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Biomedical subjects

J M Hicks

Publications and source records attributed to J M Hicks.

At least 55 records · Page 3Linked to original sources
PubMed1984

Fluorescence immunoassay.

Fluorescence immunoassay is a sensitive technique that can be used in the measurement of many compounds, including drugs, hormones, and proteins; in the identification of antibodies; and in the quantification of antigens such as viral particles and, potentially, bacteria. Homogeneous fluorescence immunoassay, fluorescent excitation transfer immunoassay, fluorescence polarization immunoassay, solid-phase "dipstick" immunoassay, solid-phase microbead fluorescence immunoassay, substrate-labeled fluorescence immunoassay, and fluorescence immunoassays using internal reflectance spectroscopy or phycobiliprotein conjugates are reviewed.

Antibodies↗
PubMed1984

Falsely increased digoxin concentrations in samples from neonates and infants.

Several previous studies have suggested the presence of a digoxin-like immunoreactive substance in the serum of infants. In this study we examined eight different immunoassay kits to confirm the presence of such a substance. The kits were evaluated using serum from newborns and infants who were not receiving digoxin. We investigated the relationship of this digoxin-like immunoreactive substance to substances that are present in unusual concentrations in newborn sera. These substances included fatty acids, cholesterol, triglycerides, bilirubin, protein, and albumin. No relationship could be established. Since serum steroid concentrations are known to be increased in the newborn and since digoxin is essentially a steroid derivative, we looked at steroids separately and collectively to see whether they mimicked the immunoreactivity of digoxin. We found that pooled steroids did indeed mimic digoxin and might be implicated as the immunoreactive substances.

Adult↗
PubMed1984

Delta bilirubin in serum of pediatric patients: correlations with age and disease.

At least four bilirubin fractions can be separated and identified by liquid chromatography, the least understood being the "delta" fraction (B delta), which apparently is covalently bound to albumin. To learn more about the incidence and significance of B delta, we assayed serum from 539 infants and children, both by the chromatographic method and the routine colorimetric Jendrassik-Grof method. The proportion of B delta appeared to correlate with both age and disease course. For infants younger than 28 days B delta generally was less than 2% of total bilirubin; for hyperbilirubinemic older infants and children the median B delta value was 35%. High B delta (greater than 50% of total bilirubin) in newborns was associated with intra- and extra-hepatic cholestasis, biliary cirrhosis, biliary atresia, and hepatitis. Among older infants and children, a proportion of low B delta (less than 10%) was found in hemolytic anemias, sepsis, shock, and other non-hepatic jaundice. In several cases, when low B delta was accompanied by increased conjugated bilirubin, the prognosis was very poor. Delayed clearance of B delta from the circulation together with its reactivity in direct diazo methods may interfere with interpretation of values for conjugated bilirubin as measured by classical methods.

Aging↗
PubMed1982

Methylmalonic acidemia with the unusual complication of severe hyperglycemia.

We describe a case of neonatal methylmalonic acidemia with the unusual complication of severe, insulin-resistant hyperglycemia. Methylmalonic acidemia, an inherited metabolic disease affecting the catabolism of propionic acid, is manifested by persistent metabolic acidosis, urinary excretion of large amounts of methylmalonic acid, and occasionally by hypoglycemia. Severe and persistent metabolic acidosis and hyperglycemia, despite large doses of insulin, were observed in this infant, who excreted large amounts of methylmalonic acid. The diagnosis of methylmalonic acidemia was confirmed by gas chromatography-mass spectroscopy, but the patient died before the defect in glucose tolerance could be delineated. We hypothesize that, in addition to the methylmalonic acidemia, the patient may have had an insulin-receptor defect, which was manifested as an inappropriate response to endogenous and exogenous insulin.

Acidosis↗
PubMed1981

Adolescent pregnancy testing: which test to use.

