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Biomedical subjects

R H Ng

Publications and source records attributed to R H Ng.

At least 19 recordsLinked to original sources
PubMed1994

Incidence of antiphospholipid antibodies in patients with monoclonal gammopathy of undetermined significance.

The incidence of antiphospholipid antibodies in patients with monoclonal gammopathy of undetermined significance (MGUS) was studied. Antiphospholipid antibodies were measured in the sera of 93 patients (49 women, 44 men; mean age 70 [+/- 21] years) with MGUS by using an enzyme-linked immunosorbent assay (ELISA). The phospholipids tested were cardiolipin (CL), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylglycerol (PG), phosphatidic acid (PA), phosphatidylcholine (PC), and phosphatidylethanolamine (PE). Positive results were defined as a value higher than the number of multiples of the mean per phospholipid, which included 76 of 80 (95%; 20 age-matched) control individuals. The immunoglobulin-G (IgG) or IgM antiphospholipid antibodies isotype varied among the patients, as did the phospholipid specificity. For IgG, PI was found elevated in 32% of the MGUS samples, whereas the other phospholipid antigens ranged from 9% to 15%. The percentage of patients with IgM antiphospholipid antibodies was higher. The authors observed PS, PI, PA, and PC as positive in 45%, 35%, 25%, and 25% of patients, respectively. Of the 12 sera studied for IgA isotype, three (25%) were positive for PS, six (50%) for CL, and none for PE. Patients with MGUS manifested a significantly higher (P < .01) incidence of antiphospholipid antibodies in their blood than did the control persons. No difference in the incidence of antiphospholipid antibodies was seen between younger and older (age-matched) control patients. No correlation was found between serum levels of immunoglobulins and optical density reading of the blank plates used as ELISA controls.

Aged↗
PubMed1992

Results of the multicenter evaluation of the CEDIA cortisol assay.

The present paper describes the multicenter evaluation of the CEDIA Cortisol test for total cortisol. The observed linearity of the test was between 1.2 and 50 micrograms/dL cortisol. The limit of detection was calculated as 1.2/dL. Imprecision studies covering the diagnostically relevant range (5-20 micrograms/dL cortisol) yielded coefficients of variation between 1.7-8.9% (within-run) and 2.7-10.5% (between-day). An interlaboratory survey using 41 human samples and three control sera demonstrated that the new CEDIA Cortisol assay has a good interlaboratory transferability. Method comparison studies between the CEDIA Cortisol test and EIA, FIA, FPIA, and various RIAs yielded an acceptable level of agreement and concordant results in most cases. Low cross-reactivity of the antibody used in the new cortisol assay was observed with precursors or metabolites of cortisol. Especially, dexamethasone did not cross-react. However, prednisolone, 6-methylprednisone, and corticosterone showed cross-reactivities. No limitation by endogenous interferences was observed. The CEDIA Cortisol assay permits the precise, fast and sufficiently specific determination of cortisol. Furthermore, it offers the advantages of a non-radioactive assay and can be performed conveniently on Boehringer Mannheim/Hitachi analyzers in combination with routine clinical chemistry.

Humans↗
PubMed1992

Colorimetric determination of potassium in plasma and serum by reflectance photometry with a dry-chemistry reagent.

We evaluated a colorimetric assay of potassium in plasma and serum with the Boehringer Mannheim Reflotron reflectance photometric analyzer, which is designed for near-patient testing in hospitals and physicians' offices. This potassium method does not require calibration or instrument maintenance by the operator. Analysis of 30 microL of plasma or serum takes approximately 140 s. Within-day imprecision (CV) was 1.0-1.2%. Total CVs over a 1-month period were 1.0-1.4%. Patients' results from the Reflotron correlated well with those from the IL 643 flame photometer and the Beckman Synchron CX3 ion-selective electrode methods. The accuracy of Reflotron values was also verified with Standard Reference Material 956 from the National Institute of Standards and Technology.

Colorimetry↗
PubMed1992

A multicenter evaluation of lipid profiling with a compact analyzer (Miles Clinistat).

We evaluated the Clinistat Analyzer (Miles Inc., Diagnostics Division, Elkhart, IN) for measuring cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol at three medical centers. The system, based on multilayer film technology, uses precalibrated, dry film reagent disks. Ten microliters of serum is applied to the dry film reagent disk in the test procedure. For HDL-cholesterol measurement, serum is pretreated by precipitation with phosphotungstic acid and magnesium chloride. Total precision (CVs) of each of the three assays was less than or equal to 5%. The assay ranges were linear and satisfactory for clinical use. Patients' results compared well with established methods. No significant interferences were found with hemolysis, icterus, and lipemia.

