Centrifugation speed affects light transmission aggregometry

Background: Light transmission aggregometry (LTA) is considered the gold standard for investigating platelet activity ex vivo. However, LTA protocols are not standardized, and differences in LTA procedure are a potential source of variance in results. Centrifugation speed is an essential component of platelet preparation in LTA, has yet to be standardized, and may affect platelet aggregation results. We sought to investigate the effect of relative centrifugal force (RCF) intensity on LTA results. Methods: Ten healthy controls had venous blood drawn and centrifuged at 150, 200, 300, and 500 g for 10 min. Cell counts in whole blood and platelet‐rich plasma (PRP) were measured using a hematology analyzer. LTA was performed using 1.0 μm adenosine diphosphate (ADP) and 0.4 μm epinephrine as an agonist. Aggregation (%) was compared at 60, 120, 180, and 300 s and at maximum aggregation. Results: Centrifugation speed was associated with decreasing platelet count (P < 0.001) and decreasing mean platelet volume (P < 0.001) in PRP. Maximum aggregation decreased with increasing speeds for ADP 1.0 μm (150 g – 89%, 200 g – 93%, 300 g – 71%, 500 g – 17%; P < 0.001). Similar findings were noted at 120 s (150 g – 69%, 200 g – 50%, 300 g – 35%, 500 g – 12%; P < 0.001), 180 s (150 g – 82%, 200 g – 74%, 300 g – 44%, 500 g – 13%; P < 0.001), and 300 s (150 g – 85%, 200 g – 88%, 300 g – 55%, 500 g – 14%; P < 0.001). Consistently, platelet aggregation in response to epinephrine 0.4 μm decreased significantly with increasing centrifuge RCF at 60, 120, 180, 300 s and at maximum aggregation (P < 0.05 for each comparison). Conclusion: Our data demonstrate the importance of centrifugation speed in the interpretation of LTA results, supporting the need for standardization of centrifugation RCF in LTA protocols.     

Assessment of platelet function on the routine coagulation analyzer Sysmex CS-2000i

Background: Light transmission aggregometry (LTA) is considered as the gold standard for testing platelet function in the setting of both platelet disorders suspicion and response to antiplatelet therapy evaluation. LTA requires however specialized equipment, substantial blood sample volumes, is technically challenging and time-consuming. Aim: To evaluate an automated platelet aggregation method performed on a routine coagulation analyzer Sysmex CS-2000i. Methods: 46 patients presenting a bleeding syndrome and 62 patients with acute coronary syndrome receiving dual antiplatelet therapy were studied in total. Platelet aggregations were performed on CS-2000i equipped with a dedicated software and on APACT-4004 (Elitech, France) as the reference instrument. Aggregation was measured by monitoring the changes in light absorbance occurring in response to ADP 2.5, 5 and 10µM, collagen 3.3 µg/mL, epinephrin 10µM, ristocetin 1.25 mg/mL and arachidonic acid 0.5 mg/mL in platelet rich plasma (PRP). PRP were tested simultaneously on both CS-2000i and APACT-4004 devices. Platelet stirred speed were 800 rpm for both instruments. Results: Significant correlations were observed between CS-2000i and LTA after all stimulations (p< 0.001). Patients presenting a bleeding syndrome had similar aggregation profiles with both methods. A single patient presented a severe platelet disorder (Glanzmann Thrombasthenia) and its PRP showed defective aggregation in response to all agonists except ristocetin with both instruments. Finally, the inter-agreement rates for CS-2000i and APACT-4004 to detect low responders to thienopyridines or aspirine were strong (weighted kappa> 0.70). Conclusion: Platelet aggregation on the routine coagulation analyzer CS-2000i is an easily accessible, handy, reliable, standardized, and rapid tool to assess platelet function which allows to skirt most of the LTA limitations.     

The assessment of aspirin resistance by using light transmission and multiple electrode aggregometry

Introduction: The issues related to aspirin [acetylsalicylic acid (ASA)] resistance are still under debate. Depending on the method of assessment and studied patients, the prevalence of ASA resistance is rather heterogeneous, ranging from 5% to 45%. The method most commonly used for assessing platelet function is their aggregation. ASA irreversibly inhibits cyclooxygenase‐1 (COX‐1) by acetylation. Methods: This study aimed to compare light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) for the measurement of ASA resistance, using arachidonic acid as an inducer of the reaction. Results: The study comprised 101 patients with stable ischemic heart disease taking a daily dose of 100 mg of ASA. The rates of ASA resistance were 22.22% and 21.21% as detected by LTA and MEA, respectively. The two methods were statistically compared using Spearman’s nonparametric correlation analysis, with a positive significant correlation (P = 0.01) and medium positive dependence between the methods (r = 0.0539). Conclusion: If ASA resistance is detected by laboratory tests, replacement of ASA or its combination with other antiplatelet drugs as well as increased dosage may be considered.     

艾滋病高发地区预防HIV母婴传播项目实施效果分析

目的了解艾滋病高流行的4省（自治区）的6个县（市、区）,预防艾滋病病毒（HIV）母婴传播项目的实施效果。方法通过全国预防艾滋病母婴传播信息管理系统,收集2007年1月至2010年9月研究地区艾滋病病毒（HIV）感染孕产妇个案卡及其所生儿童的随访登记卡,分析预防HIV母婴传播干预措施落实情况及效果。结果2007-2010年,研究地区HIV感染孕产妇抗病毒药物应用比例和孕期抗病毒药物应用比例,分别从78.4%和27.8%增加至93.7%和78.8%（趋势χ2=17.636,P〈0.01;趋势χ2=76.835,P〈0.01）;HIV感染孕产妇应用三联抗病毒药物方案的比例自19.8%增加至89.9%（趋势χ2=161.757,P〈0.01）。满18月龄艾滋病感染孕产妇所生儿童接受HIV抗体检测比例为84.8%（318/375）,13例儿童抗体检测阳性,艾滋病母婴传播水平为4.1%（95%可信区间：2.98%-5.20%）。结论研究地区预防HIV母婴传播干预措施落实指标逐年提高,HIV母婴传播水平显著下降,孕产妇及早抗病毒用药以及儿童随访检测仍为工作中的薄弱环节。