In order to study the sensitivity and efficiency of five pregnancy tests, we evaluated four types of urine tests in 162 adolescent girls in whom pregnancy was suspected; a serum test was performed in 46 of them. We found that (1) an increase in sensitivity occurred at the expense of specificity, (2) the quantitation of the beta-subunit of human chorionic gonadotropin in serum proved to be the most reliable test for pregnancy, and (3) the latex agglutination inhibition tube test (Placentex) was the most accurate of the four types of urine tests evaluated. We concluded that for adolescents, the serum pregnancy test is the preferred test, but when it is not available, the urine latex agglutination inhibition tube test offers the most reliable alternative.

Adolescent↗
PubMed1981

Adaptation of the EMIT gentamicin and tobramycin procedure to the IL microcentrifugal analyzer.

We have adapted the Syva Emit gentamicin and tobramycin procedure to the IL microcentrifugal analyzer, MCA III. With this instrument the recommended instructions for reagent preparation and reaction sequence did not produce a useable standard curve. We modified the dilutions and volumes for the working reagents and reversed the sequence of addition of the working reagents. WE assessed the linearity and precision of the analysis and compared the Syva gentamicin and tobramycin Emit procedure on the IL MCA III with the semiautomated procedure on a Gilford Stasar III spectrophotometer. With the IL MCA III only 3 to 5 microliter of serum is used, 17 analyses can be obtained in 8 min, and the reagent costs are reduced considerably.

Anti-Bacterial Agents↗
PubMed1981

Total-calcium measurement in serum from neonates: limitations of current methods.

In the routine analysis for calcium in serum from neonates we noted large discrepancies in icteric samples analyzed by several different methods. The present investigation was undertaken to demonstrate the magnitude of the problem of bilirubin interference in calcium analysis and to assess the specific applicability of commonly used micro-methods in the pediatric or neonatal laboratory. The intention is not to advocate any single methodology but rather to point out inadequacies that must be considered. Colorimetric and fluorometric methods correlated poorly with an atomic absorption spectroscopic method for samples from pediatric patients. In addition, we noted significant interference proportional to the concentration of bilirubin. A fluorescence titration method was shown to be unacceptable for pediatric use because of the variable and unpredictable response to bilirubin interference. The study emphasizes the need for thorough invesigation of methods before they are put to use in the specialized pediatric setting.

Bilirubin↗
PubMed1980

Monitoring pediatric serum theophylline, phenobarbital, and phenytoin with the IL Multistat III.

We compared results of theophylline, phenobarbital, and phenytoin assays by the EMIT method using the IL Multistat III Micro Centrifugal Analyzer with results by the EMIT semiautomated procedure on a Beckman 25 spectrophotometer equipped with a semiautomated pipettor-dilutor and a model 2400 automatic timer/printer. We assessed linearity, precision, specificity, and correlation with other methods, The IL MCA III is precise, easy to use, and suitable for routine use in a pediatric laboratory. Only 3 microliter of serum is used for each drug analysis, and 17 results can be obtained in 8 min. Reagent costs can be reduced fourfold.

Blood Chemical Analysis↗
PubMed1980

Reference values for cerebrospinal fluid glutamine concentration in infants.

We measured cerebrospinal fluid glutamine concentration in a reference group of 85 newborn to 30-month-old infants. All of the spinal taps were performed for the diagnosis of illnesses unrelated to hyperammonemia or hepatic encephalopathy. We also analyzed samples from patients with meningitis or cerebral hemorrhage, or who were receiving total parenteral nutrition. The mean glutamine concentration in cerebrospinal fluid in the reference group was somewhat lower than values reported for older children and adults. Values were significantly higher in patients with meningitis or cerebral hemorrhage and in those infants receiving total parenteral nutrition.

Age Factors↗
PubMed1979

Sweat tests.

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Cystic Fibrosis↗
PubMed1979

Limitations of immunochemical measurement of ceruloplasmin.