Chemistry, Clinical↗
PubMed1991

Direct measurement of high-density lipoprotein cholesterol by the reflotron assay with no manual precipitation step.

We evaluated the quantification of high-density lipoprotein (HDL) cholesterol in plasma with the Boehringer Mannheim Reflotron reflectance photometric analyzer. The Reflotron is designed for testing in small to medium-size laboratories and physicians' offices. This HDL method does not require a manual precipitation step because the reagent tab contains dextran sulfate (Mr 50,000) and magnesium acetate. It takes 90 s to complete an analysis of 30 microL of plasma. Within-day standard deviations (SDs) were 0.02-0.04 mmol/L (6-16 mg/L). Total SDs over a three-month period were 0.03-0.06 mmol/L (11-23 mg/L). The Reflotron values averaged 0.02 mmol/L (6 mg/L) or 1.3% lower than the Hitachi 737 values; the standard error of the estimate (Sy.x) was 0.07 mmol/L (29 mg/L).

Ascorbic Acid↗
PubMed1990

Hormonal changes in brain dead patients.

Thirty neurologically impaired (Glasgow Coma Score less than 7) patients were evaluated to determine if changes in serum levels of thyroid hormone, cortisol, insulin, or lactate suggest that replacement therapy is needed before removal of organs for donation. Serum levels of free thyroxine (fT4), thyroid-stimulating hormone (TSH), reverse T3 (rT3), cortisol, insulin, and lactate were monitored in 16 patients before and after brain death and in 14 additional patients who were similarly compromised but did not become brain dead. Low fT3, normal fT4, and normal or high rT3 as found in most patients were consistent with a variant of the euthyroid sick syndrome although TSH was elevated in some patients. Cortisol, insulin, and lactate levels were also normal or high. No correlation was found between low thyroid hormones and elevated lactate or the amount of vasopressor needed to sustain BP. No significant changes occurred in hormone or lactate levels after brain death. The explanation for an elevated lactate remains unclear but we do not believe this single finding justifies the diagnosis of a hypothyroid state in these patients or the administration of thyroid hormone to brain dead organ donors.

Adult↗
PubMed1987

Quality performance in the physician's office.

Because neither the physicians nor their office staffs are trained laboratorians, the reliability of test results from physician's office testing is of major concern. In this article, potential errors in laboratory testing are discussed, and a comprehensive quality-assurance program is presented.

Clinical Laboratory Techniques↗
PubMed1987

Measurement of six enzymes with the Kodak DTSC Module, a physician's office analyzer.

We evaluated the performance of the Kodak DTSC Module for determination of alanine aminotransferase (ALT; EC 2.6.1.2), aspartate aminotransferase (2.5.1.2), alkaline phosphatase (3.1.3.1), creatine kinase (2.7.3.2), gamma-glutamyltransferase (2.3.2.2), and lactate dehydrogenase (1.1.1.27). The DTSC is a "special chemistry" accessory for the DT60 analyzer; the same multilayer film technology as that of the Ektachem 700 is used. The overall precision, assessed over a three-month period with two serum-based quality control materials, ranged from 2.2 to 8.0%. DTSC results for patients' specimens correlated well with those by the Technicon RA-1000 analyzer. The performance of the analyzer in linearity and interference studies was satisfactory for clinical use. The DTSC is simple to operate and has no technique-dependent step; it should be useful for the physician's office laboratory.

Alanine Transaminase↗
PubMed1987

Increased activities of creatine kinase and lactate dehydrogenase isoenzymes in a patient with metastatic ovarian tumor.

A 50-year-old woman with metastatic rhabdomyosarcoma of the ovary had increased activities of creatine kinase (CK; EC 2.7.3.2), CK-MB isoenzyme, lactate dehydrogenase (LD; EC 1.1.1.27), and LD-2 isoenzyme in her serum. The isoenzyme activities did not show a pattern of increasing, then decreasing. Clinical findings, including electrocardiograms, did not support the diagnosis of myocardial infarction. We suggest that high activities of CK-MB and LD-2 in serum may serve as a marker of rhabdomyosarcoma.

Creatine Kinase↗
PubMed1986

Selecting instrumentation for physician's office testing.

Selecting instrumentation for physician's office testing requires a stepwise approach. Evaluation criteria that should be emphasized include ease of use, cost-effectiveness, analytic reliability, and test menu. Some examples of analyzers designed for physician's office testing are discussed.

Ambulatory Care↗