Dried plasma spot measurements of ferritin and transferrin receptor for assessing iron status.
(25/1207)
BACKGROUND: Efforts to reduce the high global prevalence of nutritional anemia require the use of both reliable laboratory assays to distinguish iron deficiency from other causes of anemia and cost-effective methods for collection of blood specimens under field conditions. The suitability of using small plasma samples spotted and dried on filter paper for measurements of plasma ferritin and transferrin receptor was evaluated in the present study. METHODS: Blood specimens obtained from 73 male and 83 female subjects (19-40 years) representing a wide range of iron status were used to perform parallel measurements of plasma ferritin and transferrin receptor on whole plasma and spotted plasma samples. RESULTS: Ratio plots, evaluating the acceptability and precision of the spot method in ferritin and transferrin receptor assays, showed the expected proportion of data points within the 95% prediction interval. In the composite group of 156 subjects, both the whole plasma and plasma spot methods gave a geometric mean transferrin receptor/ferritin ratio of 18. The regression equation for the ratio was logy = 1.045 logx - 0.05126; r = 0.986; P <0.0001. The ratio of transferrin receptor/ferritin determined from plasma spots correctly identified all 12 subjects with iron deficiency anemia compared with 11 of the 12 for whole plasma measurements. CONCLUSIONS: Measurements of ferritin and transferrin receptor on plasma spotted and dried on filter paper are comparable to whole plasma values for the identification of iron deficiency anemia. The use of dried plasma spots will facilitate the collection, storage, and transport of samples in epidemiological studies of anemia prevalence. (+info)
Within-person variation of plasma homocysteine and effects of posture and tourniquet application.
(26/1207)
BACKGROUND: Frequently, the result of only a single determination of total homocysteine in plasma (P-Hcy) is used to distinguish between the probability of the presence or absence of risk for vascular disease. A prerequisite for the interpretation of a single P-Hcy test is knowledge of the magnitude of within-person variation and the possible effects of preanalytical variables. However, data on within-person variation are still sparse and inconsistent, and data for the effect on P-Hcy of posture and tourniquet application during venipuncture are not available. METHODS: The within-person variation of P-Hcy and the effects of posture and tourniquet application during venipuncture were studied in 24 healthy subjects. The analytical imprecision of our stable-isotope dilution assay was 3.1%. RESULTS: The within-person variation (CV) was 8.1%. Daily supplementation with 0.4 mg of folic acid for 2 weeks produced a small but significant decrease in P-Hcy, but there were no significant changes in within-person variation before and after supplementation. After 30 min in the horizontal posture, P-Hcy declined by 6.3%. A 3-min tourniquet application caused a 2.8% increase of P-Hcy. CONCLUSIONS: Our value for within-person variation is consistent with results from studies reported recently in the literature. A 3-min tourniquet application does not add appreciable variation to the measurement of P-Hcy, but the posture of the subject during venipuncture contributes considerably to the within-person variation. We recommend that blood collection when the patient is in a supine position be avoided. (+info)
Virus levels in untreated African infants infected with human immunodeficiency virus type 1.
(27/1207)
In developed areas, human immunodeficiency virus (HIV)-infected infants have high virus levels and rapidly progress to death. HIV levels were assessed in 1994-1997 in untreated infants in Malawi by analysis of dried blood spots tested by nucleic acid silica-bound amplification. Of 24 umbilical cord blood (CB)-positive samples, 83% had >10,000 copies/mL. The median virus level was 78,000 copies/mL. First positive sample median levels were 355,000 copies/mL among 52 perinatally infected infants and 130,000 copies/mL among 43 infants infected by breast-feeding. Virus levels were stable, and initial levels predicted levels 1 year after infection (P=.005), at which time levels did not significantly differ among in utero, perinatally, or postnatally infected infants. Thus, neither age at infection nor route of infection significantly influenced HIV levels measured 1 year after infection. Most (87%) CB-positive infants were infected before labor onset, since virus levels greatly exceeded those expected in their mothers. (+info)
Anti-phenolic glycolipid-I (PGL-I) determination using blood collection on filter paper in leprosy patients.
(28/1207)
The authors studied 70 leprosy patients and 20 normal individuals, comparing the traditional sera collection method and the finger prick blood with the conservation on filter paper for specific antibodies against the native phenolic glycolipid-I (PGL-I) from Mycobacterium leprae. The finger prick blood dried on filter paper was eluated in phosphate buffer saline (PBS) containing 0.5% gelatin. The classical method for native PGL-I was performed for these eluates, and compared with the antibody determination for sera. It was observed that there is a straight correlation comparing these two methods; although the titles found for the eluates were lower than those obtained for serology. This blood collection method could be useful for investigation of new leprosy cases in field, specially in contacts individuals. (+info)
Hormone pulsatility discrimination via coarse and short time sampling.
