Ing et al reported a model and nomogram for identify a patient with possible giant cell arteritis (GCA). The authors are from multiple institutions from Canada, the United States and China.
Patient selection: suspected giant cell arteritis (GCA)
Parameters:
(1) age in years, from 40 to 100 years
(2) jaw claudication
(3) vision loss
(4) platelet count in 10^9/L
(5) serum CRP divided by the upper limit of the normal reference range (ULN)
points for age =
= (0.091667 * (age)) - 0.06667
points for platelet count =
= (0.010522 * (platelet count)) + 0.003889
points for CRP to ULN ratio =
= (0.7368 * LN(CRP ratio)) + 2.745
|
Parameter
|
Finding
|
Points
|
|
jaw claudication
|
no
|
0
|
|
|
yes
|
2.88
|
|
vision loss
|
no
|
0
|
|
|
yes
|
1.6
|
total score =
= SUM(points for all of the parameters)
Interpretation:
• minimum score: 0
• maximum score: 29.6
• The higher the score the greater the risk of GCA.
value of X =
= (0.4819 * (score)) - 8.51
probability of GCA =
= 1 / (1 + EXP((-1) * X))
Performance:
• The area under the ROC curve is 0.81.
