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E W Gunter

Publications and source records attributed to E W Gunter.

At least 37 records · Page 2Linked to original sources
PubMed1999

Comparison of plasma total homocysteine measurements in 14 laboratories: an international study.

BACKGROUND: Information on interlaboratory variation and especially on methodological differences for plasma total homocysteine is lacking. METHODS: We studied 14 laboratories that used eight different method types: HPLC with electrochemical detection (HPLC-ED); HPLC with fluorescence detection (HPLC-FD) further subdivided by type of reducing/derivatizing agent; gas chromatography/mass spectrometry (GC/MS); enzyme immunoassay (EIA); and fluorescence polarization immunoassay (FPIA). Three of these laboratories used two methods. The laboratories participated in a 2-day analysis of 46 plasma samples, 4 additional plasma samples with added homocystine, and 3 plasma quality-control (QC) pools. Results were analyzed for imprecision, recovery, and methodological differences. RESULTS: The mean among-laboratory and among-run within-laboratory imprecision (CV) was 9.3% and 5.6% for plasma samples, 8.8% and 4.9% for samples with added homocystine, and 7.6% and 4.2% for the QC pools, respectively. Difference plots showed values systematically higher than GC/MS for HPLC-ED, HPLC-FD using sodium borohydride/monobromobimane (however, for only one laboratory), and EIA, and lower values for HPLC-FD using trialkylphosphine/4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. The two HPLC-FD methods using tris(2-carboxyethyl) phosphine/ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F) or tributyl phosphine/SBD-F, and the FPIA method showed no detectable systematic difference from GC/MS. CONCLUSIONS: Among-laboratory variations within one method can exceed among-method variations. Some of the methods tested could be used interchangeably, but there is an urgent need to improve analytical imprecision and to decrease differences among methods.

Chromatography, High Pressure Liquid↗
PubMed1999

Comparison of serum and plasma methylmalonic acid measurements in 13 laboratories: An international study.

BACKGROUND: Detection of cobalamin deficiency is increasingly important, and methylmalonic acid (MMA) appears to be a useful marker. Information on interlaboratory variation and on methodological differences for MMA in serum and plasma is limited. METHODS: Using gas chromatography/mass spectrometry, 13 laboratories participated in a 2-day analysis of 8 serum and 11 EDTA-plasma specimens. Results were analyzed for imprecision, recovery, and differences among laboratories and methods. RESULTS: The mean among-laboratory imprecision (CV) was 19% and 21% for serum and plasma samples, respectively, and 9.3% and 7.8% for serum and plasma samples with added MMA, respectively. The mean within-laboratory (among-run) CV was 13% for both serum and plasma samples and 5.2% and 4.9% for serum and plasma samples with added MMA. Within-method imprecision was the same or higher than among-method imprecision. The mean among-laboratory recovery of MMA was 105% and 95% in serum and plasma, respectively. Most laboratories showed a proportional bias relative to the consensus mean of up to 15%. Two laboratories reported results that on average were almost 30% higher than the consensus mean. CONCLUSIONS: No method differences were found, but significant among-laboratory imprecision was found in the present study. Improvements are needed to reduce the analytical imprecision of most laboratories, and attention must be focused on calibration issues. Differences among laboratories can be improved by introducing high-quality reference materials and by instituting external quality assessment programs.

Calibration↗
PubMed1998

Diabetes mellitus in Egypt: glycaemic control and microvascular and neuropathic complications.

