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R Poon

Publications and source records attributed to R Poon.

At least 73 records · Page 4Linked to original sources
PubMed1988

Near-patient testing. Quality of laboratory test results obtained by non-technical personnel in a decentralized setting.

The authors evaluated the quality and reliability of four desktop analyzers in the outpatient clinic. Twenty-seven nontechnologists (NTs) participated in the study. These included nurses, physicians, and medical students. The instruments and tests evaluated were as follows: Reflotron (glucose, cholesterol, triglycerides, gamma-glutamyltransferase and urea); Seralyzer (creatinine, glucose, potassium, aspartate aminotransferase, and hemoglobin); Vision (glucose, urea, cholesterol, triglycerides, alkaline phosphatase, and uric acid); and DT60 (sodium, potassium, glucose, amylase, uric acid, bilirubin, and creatinine). For precision studies, low and high control material was used, and method comparison was done with methods in routine use in the laboratory. The range of coefficients of variation (CVs) for the analyzers with NTs was as follows: Reflotron: CV, 2.4-7.9%; Seralyzer CV, 1.4-18.7%; Vision: CV, 1.5-2.7%; DT60: CV, 2.5-46.8. The percentage results that is different by greater than 10% between the NTs and trained technologists was related to the complexicity of procedure for each analyzer and was the lowest for the Vision analyzer and greatest for the Seralyzer.

Blood Chemical Analysis↗
PubMed1988

Comparison of hospital staff performance when using desk top analysers for "near patient" testing.

The quality and reliability of four desk top analysers were evaluated. In the context of an outpatient clinic, intensive care unit, and a mock up of a physician's office. Seventeen nurses, 14 physicians, and 12 medical office personnel took part in the study. The instruments and tests evaluated were Reflotron (glucose, cholesterol, triglycerides, gamma-glutamyl transferase), Seralyzer (creatinine, glucose, potassium, aspartate aminotransferase), Vision (glucose, (creatinine, glucose, potassium, aspartate aminotransferase), Vision (glucose, urea, cholesterol, triglycerides alkaline phosphatase, uric acid), and DT60 (sodium, potassium, glucose, amylase, uric acid and creatinine). Of the 320 tests performed on the Vision, only two differed by more than 10% between the specialist staff and other groups. For those performed on the Seralyzer, 95 of 254 results differed by more than 10%, 19 of 199 by more than 10% for the Reflotron, and 50 of 318 by more than 10% for the DT60. In general, the nurses were more adept at using the analysers than the physicians and medical office personnel.

Blood Chemical Analysis↗
PubMed1988

A physician office analyzer. Evaluation of quality of results obtained by technical and nontechnical personnel.

We evaluated the Abbott Vision analyzer (Abbott Laboratories, North Chicago, Ill) both in a controlled laboratory setting and with several untrained individuals. We used control serum samples supplied by the manufacturer. Method comparison was performed with methods currently in use in our laboratory. The analytes evaluated were glucose, urea nitrogen, urate, cholesterol, triglycerides, and alkaline phosphatase. In the laboratory, the within-run precision (coefficient of variation) of all methods ranged from 0.8% to 3.4%; the range for between-run precision was 1.2% to 3.3%. Correlation between the Abbott Vision analyzer and routine methods was excellent. The upper limit of linearity for all methods was as stated by the manufacturer. The coefficient of variation obtained by ten nontechnical personnel ranged from 0.0% to 3.9%. The correlation between results obtained by the nontechnologist were excellent. Our study indicates the Abbott Vision analyzer is extremely easy to operate and provides reliable results in the hands of nontechnical personnel.

Allied Health Personnel↗
PubMed1988

Physician office analyzers. Do they satisfy medically useful criteria for analytical performance of laboratory tests?

