- Design
- Retrospective single-centre diagnostic accuracy study
- Population
- 337 paracenteses in 261 patients with malignant ascites
- Primary outcome
- Positive ascitic fluid culture
- Effect
- PMN 250 or more: sensitivity 73.7%, specificity 72.4%; 19 culture-positive samples
A retrospective single-centre study reviewed 337 paracenteses in 261 patients with malignant ascites; 19 samples grew bacteria.
The cirrhosis threshold for spontaneous bacterial peritonitis, a neutrophil count of 250 per cubic millimetre or more, had a sensitivity of 74% and specificity of 72% here, so it flags many uninfected samples. The best-performing alternatives were a neutrophil percentage of 63% or more (sensitivity 68%, specificity 91%) or a count above 1,318 (68% and 93%), but both still missed about a third of infections.
With only 19 positive cultures from one hospital, none of these cut-offs is ready to use. What changes is the interpretation: a neutrophil count just over 250 in malignant ascites does not mean infection as reliably as it does in cirrhosis, and a normal count does not exclude it.
- Send ascitic fluid for culture in blood culture bottles at the bedside, not just a cell count.
- Do not apply the cirrhosis 250 neutrophil threshold to malignant ascites as if it were validated.
- Interpret the cell count alongside fever, abdominal pain and clinical trajectory.
- These alternative thresholds are hypothesis-generating; do not adopt them yet.
Why it matters
Hospitalists often borrow the cirrhosis rule for any ascites, and here it both over- and under-calls infection.
Don't overread it
With 19 positive cultures at one centre, the suggested new thresholds are unvalidated.
The statistics, in plain English
Sensitivity is the share of true infections a test catches; specificity is the share of non-infected samples it correctly clears. With only 19 infections, each missed or caught case moves sensitivity by about 5 points, so these percentages are imprecise.
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