We performed a cross-sectional, population-based survey of persons 20 years of age and older living in Cairo and surrounding rural villages. The purpose was to describe glycaemic control and the prevalence of microvascular and neuropathic complications among Egyptians with diagnosed diabetes, previously undiagnosed diabetes, impaired glucose tolerance, and normal glucose tolerance. A total of 6052 households were surveyed. The response rate was 76% for the household survey and 72% for the medical examination. Among people with previously diagnosed diabetes, mean haemoglobin A1c, was 9.0%. Forty-two per cent had retinopathy, 21% albuminuria, and 22% neuropathy. Legal blindness was prevalent (5%) but clinical nephropathy (7%) and foot ulcers (1%) were uncommon in persons with diagnosed diabetes. Among people with diagnosed diabetes, microvascular and neuropathic complications were associated with hyperglycaemia. Retinopathy was also associated with duration of diabetes; albuminuria with hypertension and hypercholesterolaemia; and neuropathy with age, female sex, and hypercholesterolaemia. Albuminuria was as common in people with previously undiagnosed diabetes (22%) as those with diagnosed disease (21%). Mean haemoglobin A1c was lower (7.8%) and retinopathy (16%) and neuropathy (14%) were less prevalent in people with previously undiagnosed disease. Ocular conditions, blindness, and neuropathy were prevalent in the non-diabetic population. The microvascular and neuropathic complications of diabetes are a major clinical and public health problem in Egypt.

Adult↗
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

Exposure of the U.S. population to lead, 1991-1994.

Blood lead measurements were obtained on 13,642 persons aged 1 year and older who participated in Phase 2 of the Third National Health and Nutrition Examination Survey (NHANES III) from 1991 through 1994. NHANES III is a national representative survey of the civilian, noninstitutionalized U.S. population. The overall mean blood lead level for the U.S. population aged 1 year and older was 2.3 microgram/dl, with 2.2% of the population having levels >=10 microgram/dl, the level of health concern for children. Among U.S. children aged 1-5 years, the mean blood lead level was 2.7 microgram/dl, and 890,000 of these children (4.4%) had elevated blood lead levels. Sociodemographic factors associated with higher blood lead levels in children were non-Hispanic black race/ethnicity, low income, and residence in older housing. The prevalence of elevated blood lead levels was 21.9% among non-Hispanic black children living in homes built before 1946 and 16.4% among children in low-income families who lived in homes built before 1946. Blood lead levels continue to decline in the U.S. population, but 890,000 children still have elevated levels. Public health efforts have been successful in removing lead from population-wide sources such as gasoline and lead-soldered food and drink cans, but new efforts must address the difficult problem of leaded paint, especially in older houses, as well as lead in dust and soil. Lead poisoning prevention programs should target high-risk persons, such as children who live in old homes, children of minority groups, and children living in families with low income.

Adolescent↗
PubMed1998

Blood folate and vitamin B12: United States, 1988-94.

OBJECTIVES: This report presents national estimates of serum and red blood cell (RBC) folate and serum vitamin B12 distributions for persons 4 years and over, by sociodemographic variables. METHODS: The third National Health and Nutrition Examination Survey (NHANES III) (1988-94), provides information on the health and nutritional status of the civilian noninstitutionalized U.S. population. The analytic sample included 23,378 participants with serum folate data, 23,082 with RBC folate data, and 11,851 with serum vitamin B12 data. RESULTS: The mean serum and RBC folate concentrations are 7.2 and 196 nanograms per milliliter (ng/mL), respectively, and the mean serum vitamin B12 concentration is 518 picograms per milliliter (pg/mL). Non-Hispanic white people have higher mean serum and RBC folate concentrations than non-Hispanic black or Mexican American people. Serum vitamin B12 concentrations are lowest for older adults, and non-Hispanic black people have higher serum B12 concentrations than non-Hispanic white individuals. Only approximately 3 percent of the population has a serum B12 concentration less than 200 pg/mL. CONCLUSIONS: Inadequate folate status may be more prevalent among non-Hispanic black and Mexican American people. Data also suggest a modest prevalence of low serum B12 concentrations. Future assessments of folate and vitamin B12 status will be important to evaluate the impact of a recently enacted fortification policy.

Adolescent↗
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

Pervasive occult gastrointestinal bleeding in an Alaska native population with prevalent iron deficiency. Role of Helicobacter pylori gastritis.