We describe a quantitative immunochemical method for the nephelometric measurement of ceruloplasmin. Results are compared with those from a radial immunodiffusion technique. We examine factors affecting the results, such as antiserum source and calibrators, and list reference limits for a pediatric population.

Age Factors↗
PubMed1979

Evaluation of the Beckman creatinine analyzer.

We compared results obtained with the Beckman Creatinine Analyzer (Beckman Instruments, Inc.) to those with the GEMSAEC Centrifugal Analyzer (Electro-Nucleonics, Inc.) and with a manual method for determination of creatinine in serum and urine. Linearity, stability, recovery, and precision were evaluated. Interference from bilirubin, protein, lipemia, uric acid, and hemolysis is negligible, but acetone and acetoacetate can interfere.

Autoanalysis↗
PubMed1978

Chemical and immunochemical measurement of total iron-binding capacity compared.

Radiometric, colorimetric, and two immunochemical methods for measuring total iron-binding capacity are compared. We evaluated the procedures on the basis of precision, applicability to a pediatric population, and accuracy as assessed by analytical recovery of purified transferrin. The immunoephelometric assay for transferrin provides significant advantages over the other methods examined.

Adolescent↗
PubMed1978

Kinetic measurement of alpha-amylase with a centrifugal analyzer.

We compared results of an enzymic assay for alpha-amylase (EC 3.2 1.1), adapted to a centrifugal analyzer (GEMSAEC), with results by the manual dyed-starch (Phadebas) amylase assay. We assessed linearity and precision, and the stability of the reagent. The kinetic procedure is rapid, precise, requires only 25 microliter of serum, and thus is evidently suited for both pediatric and emergency use.

Amylases↗
PubMed1977

Cerebrospinal fluid lactic acid levels in meningitis.

Measurement of cerebrospinal fluid lactic acid by gas liquid chromatography and by an enzymatic Monotest lactate test was evaluated for the early detection of bacterial meningitis in 396 patients. Spinal fluid specimens from 62/62 patients with a bacterial or mycoplasma etiology yielded lactate levels greater than the upper limits of normal, whereas specimens from 334 patients with no bacterial involvement gave values within the normal range. The duration of elevated CSF lactate values coincided with the clinical response to therapy. When considered along with the history and physical examination of the patient, determination of lactic acid proved to be a rapid and reliable diagnostic test for the early detection of untreated as well as partially treated pyogenic meningitis.

Adolescent↗
PubMed1976

Evaluation of a new blood-collecting device ("microtainer") that is suited for pediatric use.

We evaluated the prototype of a "Microtainer" (800-mul) tube (Becton-Dickinson Co., Rutherford, N.J. 07070), In which a semi-solid silicone material is used to separate serum from erythrocytes on centrifugation. We compared results for 18 serum analytes with those obtained for specimens collected by the "dripping" method of capillary blood collection. The serum was examined microscopically for platelets and leukocytes from both normal and leukemic specimens. The cellular elements were all contained in the erythrocyte layer. Hemolysis was negligible. Means for paired samples did not differ significantly, except for Na+, for which the difference was not clinically significant. Values for potassium and lactate dehydrogenase were unchanged 24 h after collection, even though the serum was left in the collecting device.

Blood Chemical Analysis↗
PubMed1976

An evaluation of the Beckman chloride/carbon dioxide analyzer.

We compared the Beckman Cl/CO2 Analyzer to the American Instrument Company chloride titrator for measurement of chloride in serum, sweat, and spinal fluid. We also compared it to the Natelson gasometer and a modified continuous-flow (AutoAnalyzer) technique for measurement of carbon dioxide in serum. Effects of bilirubin and hemoglobin on results for both the CO2, and Cl were negligible. The linearity, stability, and precision of the equipment was studied. We believe the Beckman Cl/CO2 Analyzer to be ideal for simultaneous measurement of chloride and carbon dioxide in a pediatric or emergency-determination setting.

Autoanalysis↗