BLOOD PLATELETS 



46 



BLOOD PLATELETS 



TABLE 1 



Characteristics of various direct methods of platelet 

 enumeration 



1 to 2 dilution of blood, stained in the 

 usual manner, and examined with the 

 oil immersion lens have the advantage 

 of a somewhat more uniform distribu- 

 tion of erythrocytes and platelets, but 

 there is question as to whether some of 

 the platelets and/or erythrocytes may 

 not be destroyed during the process of 

 making the smears. 



The above multiplicity of methods, 

 and numerous other variations not men- 

 tioned, is not the result of idle inven- 

 tion but rather of a persistent effort on 

 the part of each investigator to over- 

 come the errors inherent in the methods 

 of his predecessors. In many instances 

 however, the successful solution of one 

 difficulty has only served to give rise 

 to other sources of error. The im- 

 possibility of achieving a uniform dis- 

 tribution of erythrocytes and platelets 

 makes it unlikely that a satisfactory 

 indirect method can be devised. On 

 the other hand the inadequate visualiza- 

 tion of platelets with the high dry lens 

 makes all direct methods in which the 

 standard 0.1 mm. depth counting cham- 

 ber is employed unreliable. The only 

 solution to the problem appears to be 

 the perfection of a technique for using 

 an oil immersion lens in conjunction 

 with a chamber of 0.02 mm. depth and 

 phase contrast lighting. 



There is, at the present time, no 

 standard procedure for the enumeration 

 of blood platelets. Numerous methods 

 have been devised, which vary in the 

 following manner: 1) Manner of count- 

 ing — direct or indirect; 2) type of dilut- 

 ing fluid — with or without a variety of 

 dyes, fixatives and anticoagulants — 

 with or without hemolytic properties; 

 3) source of specimen — capillary or 

 venous blood; 4) material on which the 

 count is made — whole blood, plasma or 

 eluate from whole blood; 5) type of 

 counting chamber — standard 0.1 mm. 

 depth or special 0.02 mm. depth with 

 thin coverslip; 6) microscopic mag- 

 nification and resolution — 430X (high 

 dry) to lOOOX (water or oil immersion) ; 

 7) microscopic illumination — bright 

 field, dark field or phase contrast (see 

 tables 1 and 2). 



Reports of average normal platelet 

 counts in man have varied from 200,000 

 per cu. mm. (1) to 800,000 per cu. mm., 



"J. A. M. A., 1923,80,621. 



* .\rch. Path., 1937, 23, 850. 



« S. Gynec. et Obst., 1927, 15, 436. 

 ^ J. Applied Physiol., 1950, 3, 365. 

 ' Exper. Med., 1924,40, 553. 

 /Am. J. Clin. Path., 1942, 12. 362. 

 9 Am. J. Clin. Path., 1949, 19, 1113. 



* Arch. f. Clin. Med., 1904, 81, 316. 



