PROGNOSIS Cohort studies. Distressed 3100g male newborn At delivery Limp, cyanotic, no spontaneous...
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Transcript of PROGNOSIS Cohort studies. Distressed 3100g male newborn At delivery Limp, cyanotic, no spontaneous...
PROGNOSIS
Cohort studies
Distressed 3100g male newborn
At delivery Limp, cyanotic, no spontaneous respiratory
effort, heart rate 50 beats/min. Suction - no grimace, cough or sneeze Vigorous resuscitation
At 1 minute: Apgar score = 1 At 5 minutes: Apgar score = 2, 110
beats/min. At 10 minutes: Apgar score = 3
APGAR SCORE FOR EVALUATION OF NEONATAL ASPHYXIAAdapted from Apgar V, James LS. Am J Dis Child 1962; 104:419
Score The values for each of the five categories are added to yield a result from 0 to 10
Sign
0
1
2
Heart rate (beats/min)
Absent
<100
≥100
Respiration
Absent
Slow, irregular
Regular, crying
Muscle tone
Limp
Slow flexion
Active motor
Colour
Blue, pale
Body pink, extremities
blue
Completely pink
Reflex response to catheter in nostril
None
Grimace
Cough, sneeze
Distressed 3100g male newborn
At delivery Limp, cyanotic, no spontaneous respiratory
effort, heart rate 50 beats/min. Suction - no grimace, cough or sneeze Vigorous resuscitation
At 1 minute: Apgar score = 1 At 5 minutes: Apgar score = 2, 110
beats/min. At 10 minutes: Apgar score = 3
PROGNOSIS??
Objectives
Cohort study describe structure and analysis interpret and calculate relative and absolute
measures of effect identify potential for bias
RCT / Cohort
EXPOSED GROUP (eg treatment) NO DISEASE DISEASE NON EXPOSED GROUP (eg no treatment)
NO DISEASE
DISEASE
START
Apgar scores as predictors of chronic neurologic disabilities
Nelson KB, Ellenberg JH, Pediatrics, 1981; 68:36 49000 infants followed for 7 years.
Apgar scores recorded at 1 and 5 minutes (and for infants with AS<8 at 10, 15 & 20 minutes)
Histories recorded at 4, 12, 18 months and then yearly to age 7
Relationship between 10-minute Apgar scores and risk of death in the 1st year of life among children with birth weight of at least 2500g
Risk in ‘exposed’ = ? Risk in ‘less’ exposed = ?Relative risk = ?Risk difference = ?Attributable risk % = RD/ R(exp) = ?
Dead Notdead
Total
'Exposed'(Apgar score 0 - 3)
42 80 122
'Not exposed'(Apgar score 4 - 6)
43 302 345
Total 85 382 467
Relationship between 10-minute Apgar scores and risk of death in the 1st year of life among children with birth weight of at least 2500gRisk in exposed = 42 / 122 = 0.344 = 34.4%
Risk in less exposed = 43 / 345 = 0.125 = 12.5%
Relative risk = 0.344 / 0.125 = 2.8
Risk difference = 34.4 - 12.5 = 21.9%
Attributable risk % = RD / R(exp) = 0.219 / 0.344 = 64%
Dead Notdead
Total
'Exposed'(Apgar score 0 - 3)
42 80 122
'Not exposed'(Apgar score 4 - 6)
43 302 345
Total 85 382 467
Bad outcome eg death, h'capped infant
If exposure good/protective If exposure harmful (folate supplements, high AS (foetal distress, smoking)
<1 1 >1Relative risk
If exposure If exposure good
harmful
Good outcome eg cure,
'normal' infant
55% of cerebral palsy (CP children had 1 minute scores >= 7
99 survivors with scores 0 - 3 (at 10, 15 or 20 minutes, all birth weights) 80% free of major handicap 12 had CP
11 mentally retarded, 1 normal10 had had seizures on day of birth
1 in 8 asphyxiated neonates have CP and developmental delays << 1in 8 of those without seizures
What is key difference between RCT and cohort study?
RCT Random allocation of intervention/exposure by
investigator
CohortSelf selection of exposure/risk factor