The diagnostic tool is designed to determine if a patient meets the criteria for spontaneous bacterial peritonitis (SBP) by analyzing the ascitic fluid. This analysis is based on two key criteria:

- Ascitic fluid neutrophil count exceeding 250 cells per cubic millimeter.
- A positive bacterial culture in the ascitic fluid.

Here's how the diagnostic process works:

- If the ascitic fluid neutrophil count is over 250 cells/mm³, this meets one of the criteria for diagnosing SBP.
- Similarly, if the bacterial culture of the ascitic fluid is positive, it also satisfies the diagnostic condition for SBP.

The evaluation operates on a straightforward logical principle:

- The presence of either a high neutrophil count or a positive bacterial culture is sufficient to confirm the diagnosis of SBP.
- Specifically, if either of these conditions is true, the result is that the patient meets the criteria for SBP.
- Conversely, if neither the neutrophil count exceeds 250 cells/mm³ nor is there a positive bacterial culture result, then the findings do not support a diagnosis of SBP.

This tool leverages a critical threshold of 250 cells/mm³ for neutrophils to streamline the diagnostic assessment, enabling healthcare providers to ascertain the presence of spontaneous bacterial peritonitis efficiently.

The calculator in question is the Diagnostic Criteria for Spontaneous Bacterial Peritonitis (SBP). This calculator is used in the patient population of individuals with ascites, particularly those with cirrhosis. The clinical utility of this calculator is to aid in the diagnosis of SBP, a potentially life-threatening infection of the ascitic fluid that can occur in patients with cirrhosis and ascites. 

The diagnostic criteria for SBP typically involve an ascitic fluid analysis with a polymorphonuclear leukocyte (PMN) count of ≥250 cells/mm³. Other supportive findings may include positive ascitic fluid bacterial culture and signs or symptoms of infection (e.g., fever, abdominal pain, altered mental status). 

There are no specific exclusion criteria for the use of this calculator. However, it is important to note that it should not be used in isolation and should be part of a comprehensive clinical assessment. Other potential causes of ascites, such as malignancy or tuberculosis, should also be considered and ruled out.

Diagnostic criteria for spontaneous bacterial peritonitis