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BACKGROUND: We determined whether whole blood impedance aggregometry using the Multiplate® detects the effects of antiplatelet drugs as reliably as does classical light transmission aggregometry (LTA) or the platelet function analyzer PFA-100®.

METHODS: Multiplate (M) assays, measuring changes in electrical resistance as aggregation units over time (AU*min), and LTA assays induced by collagen (COL), adenosine diphosphate (ADP) or arachidonic acid (AA) and PFA-100 testing, using epinephrine (PFA100-EPI) or ADP (PFA100-ADP) cartridges, were performed simultaneously using arterial blood samples obtained before induction of anesthesia in 70 consecutive patients scheduled for elective coronary artery bypass grafting. Patients in group A (n = 48) served as controls, patients in group B (n = 11) received aspirin 100 mg/d and those in group C (n = 11) aspirin 100 mg/d and clopidogrel 75 mg/d until the day before surgery.

RESULTS: In controls the median (1st, 3rd quartiles) change in impedance AU*min for M-COL (374 [231–469]) was significantly greater than in patients receiving aspirin (164 [86–211], P = 0.0009) or receiving aspirin and clopidogrel (118 [101–244], P = 0.004). M-ADP values in controls were 258 (158–389), in patients receiving aspirin 261 (159–393), and in patients receiving aspirin and clopidogrel 88 (48–231, P = 0.054). M-AA values were significantly lower in patients receiving aspirin alone (45 [28–60], P = 0.0004) or aspirin and clopidogrel (44 [26–221], P = 0.008) than in controls (200 [86–345]).

The areas under the receiver operating characteristic curves indicating the ability to discriminate patients taking aspirin from those not taking aspirin were comparable for COL and AA assays using whole blood impedance aggregometry or classical LTA (M-COL 0.84 [P = 0.001], LTA-COL 0.85 [P = < .001], M-AA 0.84 [P = < .001] and LTA-AA 0.87 [P = < .001]), but only 0.74 for PFA-100-EPI (P = 0.03). Similarly, for discrimination of patients not taking antiplatelet drugs from patients taking clopidogrel and aspirin the areas under the receiver operating characteristic curve were also comparable for both aggregometry methods M-COL 0.77 (P = 0.006), LTA-COL 0.78 (P = 0.004), M-ADP 0.74 (P = 0.015), LTA-ADP 0.73 (P = 0.018).

CONCLUSION: Results achieved with the bedside Multiplate assays were not different than those obtained with classical aggregometry for detecting the effects of aspirin and clopidogrel in preoperative patients scheduled for elective cardiac surgery.

The Origin of Species
Written by Charles Darwin

Perhaps the most readable and accessible of the great works of scientific imagination, The Origin of Species sold out on the day it was published in 1859. Theologians quickly labeled Charles Darwin the most dangerous man in England, and, as the Saturday Review noted, the uproar over the book quickly "passed beyond the bounds of the study and lecture-room into the drawing-room and the public street." Yet, after reading it, Darwin's friend and colleague T. H. Huxley had a different reaction: "How extremely stupid not to have thought of that."
Based largely on Darwin's experience as a naturalist while on a five-year voyage aboard H.M.S. Beagle, The Origin of Species set forth a theory of evolution and natural selection that challenged contemporary beliefs about divine providence and the immutability of species. A landmark contribution to philosophical and scientific thought, this edition also includes an introductory historical sketch and a glossary Darwin later added to the original text.

Charles Darwin grew up considered, by his own account, "a very ordinary boy, rather below the common standard of intellect." A quirk of fate kept him from the career his father had deemed appropriate--that of a country parson--when a botanist recommended Darwin for an appointment as a naturalist aboard H.M.S. Beagle from 1831 to 1836. Darwin is also the author of the five-volume work Zoology of the Voyage of the Beagle (1839) and The Descent of Man (1871).


From the Trade Paperback edition.