Patients with leukemia may have symptoms of hyperviscosity if the white blood cell count becomes sufficiently high. The viscosity can be estimated based on the type of leukemia, the white blood cell count and the hematocrit.
Steps:
(1) Measure the white blood cell count and estimate the blast volume
(2) Estimate the observed leukocrit
(3) Estimate the viscosity due to the eythrocrit and leukocrit
Measure White Blood Cell Count and Estimate Blast Volume
blast volume in cubic microns =
= 4/3 * π * ((radius of blast in microns) ^ 3)
Estimate the Observed Leukocrit
The "true" leukocrit can be estimated from the type of leukemia, the blast volume and the white blood cell count (Figure 2, page 727, Lichtman 1987; Figure 3, page 280, Lichtman 1982).
For white blood cells with volume from 200 to 600 cubic microns:
"true" leukocrit in mL packed leukocytes per dL blood =
= ((blast volume in cubic microns) / 10,000) * ((WBC count per µL) / 1,000)
|
Blast Volume in cubic microns |
WBC Count with Leukocrit = 20 |
Diameter of Blast in Microns |
Slope of Line |
|---|---|---|---|
|
200 |
1,000 thousand/µL |
7.24 |
0.02 |
|
300 |
667 thousand/µL |
8.3 |
0.03 |
|
400 |
500 thousand/µL |
9.14 |
0.04 |
|
500 |
400 thousand/µL |
9.85 |
0.05 |
|
600 |
333 thousand/µL |
10.46 |
0.06 |
"observed" leukocrit =
= ("true" leukocrit) / 0.65
Estimate of Viscosity from Erythrocrit and Leukocrit
Viscosity from observed leukocrit and erythrocrit (Figure 1, page 726, Lichtman 1987; Figure 2, page 280, Lichtman 1982). Equations derived in JMP from points read from diagram. The viscosity associated with the hematocrit is linear in a semi-logarithmic plot; the viscosity associated with the leukocrit is exponential in a semi-logarithmic plot.
LOG10(viscosity due to erythrocrit) = X =
= (0.01138 * (hematocrit in percent)) + 0.03699
viscosity due to erythrocrit in centipoise =
= 10 ^ (X)
LOG10(viscosity due to observed leukocrit) = Y =
= (0.0003125 * ((observed leukocrit in percent) ^ 2)) + (0.010656 * (observed leukocrit in percent)) + 0.0577731
viscosity due to observed leukocrit in centipoise =
= 10 ^ (Y)
Anemia can help reduce the viscosity due to hyperleukocytosis.
Minimum Apparent Viscosity in Centipoise
|
Hct |
Observed Leukocrit in Percent |
|||||||
|---|---|---|---|---|---|---|---|---|
|
|
5% |
10% |
15% |
20% |
25% |
30% |
35% |
40% |
|
40% |
4.4 |
4.5 |
4.8 |
5.3 |
6.0 |
7.0 |
8.8 |
13.3 |
|
35% |
4.1 |
4.2 |
4.5 |
5.0 |
5.7 |
6.7 |
8.5 |
12.0 |
|
30% |
3.8 |
3.9 |
4.2 |
4.7 |
5.4 |
6.4 |
8.2 |
11.7 |
|
25% |
3.4 |
3.7 |
4.0 |
4.5 |
5.2 |
6.2 |
8.0 |
11.5 |
|
20% |
3.2 |
3.5 |
3.8 |
4.3 |
5.0 |
6.0 |
7.8 |
11.3 |
|
15% |
3.0 |
3.1 |
3.4 |
3.9 |
4.6 |
5.6 |
7.4 |
10.9 |
|
10% |
2.7 |
2.9 |
3.2 |
3.7 |
4.4 |
5.4 |
7.2 |
10.7 |
Figure 6, page 282, Lichtman 1982
Limitations:
• This model does not include the interactions between leukemic cells, with increased interactions increasing the observed viscosity.
Specialty: Hematology Oncology