The coefficients of variation (CVs) for several tests on physician office analyzers were compared with published data for medically useful criteria of these tests. Medically useful CVs were based on physicians' opinions of significant changes in laboratory tests. Precision studies using control material were carried out on four physician office analyzers by both a trained technologist and nontechnical personnel, such as physicians, nurses, and medical office personnel. This study was carried out during a six-month period. The instruments that were evaluated were the Reflotron, Seralyzer, Vision, and DT60. Low and high concentrations of quality control material, supplied by the manufacturer and those in use in the study laboratory (Omega I and II, Cooper Biomedical, Fairhaven, NJ), were used. With few exceptions, all instruments satisfied the medically useful CVs criteria, ie, the precision obtained by both the technologist and nontechnical personnel either equaled or exceeded the precision requirements set by physicians.

Autoanalysis↗
PubMed1987

Interference by cephalosporins with creatinine measurement by desk-top analyzers.

We have carried out a study to evaluate the interference by cephalosporins with the measurement of creatinine by desk-top analyzers. The cephalosporins evaluated at concentrations of 0-250 mg/l were cefazolin sodium, cefoxitin sodium, cefotaxime sodium, and ceftazidime pentahydrate. The instruments evaluated were DT60 (Kodak, Rochester, USA), Seralyzer (Ames Division, Miles Laboratories, IN, USA), and Vision (Abbott Labs, Chicago, USA). All studies were done in plasma. None of the cephalosporins showed any interference with the DT60 analyzer. With the Vision and Seralyzer no interference was seen with cefotaxime or cefazolin. With cefazolin an increase of 10-20 mumol/l creatinine was seen for every 20 mg/l of drug; with cefoxitin there was an increase of 50-80 mumol/l of creatinine for every 100 mg/l of drug. Erroneous creatinine values may be found in patients taking cefazolin and cefoxitin and may lead to inappropriate clinical management.

Cefazolin↗
PubMed1985

Indican interference with six commercial procedures for measuring total bilirubin.

We have studied the effect of indican on six commercial procedures for the measurement of total bilirubin in serum. Total bilirubin measured by the Bilirubin A-Gent (Abbott) 2,4-dichlorophenyl diazonium procedure increased by 50 mg/L for each 1 mmol/L of added indican. Similarly, total bilirubin measured by the Bilirubin C-System (Boehringer Mannheim) 2,5-dichlorophenyl diazonium procedure increased by 33 mg/L per mmol/L of indican. Indican also interfered with the Micro Bilirubin Reagent Set (Harleco) Malloy-Evelyn procedure, but to a much lesser extent. The Jendrassik Bilirubin Reagent System (American Monitor) and a modified Jendrassik-Grof procedure (Hoffmann-LaRoche) adapted to the Cobas Bio analyzer were unaffected by the presence of indican. The amount of interference with the 2,5-dichlorophenyl diazonium procedure increased significantly with color development time and was twice the initial amount after 30 min. Concentrations of indican as high as 0.38 mmol/L have been found in sera of patients with renal failure, which would increase total bilirubin values measured by the first two procedures above by 19 and 12 mg/L, respectively. Users of these procedures should therefore be suspicious of unexpectedly high bilirubin values obtained with sera from patients with chronic renal disease.

Autoanalysis↗
PubMed1983

The dynamics of ingested methyl mercury in growing and laying chickens.

Growing and laying chickens were fed practical-type diets containing 0, .05, .15, .45, and 1.35 ppm of mercury as methyl mercuric chloride. Chicks that had been fed mercury throughout life retained 61, 82, 91, and 95% of the mercury ingested from the respective diets at 8 weeks of age. The half-retention times of mercury, following withdrawal of dietary mercury after the 8-week period, were 8.4 and 23.4 days, respectively, for liver and kidney in chicks fed 1.35 ppm of mercury. Half-retention times in kidney and liver decreased with lower mercury intake, i.e., with lower concentrations in the tissues at the time of mercury withdrawal. Adult laying birds, continuously fed diets containing methyl mercuric chloride, laid eggs with gradually increasing concentrations of mercury until plateau concentrations reflecting the respective dietary concentrations were reached. Upon withdrawal of mercury from the diet, mercury concentrations in the eggs laid by the birds fed .05, .15, .45 and 1.35 ppm declined to reach half of the concentrations at the time of withdrawal in 17, 13, 10, and 9 days, respectively. Likewise, the half-retention time of mercury in the liver, kidney, heart muscle, pectoral muscle, and brain tissue of the adult birds depended upon the tissue concentration at the time mercury was withdrawn from the diet and was inversely proportional to initial tissue concentration according to the equation: 1n y = 1.92 - .39 1n (7 x-5), where x is the initial tissue concentration in ppm and y is half-retention time in weeks, r = -.95.

