Fluid Analysis Test

The shipment of biological specimens must comply with the protocols established by the courier or transport service used. In some cases, air transport requires compliance with the regulations of the International Air Transport Association (IATA) for dangerous goods.

The analysis of cavitary effusions (peritoneal, pleural and pericardial) and other fluids (e.g., synovial fluid, CSF) includes determination of protein content, total erythrocyte and white blood cell counts, and cytological evaluation. Other tests may be performed depending on the origin or appearance (e.g., chylous fluid) of the effusion.

A fluid sample should be collected in a tube with EDTA (purple cap) for routine analysis. A second sample should be collected in a serum tube (red cap) if microbial culture and antimicrobial susceptibility testing or biochemical analyses are planned. These samples should be sent refrigerated but not frozen.

Cytological evaluation without measurement of other parameters (e.g., total protein concentration, cell counts) is usually acceptable for mass lesions characterised by a fluid component.

Smears for cytological evaluation should be prepared from a drop of the fluid immediately after the sample has been collected to minimise cell deterioration and other in vitro artefacts. Cytology slides should be labelled with the patient identification, the source and type of preparation (e.g., direct, concentrated/sedimented) and the fluid, and then sent to the laboratory.

CSF samples should be collected in small EDTA tubes and sent immediately with high priority; the cytological value of CSF samples degrades rapidly and the low cellularity makes direct smear examination unrewarding. If sufficient CSF is available, a serum tube sample (yellow cap) may be useful for serological evaluation or culture attempts.