(29/1207)
Pulsatile hormonal secretion is a ubiquitous finding in endocrinology. However, typical protocols employed to generate data sets suitable for "pulsatility analysis" have required 60-300 samples, rendering such studies largely research methodologies, due primarily to considerable assay expense. One successful mathematical strategy in calibrating changes in pulsatility modalities is approximate entropy (ApEn), a quantification of sequential irregularity. Given the degree of differences between ApEn values in pathophysiological subjects vs. healthy controls reported in several recent studies, we queried to what extent coarser (less frequent) and shorter duration time sampling would still retain significant ApEn differences between clinically distinct cohorts. Accordingly, we reanalyzed data from two studies of 24-h profiles of healthy vs. tumoral hormone secretion: 1) growth hormone comparisons of normal subjects vs. acromegalics, originally sampled every 5 min; and 2) ACTH and cortisol comparisons of normal subjects vs. Cushing's disease patients, originally sampled every 10 min. By multiple statistical analyses, we consistently and highly significantly (P < 0.0001) established that serum concentration patterns in tumor patients are more irregular than those of controls, with high sensitivity and specificity, even at very coarse (e.g., 60 min) sampling regimens and over relatively short (2-4 h) time intervals. The consistency of these findings suggests a broadly based utility of such shorter and/or coarser sampling methodologies. Substantial reduction in sampling requirements holds the potential to move analysis of pulsatile hormone release from a primarily research tool to a clinically applicable protocol, in appropriate diagnostic and therapeutic contexts. (+info)
Distribution and repeatability of anterior pituitary responses to GnRH and relationship of response classification to the postpartum anovulatory interval of beef cows.
(30/1207)
Our objectives were to investigate the phenotypic variation in anterior pituitary responsiveness to GnRH (100 microg, i.v.) of beef cows between d 5 and 8 postpartum, estimate repeatability, and determine the relationship between response classification and duration of the postpartum anovulatory interval (PPI). Brahman x Hereford (F1) cows (n = 137) and primiparous heifers (n = 58) were evaluated. Response classifications (Class) included peak LH (Low, Intermediate, or High; Class I) and time to peak LH (Early, 10 to 30 min or Late, 60 to 120 min; Class II). The independent effects of Class I and II on PPI were determined in 145 of 195 cows through twice-weekly serum samples analyzed for progesterone. For Class I, pituitary responses to GnRH approximated a normal distribution and, by definition, differed (P < .001) in magnitudes of peak LH and area under the curve (AUC). For Class II, 111 and 84 cows exhibited early and late peaks, respectively; mean AUC was greater (P < .05) in cows exhibiting late compared with early peaks. Pretreatment LH (P < .01) and estradiol-17beta (P < .004) influenced responses in one or both response classes. Pluriparous cows had shorter (P < .035) PPI than primiparous cows. Class I did not influence the duration of the PPI; however, in Class II, cows with late peaks exhibited an average PPI that was 8 d shorter (P < .025) than in those with an early peak. To estimate repeatability of pituitary responses, 18 classified cows were subsequently rechallenged with GnRH at d 170 of gestation and at the next postpartum period. Although means for each of these challenges differed (P < .05) throughout in both Classes I and II, the small sample size used to make the estimate failed to yield significant (P > .10) interclass correlations. Nevertheless, overall results provide evidence that variability in individual pituitary responses to GnRH could be targeted as a selection marker to improve reproduction. (+info)
Use of a dried plasma collection card for simplified diagnosis of Helicobacter pylori infection.
(31/1207)
OBJECTIVES: To compare testing for Helicobacter pylori IgG antibodies using a dried plasma collection card device with specimens obtained by venepuncture. METHODS: Eighty-four patients underwent testing for H. pylori IgG antibodies by venepuncture and by fingerstick using a single drop of blood placed on each of two dried plasma collection card devices. The correlation of venepuncture results to dried plasma card results was assessed. RESULTS: There was a high degree of correlation of EIA results between venepuncture and dried plasma card specimens (r=0.98). The qualitative result of the first dried plasma card and venepuncture specimen testing differed in 7 of 84 patients and for the second dried plasma card differed in 7 of 82 patients. The first dried plasma card was 93% sensitive and 100% specific and the second was 93% sensitive and 98% specific as compared to the venepuncture result. There was a high degree of correlation between the first and second dried plasma cards (r=0.996). CONCLUSIONS: The dried plasma collection card has adequate sensitivity and excellent specificity as compared to venepuncture specimens and is a feasible alternative for H. pylori IgG antibody testing. (+info)
Influence of repetitive finger puncturing on skin perfusion and capillary blood analysis in patients with diabetes mellitus.
(32/1207)
BACKGROUND: Frequent puncturing of fingers to check blood glucose in patients with type 1 diabetes might alter skin perfusion and, hence, influence the representativeness of the blood sample. We investigated the influence of repetitive puncturing on skin microcirculatory perfusion using laser Doppler fluxmetry and on the preanalytical phase of capillary blood analysis for small molecules (glucose) and large particles (cholesterol). METHODS: In 49 patients with long-standing (mean, 21 years) type 1 diabetes, with a mean puncture frequency of three times daily for a mean duration of 13 years, laser Doppler skin perfusion was measured in a finger at a frequently punctured site and compared with a similar site of another finger of the same hand, which was never punctured. In the supine position with the hand level with the heart, resting flux (RF), peak flux (PF), and the microcirculatory reserve capacity (MRC; PF - RF) were assessed. Subsequently, blood samples for capillary whole blood glucose and cholesterol analyses were taken from the same sites. RESULTS: No significant differences were found between the puncture and control sites in mean RF (2.3 vs 2.0 V; P = 0.14, paired-samples t-test), PF (3.3 vs 3.1 V; P = 0.24), MRC (1.0 vs 1.0 V; P = 0.65), glucose (10.2 vs 10.2 mmol/L; P = 0.69), or cholesterol (5.1 vs 5.2 mmol/L; P = 0.26). Power calculation for a RF of 2.0 V and the SD and n of this study indicate a power (beta) of 80% to detect a 25% change in RF at P <0.05. CONCLUSIONS: Repetitive finger puncturing in diabetics appears not to injure local skin microcirculatory perfusion nor to influence results of capillary blood analysis for glucose and cholesterol. (+info)