An Accurate and Practical Method for Blood Platelet Counting

Abstract

A new method of blood platelet counting involving no additional technical procedure has been devised which has been found to be as accurate and as rapid as the usual method of red cell enumeration. Its essential features are: (1) the red blood cells and blood platelets are counted on the same field in the same counting chamber preparation; (2) the low power lens is used for both red and platelet counts; (3) the platelets are counted in the 3 middle vertical columns of a Neubauer chamber, comprising 240 small squares and the resultant figure divided by 3; (4) Ringer's solution, to which a small amount of heparin (1 mg. per 5 cc.) has been added, is used as the diluting fluid.∗

Parallel counts indicate that as accurate red cell counts may be obtained by this method as with Hayem's solution. In a series of consecutive pipettes upon the same animal, the mean red blood count was 5,042,500 and the mean platelet count 536,000. The coefficient of variation for the red counts was 6.8% and for the platelets 7.4%, demonstrating that the error in making a platelet count was no greater than that in making a red cell count. Counts made after standing 40 minutes on the counting chamber are as accurate as those made after 5 or 10 minutes, while shaking in a shaking machine for one hour, or storage for 24 hours in the icebox does not essentially alter the red cell count or the blood platelet count.

The solution is evidently a favorable medium for the preservation of these blood constituents.

Fading and disintegration of the red blood cells and fragmentation and degeneration of the platelets, which are the usual sources of error in current direct methods of blood examinations, are essentially eliminated when Ringer-heparin solution is used as the diluting fluid.