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. Author manuscript; available in PMC: 2010 Mar 1.
Published in final edited form as: Ann Intern Med. 2009 Sep 1;151(5):297–305. doi: 10.7326/0003-4819-151-5-200909010-00003

Table 2.

Adjusted rates* and rate differences for thromboembolism (TE) and intracranial hemorrhage (ICH) by warfarin status

Risk
Factor		 Risk Factor
Level		 TE ICH
Off Warfarin On Warfarin Difference
in Rate of
TE† 		Off Warfarin On Warfarin Difference
in Rate of
ICH†
PY Annual
Rate/100		 PY Annual
Rate/100		 PY Annual
Rate/100		 PY Annual
Rate/100
All Patients All Patients 32611 2.29 32130 1.25 1.04 32994 0.33 33415 0.57 0.24
Age Group <65 7752 0.64 5006 0.59 0.05 7762 0.10 5122 0.30 0.20
65-74 8421 1.57 10131 0.98 0.59 8482 0.12 10379 0.44 0.32
75-84 11116 2.80 13651 1.54 1.26 11317 0.43 14327 0.60 0.17
≥ 85 5322 4.70 3342 1.84 2.86 5433 0.79 3587 1.14 0.35
Sex Male 18649 1.70 18809 1.13 0.57 18781 0.32 19408 0.61 0.29
Female 13962 3.09 13320 1.39 1.70 14214 0.34 14007 0.51 0.17
Prior
Stroke		 N 31133 1.98 29232 1.09 0.89 30923 0.29 29286 0.51 0.22
Y 1478 6.57 2897 3.46 3.11 2072 0.75 4128 1.16 0.42
Hyper-
tension		 N 14307 1.73 12583 0.78 0.95 14406 0.30 12896 0.44 0.14
Y 18304 2.68 19547 1.57 1.11 18589 0.35 20519 0.66 0.31
CHF N 24090 1.84 20088 1.10 0.74 24320 0.29 20872 0.51 0.22
Y 8521 3.28 12041 1.58 1.70 8674 0.42 12543 0.70 0.28
Diabetes N 27395 2.06 25500 1.08 0.98 27625 0.32 26453 0.58 0.26
Y 5216 3.29 6629 1.98 1.31 5369 0.38 6962 0.53 0.16
CHADS2
Score* 		0 6143 0.37 3414 0.38 (0.01) 6133 0.05 3413 0.12 0.07
1 10262 1.19 9083 0.59 0.59 10191 0.22 9082 0.48 0.27
2 9741 2.54 10810 1.26 1.28 9677 0.40 10897 0.61 0.20
3 4761 3.89 5965 1.86 2.03 4835 0.64 6236 0.61 (0.03)
4-6 1704 6.34 2857 3.25 3.08 2158 0.51 3787 1.08 0.57
*

All rates and rate differences, except those for CHADS2, strata are adjusted to account for the effects of the remaining risk factors listed in this table plus coronary artery disease (see METHODS). The rates presented for CHADS2 are stratum-specific crude rates, i.e., not adjusted further since these strata themselves are based on multivariable models.

†

Difference in Rate of TE = (TE rate off warfarin−TE rate on warfarin);

Difference in Rate of ICH= (ICH rate on warfarin −ICH rate off warfarin)

TE=thromboembolic event; ICH=intracranial hemorrhage; PY=person-years; CHF=congestive heart failure; CHADS2 is the acronym for the stroke risk scoring system for patients with atrial fibrillation where C=congestive heart failure, H=hypertension, A=age ≥75 years, D=diabetes, and S=prior stroke (risk factors C, H, A and D are given 1 point each, S is doubly weighted, hence S2).