Blood, 1946, Vol. 1, No. 6, pp. 472-496.
© 1946 American Society of Hematology, Inc.
PLATELET COUNTS AND PLATELET FUNCTION
PAUL M. AGGELER M.D.1,
JOAN HOWARD A.B.1,
S. P. LUCIA M.D.1, and
EDITH MILLS M. A.1
1 Division of Preventive Medicine, University of California Medical School, San Francisco, California.
Determinations of the platelet count, clot retraction, bleeding time, capillary
fragility, and coagulation time were made in 64 normal subjects and in 404 patients
suffering from various diseases.
The normal values for the platelet count done by an experienced technician using
the Rees and Ecker method were: mean, 409,000 per cu. mm.; standard deviation,
68,000 per cu. mm.; normal range (M ± 2.
), 273,000 per cu. mm. to 545,000 per
cu. mm.
There was a statistically significant relationship between the platelet count and
the results of tests of clot retraction, bleeding time, and capillary fragility, but
there was no significant relationship between the platelet count and the coagulation time. Factors other than platelet count or platelet function which may influence the results of these tests are discussed.
The critical level of the platelet count, below which abnormal bleeding is likely
to occur, was found to be approximately 190,000 per cu. mm. in primary thrombocytopenic purpura and 230,000 per cu. mm. in secondary thrombocytopenic
purpura. However, platelet counts as low as 100,000 per cu. mm. were found in one
patient without abnormal bleeding, and counts as high as 280,000 per cu. mm. were
found in another patient with classical primary thrombocytopenic purpura.
In all patients in the active phase of bleeding in primary thrombocytopenic
purpura and in most with secondary thrombocytopenic purpura, the bleeding time
was markedly prolonged and clot retraction was definitely diminished. In approximately one half of the patients suffering from thrombocytopenia without
bleeding or from thrombocytopenia complicating other hemorrhagic states, the
results of these tests were abnormal. Capillary fragility was increased in approximately three fourths of the patients with primary thrombocytopenic purpura,
one half with secondary thrombocytopenic purpura, and less than one half with
thrombocytopenia without bleeding or with thrombocytopenia complicating other
hemorrhagic states.
In the stage of recovery from thrombocytopenic purpura, dissociation of the
results of the various tests was sometimes found. In some patients the platelet
counts returned to normal hut abnormalities persisted in the tests of the bleeding
time, clot retraction, or capillary fragility. In other patients the results of one or
all of these tests returned to normal before the platelet count had reached the
normal range. These results have been interpreted as evidence of variability in the
functional capacity of the platelets.
