The role of platelet function analyzer-200 in predicting perioperative bleeding risk

BACKGROUND/AIMS

Various preoperative screening tests, such as platelet count, prothrombin time, activated partial thromboplastin time, and bleeding time, have been widely used to evaluate the risk of bleeding during surgery. Use of platelet function analyzer (PFA)-100/200 for assessing platelet function instead of bleeding time is increasing. However, its role in predicting the perioperative risk of bleeding remains controversial.

METHODS

Data of 703 patients who underwent surgery under general anesthesia were retrospectively analyzed. Preoperative platelet function was measured using PFA-200 system and the association with intraoperative bleeding was assessed. Additionally, other variables that could affect PFA-200 results were assessed by logistic regression analysis.

RESULTS

Collagen/epinephrine (COL/EPI) test was prolonged in 199/703 (28.3%) patients (EPI group), while 99/212 (46.7%) patients showed COL/adenosine diphosphate test abnormalities. Bleeding over 300 mL during surgery occurred in 14.3% and 20.1% of patients in the normal and EPI groups, respectively (p = 0.058). In addition, red blood cell transfusion within 72 hours after surgery rate was significantly higher in the EPI group than in the normal group (31.7% vs. 23.4%, p = 0.024). In multivariate logistic analysis, prolongation closure time with COL/EPI (p = 0.068) was marginally associated with risk of bleeding during surgery. Furthermore, PFA-200 results were influenced by various factors, such as nonsteroidal anti-inflammatory drug use, blood group, hematocrit, and time of blood collection.

CONCLUSION

Preoperative PFA-200 test may be helpful in predicting the risk of perioperative bleeding. However, its results should be carefully interpreted because they are affected by several factors.

Effectiveness of Platelet Function Analyzer-100 for Laboratory Detection of Anti-Platelet Drug-Induced Platelet Dysfunction

BACKGROUND

High on-treatment platelet reactivity (HTPR) is the phenomenon wherein patients exhibit normal platelet activity in laboratory testing despite adequate adherence to anti-platelet treatment. We investigated the detection rates of Platelet Function Analyzer (PFA)-100 (Dade Behring AG, Düdingen, Switzerland) for drug-induced platelet dysfunction and analyzed potential contributors to HTPR with practical PFA-100 data over six years.

METHODS

We used data from 6,957 patients who underwent PFA-100 testing after receiving aspirin, clopidogrel, or non-steroidal anti-inflammatory drugs (NSAIDs). Of these, 6,163 patients were tested with only the collagen/epinephrine cartridge (Col/EPI) of PFA-100; 794 were tested with both Col/EPI and the collagen/ADP cartridge (Col/ADP). We calculated PFA-100 closure time (CT) for each drug and compared the clinical and laboratory characteristics of the patients with prolonged CTs and normal CTs (i.e., HTPR).

RESULTS

In Col/EPI, 73.2% (365/499), 72.6% (390/537), and 55.3% (3,442/6,228) patients showed prolonged CTs for aspirin, clopidogrel, and NSAIDs, respectively. In Col/ADP, prolonged CTs were observed in 37.4% (34/91), 43.2% (35/81), and 29.6% (200/676) of patients receiving aspirin, clopidogrel, and NSAIDs, respectively. Of the patients tested with both cartridges, 88.9% (48/54), 95.3% (41/43), and 89.0% (577/648) of the patients receiving aspirin, clopidogrel, and NSAIDs had prolonged CTs, and 10.0% (79/794) showed normal CTs regardless of drugs. For clopidogrel users (both cartridges), there were more patients with malignancies in the normal CT than prolonged CT group.

CONCLUSIONS

PFA-100 is not sufficiently effective for laboratory screening of drug-induced platelet dysfunction. Malignancy may contribute to clopidogrel-related HTPR in PFA-100.