OBJECTIVE: To confirm prevalent iron deficiency among Yupik Eskimos living in Alaska and to explore the frequency of and potential lesions accounting for occult gastrointestinal bleeding. DESIGN: Descriptive survey. SETTING: Rural Arctic community. SUBJECTS: A total of 140 adult volunteers from 3 villages in the Yukon-Kuskokwim Delta region of western Alaska. MAIN OUTCOME MEASURES: Daily iron intake, hematologic and biochemical indexes of iron status, fecal hemoglobin levels, stool parasites, and endoscopic findings. RESULTS: While dietary iron intake by Yupiks was similar to that of a reference population, iron deficiency prevalence was increased 13-fold in Yupik men and 4-fold in Yupik women. Fecal hemoglobin levels were elevated in 90% of subjects contrasted with only 4% of a reference group; median levels were 5.9 and 0.5 mg of hemoglobin per gram of stool, respectively. Among 70 Yupik subjects with elevated fecal hemoglobin levels who had endoscopy performed, 68 (97%) had an abnormal gastric appearance consisting of erythema, mucosal thickening, diffuse mucosal hemorrhages, erosions, or ulcerations. Gastric biopsies revealed chronic active gastritis with associated Helicobacter pylori in 68 (99%) of 69. No other hemorrhagic gastrointestinal disease was detected. CONCLUSIONS: Based on this study sample, occult gastrointestinal bleeding appears to be pervasive in the Yupik population and likely underlies the prevalent iron deficiency. An atypical hemorrhagic gastritis associated with H pylori infection is present almost universally and may represent the bleeding source.

Adult↗
PubMed1997

Prevalence of iron deficiency in the United States.

OBJECTIVE: To determine the prevalence of iron deficiency and iron deficiency anemia in the US population. DESIGN: Nationally representative cross-sectional health examination survey that included venous blood measurements of iron status. MAIN OUTCOME MEASURES: Iron deficiency, defined as having an abnormal value for at least 2 of 3 laboratory tests of iron status (erythrocyte protoporphyrin, transferrin saturation, or serum ferritin); and iron deficiency anemia, defined as iron deficiency plus low hemoglobin. PARTICIPANTS: A total of 24,894 persons aged 1 year and older examined in the third National Health and Nutrition Examination Survey (1988-1994). RESULTS: Nine percent of toddlers aged 1 to 2 years and 9% to 11% of adolescent girls and women of childbearing age were iron deficient; of these, iron deficiency anemia was found in 3% and 2% to 5%, respectively. These prevalences correspond to approximately 700,000 toddlers and 7.8 million women with iron deficiency; of these, approximately 240,000 toddlers and 3.3 million women have iron deficiency anemia. Iron deficiency occurred in no more than 7% of older children or those older than 50 years, and in no more than 1% of teenage boys and young men. Among women of childbearing age, iron deficiency was more likely in those who are minority, low income, and multiparous. CONCLUSION: Iron deficiency and iron deficiency anemia are still relatively common in toddlers, adolescent girls, and women of childbearing age.

Adolescent↗
PubMed1997

Serum ferritin iron, a new test, measures human body iron stores unconfounded by inflammation.

