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Interindividual variability of whole blood viscosity improved with standardized hydration
Clinica Chimica Acta 337 (2003) 181 – 182 www.elsevier.com/locate/clinchim
Letter to the Editor
Interindividual variability of whole blood viscosity improved with standardized hydration
Dear Editor: Whole blood viscosity (WBV) has been identified as an independent risk factor for atherosclerosis and cardiovascular events [1]. Measurements of WBV in clinical practice have been limited with rotational viscometers because they are complex, operator dependent, and can measure viscosity of blood or plasma at a single shear rate at a time, while abnormalities of viscosity may reveal themselves at only one end of the viscosity spectrum. Further, the necessity to treat blood samples with anticoagulants such as ethylenediaminetetraacetic acid (EDTA) or heparin to prevent blood coagulation during viscosity measurements can interfere with the results, and the technology requires open handling of blood, with associated risk of transfer of infectious agents. Despite these limitations, prospective epidemiological studies have compellingly demonstrated an association between elevated viscosity and increased frequency of cardiovascular events [2]. In a previous study, we evaluated variations of WBV using a new type of viscometer, Rheologk, in a single-centered study involving 24 healthy males for 14 days [3]. We measured the fasting WBV in 6 separate days, and analyzed data for 21 subjects who finished the study. We found that interindividual variations in WBV were higher after 10-h overnight fast compared to pre-meal, post-meal (2 h), or all measurements. We theorized that different responses to dehydration induced by fasting contribute to the larger variations found with fasting measurements. We also hypothesized that oral rehydration with 500 ml water at least 90 min before WBV measurements would allow for restoration of fluid homeostasis and lower WBV interindividual variability [3,4]. 0009-8981/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.cccn.2003.07.003
In the current study, we measured WBV after a minimum 10-h fast in 98 healthy males between 18 and 75 years old. All subjects were provided 500 ml water 45 min prior to the viscosity measurements. These subjects were nonsmokers and free of drugs that change blood viscosity. The fasting was for at least 10 h overnight. The study protocol and consent form were approved by Northwestern University Institute Review Board (IRB), and all were consented before enrolled in the study. Values of WBV interindividual variability at different shear rates are shown in Table 1 for single baseline measurement per subject in the current study. To make validated comparison, we reanalyzed the WBV interindividual variability in the previous study based on the single measurement of fasting WBV per subject on day 1 of the study, and the values are also compiled in Table 1. The mean values of viscosity at lower shear rates ( V 10 s 1) in the current study were lower than the previous study presumably due to the effects of rehydration, but the differences were not statistically significant (Student’s t-test, two-tailed analysis). We then compared the standard deviations (S.D.) from the two studies and calculated the percent changes due to the standardized rehydration [(differ-
Table 1 Interindividual variability of fasting blood viscosity Shear rate (s
300 150 100 50 10 5 2 1
Current study
Previous study
1
)
Mean (mPa s)
S.D. (mPa s)
Mean (mPa s)
S.D. (mPa s)
4.40 4.63 4.81 5.24 7.22 8.93 12.86 18.17
0.31 0.35 0.38 0.46 0.97 1.49 2.81 4.75
4.24 4.50 4.71 5.20 7.53 9.57 14.36 20.92
0.39 0.42 0.45 0.53 1.07 1.64 3.13 5.34
182
Letter to the Editor
ence of the S.D. at a given shear rate from the two studies)/(S.D. from the previous study) 100%]. The administration of oral fluids before WBV measurements in the current study was accompanied by 9.4 – 19.5% lower interindividual variations compared to previous study as shown in Table 1, indicating that standardized rehydration for WBV measurement improves interindividual variability. Current standardization on sample collection for fasting blood viscosity offered benefit on interindividual variability and should be considered when WBV is measured.
References [1] Rosenson RS, McCormick A, Uretz EF. Distribution of blood viscosity values and biochemical correlates in healthy adults. Clin Chim Acta 1996;42:1189 – 95. [2] Danesh J, Collins R, Peto R, Lowe GDO. Haematocrit, viscosity, erythrocyte sedimentation rate: meta-analyses of prospective studies of coronary heart disease. Eur Heart J 2000;21:515 – 20. [3] Wang S, Boss AH, Kensey KR, Rosenson RS. Variations of whole blood viscosity using Rheolog—a new scanning capillary viscometer. Clin Chim Acta 2003;332:79 – 82. [4] Vlastos GA, Tangney CC, Rosenson RS. Effects of hydration on blood rheology. Clin Hemorheol Microcirc 2003;28:41 – 9.
Sihe Wang Department of Pathology & Laboratory Medicine, Northwestern University, The Feinberg School of Medicine, 2300 Children’s Plaza, Chicago, IL 60614, USA Kenneth Kensey Rheologics, Incorporated, 15 E. Uwchlan Ave., Suite 414, Exton, PA 19341, USA Robert Rosenson * Division of Cardiology, Preventive Cardiology Center, Departments of Medicine and Preventive Medicine, Northwestern University, The Feinberg School of Medicine, 201 East Huron Street, Galter Pavilion, Suite 11-120 Chicago, IL 60611, USA E-mail address: [email protected] 27 June 2003
* Corresponding author. Tel.: +1-312-695-0013; fax: +1-312695-0047.
