A Method For The Determination Of Circulating Aggregated Platelets And Its Application To Patients In The Course Of Unstable Angina

A method for the quantitative and qualitative determination of the number of aggregated platelets is described. One milliliter of venous blood was separated equally into two solutions. One solution composed of EDTA (ethylenediaminetetraacetic acid) and formaldehyde (solution F) contained reversibly and irreversibly aggregated platelets, and the second solution, composed of EDTA alone (solution E), contained irreversibly aggregated platelets. By microscopic readings, the percentage of platelets forming aggregates was determined. Reversibly aggregated platelets were estimated by subtracting the percentage of aggregated platelets in solution E from that in solution F. The average amount of platelets per aggregate was calculated by dividing the number of aggregated platelets in solution F by the number of aggregates per 1000 platelets counted. The reference ranges (means +/- SDs) established in 100 healthy persons were 5.8% +/- 2.4% (1% to 9%) for solution F, 3.9% +/- 1.8% (0% to 7%) for solution E, and 2.2 +/- 0.18 (2.0 to 2.5) for the average number of platelets per aggregate. Twenty hospitalized patients without heart disease had values similar to those of 100 normal subjects. In 50 patients with acute myocardial infarction, the percentage of aggregated platelets in solution F was 23.8% +/- 10.3%; in solution E, 4.0% +/- 3.0%; and the average number of platelets per aggregate, 2.9 +/- 0.7. The mean variance for five daily consecutive measurements was 0.52% for solution F, 0.63% for solution E, and 0.002 for the average number of platelets per aggregate. An even lesser mean variance was observed when the interobserver-vs-intraobserver and the intersmear-vs-intrasmear variations were tested. In patients with acute myocardial infarction, the interobserver-vs-intraobserver variance was 5.6% for solution F, 2.2% for solution E, and 0.005 for the average number of platelets per aggregate. The parameters studied were unaffected by different blood drawings, assay tubes, or venous stasis. In 80 patients with unstable angina, the studied parameters as well as the percentage of "big" platelets were measured on hospital days 1, 2, and 5. In 25 patients in whom acute myocardial infarction developed during hospitalization, the percentage of aggregated platelets was 28.1% +/- 8.3%. Most of them (71%) were reversibly aggregated and did not change during hospitalization. The average number of platelets per aggregate was 3.9 +/- 1.6, and the percentage of big platelets was 12.5% +/- 7.2%, both values not undergoing subsequent changes. In patients in whom acute myocardial infarction did not develop, the percentage of aggregated platelets decreased to 14.2% +/- 6.1% on day 5. Most aggregated platelets (58.8% to 90%) were irreversibly aggregated.(ABSTRACT TRUNCATED AT 400 WORDS)