Serum ferritin protein is an acute phase reactant. We hypothesized that serum ferritin protein generated in response to an inflammatory process would have much less iron (Fe) in it than would "normal" ferritin protein, and therefore measuring serum ferritin iron would assess human body iron status unconfounded by inflammation. BASIC METHODS: We measured serum ferritin iron in 140 clinical samples obtained from the serum banks of Bronx VA Medical Center Hematology and Nutrition Laboratory (Bronx, NY), the CDC Nutritional Biochemistry serum sample bank (Atlanta, GA), and the sample bank from patients with thalassemia and iron overload treated at New York Hospital (New York, NY). Each was analyzed for three conventional criteria of iron status: serum iron, percentage of transferrin saturation and ferritin protein. In addition, tests for inflammation were also performed: C-reactive protein, WBC and transaminases. Seventy-seven patients' sera from 140 screened met each of three consistent criteria for stages of iron status. Serum ferritin was immobilized by immunoprecipitation with rabbit antihuman polyclonal antibody bound to agarose and separated from other iron-containing proteins, digested with 0.2 ml of 3N nitric acid and analyzed for iron content by atomic absorption spectroscopy. RESULTS: Serum ferritin iron ranged in normal controls from 10 ng to 35 ng Fe/ml. The patients with iron deficiency (4/4) and those in negative iron balance (5/6) had values < or = 10 ng. Positive iron balance (8/9) and iron overload (22/22) values were > 35 ng/ml, in contrast to 11/19 with inflammation. Seventeen of twenty-two with overload had values > 100 ng/ml while only 1/19 with inflammation had such a value. Ferritin iron in ferritin protein was > 15% by weight in 14/22 with iron overload but in 0/19 with inflammation. IMPLICATIONS OF THE WORK: Serum ferritin iron is a simple, direct measure of iron stores that we propose, in conjunction with measuring serum ferritin protein, as a minimally invasive screening procedure for accurately assessing the whole range of human body iron status, unconfounded by inflammation.

Blood Chemical Analysis↗
PubMed1997

Biological and environmental specimen banking at the Centers for Disease Control and Prevention.

Scientific programs at the Centers for Disease Control and Prevention encompass diverse public health interests. These programs include investigations of newly emerging infectious diseases, assessments of chronic disease risk factors, and evaluations of environmental health hazards. Since the early 1960s, CDC has maintained a specimen bank to retain aliquots of biological specimens collected from a variety of epidemiologic investigations as well as from the National Health and Nutrition Examination Surveys (NHANES). CDC's National Institute of Occupational Safety and Health (NIOSH) also maintains a repository of environmental materials from its investigations. To extend its repository capabilities more effectively, CDC has begun developing a new facility that, when finished, will meet CDC's storage needs for both biological and environmental specimens. A highly complex but very flexible information management system for this project, enabling the storage of data related to studies for which these specimens were originally collected, has already been completed. Proper specimen collection, archiving, and short- or long-term storage of specimens for environmental health-related analyses is critical for the work of the staff of the Division of Environmental Health Laboratory Sciences, National Center for Environmental Health, who perform a variety of biochemical analyses on biological specimens, including quantitation of dioxins, furans, coplanar PCBs, pesticides, volatile organic compounds, metabolites, essential and toxic trace elements, vitamins, and lipids, and also conduct genetic screening. Information regarding these analytes is an essential part of the CDC Repository Database.

Biological Specimen Banks↗
PubMed1997

Field-study screening of blood folate concentrations: specimen stability and finger-stick sampling.

We describe optimized procedures for field studies of blood folate concentrations by using finger-stick blood sampling and include relevant studies on blood folate stability. We introduce whole-blood folate adjustment using sample hemoglobin (folate/hemoglobin, nmol/g) as a novel and practical tool yielding accurate and precise results when blood volume or dilution is unknown. Red cell folate concentrations (nmol/L) of 11,887 Americans correlated well with hemoglobin-corrected whole-blood folate concentrations (r2 = 0.993; red cell folate = 0.347 x hemoglobin folate + 1 nmol/L), which supports the approach of using the mean cell hemoglobin concentration (g/L) to interconvert red cell and hemoglobin folate data. Folate concentrations in capillary (finger stick) and venous blood samples from 28 normal donors were similar (P > 0.87), correlating closely (r = 0.98, P < 0.001). Whole-blood samples (collected into K2-EDTA-containing evacuated tubes) in field studies are best stored intact at 4 degrees C until they can be processed and frozen (-20 degrees C). Specific knowledge of blood folate stability is essential in planning and designing field studies.

Blood Specimen Collection↗
PubMed1997

Development and validation of sensitive method for determination of serum cotinine in smokers and nonsmokers by liquid chromatography/atmospheric pressure ionization tandem mass spectrometry.

