In vitro platelet function in controlled ovarian hyperstimulation cycles.

OBJECTIVE: To determine the effects of elevated endogenous E2 levels on in vitro platelet function in patients undergoing controlled ovarian hyperstimulation (COH). DESIGN: Women with normal ovulatory cycles and patients undergoing COH on cycle day 3 and near ovulation (preovulatory follicles were at least 16 mm in diameter) were studied. Serum E2, Thrombostat 4000, (V. d. Goltz, Seeon, Germany), von Willebrand factor antigen (vWF-Ag), and platelet aggregation and adenosine triphosphate (ATP) release to adenosine diphosphate (ADP), collagen (COL), and arachidonic acid (AA) were measured. SETTING: University-based outpatient infertility clinic. PATIENT(S): Twenty-two consenting infertile women undergoing COH cycles and 14 women with documented ovulatory cycles. MAIN OUTCOME MEASURE(S): Whole blood platelet aggregation with ADP, COL, AA, and Thrombostat 4000. RESULTS(S): Estradiol levels rose significantly at peak times (P = 0.011). No changes were noted in in vitro platelet function measured by the Thrombostat 4000 and by whole blood platelet aggregation with ADP and AA and in ATP release with ADP, COL, or AA. Aggregation with collagen was increased because of likely elevations in vWF-Ag levels. CONCLUSION(S): No significant changes in in vitro platelet function were noted in 19 women undergoing COH with E2 levels two to three times that observed in oral contraceptive or hormone replacement therapy users, suggesting no increased risk for arterial thromboembolism.

Performance characteristics and clinical evaluation of an in vitro bleeding time device--Thrombostat 4000.

The performance characteristics of an in vitro bleeding time device--Thrombostat 4000 were evaluated and compared with the Simplate bleeding time in healthy individuals and patients with disorders of primary hemostasis. Reference ranges were established using 30 normal volunteers. Although there were variations between different filter batches, reproducibility was good within a single batch. There were no differences between the two channels of the instrument and between male and female subjects. Hematocrit correlated negatively with the initial flow (IF) and IF correlated positively with closure time (T) and bleeding volume (V). Aspirin could be detected only when the traditional addition of ADP was replaced with CaCl2. Both, closure time (T) or bleeding volume (V) were more sensitive than Simplate bleeding time and T was more sensitive than V in detecting patients with disorders of primary hemostasis. We conclude that the Thrombostat 4000 is a reproducible, reliable, sensitive and easy to use instrument. It is superior to the traditional in vivo bleeding times for investigations of disorders of primary hemostasis (screening, diagnosis, monitoring, etc.).

Hormonal contraception and platelet function.

PIP: 73 healthy women (29 controls, 25 using OCs, and 19 using Norplant) were selected from the clinic population at North Oakland Medical Center for inclusion in this study after obtaining informed consent. Age, race, height, weight, blood pressure, and cigarette smoking were recorded for each subject. 12 patients were on monophasic OCs while 13 were on triphasic preparations. Both hormonal contraceptive groups had used their particular contraceptive for at least 3 months prior to blood drawing. Platelet tests were performed within 2 hours of sample collection: platelet counts (PLC) and mean platelet volume (MPV) were determined on an Automated Platelet Counter (Baker 810 Platelet Analyzer). Whole blood aggregation was performed on a platelet aggregometer (Chrono-Log, Model 550) using both ADP (ADP, 5 mM) and collagen (COLL, 2 mcg/ml) as inducing agents. Demographic differences were not significant (p 0.05) among the 3 treatment groups, whose average age was 25.3-25.8 years old. Furthermore, no significant differences (p 0.05) in platelet function were detected among controls or subjects receiving either oral contraceptives or Norplant, compared to control patients. The mean platelet counts (X 10/9/L) were 223 for OC users, 231 for Norplant users, and 232 for controls. The respective platelet aggregation (ADP, ohms) values were 12.5, 18.0, and 19.2 as well as (COLL, ohms) 35.6, 40.7, and 39.0. These results demonstrated that there is no evidence for altered platelet function, with the testing methods employed, in women using either Norplant or combination low dose oral contraceptives. To date, several studies have examined this issue, with contradictory reports about the effects of hormonal contraceptives in platelet function. After controlling for differences between various steroid preparations and other such confounding variables, some of these conflicting conclusions could be the result of a lack of uniformity among the methods used to evaluate platelet aggregation. The ability to draw conclusions regarding altered in vivo thrombotic potential from these studies is thus questionable.^ieng

Clinical experience with the Thrombostat 4000.

Bleeding times are presently widely used to screen patients with primary hemostasis defects although their accuracy and reliability has been questioned by many investigators. Platelet aggregation studies are not suited for routine use. We investigated the performance characteristics of the Thrombostat 4000, a device that assesses primary hemostasis. Tests can be performed by adding ADP, epinephrine, CaCl2 or NaCl to the collagen onto which platelets adhere. It was found, using normal volunteers and patients, that ADP and epinephrine had acceptable reference ranges with coefficients of variance between 9-12% for within run and between runs. However, major differences were seen when different filter badges were used--a reflection of differences in collagen. Regular citrated blood, routinely drawn for coagulation studies, can be used; test performance can be delayed for up to five hours when the blood is kept at room temperature. The effects of aspirin on volunteers could be detected when epinephrine was used, but not with ADP. ADP addition allowed the detection of more patients with primary hemostasis defects than bleeding times, and epinephrine was as useful as ADP in detecting these abnormalities. The data suggest that the broadest spectrum of platelet defects (ASA use and platelet dysfunction) can be detected with epinephrine. Inconsistencies in collagen used for coating of the filters is a major drawback for the routine use of this device in screening primary hemostasis defects.

Preliminary data from a field trial of the PFA-100 system.

The PFA-100 system (Dade International Inc., Miami, FL) is a platelet function analyzer, the design of which is based on the technology of the Thrombostat 4000 VDG, Seeon, Germany. It was developed to measure primary, platelet dependent hemostasis in citrated whole blood in vitro. A first pilot study was conducted with the instrument to assess performance characteristics. Healthy subjects (normals) who had not ingested any medications, and patients (abnormals) with primary, platelet-related hemostasis defects, which included users of aspirin, were studied with two test cartridges; collagen/ADP and collagen/epinephrine. Before the study certain variables were tested that ascertained that blood drawn into either 3.8% or 3.2% sodium citrate containing vacutainers (rather than syringes) could be used for testing. Tests must be performed within a five-hour time span from drawing to testing, and blood must be kept at room temperature. Normal reference values were 77-133 seconds closure times for collagen/ADP and 98-185 seconds for collagen/epinephrine. Precision testing revealed a CV of < 10% for within-day and between-day (five days) analyses on collagen/ADP cartridges and a CV of 5-14% for both runs on the collagen/epinephrine cartridges. No clinically important differences were found between measurements in the two positions of the instrument, although one follows the other.(ABSTRACT TRUNCATED AT 250 WORDS)