Patient selection: acute pancreatitis
Parameters:
(1) body mass index in kg per square meter (BMI)
(2) serum amylase in U/L on day 2
(3) serum amylase in U/L day 1 (day of admission)
percent change in amylase =
= ((amylase day 2) - (amylase day 1)) / (amylase day 1) * 100
X =
= (0.14 * BMI) + (0.01 * (percent change in amylase day 2)) - 5.9
where:
• The 0.01 and 100 would cancel each other out.
probability of severe pancreatitis =
= 1 / (1 + EXP((-1) * X))
Interpretation:
• A probability > 9% was considered positive.
Performance:
• The area under the ROC curve was 0.73 to 0.79.
• Using a probability > 9% the sensitivity was 75% and specificity 65%. The negative predictive value was 95% vs positive predictive value of 22%.
