Diagnostic peritoneal lavage: it's red but is it positive?

The aim of this study was to ascertain whether qualitative assessment could accurately determine a concentration of 100,000 RBC/mm3 in simulated peritoneal lavage fluid. The results show that the qualitative methods used are inaccurate and do not reliably predict a red cell concentration of 100,000 per mm3. We therefore recommend that the red cell concentration of peritoneal lavage fluid is always measured before the result is considered 'positive'.