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Centre for Evidence-
Based Medicine

Completed Prognosis Worksheet for Critical Care Medicine

Citation

Edgren E, Hedstrand U, Sutton-Tyrell K, Safar P, and BRCTI study group.
Assessment of neurological prognosis in comatose survivors of cardiac arrest.
Lancet 1994;343:1055-59.

Are the results of this prognosis study valid?

  1. Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
    Yes.
  2. Was patient follow-up sufficiently long and complete?
    Yes. 12 months
  3. Were objective outcome criteria applied in a "blind" fashion?
    Objective outcome criteria applied (Cerebral performance categories) but did not state if blinded.

    Patients were part of a clinical trial but unclear if people were blind to neuro exam results.
  4. If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?
    Groups did not appear to be different.
  5. Was there validation in an independent group ("test-set") of patients?
    No.

Are the valid results of this randomised trial important?

  1. How likely are the outcomes over time?
    0 % (0 out of 43) of patients without motor response on day 3 recovered.
  2. How precise are the prognostic estimates?
    95% CI: -2% to 2%

If you want to calculate a Confidence Interval around the measure of Prognosis

Clinical Measure Standard Error (SE) Typical calculation of CI
Proportion (as in the rate of some prognostic event, etc) where:

the number of patients = n

the proportion of these patients who experience the event = p
sqrt((px(1-p))/n)
where p is proportion and n is number of patients
If p = 24/60 = 0.4 (or 40%) and n=60
sqrt((0.4x(1-0.4))/60)
= 0.063 (or 6.3%)

95% CI is 40% +/- 1.96 x 6.3% or 27.6% to 52.4%
n from your evidence: ___69_____

p from your evidence: ___0_____
sqrt((px(1-p))/n)
where p is proportion and n is number of patients
Your calculation:
SE = sqrt(0.005x(1-(0.005/43)))
= 0.005 (0.1%)._________

95% CI: 0% +/- 1.96 x 0.0012= -2% to 2%

Can you apply this valid, important evidence about prognosis in caring for your patient?

  1. Were the study patients similar to your own?
    Yes
  2. Will this evidence make a clinically important impact on your conclusions about what to offer or tell your patient?
    Yes

Additional Notes

This paper evaluated the prognostic ability of several other physical exam findings however, we focused only on motor response.

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