Atrial fibrillation: a clinical prediction rule helped identify patients at increased risk for a stroke

Clinical bottom line (level 2a)

  1. One in eighteen patients with non-rheumatic atrial fibrillation had a first ischaemic stroke within 1.2 years.
  2. A clinical prediction rule based on 5 clinical factors helped identify patients at increased risk.
Gage et al: Journal of the American Medical Association 2001; 285 : 2564-2870
Expires November 2003

The study

Inception cohort study with objective outcomes, adjusted for confounding factors, validated in an independent set of patients.

Setting: 7 states, USA

1733 patients (aged 65 to 95, 58% female) discharged from hospital with a diagnosis of non-rheumatic atrial fibrillation

Excluded if
  • prescribed warfarin therapy on hospital discharge

    Clinical prediction rule: CHADS-2 - score for each risk factor:
    • congestive heart failure: 1
    • hypertension: 1
    • aged 75 or older: 1
    • diabetes mellitus: 1
    • history of stroke or transient ischaemic attack: 2


    100% followed for mean 1.2 years
    Outcomes studied:
  • first ischaemic stroke
  • score 6
  • score 5
  • score 4
  • score 3
  • score 2
  • score 1
  • score 0
    • 5 quality improvement/peer review organisations assembled 5 cohorts of patients, and reviewed Medicare records to determine presence of AF and associated conditions and subsequent hospital admissions with a first ischaemic stroke.
    • CHADS-2 was based on the prognostic factors identified in the AFI and SPAF studies.

    The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)    		 NNF
    (95% CI)
    first ischaemic stroke 1.2 years 94/1733 5.4%
    (4.4% to 6.5%)    		 18
    (15 to 23)
    score 6 1.2 years 2/5 40.0%
    (0.0% to 82.9%)    		 3
    (1 to infinity)
    score 5 1.2 years 6/65 9.2%
    (2.2% to 16.3%)    		 11
    (6 to 46)
    score 4 1.2 years 19/220 8.6%
    (4.9% to 12.3%)    		 12
    (8 to 20)
    score 3 1.2 years 25/337 7.4%
    (4.6% to 10.2%)    		 13
    (10 to 22)
    score 2 1.2 years 23/523 4.4%
    (2.6% to 6.2%)    		 23
    (16 to 38)
    score 1 1.2 years 17/463 3.7%
    (2.0% to 5.4%)    		 27
    (19 to 51)
    score 0 1.2 years 2/120 1.7%
    (0.0% to 4.0%)    		 60
    (25 to infinity)

    Comments

    1. CHAD-2 was found to be more accurate than the scoring systems developed using from the AFI and SPAF studies, but it needs to be validated in a separate set of patients.

    Citation

    1. Gage BF, Waterman AD, Shannon W, et al: validation of clinical classification schemes for predicting stroke: results from the national registry of atrial fibrillation. Journal of the American Medical Association 2001; 285 : 2564-2870
    Search Terms: from Bandolier
    Contributor: Chris Ball, November 2001
    Reviewer:

    Clinical Question.
    Patient atrial fibrillation
    Intervention or Exposure clinical predication rule: CHADS-2
    Outcome first ischaemic stroke
    		•