Animals↗
PubMed1982

The relationship between plasma membrane lipid composition and physical-chemical properties. III. Detailed physical and biochemical analysis of fatty acid-substituted EL4 plasma membranes.

Murine leukemia EL4 cells were modified by supplementation of culture media with fatty acids for 24 h. A plasma membrane-enriched fraction was prepared from substituted and normal cells. Analyses were performed to determine fatty acyl composition, phospholipid headgroup composition and cholesterol content. The two major membrane phospholipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were isolated by thin-layer chromatography and ESR measurements were done on liposomes prepared from these lipids as well as on the intact plasma membrane preparations. Slight perturbations in overall plasma membrane lipid composition were observed when EL4 cells were supplemented with a single exogenous fatty acid. This may be consistent with the idea that the incorporation of exogenous fatty acid induces compensatory changes in membrane lipid composition. On the other hand, we observed no significant difference in two ESR motional parameters between the unsubstituted control and various fatty acid-substituted plasma membranes. ESR measurements carried out on PE and PC liposomes derived from 17:0- and 18:2c-substituted membranes also failed to detect major differences between these liposomes and those made from normal EL4 phospholipids. In the case of liposomes prepared from 18:2t,-substituted membranes, the order parameter was significantly changed from the normal. However, the change was in opposite directions in PE and PC, perhaps accounting for the fact that no change parameter is seen in intact 18:2t-substituted plasma membrane. Measurements of order parameter (S) in mixed lipid vesicles showed that at up to 50 mol% mixture of a synthetic PC with plasma membrane PC, the value of S was only marginally different from that of the plasma membrane PC vesicles. We interpret these data as an indication that the two ESR parameters used are not sufficiently sensitive to detect changes due to modifications of the acyl chain composition of a complex biological membrane.

Animals↗
PubMed1981

The relationship between plasma membrane lipid composition and physical-chemical properties. II. Effect of phospholipid fatty acid modulation on plasma membrane physical properties and enzymatic activities.

The fatty acid composition of plasma membrane phospholipids of the murine T lymphocyte tumor EL4 were systematically modified in an attempt to understand the relationship between lipid bilayer composition and plasma membrane physical and biological properties. Two plasma membrane enzyme activities, adenylate cyclase and ouabain-sensitive (Na+ + K+)-ATPase, were measured in normal and fatty acid-substituted EL4 plasma membrane fractions. The fatty acid effect on enzyme activities was similar to previously reported effects of fatty acids on cytotoxic T cell function. The activity of both enzymes was inhibited by saturated fatty acids, while unsaturated fatty acids had a moderate enhancing effect on both enzyme activities. Using two different nitroxide derivatives of stearic acid, the order parameter and approximate rotational correlation times were calculated from ESR spectra of normal and fatty acid-modified plasma membranes. No significant differences was found in either parameter in these membranes. These results, in conjunction with earlier data from our laboratory and others, suggest that caution should be exercised in inferring changes in membrane 'fluidity' based on lipid modulation of biological membranes.

Adenylyl Cyclases↗
PubMed1981

Congenital hip dislocation and dysplasia in Southern Chinese.

In 1975 we carried out a survey in Hong Kong to locate Chinese children with congenital dislocation of the hip. Analysis of the available records between 1960 and 1975 gave an observed incidence which was at least 10 times less than found in Caucasians. The age and sex distribution, radiographic findings and the left-sided predominance were similar to Caucasians with congenital dislocation of the hip. However, unlike Caucasian children, the Chinese presented with dislocation and not dysplasia. The mothers of children with congenital dislocation of the hip were compared with a control group with normal children to assess their use of the "Hong Kong" position, in which the children are carried on the back of their mother with their hips in a position of wide abduction. Since only half of the children in either group were carried in this manner, other factors must be responsible for the low incidence of congenital dislocation of the hip in southern Chinese.

Adolescent↗