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R Yip

Publications and source records attributed to R Yip.

100 records · Page 6Linked to original sources
PubMed1983

Red cell membrane stiffness in iron deficiency.

The purpose of this study was to characterize red blood cell (RBC) deformability by iron deficiency. We measured RBC deformability to ektacytometry, a laser diffraction method for determining the elongation of suspended red cells subjected to shear stress. Isotonic deformability of RBC from iron-deficient human subjects was consistently and significantly lower than that of normal controls. In groups of rats with severe and moderate dietary iron deficiency, RBC deformability was also reduced in proportion to the severity of iron deficiency. At any given shear stress value, deformability of resealed RBC ghosts from both iron-deficient humans and rats was lower than that of control ghosts. However, increase of applied shear stress resulted in progressive increase in ghost deformation, indicating that ghost deformability was primarily limited by membrane stiffness rather than by reduced surface area-to-volume ratio. This was consistent with the finding that iron-deficient cells had a normal membrane surface area. In addition, the reduced mean corpuscular hemoglobin concentration (MCHC) and buoyant density of the iron-deficient rat cells indicated that a high hemoglobin concentration was not responsible for impaired whole cell deformability. Biochemical studies of rat RBC showed increased membrane lipid and protein crosslinking and reduced intracellular cation content, findings that are consistent with in vivo peroxidative damage. RBC from iron-deficient rats incubated in vitro with hydrogen peroxide showed increased generation of malonyldialdehyde, an end-product of lipid peroxidation, compared to control RBC. Taken together, these findings suggest that peroxidation could contribute in part to increased membrane stiffness in iron-deficient RBC. This reduced membrane deformability may in turn contribute to impaired red cell survival in iron deficiency.

Anemia, Hypochromic↗
PubMed1983

Screening for iron deficiency with the erythrocyte protoporphyrin test.

Elevation of erythrocyte protoporphyrin (EP) level is one of the consequences of iron deficiency. As the EP test has been established to be a screening test for lead poisoning, the screening capability of the EP test for iron deficiency was investigated. A total of 4,160 children between ages 6 months to 12 years had EP determined together with serum ferritin and hematocrit. Comparing the relationship of EP to serum ferritin and using a serum ferritin value less than or equal to 15 micrograms/L as the criterion of iron deficiency, the optimal cutoff limit for the EP test appears to be 35 micrograms/dL of whole blood. At this level, 88% of the subjects with low levels of serum ferritin can be detected (sensitivity), in contrast to the 53% detected at a higher cutoff value (greater than or equal to 50 micrograms/dL) used to screen for lead toxicity, or to the 59% detected by age-related hematocrit value. At an EP screening level of 35 micrograms/dL of whole blood, 90% of the subjects with normal serum ferritin level are correctly determined to be screen negative (specificity). The predictive value of low levels of serum ferritin for all subjects above screening level is 38%. In general, an elevated EP level, by itself, represents inadequate iron supply for hematopoiesis and signals iron deficiency regardless of whether the serum ferritin value is below the diagnostic level or not. A trial course of orally administered iron is suggested for children who are found to have an elevated EP value, with an increase in hemoglobin or hematocrit value serving, retrospectively, as confirmation of prior iron deficiency.

Anemia, Hypochromic↗
PubMedDate not supplied

Using linked program and birth records to evaluate coverage and targeting in Tennessee's WIC program.

Public health nutrition programs are intended to serve low-income families who are at greater nutritional risk than the general population. Not all persons who are program-eligible are at equal risk, however. It would be desirable to evaluate a program's ability to enroll persons from higher risk backgrounds in the population (coverage) and, conversely, the extent to which those enrolled in this program are at higher risk (targeting). A method for the evaluation of coverage and targeting was developed using data from the Tennessee Women, Infants, and Children Special Supplemental Food Program (WIC) linked with birth certificates. The linked computer file was created by matching the name and date of birth in both record files. The birth records were the common source of information used to characterize the risk background for both the WIC and non-WIC participants. Maternal sociodemographic information on the birth records was used to define the health risk background of each child. The coverage and targeting of "at-risk" children were computed and compared for 50 counties or county-aggregates in Tennessee. Considerable variation in the coverage and targeting rates of at-risk children was observed among Tennessee counties, although the counties within each WIC administrative region tended to have similar coverage and targeting patterns. Using the existing data in linked program and vital records provides a direct evaluation of a program. Coverage and targeting evaluation can be used to detect underserved populations within small geographic areas.

Birth Certificates↗
PubMedDate not supplied

Validation of maternally reported birth weights among 46,637 Tennessee WIC program participants.

To assess the accuracy of maternally reported birth weights, we compared birth weights reported by mothers in the Tennessee Women, Infants, and Children Supplemental Feeding Program (WIC) from 1975 to 1984 with the birth weights recorded on the corresponding Tennessee birth certificate file. Differences in birth weights between these two sources were compared for the total group and were also stratified by sociodemographic and medical variables that might influence the accuracy of birth weight recall. An accurate birth weight was defined as one reported within 1 ounce of the birth certificate birth weight. We also calculated the proportion of birth weights that would be incorrectly classified as low or normal by maternal reporting. A total of 72,245 WIC records were matched with their corresponding birth certificates. Of these, 46,637 had WIC birth weights recorded within the specified birth weight range. Eighty-nine percent of birth weights were reported within 1 ounce of birth certificate birth weights. Lower accuracy of birth weight reporting was associated with the infant's low birth weight, preterm delivery, and low Apgar scores, and with the mother's grand multiparity, less than a high school education, black race, single marital status, and young age. Only 1.1 percent of birth weights would have been incorrectly classified into low or normal birth weight categories based on maternal reporting. Overall, our results suggest that maternally reported birth weights are sufficiently accurate for research and programmatic purposes when birth certificate information is not readily available.

Birth Certificates↗