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Biomedical subjects

W H Hannon

Publications and source records attributed to W H Hannon.

At least 19 recordsLinked to original sources
PubMed2001

Measures of maternal tobacco exposure and infant birth weight at term.

This study was undertaken to determine the relation between self-reported number of cigarettes smoked per day and urine cotinine concentration during pregnancy and to examine the relations between these two measures of tobacco exposure and birth weight. Data were obtained from the Smoking Cessation in Pregnancy project, conducted between 1987 and 1991. Cigarette smoking information and urine cotinine concentration were collected for 3,395 self-reported smokers who were receiving prenatal care at public clinics in three US states (Colorado, Maryland, and Missouri) and who delivered term infants. General linear models were used to quantify urine cotinine variability explained by the number of cigarettes smoked per day and to generate mean adjusted birth weights for women with different levels of tobacco exposure. Self-reported number of cigarettes smoked per day explained only 13.9% of the variability in urine cotinine concentration. Birth weight declined as tobacco exposure increased; however, the relation was not linear. The sharpest declines in birth weight occurred at low levels of exposure. Furthermore, urine cotinine concentration did not explain more variability in birth weight than did number of cigarettes smoked. These findings should be considered by researchers studying the effects of smoking reduction on birth outcomes.

Adolescent↗
PubMed2001

Use of filter paper for the collection and analysis of human whole blood specimens.

The Centers for Disease Control and Prevention and its partners have been operating the Newborn Screening Quality Assurance Program for >20 y. The program helps participating laboratories to evaluate and improve the quality of their newborn-screening testing efforts by providing quality control dried blood spot materials and proficiency-testing materials for the external evaluation of screening programs. The Newborn Screening Quality Assurance Program provides an independent evaluation of filter papers approved by the Food and Drug Administration for the collection of blood for clinical tests. These activities have created a mechanism for the validation of the filter paper blood collection device and the standardization of materials and methods for the analysis of dried blood spots.

Antibodies↗
PubMed2000

Oral zidovudine during labor to prevent perinatal HIV transmission, Bangkok: tolerance and zidovudine concentration in cord blood. Bangkok Collaborative Perinatal HIV Transmission Study Group.

OBJECTIVES: To evaluate tolerance for the oral administration of zidovudine (ZDV) during labor and measure the resulting ZDV concentrations in umbilical cord blood. DESIGN: A cross-sectional study of women in a placebo-controlled trial of short-course ZDV (twice a day from 36 weeks' gestation until labor and every 3 h during labor) to prevent perinatal HIV transmission in Bangkok. METHODS: Umbilical cord blood was collected. Sixty control specimens and specimens from 372 women (182 in the ZDV group, 190 in the placebo group) were tested for ZDV by radioimmunoassay (lower detection limit < 1 ng/ml). RESULTS: All women in the ZDV group took one or more labor dose, 170 (93%) took their last dose within 3 h of delivery, and only five (3%) experienced nausea or vomiting, a proportion similar to the placebo group. The median concentration of ZDV in the cord blood in the ZDV group was 252 ng/ml (range, < 1-1133 ng/ml); 31 (17%) specimens were less than 130 ng/ml (0.5 microM), the concentration thought to be active against HIV in vitro. Median concentrations were 189 ng/ml in specimens from women taking one or two labor doses, 290 ng/ml in those taking three or four doses, and 293 ng/ml in those taking more than four doses (P < 0.01). The ZDV concentration was not associated with time since the last dose, body weight, or perinatal transmission. CONCLUSION: Oral intrapartum ZDV was feasible and well tolerated. Most ZDV concentrations in the cord blood after oral dosing during labor were at therapeutic concentrations but were lower than those reported after continuous intravenous administration. Although concentrations were not associated with perinatal transmission, these data do not exclude the possibility that intrapartum and neonatal chemoprophylaxis is effective.

Administration, Oral↗
PubMed2000

Fluorescence intensity calibration for immunophenotyping by flow cytometry.

Fluorescence intensity (FI) is the basis for classifying phenotypes by fluorescence-label flow cytometry. FI is customarily recorded as an arbitrary relative value, but with proper calibration it can be expressed in stoichiometric units called molecules of equivalent soluble fluorochrome (MESF) that reflect the concentrations of the fluorescent conjugates and the receptors they stain. Forthcoming availability of authoritative standards and consensus methods will alleviate many of the difficulties encountered in making valid MESF measurements. FI calibration establishes the true values for the critical parameters of the fluorescence measurement, a useful feature for quality control. It further allows the establishment of a comparable window of analysis across different times and laboratories, and it permits numeric assessment of antibody-binding capacity (ABC) values in selected cell populations. The relation between ABC values and receptor expression is complicated by several factors, but careful assessment of the binding chemistry can establish the actual number of receptors on cells stained by fluorescent conjugates.

