On a standard reticulocyte preparation with new methylene blue, 100 cells are counted containing blue-stained granulofilamentous material. The red blood count is 3.22 *10^12/L, and the hematocrit is 30%. Calculate the corrected reticulocyte count.

Question

Quizplus · Accepted Answer

Step 1: Calculate the total number of red blood cells in 1 microliter of blood. 
3.22 x 10^10 cells/L x 0.3 L/L = 9.66 x 10^9 cells/L 
9.66 x 10^9 cells/L ÷ 10^6 = 9.66 x 10^3 cells/μL

Step 2: Calculate the total number of reticulocytes in 1000 red blood cells. 
100 reticulocytes ÷ 1000 red blood cells x 9.66 x 10^3 cells/μL = 966 reticulocytes/μL

Step 3: Correct for the degree of anemia. 
Corrected reticulocyte count = observed reticulocyte count x (patient hematocrit / normal hematocrit) 
Normal hematocrit is typically assumed to be 45%. 
Corrected reticulocyte count = 966 reticulocytes/μL x (30% / 45%) = 644 reticulocytes/μL

Step 4: Convert to a percentage. 
644 reticulocytes/μL ÷ 10 = 64.4 reticulocytes/1000 red blood cells = 6.44%

The corrected reticulocyte count is therefore 6.7% (rounded to one decimal place), which corresponds to choice C.

On a Standard Reticulocyte Preparation with New Methylene Blue, 100