Blood investigations – complete blood count, kidney function tests, liver function, serum calcium, serum amylase and lipase
Imaging – A triple phase abdominal CT and abdominal ultrasound are together considered the gold standard for the evaluation of acute pancreatitis. Other modalities including the abdominal x-ray lack sensitivity and are not recommended. An important caveat is that imaging during the first 12 hours may be falsely reassuring as the inflammatory and necrotic process usually requires 48 hours to fully manifest. Differential diagnosis
The differential diagnosis includes:
Perforated peptic ulcer
Biliary colic
Acute cholecystitis
Pneumonia
Pleuritic pain
Myocardial infarction

Biochemical
Elevated serum amylase and lipase levels, in combination with severe abdominal pain, often trigger the initial diagnosis of acute pancreatitis. However, they have no role in assessing disease severity. Serum lipase rises 4 to 8 hours from the onset of symptoms and normalizes within 7 to 14 days after treatment. Serum amylase may be normal (in 10% of cases) for cases of acute or chronic pancreatitis (depleted acinar cell mass) and hypertriglyceridemia. Reasons for false positive elevated serum amylase include salivary gland disease (elevated salivary amylase), bowel obstruction, infarction, cholecystitis, and a perforated ulcer. If the lipase level is about 2.5 to 3 times that of amylase, it is an indication of pancreatitis due to alcohol.Decreased serum calcium
GlycosuriaRegarding selection on these tests, two practice guidelines state:

"It is usually not necessary to measure both serum amylase and lipase. Serum lipase may be preferable because it remains normal in some nonpancreatic conditions that increase serum amylase including macroamylasemia, parotitis, and some carcinomas.
If the score < 3, severe pancreatitis is unlikely
Or
Score 0 to 2 : 2% mortality
Score 3 to 4 : 15% mortality
Score 5 to 6 : 40% mortality
Score 7 to 8 : 100% mortality

APACHE II score
"Acute Physiology And Chronic Health Evaluation" (APACHE II) score > 8 points predicts 11% to 18% mortality
Hemorrhagic peritoneal fluid
Obesity
Indicators of organ failure
Hypotension (SBP <90 mmHG) or tachycardia > 130 beat/min
PO2 <60 mmHg
Oliguria (<50 mL/h) or increasing BUN and creatinine
Serum calcium < 1.90 mmol/L (<8.0 mg/dL) or serum albumin <33 g/L (<3.2.g/dL)>

Balthazar score
Developed in the early 1990s by Emil J. Balthazar et al., the Computed Tomography Severity Index (CTSI) is a grading system used to determine the severity of acute pancreatitis. The numerical CTSI has a maximum of ten points, and is the sum of the Balthazar grade points and pancreatic necrosis grade points:
Balthazar grade

Necrosis score

CTSIs staging of acute pancreatitis severity has been shown by a number of studies to provide more accurate assessment than APACHE II, Ranson, and C-reactive protein (CRP) level. However, a few studies indicate that CTSI is not significantly associated with the prognosis of hospitalization in patients with pancreatic necrosis, nor is it an accurate predictor of AP severity. Glasgow score
The Glasgow score is valid for both gallstone and alcohol induced pancreatitis, whereas the Ranson score is only for alcohol induced pancreatitis. If a patient scores 3 or more it indicates severe pancreatitis and the patient should be considered for transfer to ITU.