What error was probably made if red cells are seen when ...

[karen]

What error was probably made if red cells are seen when attempting to manually count white blood cell (WBCs) on a hemocytometer?
 
  a. The Unopette was not mixed before charging the hemocytometer.
  b. Diluent was squeezed out and lost when filling the Unopette.
  c. The wrong dilution was made.
  d. The Unopette was not allowed to sit for 10 minutes for complete red blood cell (RBC) lysis.

Question 2

Twenty cells are counted in one of the nine large squares of a hemocytometer. The sample is diluted 1:10. How many cells are present per mL?
 
  a. 200
  b. 1000
  c. 2000
  d. 20,000

[dyrone]

Answer to Question 1

ANS: D
It requires about 10 minutes for complete lysis of RBCs in the WBC Unopette. If this time is shortened, then red cells may still be intact and therefore visible when the chamber is examined under the microscope. It will be almost impossible to count the white cells because their relative number is so small compared with that of the red cells.

Answer to Question 2

ANS: C
Plugging the appropriate numbers into the formula: (20  10)/(1 mm2  0. 1 mm) = 2000/mm3 = 2000/mL (= 2.0  103/mL = 2.0  109/L).

[karen]

Gracias!

[tuate]

Thanks for the timely response, appreciate it