Population pharmacodynamics of cilostazol in healthy Korean subjects

Cilostazol is used for the treatment of intermittent claudication, ulceration and pain. This study was conducted to develop a population pharmacodynamic (PD) model for cilostazol's closure time (CT) prolongation effect in healthy Korean subjects based on a pharmacokinetic (PK) model previously developed. PD data were obtained from 29 healthy subjects who participated in a study conducted in 2009 at Severance Hospital. The PK model used was a two-compartment model with first order absorption. CT data were best described by a turnover model with a fractional turnover rate constant (K_out) inhibited by drug effects (Eff), which were represented by a sigmoid E_max model [Eff = E_max · C^γ / (EC₅₀^γ+Cγ)] with E_max being maximum drug effect, EC₅₀ drug plasma concentration at 50% of E_max, C drug plasma concentrations, and γ the Hill coefficient. For the selected PD model, parameter estimates were 0.613 hr⁻¹ for K_out, 0.192 for E_max, 730 ng/ml for EC₅₀ and 5.137 for γ. Sex and caffeine drinking status significantly influenced the baseline CT, which was 85.36 seconds in male non-caffeine drinkers and increased by 15.5% and 16.4% in females and caffeine drinkers, respectively. The model adequately described the time course of CT. This was the first population PD study for cilostazol's CT prolongation effect in a Korean population.

Human cells involved in atherosclerosis have a sex

The influence of sex has been largely described in cardiovascular diseases. Atherosclerosis is a complex process that involves many cell types such as vessel cells, immune cells and endothelial progenitor cells; however, many, if not all, studies do not report the sex of the cells. This review focuses on sex differences in human cells involved in the atherosclerotic process, emphasizing the role of sex hormones. Furthermore, we report sex differences and issues related to the processes that determine the fate of the cells such as apoptotic and autophagic mechanisms. The analysis of the data reveals that there are still many gaps in our knowledge regarding sex influences in atherosclerosis, largely for the cell types that have not been well studied, stressing the urgent need for a clear definition of experimental conditions and the inclusion of both sexes in preclinical studies.

Association Between Platelet Function and Disc Hemorrhage in Patients With Normal-Tension Glaucoma: A Prospective Cross-Sectional Study

PURPOSE

To evaluate the association between platelet function and disc hemorrhage in patients with normal-tension glaucoma.

DESIGN

Prospective, cross-sectional study.

METHODS

Study involved a total of 315 subjects, including patients with normal-tension glaucoma and disc hemorrhage (n = 120), patients with normal-tension glaucoma without disc hemorrhage (n = 75), and healthy individuals (control group, n = 120). A detailed eye examination including visual field testing, color disc photography, optical coherence tomography scanning, and measurement of collagen/epinephrine closure time using a platelet function analyzer were performed for all subjects.

RESULTS

The collagen/epinephrine closure time (s) as measured by the platelet function analyzer was approximately 14%-24% longer in the normal-tension glaucoma and disc hemorrhage group compared with the other groups (141.92 ± 53.44 [with normal-tension glaucoma and disc hemorrhage] vs 124.60 ± 46.72 [with normal-tension glaucoma without disc hemorrhage] vs 114.84 ± 34.84 [healthy individuals], 1-way analysis of variance test, P < .001). The activated partial thromboplastin time (s) value of the normal-tension glaucoma with disc hemorrhage group was also higher than the control group. Stepwise multiple logistic regression analysis revealed that only a longer collagen/epinephrine closure time (OR adjusted for age, sex, prothrombin time, activated partial thromboplastin time, diabetes mellitus, hypertension, hypotension, heart disease, hypothyroidism, migraine, stroke, hypercholesterolemia: 2.94; 95% CI: 1.40-6.17) was independently associated with disc hemorrhage. A similar trend was observed when platelet function was compared among the 3 groups with respect to age.

CONCLUSIONS

Our results suggest that platelet function is significantly associated with disc hemorrhage in patients with normal-tension glaucoma. Delayed absorption resulted from prolonged bleeding due to delayed platelet aggregation may have an effect on the detectability of disc hemorrhage in patients with normal-tension glaucoma.

Age-related changes in platelet function are more profound in women than in men

Age is a risk factor for cardiovascular disease (CVD), however the effect of age on platelet function remains unclear. Ideally, platelet function should be assayed under flow and shear conditions that occur in vivo. Our study aimed to characterise the effect of age on platelet translocation behaviour using a novel flow-based assay that measures platelet function in less than 200 μl of blood under conditions of arterial shear. Blood from males (n = 53) and females (n = 56), ranging in age from 19–82 and 21–70 respectively were perfused through custom-made parallel plate flow chambers coated with immobilised human von Willebrand Factor (VWF) under arterial shear (1,500s⁻¹). Platelet translocation behaviour on VWF was recorded by digital-image microscopy and analysed. The study showed that aging resulted in a significant decrease in the number of platelet tracks, translocating platelets and unstable platelet interactions with VWF. These age related changes in platelet function were more profound in women than in men indicating that age and gender significantly impacts on platelet interactions with VWF.