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Abstract
Background:
Whole blood viscosity (WBV) refers to the internal resistance that occurs when blood flows through blood vessels. WBV is known to be related to many diseases including cardiovascular and neurovascular diseases. We have investigated the analytical performance and established reference intervals for a newly developed microfluidic viscometer, Viscore-300 (NanoBiz, Korea), used for the measurement of WBV.
Methods:
We performed a precision test of 240 measurements over 20 days using three control materials. For evaluation of repeatability, a total of 60 WBV measurements were made in 3 whole blood samples 20 times a day. A total of 100 whole blood samples were used to evaluate the accuracy of the Viscore-300 in comparison to a rotating viscometer, DV3T (Brookfield, USA), in accordance with the the Clinical and Laboratory Standards Institute's guidelines. To establish the reference intervals, 122 healthy individuals were enrolled in this study.
Results:
The precision and repeatability results showed that the CV was less than 5% for three samples and two shear rates. In the accuracy test, the mean differences between two viscometers were 0.09 cP (0.9%) and –0.07 cP (–1.4%) at shear rates of 10 s–1 and 300 s–1, respectively. The reference intervals of WBV for men were 6.88–13.52 cP at 10 s–1 and 4.32–6.43 cP at 300 s–1; those of women were 5.74–13.29 cP at 10 s–1 and 3.60–6.12 cP at 300 s–1.
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REFERENCES
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 | Fig. 1.The core chip and measurement processes of Viscore. (A) The microfluidic chip (V-Chip) and dual syringes for whole blood and reference fluid are mounted in a disposable cartridge (a photograph of a finished product). (B) Initial step of fluid injection (an experiment photograph of V-Chip). (C) Late step to measure whole blood viscosity (an experiment photograph of V-Chip). The number of microchannels filled with whole blood and reference fluid are directly counted, and viscosity is determined accordingly. |
 | Fig. 2.Results of accuracy test using 100 whole blood samples at a high shear rate, 300 s-1, between DV3T and Viscore. (A) Passing-Bablok regression plot. X-axis represents the viscosity measured by DV3T as a reference method. Y-axis represents the viscosities measured by the Viscore, as a comparative method. The black dash line is an identity line (y=x), the blue solid line is a regression line, and the shade area presents 95% confidence interval of the Passing-Bablok regression. (B) Bland-Altman difference plot. X-axis represents the average viscosity measured by DV3T and Viscore as a reference method. Y-axis represents the difference of viscosities between Viscore and DV3T. The black dash line is a base line (difference=0), the blue solid line is a mean difference between the two viscometers, and the red dash lines presents ±1.96 SD of mean bias. 3 samples were out of ±1.96 SD of mean bias. |
Table 1.
Precision of Viscore-300 using three control materials at shear rates of 10 and 300 s–1 (total 240 tests)
Table 2.
Repeatability of Viscose-300 using whole blood samples at shear rates of 10 and 300 s–1 (total 60 tests)
| Specimen concentration | Shear rate (s-1) | Average viscosity (cP) | Coefficient of variance, CV (%) |
|---|---|---|---|
| Low | 10 | 6.98 | 4.21 |
| 300 | 3.36 | 3.34 | |
| Medium | 10 | 9.45 | 3.88 |
| 300 | 4.54 | 2.90 | |
| High | 10 | 12.68 | 4.80 |
| 300 | 5.16 | 3.61 |
Table 3.
Results of WBV measured by Viscore-300 and DV3T
Table 4.
Parameters of Passing-Bablok regression line between Vis-core-300 and DV3T
| Shear rate (s–1) | Parameter of regression | Values (95% CI) |
|---|---|---|
| 10 | Intercept | 0.08 (–0.43–0.54) |
| Slope | 1.00 (0.95–1.05) | |
| R | 0.974 | |
| 300 | Intercept | –0.33 (–0.85–0.11) |
| Slope | 1.05 (0.95–1.15) | |
| R | 0.925 |
Table 5.
The characteristics and hematological profiles of healthy individuals for determination of reference interval
| Variable | Total | Men (N=82) | Women | P∗ |
|---|---|---|---|---|
| (N=122) | (N=40) | |||
| Age (year) | 36.5±9.5† | 37.8±9.1† | 34.0±10.1† | 0.042 |
| White blood cell (×103/µL) | 6.6±1.8 | 6.8±1.8 | 6.0±1.7 | 0.022 |
| Red blood cell (×103/µL) | 4.8±0.4 | 5.0±0.3 | 4.5±0.2 | <0.001 |
| Hemoglobin (g/dL) | 14.8±1.5 | 15.6±0.9 | 13.2±1.3 | <0.001 |
| Hematocrit (%) | 43.0±3.7 | 44.8±2.4 | 39.0±3.0 | <0.001 |
| Platelets (×103/µL) | 258.0±54.6 | 252.4±50.2 | 269.9±62.1 | 0.104 |
Table 6.
Reference intervals (2.5th–97.5th percentiles) of human whole blood viscosity measured by Viscore-300
| Shear rate (s-1) | Group | Median WBV (cP) | Reference Intervals∗ (cP) |
|---|---|---|---|
| 10 | Total (N=122) | 9.46 | 6.55–13.40 |
| Men (N=82) | 9.95 | 6.88–13.52 | |
| Women (N=40) | 8.39 | 5.74–13.29 | |
| 300 | Total (N=122) | 4.96 | 3.76–6.26 |
| Men (N=82) | 5.15 | 4.32–6.43 | |
| Women (N=40) | 4.50 | 3.60–6.12 |
∗ Healthy individuals were selected as those without any cardiovascular disease, neurovascular disease, liver disease, diabetes, dyslipidemia, and history of medication. Non-parametric estimation was used to establish reference intervals for WBV. Abbreviations: cP, centipoise; WBV, whole blood viscosity.
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