Antibodies↗
PubMed1999

Current activities at the Centers for Disease Control and Prevention's National Diabetes Laboratory.

In 1997, the Centers for Disease Control and Prevention established the National Diabetes Laboratory in order to help prevent and treat type 1 diabetes. This state-of-the-art laboratory collaborates with research scientists and key national and international organizations throughout the world to identify and study risk factors for type 1 diabetes by developing measurements for glycosylated proteins, developing and evaluating technology for measuring genetic risk factors for the disease, and working to standardize autoantibody measurements. Developing improved technologies for diagnosing and managing diabetes and developing reference materials for properly calibrating and standardizing blood glucose meters are also critical aspects of the laboratory's work. In addition, the laboratory provides quality storage for valuable collections of biologics and other materials and facilitates sharing of specimens, associated epidemiologic data, and test results. Working with our partners in diabetes research, we are improving the diagnosis, treatment, and prevention of type 1 diabetes.

Autoantibodies↗
PubMed1999

Quality assurance and standardization: summary of the satellite meeting, Turku, Finland, 11-12 June 1999.

The Quality Assurance (QA) and Standardization satellite meeting addressed five major issues in newborn screening: (i) Pre- and post-analytical phases are important in the overall quality of screening, and quality assurance programs should include these aspects. (ii) It is possible to run a single screening program using laboratories on more than one site, as is done in Europe, California and Cuba. Special quality assurance procedures are necessary for success. (iii) It is possible to achieve improved analytical quality and international comparison of results by use of common reference materials such as the amino acid materials developed in Europe and the US. It will be important to use tested paper with defined performance characteristics. (iv) It is appropriate for newborn screening programs to be accredited, but it will also be important to develop criteria for pre- and post-analytic phases of screening. (v) A new QA program is being developed for Latin America. The Australasian QA program now includes amino acids and acylcarnitines in a form suitable for tandem mass spectrometry blind QA. The European Society for Paediatric Endocrinology has developed guidelines for CAH screening.

Accreditation↗
PubMed1999

Validation of accuracy-based amino acid reference materials in dried-blood spots by tandem mass spectrometry for newborn screening assays.

BACKGROUND: Advances in technology and the earlier release of newborns from hospitals have pressed the demand for accurate calibration and improved interlaboratory performance for newborn screening tests. As a first step toward standardization of newborn screening aminoacidopathy tests, we have produced six-pool sets of multianalyte dried-blood-spot amino acid reference materials (AARMs) containing predetermined quantities of five amino acids. We describe here the production of the AARMs, validation of their amino acid contents, and characterization of their homogeneity and their stability in storage. METHODS: To each of six portions of a pool of washed erythrocytes suspended in serum we added Phe (0-200 mg/L), Leu (0-200 mg/L), Met (0-125 mg/L), Tyr (0-125 mg/L), and Val (0-125 mg/L). Six-pool sets (1300) were prepared, dried, and packaged. We used isotope-dilution mass spectrometry to estimate the endogenous amino acid concentrations of the AARMs and validate their final amino acid concentrations. We used additional tandem mass spectrometry analyses to examine the homogeneity of amino acid distribution in each AARM, and HPLC analyses to evaluate the stability of the amino acid contents of the AARMs. RESULTS: The absolute mean biases across the analytic range for five amino acids were 2.8-9.4%. One-way ANOVAs of the homogeneity results predicted no statistically significant differences in amino acid concentrations within the blood spots or within the pools (P >0.05). Regression slopes (0 +/- 0.01) for amino acid concentrations vs storage times and their P values (>0.05) showed no evidence of amino acid degradation at ambient temperatures, 4 degrees C, or -20 degrees C during the intervals tested. CONCLUSION: The validation, homogeneity, and stability of these blood spots support their use as a candidate national reference material for calibration of assays that measure amino acids in dried-blood spots.

Amino Acids↗
PubMed1998

Terminology and nomenclature for standardization in quantitative fluorescence cytometry.

Terminology in any field is a complex mix of established conventions, accepted usages, disputed terms, and occasional misnomers. The terminology that has evolved for quantitative fluorescence cytometry (QFCM) is especially multifarious, in part because QFCM encompasses a range from subjective visual assessments to objective photon counts. Thus, while descriptive terms such as "dim" and "bright" are still quite useful, quantitative terms such as "binding capacity" should be used with collective understanding of their exact meanings. This article reviews current usage and proposes definitions that, with refinement from suppliers and users of QFCM technology, can provide the required clarity.