We describe a sensitive and specific method for measuring cotinine in serum by HPLC coupled to an atmospheric pressure chemical ionization tandem mass spectrometer. This method can analyze 100 samples/day on a routine basis, and its limit of detection of 50 ng/L makes it applicable to the analysis of samples from nonsmokers potentially exposed to environmental tobacco smoke. Analytical accuracy has been demonstrated from the analysis of NIST cotinine standards and from comparative analyses by both the current method and gas chromatography/high-resolution mass spectrometry. Precision has been examined through the repetitive analysis of a series of bench and blind QC materials. This method has been applied to the analysis of cotinine in serum samples collected as part of the Third National Health and Nutrition Examination Survey (NHANES III).

Chromatography, High Pressure Liquid↗
PubMed1996

Comparison of methods of assessing vitamin A status in children.

OBJECTIVE: A study of children (2-8 years; n = 613) in Belize, Central America, was conducted to determine what proportion of the children might be at risk of vitamin A (vit A) deficiency. The data provide an opportunity to compare results of three methods of assessing vit A status in a population which was not severely malnourished. Serum retinyl ester concentrations were also determined; their relevance to one of the tests, the relative dose response (RDR) test, is discussed. METHODS: The three methods of assessing vit A status were: RDR test, fasting serum retinol concentration, and conjunctival impression cytology (CIC). Retinol-binding protein (RBP), serum retinyl esters and serum zinc concentrations were also determined. RESULTS: Inadequate vit A status was indicated for 17% of subjects by the RDR test (14% cutoff), for 24% by fasting serum retinol concentration (< 0.87 mumol/L), and for 49% by "abnormal" CIC score. Retinyl esters constituted 24% of serum retinoids at the time (5 hours after a retinyl palmitate dose) at which the second blood sample is taken for the RDR test. Regression tree analyses (CART) indicated ethnicity was a predictor of RDR score; ethnicity, stunting and age were predictors of fasting serum retinol concentration; ethnicity and stunting were predictors of 0-hour retinyl ester concentration. CONCLUSION: The three indices of vit A status did not identify the same individuals nor indicate the same percentage of the population to be at risk for vit A deficiency. Increased concentrations of retinyl esters at 5 hours compared to those at 0 hours suggest that insufficient retinol may have been taken up by the liver at 5 hours to release all accumulated retinol-binding protein (RBP) in deficient individuals; prevalence of vit A deficiency might therefore be underestimated by the RDR test. The selection of ethnicity as a predictor of RDR score and of 0-hour retinol and retinyl ester concentrations suggests that factors other than vit A status affect vit A metabolism and may affect the RDR test.

Belize↗
PubMed1996

Reproducibility of relative dose response (RDR) test and serum retinol and retinyl ester concentrations in children after a 2-week interval.

OBJECTIVE: Reproducibility of the relative dose response test (RDR), a test designed to measure vitamin A status, was tested in 23 Belizean children, 5-8 years after 2-week interval during which no treatment was given. METHODS: As required for the RDR test, serum retinol concentrations were determined before and 5 hours after an oral dose of vitamin A. An RDR score > 14% was used as the criterion of inadequate vitamin A status. The HPLC method used to measure serum retinol concentrations also determined the concentrations of four retinyl esters. RESULTS: The RDR test was reproducible for 17 of 23 subjects: 3 scored > 14% on both tests; 14, < 14% on both. Six subjects scored > 14% on only one test. The concordance correlation coefficient (rc) for the percent change in the two tests was 0.24; for fasting serum retinol concentration, rc = 0.81. For retinyl palmitate and stearate, the esters present in highest concentrations at 5 hours, concordance correlation coefficients were 0.75 and 0.59, respectively. CONCLUSION: The failure of the RDR test to classify 26% of the subjects reproducibly reduces the usefulness of the test. In addition, the reproducibility of the retinyl ester concentrations in serum 5 hours after the retinyl palmitate dose and the relatively high concentrations in some subjects suggests that some individuals may not metabolize sufficient retinol in 5 hours to cause a maximal increase in serum retinol, resulting in an underestimation of deficiency in a population in which the RDR test is used.

Anticarcinogenic Agents↗