Measurement of immunoreactive angiotensin-(1-7) heptapeptide in human blood.

BACKGROUND: The renal enzyme renin cleaves from the hepatic alpha(2)-globulin angiotensinogen angiotensin-(1-10) decapeptide [Ang-(1-10)], which is further metabolized to smaller peptides that help maintain cardiovascular homeostasis. The Ang-(1-7) heptapeptide has been reported to have several physiological effects, including natriuresis, diuresis, vasodilation, and release of vasopressin and prostaglandins. METHODS: To investigate Ang-(1-7) in clinical settings, we developed a method to measure immunoreactive (ir-) Ang-(1-7) in 2 mL of human blood and to estimate plasma concentrations by correcting for the hematocrit. A sensitive and specific antiserum against Ang-(1-7) was raised in a rabbit. Human blood was collected in the presence of an inhibitor mixture including a renin inhibitor to prevent peptide generation in vitro. Ang-(1-7) was extracted into ethanol and purified on phenylsilylsilica. The peptide was quantified by radioimmunoassay. Increasing doses of Ang-(1-7) were infused into volunteers, and plasma concentrations of the peptide were measured. RESULTS: The detection limit for plasma ir-Ang-(1-7) was 1 pmol/L. CVs for high and low blood concentrations were 4% and 20%, respectively, and between-assay CVs were 8% and 13%, respectively. Reference values for human plasma concentrations of ir-Ang-(1-7) were 1.0-9.5 pmol/L (median, 4.7 pmol/L) and increased linearly during infusion of increasing doses of Ang-(1-7). CONCLUSIONS: Reliable measurement of plasma ir-Ang-(1-7) is achieved with efficient inhibition of enzymes that generate or metabolize Ang-(1-7) after blood sampling, extraction in ethanol, and purification on phenylsilylsilica, and by use of a specific antiserum.

Misleading tacrolimus concentration value in blood taken from a catheter used for tacrolimus administration.

PURPOSE: A misleading blood tacrolimus concentration (BTC) value caused by the contamination of a central venous catheter previously used for tacrolimus administration is described. SUMMARY: A 59-year-old woman with severe chronic obstructive pulmonary disease successfully underwent double lung transplantation. In the intensive care unit, she received a continuous i.v. infusion of tacrolimus from days 1 to 5 after transplantation through the distal lumen of a polyurethane triple-lumen central venous catheter. The catheter lumen was flushed twice a day with 0.9% sodium chloride injection. The proximal lumen was used for blood sampling after being flushed; the first 10 mL of blood was discarded. BTCs determined in whole blood one, four, and five days after transplantation were within the therapeutic range of 5-15 ng/mL. On day five the patient was transferred to the thoracic surgery ward and was switched to oral tacrolimus 1.5 mg twice daily. The BTC on day 6 was unexpectedly high at 134.5 ng/mL. The patient's clinical status was normal, and no signs of tacrolimus toxicity were observed. On day 7, blood samples were drawn from a peripheral vein and simultaneously through the central venous catheter. Although the central venous catheter had not been exposed to tacrolimus during the preceding two days, it yielded blood with a BTC eight times higher than the BTC in blood from the peripheral vein (41.4 ng/mL versus 5.1 ng/mL). CONCLUSION: The collection of blood from a central venous catheter lumen that had been used for tacrolimus administration resulted in a BTC about eight times higher than what was measured in peripheral blood.

European Society of Hypertension guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring

This document summarizes the available evidence and provides recommendations on the use of home blood pressure monitoring in clinical practice and in research. It updates the previous recommendations on the same topic issued in year 2000. The main topics addressed include the methodology of home blood pressure monitoring, its diagnostic and therapeutic thresholds, its clinical applications in hypertension, with specific reference to special populations, and its applications in research. The final section deals with the problems related to the implementation of these recommendations in clinical practice.

Stability and robustness of blood variables in an antidoping context.

Introduction:  With the setting up of the newly Athlete's Biological Passport antidoping programme, novel guidelines have been introduced to guarantee results beyond reproach. We investigated in this context, the effect of storage time on the variables commonly measured for the haematological passport. We also wanted to assess for these variables, the within and between analyzer variations. Methods:  Blood samples were obtained from top level male professional cyclists (27 samples for the first part of the study and 102 for the second part) taking part to major stage races. After collection, they were transported under refrigerated conditions (2 °C < T < 12 °C), delivered to the antidoping laboratory, analysed and then stored at approximately 4 °C to conduct analysis at different time points up to 72 h after delivery. A mixed-model procedure was used to determine the stability of the different variables. Results:  As expected haemoglobin concentration was not affected by storage and showed stability for at least 72 h. Under the conditions of our investigation, the reticulocytes percentage showed a much better stability than previous published data (> 48 h) and the technical comparison of the haematology analyzer demonstrated excellent results. Conclusion:  In conclusion, our data clearly demonstrate that as long as the World Anti-Doping Agency's guidelines are followed rigorously, all blood results reach the quality level required in the antidoping context.