- Design
- Retrospective single-centre diagnostic study
- Population
- 261 patients with malignant ascites (337 paracenteses)
- Primary outcome
- Positive ascitic fluid culture
- Effect
- PMN ≥250: sensitivity 73.7%, specificity 72.4%; PMN >1318: 68.4% and 93.0%
A single-centre retrospective study in the Journal of Hospital Medicine (18 September) reviewed 337 paracenteses in 261 patients with malignant ascites; 19 samples grew bacteria.
The cirrhosis threshold of 250 neutrophils per mm³ had a sensitivity of 74% and a specificity of 72% — it flagged many patients without infection. Higher cut-offs, a neutrophil count above about 1,300 or a neutrophil percentage of 63% or more, were more specific (around 91% to 93%) but missed about a third of infections.
No threshold performed well, and the numbers are small. The practical point is that the familiar cirrhosis rule cannot be borrowed for malignant ascites; culture and the clinical picture carry more weight.
- Do not apply the cirrhosis 250-neutrophil rule to malignant ascites without caution
- Send fluid for culture in blood-culture bottles at the bedside
- Weigh the clinical picture — fever, pain, rising inflammatory markers — alongside the count
- These thresholds are hypothetical and need validation before use
Why it matters
A rule learned for cirrhosis is routinely applied to cancer patients, where it misleads.
Don't overread it
Only 19 positive cultures at one centre — the proposed cut-offs are not ready for practice.
The statistics, in plain English
A specificity of 72% means about one in four uninfected patients would be labelled infected at the 250 threshold. With so few infections, each sensitivity figure rests on 19 samples, so it could easily be 10 or more points off.
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