic disease. This study examines the expression of CA-549 using immunohistochemistry in normal breast, benign breast disease, breast carcinoma, and a variety of other carcinomas. In addition, in 29 patients both serum and tissue samples were available for correlation. CA-549 was constitutively expressed in normal breast tissue, but immunohistochemical positivity was restricted either to the luminal aspect or entire cell membrane. All patients with benign breast disease had normal levels of CA-549 despite immunohistochemical positivity. Nearly all (98 percent) of breast carcinomas showed reactivity for CA-549, with a majority (82 percent) of the cases showing cytoplasmic positivity. In patients with both serum and tissue studied, those with cytoplasmic staining of the breast carcinomas had mean serum level of 174 U per ml (range 1.9 to 785), compared to 37.3 U per ml (range 2.1 to 86.8) in those with only membrane or luminal staining of tumor (p = 0.0578). Immunoreactive CA-549 was found in many normal epithelia and in other types of carcinomas. CA-549 is [1] constitutively expressed on the cell membrane of normal breast epithelium, [2] commonly present in the cytoplasm of breast carcinomas, and [3] found often in a variety of carcinomas.

Adenocarcinoma↗