 ### Description

The Children's Hospital of Philadelphia (CHOP) has reported a nomogram for predicting the risk of retinopathy of prematurity (ROP).

Parameters:

(1) birth weight in grams from 400 to 1800 grams

(2) daily weight gain rate in grams per day, from -40 to 80

(3) gestational age in weeks, with lower limit 23 weeks

The model consists of a nomogram with multiple lines:

(1) a line connecting the line for birth weight to daily weight gain

(2) the intersection of this line with an auxiliary axis this is about midway

(3) a line from the point of intersection in 2 to a line showing the gestational age in weeks

(4) this line in turn intersects a probability line for the risk of ROP

 Point X value Y value birth weight (0.11925 * (birthweight)) - 36.947 0 daily weight gain (0.6 * (weight gain)) + 196.5 60 intersection on auxiliary line (30-(intersection line 1)) / (slope line 1) 30 gestational age see table below 123 intersection on probability line (85.5-(intersection line 2)) / (slope line 2) 85.5

 Gestational Age X value 23 weeks 0 24 or 25 weeks 13 26 or 27 weeks 26 28 weeks 39 >= 29 weeks 52

 Line Slope Intersect between birth weight and daily weight gain (line 1) (y2-y1) / (x2-x1) y2 - ((slope 1) * x2) between gestational age and auxilliary line (line 2) (y2-y1) / (x2-x1) y2 - ((slope 1) * x2)

LOG10(probability) = P =

= (3.0754 - (0.058829 * (X value at intersection with probability line))

probability of ROP =

= 10^P

Interpretation:

• A probability of type 1 ROP >= 1.4% (0.014) is considered higher risk and underwent eye exam for ROP.