**Core Concept**
Ranson's criteria are a scoring system used to predict the severity and mortality of acute pancreatitis. The system was developed by John Ranson in 1974 and is based on clinical and laboratory findings, including age, sex, and several physiological and biochemical parameters.

**Why the Correct Answer is Right**
Ranson's scoring system includes 11 criteria, which are divided into three categories: clinical (three criteria), biochemical (five criteria), and age (three criteria). The criteria include factors such as age, sex, white blood cell count, serum glucose, blood urea nitrogen, serum calcium, and base deficit. These parameters are used to calculate a score, which can predict the severity of pancreatitis and mortality.

**Why Each Wrong Option is Incorrect**
* **Option A:** Serum albumin is not one of the criteria in Ranson's scoring system.
* **Option B:** Serum calcium is one of the criteria in Ranson's scoring system.
* **Option C:** White blood cell count is one of the criteria in Ranson's scoring system.
* **Option D:** Blood urea nitrogen is one of the criteria in Ranson's scoring system.

**Clinical Pearl / High-Yield Fact**
Ranson's criteria are a useful tool for predicting the severity of acute pancreatitis, but they should be used in conjunction with other clinical and laboratory findings to make a diagnosis.

**Correct Answer: A. Serum albumin is not one of the criteria in Ranson's scoring system.**