Ma et al reported a nomogram and equation for predicting surgical site infection in an HIV-positive patient following orthopedic surgery. The authors are from Beijing Ditan Hospital and Capital Medical University in Beijing.
Patient selection: HIV-positive patient having orthopedic surgery
Parameters from the nomogram:
(1) absolute CD4 lymphocyte count per microliter, from 0 to 1800
(2) ESR in mm during first hour, from 0 to 100 mm
(3) serum procalcitonin (PCT), from 0 to 2, units not given but presumably ng/mL
points for CD4 count =
= 96 - (0.05333 * (CD4))
points for ESR =
= 0.8 * (ESR)
points for procalcitonin =
= 50 * (PCT)
total score =
= SUM(points for all 3 parameters)
Interpretation:
• minimum score: 0
• maximum score: 276
value of X =
= (0.05876 * (score)) - 8.306
probability of surgical site infection =
= 1 / (1 + EXP((-1) * X))
Alternatively, the paper reports the following equation:
logit for SSI =
= (0.04695 * (ESR points)) + (2.93694 * (PCT points)) - (0.00314 * (CD4 points)) - 2.63589
where:
• ESR points: 1 if < 17.46, else 0 (the "<" may need to be ">")
• PCT points: 1 if < 0.22 else 0(the "<" may need to be ">")
• CD4 points: 1 if < 430.75 else 0 (the "<" may need to be ">")
Performance:
• The area under the ROC curve is 0.95.
