View source for Hematology Calculations

The following are common calculations used in the hematology discipline.

==== RBC Indices ====
There are 3 RBC indices that are calculated from measured RBC parameters: MCH, MCV, MCHC.

==== Mean Cell Hemoglobin MCH (g/L) ====
Average amount of hemoglobin present per red blood cell.

<math display="block">MCH=\frac{HGB}{RBC}</math>

==== Mean Cell Volume MCV (fL) ====
Average size (volume) of red blood cell.

<math display="block">MCV=\frac{HCT*1000}{RBC}</math>

==== Mean Cell Hemoglobin Concentration MCHC (g/L) ====
<math display="block">MCHC=\frac{HGB}{HCT}</math>

==== Rule of Three ====
In normal RBCs, the HCT value should be approximately 3x the hemoglobin. Used as a quick check of the CBC results for interfering substances or other issues with the blood.

<math display="block">\frac{HGB*3}{1000}=HCT\pm0.03</math>

==== Citrate Adjustment for High Hematocrit ====
Used when hematocrit > 0.55 L/L as high hematocrit means that there is less plasma present (therefore, the plasma-anticoagulant ratio is incorrect). This can result in excess sodium citrate, which can falsely prolong the clotting time.

<math display="block">C=(1.85*10^{-3})(100-HCT)(V)</math>

* C = citrate volume that needs to be remaining in tube
* HCT = hematocrit
*V = volume of blood drawn
Then, use this value to determine that volume of citrate that needs to be removed.

<math display="block">R=V_c-C</math>

* R = volume to be removed from tube
* V<sub>c</sub> = volume of citrate present in tube
* C = citrate volume remaining

==== Reticulocyte Count (%) ====
For 1000 RBCs

<math display="block">\mbox{Relative reticulocyte count}=\frac{\mbox{Retics per 1000 RBCs}}{10}</math>

For >1000 RBCs

<math display="block">\mbox{Relative reticulocyte count}=\frac{Retics*1000}{\mbox{RBC count}}</math>

==== Corrected Reticulocyte Count (%) ====
The retic count should be corrected if there is a low hematocrit (less RBCs present), as this will falsely increase the reticulocyte count.

<math display="block">\mbox{Corrected retic count}=\frac{\%\mbox{ Relative Retics * Patient HCT}}{\mbox{Average Normal HCT}}</math>

* Average normal HCT (male): 0.45 L/L
* Average normal HCT (female): 0.42 L/L

==== Absolute Reticulocyte Count (x10<sup>9</sup>/L) ====
To determine the actual number of retics present in the blood.

<math display="block">\mbox{Abs Retic}=\frac{\%\mbox{ Relative Retics * RBC}}{100}</math>

==== Corrected WBC Count for NRBC ====
Used to correct the WBC count for NRBCs as they may be mistaken for WBCs by the analyzer, giving a falsely elevated result.

<math display="block">\mbox{Corrected WBC}=\frac{\mbox{100 * WBC Count}}{100+NRBC}</math>

* NRBC = # NRBCs counted per 100 WBC

==== International Normalized Ratio (INR) ====
<math display="block">INR=\left ( \frac{\mbox{Patient PT}}{\mbox{Control PT}} \right )^{ISI}</math>

==== Neubauer Chamber Total Cell Counts ====
To determine cell counts based on the amount of cells counted in the Neubauer Chamber. Values change depending on the fluid and cell being counted (fluid may be diluted, and the amount of squares counted depends on the cell type)
[[File:Neubauer counts.jpg|thumb|Neubauer counts calculation for various fluids.]]

* Average cell count = average (taken using both sides of the chamber)
* DF = dilution factor (reciprocal of dilution)



{| class="wikitable"
|+
|Fluid
|Cell  Type
|Squares  Counted
|Dilution
|DF
|-
| rowspan="3" |CSF
| rowspan="3" |All  cells! (WBC & RBC)
| rowspan="3" |9  (all)
|Clear:  none
|1
|-
|Bloody  WBC: 1:2
|2
|-
|Bloody:  1:10-1:200
|10-200
|-
| rowspan="2" |Whole  Blood
|WBCs
|4  (outer corners)
|1:20
|20
|-
|Platelets
|1  (large central square)
|1:100
|100
|-
|Synovial  Fluid
|
|
|
|
|}
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