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Centre for Evidence-
Based Medicine

Completed Prognosis Worksheet for Evidence-Based Neonatal Medicine


Aziz K., Vickar D.B., Sauve R.S., et al. Province-Based Study of Neurologic Disability of Children Weighing 500 Through 1249 Grams at Birth in Relation to Neonatal Cerebral Ultrasound Findings. Pediatrics 1995; 95(6): 837-44.

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. A provincial cohort of preterm infants with birth weights between 500 gm and 1249 gm who survived beyond one year of age was prospectively evaluated.
  2. Was patient follow-up sufficiently long and complete?
    Yes. 97% of the infants who survived beyond one year (646 out of 669) were assessed at 2-3 years of age.
  3. Were objective outcome criteria applied in a "blind" fashion?
    It is not clearly stated that follow-up assessments were performed without knowledge of the neonatal ultrasound findings!
  4. If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?
    No subgroups with different prognoses were identified.
  5. Was there validation in an independent group ("test-set") of patients?

Are the valid results of this prognosis study important?

  1. How likely are the outcomes over time?
    Serial assessments are not reported; however, a diagnosis of disability at 2-3 years of age is unlikely to change much in later childhood.
  2. How precise are the prognostic estimates?
    24 of 50 children with transient or permanent unilateral or bilateral cerebral ventriculomegaly were disabled: 48% (95% CI: 34-62%).

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
where p is proportion and n is number of patients
For pCV or tCV:

If p = 24/50 = 0.48 (or 48%) and n=50
SE = sqrt((0.48x(1-0.48))/50) = 0.071
95% CI is 48% ± 1.96 x 7.1% or 34.1% to 61.9%

Can you apply this valid, important evidence about a diagnostic test in caring for your patient?

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

Additional Notes


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