Letter to the Editor
Interindividual variability of whole blood viscosity improved with standardized hydration
Dear Editor: Whole blood viscosity (WBV) has been identified as an independent risk factor for atherosclerosis and cardiovascular events [1]. Measurements of WBV in clinical practice have been limited with rotational viscometers because they are complex, operator dependent, and can measure viscosity of blood or plasma at a single shear rate at a time, while abnormalities of viscosity may reveal themselves at only one end of the viscosity spectrum. Further, the necessity to treat blood samples with anticoagulants such as ethylenediaminetetraacetic acid (EDTA) or heparin to prevent blood coagulation during viscosity measurements can interfere with the results, and the technology requires open handling of blood, with associated risk of transfer of infectious agents. Despite these limitations, prospective epidemiological studies have compellingly demonstrated an association between elevated viscosity and increased frequency of cardiovascular events [2]. In a previous study, we evaluated variations of WBV using a new type of viscometer, Rheologk, in a single-centered study involving 24 healthy males for 14 days [3]. We measured the fasting WBV in 6 separate days, and analyzed data for 21 subjects who finished the study. We found that interindividual variations in WBV were higher after 10-h overnight fast compared to pre-meal, post-meal (2 h), or all measurements. We theorized that different responses to dehydration induced by fasting contribute to the larger variations found with fasting measurements. We also hypothesized that oral rehydration with 500 ml water at least 90 min before WBV measurements would allow for restoration of fluid homeostasis and lower WBV interindividual variability [3,4]. 0009-8981/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.cccn.2003.07.003
In the current study, we measured WBV after a minimum 10-h fast in 98 healthy males between 18 and 75 years old. All subjects were provided 500 ml water 45 min prior to the viscosity measurements. These subjects were nonsmokers and free of drugs that change blood viscosity. The fasting was for at least 10 h overnight. The study protocol and consent form were approved by Northwestern University Institute Review Board (IRB), and all were consented before enrolled in the study. Values of WBV interindividual variability at different shear rates are shown in Table 1 for single baseline measurement per subject in the current study. To make validated comparison, we reanalyzed the WBV interindividual variability in the previous study based on the single measurement of fasting WBV per subject on day 1 of the study, and the values are also compiled in Table 1. The mean values of viscosity at lower shear rates ( V 10 s 1) in the current study were lower than the previous study presumably due to the effects of rehydration, but the differences were not statistically significant (Student’s t-test, two-tailed analysis). We then compared the standard deviations (S.D.) from the two studies and calculated the percent changes due to the standardized rehydration [(differ-
Table 1 Interindividual variability of fasting blood viscosity Shear rate (s
300 150 100 50 10 5 2 1
Current study
Previous study
1
)
Mean (mPa s)
S.D. (mPa s)
Mean (mPa s)
S.D. (mPa s)
4.40 4.63 4.81 5.24 7.22 8.93 12.86 18.17
0.31 0.35 0.38 0.46 0.97 1.49 2.81 4.75
4.24 4.50 4.71 5.20 7.53 9.57 14.36 20.92
0.39 0.42 0.45 0.53 1.07 1.64 3.13 5.34
182
Letter to the Editor
ence of the S.D. at a given shear rate from the two studies)/(S.D. from the previous study) 100%]. The administration of oral fluids before WBV measurements in the current study was accompanied by 9.4 – 19.5% lower interindividual variations compared to previous study as shown in Table 1, indicating that standardized rehydration for WBV measurement improves interindividual variability. Current standardization on sample collection for fasting blood viscosity offered benefit on interindividual variability and should be considered when WBV is measured.
References [1] Rosenson RS, McCormick A, Uretz EF. Distribution of blood viscosity values and biochemical correlates in healthy adults. Clin Chim Acta 1996;42:1189 – 95. [2] Danesh J, Collins R, Peto R, Lowe GDO. Haematocrit, viscosity, erythrocyte sedimentation rate: meta-analyses of prospective studies of coronary heart disease. Eur Heart J 2000;21:515 – 20. [3] Wang S, Boss AH, Kensey KR, Rosenson RS. Variations of whole blood viscosity using Rheolog—a new scanning capillary viscometer. Clin Chim Acta 2003;332:79 – 82. [4] Vlastos GA, Tangney CC, Rosenson RS. Effects of hydration on blood rheology. Clin Hemorheol Microcirc 2003;28:41 – 9.
Sihe Wang Department of Pathology & Laboratory Medicine, Northwestern University, The Feinberg School of Medicine, 2300 Children’s Plaza, Chicago, IL 60614, USA Kenneth Kensey Rheologics, Incorporated, 15 E. Uwchlan Ave., Suite 414, Exton, PA 19341, USA Robert Rosenson * Division of Cardiology, Preventive Cardiology Center, Departments of Medicine and Preventive Medicine, Northwestern University, The Feinberg School of Medicine, 201 East Huron Street, Galter Pavilion, Suite 11-120 Chicago, IL 60611, USA E-mail address: [email protected] 27 June 2003
* Corresponding author. Tel.: +1-312-695-0013; fax: +1-312695-0047.