Enumeration of Platelets AARON P. ABBEY AND ROBERT R. BELLIVEAU, M.D.
Abbey, Aaron P., and Belliveau, Robert R.: Enumeration of platelets. Am J Clin Pathol 69: 55-56, 1978. A correlation of the enumeration of platelets in peripheral smears with platelet counts performed by a direct method is presented. A ratio of 1 platelet per oil-immersion held for every 21,000 platelets of the chamber count indicates the normal average range of platelets to be approximately 7-21 per oil-immersion field. (Key words: Platelet enumeration; Peripheral smears; Direct counting.)
Department of Pathology, Southern Nevada Memorial Hospital, Las Vegas, Nevada
Method
Results The numbers of platelets in the first and second groups of 25 fields on each slide were compared to give an indication of how evenly the platelets were distributed on the slides. The mean number of platelets in the first group of 25 fields was 311.39, compared with 319.52 in the second group of 25 fields. The standard deviation of the difference of the means was 51.53. Employing the null hypothesis, t = 1.25 indicating that the two groups of squares did not contain significantly different numbers of platelets, and that the platelets were evenly distributed over the feathered edge of the slides. The range of the platelet counts by microscopy was 19,000 to 1,172,000/mm3, with a mean of 266,000. The coefficient of correlation between the chamber count and the peripheral smear count was .78. The average platelet count of 266,000 gives a ratio of 1 platelet per oil-immersion field for every 21,000 platelets of the chamber count. If the accepted normal
Received November 15, 1976; accepted for publication December 10, 1976. Address reprint requests to Dr. Belliveau: Department of Pathology, Southern Nevada Memorial Hospital, 1800 W. Charleston Blvd., Las Vegas, Nevada 89102. 0002-!
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3-78-0100—0055S00.50 © American Society of Clinical Pathologists
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 6, 2016
One hundred patients for whom platelet counts were requested by clinicians had platelet counts performed by phase contrast according to the method described by Davidsohn and Henry. 1 Simultaneously, these patients also had peripheral blood smear slides made and stained with Wright's stain as for a routine differential count. Without knowledge of the phase contrast platelet count, the peripheral blood smears were examined using an oil immersion lens (lOOx) in conjunction with a lOx ocular. The slides were counted in the feathered edge of the blood smear where the erythrocytes abutted each other without overlapping. The number of platelets in 50 oil-immersion fields was counted in two groups of 25 fields on each of the 100 slides.
AS A STANDARD PART of training in hematology, most medical technologists are taught to estimate the adequacy of platelets from the peripheral smear. In a recent survey of technologists in five local hospitals, a remarkable variation in the range of the numbers of platelets per oil-immersion field that were considered adequate was found. A review of standard laboratory textbooks likewise does not reveal accepted uniform criteria for determining platelet adequacy. The recent edition of the textbook by Davidsohn and Henry 2 states ' 'a remark regarding platelets should be a part of the report on the differential count in the form of a reference to their . . . inadequacy of number, if noted." However, no guidelines for how to determine inadequacy are presented. The recent edition of Hematology, by Williams and associates, 4 states, "There should be one platelet for every 10 to 20 erythrocytes." Miale3 says, "When the platelet count is normal an average of 3 - 5 platelets is seen per oil immersion field." Wintrobe, 5 referring to enumeration of platelets, states, "In all cases, it is wise to check the platelet count as obtained, by making a rough survey of the platelets as seen in a blood smear . . . " However, no guidelines for comparison of peripheral smears with chamber counts are presented. In addition, review of the English-language literature fails to reveal a single article in which the number of platelets seen in peripheral smears was actually correlated with platelet counts performed by any direct or indirect method. The results of such a study are presented herein.
56
A.J.C.P. • January 1978
ABBEY AND BELLIVEAU
range of platelets is 140-440,000/ then the normal range of platelets per oil-immersion field is approximately 7-21.
range of 3-5 platelets per oil-immersion field suggested by Miale.2
Discussion
1. Belliveau RR: Unpublished data 2. Davidsohn I, Henry JB: Clinical Diagnosis by Laboratory Method. 15th edition. W. B. Saunders, Philadelphia, 1976, p 126 3. Miale JB: Differential leukocyte count. Laboratory Medicine Hematology. Fourth edition. St. Louis, C. V. Mosby, 1972, p 1210 4. Williams WJ, Beutler E, Erslev AJ, et al: Examination of the peripheral blood. Hematology. New York, McGraw-Hill, 1972, p 18 5. Wintrobe MM: Blood platelets and coagulation, Clinical Hematology. Sixth edition. Lea and Febiger, Philadelphia, 1967, p 302
This paper presents the first correlation of enumeration of platelets on peripheral smears with platelet counts performed by any direct or indirect method. It is somewhat surprising that this correlation has not been previously documented. It would undoubtedly be of value if other laboratories would undertake similar studies. Certainly, our finding of 7-21 platelets per oil-immersion field differs significantly from the normal
References
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 6, 2016
Abbey, Aaron P., and Belliveau, Robert R.: Enumeration of platelets. Am J Clin Pathol 69: 55-56, 1978. A correlation of the enumeration of platelets in peripheral smears with platelet counts performed by a direct method is presented. A ratio of 1 platelet per oil-immersion held for every 21,000 platelets of the chamber count indicates the normal average range of platelets to be approximately 7-21 per oil-immersion field. (Key words: Platelet enumeration; Peripheral smears; Direct counting.)
