Review Article

Biochemical analysis of ascitic (peritoneal) fluid: what should we measure?

A C Tarn1 and R Lapworth2

1 Department of Clinical Biochemistry, Mayday University Hospital, Mayday Road, Thornton Heath, Surrey CR7 7YE; 2 Department of Clinical Biochemistry, William Harvey Hospital, Kennington Road, Willesborough, Ashford, Kent TN24 0LZ, UK

Corresponding author: Dr A C Tarn. Email: [email protected]

Ascitic fluid samples are frequently sent to the laboratoryfor analysis. Although the underlying cause of the ascites isoften thought to be clinically obvious, it is important to establisha definitive diagnosis. The value of a cell count and bacterialculture of the ascitic fluid is not disputed, but the role ofbiochemical testing is less clear. The use of ascitic fluidtotal protein to try to classify ascitic fluids as either anexudate or a transudate has contributed to this. The use ofthe physiologically based serum ascites albumin gradient todifferentiate ascites caused by portal hypertension from othercauses provides a better diagnostic approach. We recommend thatthe serum ascites albumin gradient is performed by laboratoriesas the first-line test and that interpretative reports are provided.Additional testing should be restricted to specific diagnosticqueries and requires close collaboration between the laboratoryand the clinician.