The effects of time from venepuncture and choice of anticoagulant on mean platelet volume estimations.

The Mean Platelet Volume (MPV) is a readily measured parameter using modern automated cell counters. Despite studies which indicate that MPV may be altered in various disease states, its widespread application has been hindered by its known dependence on factors such as time from venepuncture, choice of anticoagulant and sample storage temperature. In this report we describe the changes in MPV measured on a Technicon H1 analyser with time from sampling using two different anticoagulants under clinical laboratory conditions. Small changes in MPV with time were seen in both anticoagulants. These were statistically significant by Student's paired t-test but, on analysis of variance, were not significant compared with the variation in MPV between individuals. The well-documented effects of time, temperature and anticoagulant on MPV need not interfere with the interpretation of a result from a sample dealt with under similar conditions to those applying in this study.

Regulation of intestinal iron absorption and mucosal iron kinetics in hereditary hemochromatosis.

In hereditary hemochromatosis (HH), increased intestinal iron absorption leads to the development of iron overload. To examine the abnormal regulation of iron absorption in this disorder, we analyzed mucosal iron kinetics in six patients with HH and in five normal subjects by using a compartmental model of intestinal iron absorption and systemic ferrokinetics. Subjects were given simultaneous oral and intravenous tracer doses of iron 59-labeled citrate and iron 55-labeled transferrin, respectively. Plasma and whole-body radioactive iron levels were then monitored serially during the next 2 weeks, and mucosal iron transport rate constants were estimated by non-linear least-squares fit of the model to these data. Iron absorption was inversely related to serum ferritin concentration in both normal subjects and patients with HH but was higher in relation to serum ferritin level among the latter (p less than 0.0002). Analysis of mucosal iron kinetics demonstrated a similar inverse relationship between the rate constant for mucosal iron uptake and serum ferritin among all subjects combined, but the mean uptake rate constant in patients with HH did not differ from that of normal subjects (p = 0.71). The mean rate constant for incorporation of iron into the mucosal storage pool in patients with HH also was comparable to that of normal subjects (p = 0.94). In contrast, the rate constant for transfer of mucosal iron to the plasma was higher in patients with HH than in normal subjects for any given serum ferritin level (p less than 0.0001), and the transfer rate constant accounted for 87% of the variability in iron absorption among all subjects. We conclude that the increased iron absorption in HH is mediated primarily by an increase in the rate constant for transfer of mucosal iron to the plasma.

Biotin labeling of red cells in the measurement of red cell volume in preterm infants.

Determination of circulating red cell volume (RCV) in anemic preterm infants is, in theory, a better indicator of transfusion needs than Hb concentration. Our study reports the results of RCV measurement using biotin labeling of red cells on 40 occasions in preterm infants of 25-34 wk gestation. In 20 infants, who had estimations made within 24 h of birth, the RCV varied between 17.7 and 66 mL/kg. Twenty measurements were made at a later age at the time of a blood transfusion. RCV values were between 13.1 and 41.5 mL/kg before transfusion. In 13 infants, RCV was determined simultaneously using two methods, biotin and dilution of autologous HbF with donor HbA at transfusion. There was no significant difference between the results of RCV estimations using these two methods. Our study demonstrates that biotin labeling is an effective method for determining RCV in preterm infants.

The measurement of the total volume of red cells in man: a non-radioactive approach using biotin.

Present methods for measuring red cell volume are based on the dilution of radioactively labelled cells. This precludes the investigation in neonates and pregnant women. We present a simple method for labelling red cells with biotin. These cells may be injected intravenously and subsequently detected using streptavidin-FITC and flow-cytometry. A comparison of the red cell volume estimated using both 51Cr and biotin labelled cells in 19 patients showed no consistent clinically significant difference between the two. This novel label appears to allow red volume to be reliably estimated without using radioactivity.

Erythropoiesis and iron metabolism in Hodgkin's disease.

Recently developed techniques for the investigation of iron kinetics were used to study the disturbance of iron metabolism in 19 untreated patients with Hodgkin's diseases (HD). The erythroid abnormality in newly diagnosed HD appears to be confined to those patients with systemic symptoms of weight loss, night sweats and fever, and consists of depression of marrow erythroid activity. These patients had a significnatly lower haemoglobin and serum iron concentration and a higher serum ferritin concentration, both when compared to normal subjects and to those patients with HD who lacked systemic symptoms. Ineffective erythropoiesis and red-cell destruction were not significantly increased. The present findings, confirm that HD patients with systemic symptoms have a depression of erythropoiesis, and that in these patients the marrow fails to respond to the stimulus of mild anaemia.

Iron absorption in normal subjects and patients with idiopathic haemochromatosis: relationship with serum ferritin concentration.

In 52 normal subjects there was an inverse relationship between serum ferritin concentration and iron absorption. In 21 measurements in 15 patients with idiopathic haemochromatosis there was a similar inverse relationship but absorption was higher in relation to iron stores at all levels. Haemochromatotic patients with normal serum ferritin levels had abnormally high values for desferrioxamine chelatable iron and there was no correlation between chelatable iron and iron absorption.

Iron metabolism in Hodgkin's disease.

An evaluation of iron metabolism has been carried out in 23 untreated patients with Hodgkin's disease and 6 patients with other lymphomata. The reduction in red cell life span is related to the stage of the disease. There is an almost universal impairment of iron release from the reticuloendothelial system with a consequent sideropenia and failure of iron delivery to the bone marrow for erythropoiesis. This defect is found in all stages of the disease and is not related to systemic symptoms.