A cerebrospinal fluid has 285 RBCs counted in the 5 RBC squares after being diluted in a Unopette (1:100). What is the calculated RBC count per microliter?

To determine the calculated RBC count per microliter from the cerebrospinal fluid sample, you can follow this method.

First, note that the RBC count obtained from the counting chamber was 285 RBCs counted in the 5 squares of the hemocytometer after a dilution of 1:100 using a Unopette.

When using a hemocytometer, the standard volume that each square represents is known. In this case, the total volume counted in the 5 squares can be calculated based on the total volume of the dilution and the dilution factor. Since each of the 5 squares represents 1/20 of the total counting area of a standard hemocytometer and given that the volume per square is 0.1 mm³, the total volume counted is 5 x 0.1 mm³ = 0.5 mm³ (or 0.5 μL).

Next, because the sample was diluted 1:100, you need to multiply the number of RBCs counted by this factor to account for the dilution.

The total RBC count in the original sample can be calculated as follows:

Total RBC count per μL = (Count in hemocytometer) × (Dilution Factor) / (Volume