OBJECTIVE: To visually count platelets in a peripheral blood smear and compare with an automated machine platelet count. METHODS: Thirty-five peripheral blood smears were made from blood specimens counted on an automated blood cell machine: twenty-three thrombocytopenic specimens, 1 with high platelet count and 11 with normal counts. Ten and 25 high-power fields were microscopically averaged and then multiplied by 15,000 and 20,000 to arrive at a platelet count in 1,000 per microliter. Comparisons between visual and machine counts were drawn. RESULTS: There was fair concordance in 27 specimens. In three specimens underestimation was found, overestimation in five. A 15,000 multiplier gave slightly better results than 20,000. Average in 10 high-power fields was as good as 25. Abnormal counts could be assessed as well as normal. CONCLUSION: Average in 10 high-power field on a blood film microscopically and multiplying by 15,000 gives a platelet count reasonably close to automated machine counts in thousands per microliter.
OBJECTIVE: To visually count platelets in a peripheral blood smear and compare with an automated machine platelet count. METHODS: Thirty-five peripheral blood smears were made from blood specimens counted on an automated blood cell machine: twenty-three thrombocytopenic specimens, 1 with high platelet count and 11 with normal counts. Ten and 25 high-power fields were microscopically averaged and then multiplied by 15,000 and 20,000 to arrive at a platelet count in 1,000 per microliter. Comparisons between visual and machine counts were drawn. RESULTS: There was fair concordance in 27 specimens. In three specimens underestimation was found, overestimation in five. A 15,000 multiplier gave slightly better results than 20,000. Average in 10 high-power fields was as good as 25. Abnormal counts could be assessed as well as normal. CONCLUSION: Average in 10 high-power field on a blood film microscopically and multiplying by 15,000 gives a platelet count reasonably close to automated machine counts in thousands per microliter.