Department of Pathology, Southern Nevada Memorial Hospital, Las Vegas, Nevada
Method
Results The numbers of platelets in the first and second groups of 25 fields on each slide were compared to give an indication of how evenly the platelets were distributed on the slides. The mean number of platelets in the first group of 25 fields was 311.39, compared with 319.52 in the second group of 25 fields. The standard deviation of the difference of the means was 51.53. Employing the null hypothesis, t = 1.25 indicating that the two groups of squares did not contain significantly different numbers of platelets, and that the platelets were evenly distributed over the feathered edge of the slides. The range of the platelet counts by microscopy was 19,000 to 1,172,000/mm3, with a mean of 266,000. The coefficient of correlation between the chamber count and the peripheral smear count was .78. The average platelet count of 266,000 gives a ratio of 1 platelet per oil-immersion field for every 21,000 platelets of the chamber count. If the accepted normal
Received November 15, 1976; accepted for publication December 10, 1976. Address reprint requests to Dr. Belliveau: Department of Pathology, Southern Nevada Memorial Hospital, 1800 W. Charleston Blvd., Las Vegas, Nevada 89102. 0002-!
55
3-78-0100—0055S00.50 © American Society of Clinical Pathologists
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 6, 2016
One hundred patients for whom platelet counts were requested by clinicians had platelet counts performed by phase contrast according to the method described by Davidsohn and Henry. 1 Simultaneously, these patients also had peripheral blood smear slides made and stained with Wright's stain as for a routine differential count. Without knowledge of the phase contrast platelet count, the peripheral blood smears were examined using an oil immersion lens (lOOx) in conjunction with a lOx ocular. The slides were counted in the feathered edge of the blood smear where the erythrocytes abutted each other without overlapping. The number of platelets in 50 oil-immersion fields was counted in two groups of 25 fields on each of the 100 slides.
AS A STANDARD PART of training in hematology, most medical technologists are taught to estimate the adequacy of platelets from the peripheral smear. In a recent survey of technologists in five local hospitals, a remarkable variation in the range of the numbers of platelets per oil-immersion field that were considered adequate was found. A review of standard laboratory textbooks likewise does not reveal accepted uniform criteria for determining platelet adequacy. The recent edition of the textbook by Davidsohn and Henry 2 states ' 'a remark regarding platelets should be a part of the report on the differential count in the form of a reference to their . . . inadequacy of number, if noted." However, no guidelines for how to determine inadequacy are presented. The recent edition of Hematology, by Williams and associates, 4 states, "There should be one platelet for every 10 to 20 erythrocytes." Miale3 says, "When the platelet count is normal an average of 3 - 5 platelets is seen per oil immersion field." Wintrobe, 5 referring to enumeration of platelets, states, "In all cases, it is wise to check the platelet count as obtained, by making a rough survey of the platelets as seen in a blood smear . . . " However, no guidelines for comparison of peripheral smears with chamber counts are presented. In addition, review of the English-language literature fails to reveal a single article in which the number of platelets seen in peripheral smears was actually correlated with platelet counts performed by any direct or indirect method. The results of such a study are presented herein.
56
A.J.C.P. • January 1978
ABBEY AND BELLIVEAU
range of platelets is 140-440,000/ then the normal range of platelets per oil-immersion field is approximately 7-21.
range of 3-5 platelets per oil-immersion field suggested by Miale.2
Discussion
1. Belliveau RR: Unpublished data 2. Davidsohn I, Henry JB: Clinical Diagnosis by Laboratory Method. 15th edition. W. B. Saunders, Philadelphia, 1976, p 126 3. Miale JB: Differential leukocyte count. Laboratory Medicine Hematology. Fourth edition. St. Louis, C. V. Mosby, 1972, p 1210 4. Williams WJ, Beutler E, Erslev AJ, et al: Examination of the peripheral blood. Hematology. New York, McGraw-Hill, 1972, p 18 5. Wintrobe MM: Blood platelets and coagulation, Clinical Hematology. Sixth edition. Lea and Febiger, Philadelphia, 1967, p 302
This paper presents the first correlation of enumeration of platelets on peripheral smears with platelet counts performed by any direct or indirect method. It is somewhat surprising that this correlation has not been previously documented. It would undoubtedly be of value if other laboratories would undertake similar studies. Certainly, our finding of 7-21 platelets per oil-immersion field differs significantly from the normal
References
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 6, 2016
