No case of COX-1-related aspirin resistance found in 289 patients with symptoms of stable CHD remitted for coronary angiography.
OBJECTIVE
To assess the prevalence of a lacking aspirin effect on cyclooxygenase-1 (COX-1) ("aspirin resistance") in patients with symptomatic, stable coronary heart disease (CHD) using test methods directly reflecting inhibition of COX-1.


METHODS
Arachidonic acid (AA)-induced platelet aggregation and plasma thromboxane B2 (TXB2) were determined twice 3 weeks apart - prior to elective coronary angiography - in 289 patients on 75 or 160 mg aspirin daily, all prompted to take aspirin before testing. Subjects who demonstrated lacking any effect of aspirin (>/=20 % AA-induced aggregation) on one or both occasions were later given a third test. Forty-two patients not taking aspirin were used as TXB2 controls.


RESULTS
Eleven (3.8 %) had aggregation > or = 20 % in at least one of the two initial tests, but only two on both occasions. During the third test, all 11 patients had aggregation <20 %. The TXB2 distributions in controls and study patients differed markedly (mean 173 versus 19 pg/mL). Taking 45 pg/mL as the TXB2 cut-off level, sensitivity and specificity for detecting subjects taking aspirin were 90 % and 89 %, respectively. The area under the ROC curve was 0.96.


CONCLUSIONS
Repeated AA-induced platelet aggregometry showed that COX-1 could be blocked by low-dose aspirin in all 289 tested patients, suggesting that aspirin resistance is rare in patients with stable CHD.
Meen
O
O
Department of Medicine, Blefjell Hospital HF, Oslo, Norway.
Brosstad
F
F
Khiabani
H
H
Gjertsen
E
E
Lauritsen
M E
ME
Pedersen
T M
TM
Bjørnsen
S
S
Schjelderup
N M
NM
Ameln
W
W
Ng
E C
EC
Wettergreen
M
M
Siddique
S P
SP
Erikssen
G
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001241:Aspirin / Q000494:pharmacology*; D017023:Coronary Angiography; D003327:Coronary Disease / Q000097:blood / Q000175:diagnosis*; D051545:Cyclooxygenase 1 / Q000187:drug effects*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004351:Drug Resistance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D012016:Reference Values; D013929:Thromboxane B2 / Q000097:blood*
D016861:Cyclooxygenase Inhibitors; D013929:Thromboxane B2; D051545:Cyclooxygenase 1; D001241:Aspirin