Prognosis Scenario

A 27 week gestation infant is born with a birth weight of 900 grams. Cranial ultrasound at one week of age shows a small amount of blood in both ventricles. On repeat ultrasound at one month, the intraventricular hemorrhage is no longer visible, but the left lateral ventricle is dilated beyond the 97th centile for postconceptual age. The infant remains well with no abnormal neurological symptoms or signs. The parents ask you whether their child will have any long term disability. You are uncertain about the implications of unilateral ventriculomegaly that does not require the placement of a ventriculo-peritoneal shunt. .

You formulate the question. “In a premature infant with very low birth weight who is expected to survive, and who has posthemorrhagic ventriculomegaly, what is the risk of future neurological disability?”

A PubMed search is performed: “infant, newborn” (MeSH), “ventriculomegaly” (text word), and “disability” (text word). Three articles are retrieved; one is a perfect match: a recent population-based study of children weighing 500 through 1249 grams at birth Pediatrics 1995; 95(6): 837-44.

Read the article and decide:

Is the evidence from this randomised trial valid?
If valid, is this evidence important?
If valid and important, can you apply this evidence in caring for your patient?

Completed Prognosis Worksheet for Evidence-Based Neonatal Medicine

Citation

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?

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.
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.
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!
If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?: No subgroups with different prognoses were identified.
Was there validation in an independent group (“test-set”) of patients?: No.

Are the valid results of this prognosis study important?

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.
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	$$ sqrt{frac{ptimes(1-p)}{n}}\\$$ 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 $$ mathit{SE} = sqrt{frac{0.48times(1-0.48)}{50}} = 0.071\\ $$ 95% CI is 48% ± 1.96 x 7.1% or 34.1% to 61.9%

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

$$ sqrt{frac{ptimes(1-p)}{n}}\\$$
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
$$ mathit{SE} = sqrt{frac{0.48times(1-0.48)}{50}} = 0.071\\ $$
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?

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

Additional Notes

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Patent Ductus Arteriosus: Risk of disability

Clinical Bottom Line

A premature infant with cranial ultrasound finding of posthemorrhagic ventriculomegaly has a 48% chance of being disabled, if he survives beyond one year of age.

Citation

Clinical Question

In a preterm infant who is expected to survive with posthemorrhage ventriculomegaly, what is the risk of future neurological disability?

Search Terms

PubMed search using MeSH term “infant, newborn”, and text words “ventriculomegaly” and “disability”.

The Study

The Study Patients: Provincial cohort of 646 preterm infants with birth weights 500 gm to 1249 gm who survived beyond the first year of age.
Prognostic Factor: Cranial ultrasounds performed prior to discharge to detect intraventricular hemorrhage (IVH) or cerebral ventriculomegaly (CV). Follow-up assessments were performed at 2 to 3 years of age, and included physical, sensory and psychological assessment.
The Outcome: Disability (which included CP, visual loss, mental retardation, epilepsy, and neurosensory hearing loss).
A well-defined sample at uniform stage of illness, follow-up sufficiently long and complete, can’t tell if blinded objective outcome criteria, no adjustment for other prognostic factors, no validation in an independent test-set of patients.

The Evidence

Prognostic Factor	Outcome	Time	Measure	Confidence Interval	Independent?
Isolated free blood or a clot in ventricles (IVH)	Percent disabled	2-3 yrs	0%		No
CV with any other defect(s)	Percent disabled	2-3 yrs	48%	(34%, 62%)	No
IVH with CV	Percent disabled	2-3 yrs	29%	(10%, 48%)	No

Comments

Uncertain whether outcome assessors were blinded
Despite large cohort, small number of patients in each category

Appraised By

Aaron Chiu