### Description

The "pain rate" for a patient with sickle cell disease refers to the number of pain episodes per year. This is a measure of disease severity and is one of the factors associated with premature death in a patient who is over 20 years old. Platt et al developed an equation using a Poisson model to predict the pain rate for a patient with sickle cell disease.

Parameters:

(1) age in years

(2) fetal hemoglobin level, in percent

(3) hematocrit in percent

(4) gender

where:

• A high percent of fetal hemoglobin is protective, while a low percent is associated with an increased risk.

• The rate for males shows a peak from 20-29 years of age.

• The rate for females is lower before 10 and from 40-49 but otherwise is fairly constant.

• The pain rate is higher for a high hematocrit vs a low hematocrit.

Parameter

Finding

Points

age in years

5 – 9

0

10 – 19

0.3631

20 – 29

0.5729

30 – 39

0.3785

40 – 49

-0.0973

>= 50

-0.1641

gender

female

0

male

1

X =

= (-2.3190) + (points for age) – (0.0032 * ((fetal hemoglobin in percent)^2)) + (0.0860 * (hematocrit in percent)) – (0.3044 * (points for gender))

estimated pain rate in pain episodes per year =

= EXP(X)