Calibration↗
PubMed1998

Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994)

Iodine deficiency in a population causes increased prevalence of goiter and, more importantly, may increase the risk for intellectual deficiency in that population. The National Health and Nutrition Examination Surveys [NHANES I (1971-1974) and (NHANES III (1988-1994)] measured urinary iodine (UI) concentrations. UI concentrations are an indicator of the adequacy of iodine intake for a population. The median UI concentrations in iodine-sufficient populations should be greater than 10 microg/dL, and no more than 20% of the population should have UI concentrations less than 5 microg/dL. Median UI concentrations from both NHANES I and NHANES III indicate adequate iodine intake for the overall U.S. population, but the median concentration decreased more than 50% between 1971-1974 (32.0+/-0.6 microg/dL) and 1988-1994 (14.5+/-0.3 microg/dL). Low UI concentrations (<5 microg/dL) were found in 11.7% of the 1988-1994 population, a 4.5-fold increase over the proportion in the 1971-1974 population. The percentage of people excreting low concentrations of iodine (UI, <5 microg/dL) increased in all age groups. In pregnant women, 6.7%, and in women of child-bearing age, 14.9% had UI concentrations below 5 microg/dL. The findings in 1988-1994, although not indicative of iodine deficiency in the overall U.S. population, define a trend that must be monitored.

Adolescent↗
PubMed1998

Radioimmunoassay for monitoring zidovudine in dried blood spot specimens.

We modified and evaluated a RIA for serum and used the modified RIA to measure zidovudine in dried blood spot specimens (DBSs) routinely collected for newborn screening and tested anonymously for maternally acquired HIV antibodies in the national HIV Seroprevalence Survey Among Childbearing Women. DBS calibration and quality-control materials were used to adapt the serum assay to the DBS matrix. The assay had a limit of detection of 24 micrograms/L serum and was used to measure zidovudine from both whole DBSs and the eluate remaining after HIV antibody screening. We initiated a pilot study to investigate the assay's performance and assess its potential to determine the implementation of the US Public Health Service recommendations that HIV-infected pregnant women and newborns receive zidovudine treatment to reduce the risk of perinatal HIV transmission.

Adult↗
PubMed1997

Stability of urine creatinine.

The measurement of urinary creatinine is important in many situations, but perhaps most important when measuring the urinary content of substances other than creatinine. Because urine flow changes unpredictably during the day, but total creatinine output is generally constant, many investigators normalize their results to creatinine content (i.e. mg chromium/mg creatinine). Because the widespread use of creatinine levels make the reliability of their measurement important, we decided to test this by studying the effects of storage time and temperature on urine specimens obtained from 10 healthy adults. Our results showed that only prolonged storage time at high temperatures (30 days, 55 degrees C) could cause significant decreases in urine creatinine levels. When stored for 2 days at 55 degrees C the decrease in urine creatinine levels was < 3%. We conclude that in all but extreme cases urine creatinine is virtually unaffected by storage time and temperature.

Adult↗
PubMed1997

Preliminary investigation of the use of dried-blood spots for the assessment of in utero exposure to environmental pollutants.

We determined the concentration of dichlorodiphenyldichloroethylene (p,p'-DDE) in dried-blood spot specimens from 2-day-old infants from rural Texas who had never been breast fed. Anonymous, residual whole blood spots on filter paper, previously used for routine newborn screening procedures, were soaked in a phosphate buffer, extracted with an organic solvent, and eluted through silica gel. The concentrated eluates were analyzed by capillary gas chromatography with electron capture detection (ECD). The blood collected from 10 newborns was analyzed and found to contain DDE concentrations ranging from 0.13 to 1.87 pg/microliter with a mean of 0.72 pg/microliter. One of the 10 newborns had a whole blood DDE concentration of 1.87 pg/microliter, which was greater than the concentration of 1.34 pg/microliter in a freshly drawn sample from an adult donor whose blood serum was shown to contain DDE. With improvement in detection limits, this approach has the potential to displace the analyses of mothers' blood (as a surrogate indicator of infants' exposures) and cord blood as standard procedures for determining the newborns' body burden of environmental pollutants.

Adult↗
PubMed1997

An evaluation of the use of dried blood spots from newborn screening for monitoring the prevalence of cocaine use among childbearing women.

A collaborative March of Dimes study was designed to examine the utility of dried blood spot (DBS) materials routinely collected from newborns as a source for monitoring cocaine exposure and to assess the prevalence of cocaine use among childbearing women in Georgia. We used a modified urinary radioimmunoassay (RIA) to anonymously detect the cocaine metabolite benzoylecgonine (BE) in DBSs. Extensive efforts were undertaken to assure absolute nonlinkage of BE data to any individual. The positive results found by RIA were confirmed by a mass spectrometry (MS) method specifically developed to detect BE in DBSs. BE was measured in 23,141 DBSs collected during 2 months of routine newborn screening in Georgia. A good correlation was observed for RIA results versus MS results (r2 = 0.97). The estimated minimal statewide BE prevalence was 4.8 per 1000 childbearing women. We demonstrated that immunoassay testing for cocaine without confirmatory testing can yield falsely elevated prevalence rates. When proper confirmatory testing is done, DBSs are a valuable source for population-based monitoring of substance abuse among childbearing women.

Blood Specimen Collection↗