A feasibility study investigating the utility of a point-of-care rapid immunoassay for detecting septic peritoneal effusion in dogs

Diagnosis of Septic Body Cavity Effusion in Dogs and Cats: Cytology vs. Bacterial Culture

The elective test for the determination of the effusions etiopathogenesis is represented by physico-chemical analysis and cytology. Nevertheless, the bacterial culture and antibiotic sensitivity tests are crucial for setting therapy and for the outcome. This study compared cytology with microbiology in the etiologic diagnosis of exudative body cavity effusions in dogs and cats collected from October 2018 to October 2022. All samples underwent aerobic and anaerobic culture and cytology examination. Bacterial identifications were confirmed using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, whereas cytological samples were blindly evaluated either in May Grunwald-Giemsa (MGG) or Gram-stained samples by two board-certified clinical pathologists. A moderate agreement (κ = 0.454) between cytology and bacterial culture was revealed. The sensitivity of the cytological evaluation in our study ranged from 38.5% to 67.9%, and the specificity ranged from 88.9% to 100%, depending on the type of the effusion, so cytology may not be representative of the etiopathogenesis, whereas bacterial culture can misidentify or fail to isolate the correct pathogen for difficult in vitro growing due to the presence of inhibitory substances or contamination. Cytology and bacterial culture results for exudative body cavity effusions in dogs and cats can be misleading if conducted separately, so these two tests should be performed together to increase diagnostic accuracy.

Performance evaluation of a Test&Treat rapid detection kit for the diagnosis of septic effusions in dogs and cats

OBJECTIVE

To evaluate the sensitivity and specificity of a veterinary point-of-care (POC) luminometer-based kit for the diagnosis of septic peritoneal or pleural effusion in dogs and cats.

DESIGN

Prospective study performed between January 2020 and July 2021.

SETTING

University teaching hospital.

ANIMALS

Forty-eight animals with naturally occurring peritoneal or pleural effusion collected by aseptic abdominocentesis or thoracocentesis.

PROCEDURES

Effusion samples were split into filtered (using a 10-micron filter) and unfiltered aliquots and analyzed by the POC instrument according to the manufacturer's instructions and following variable incubation periods. Samples were also plated aerobically on standard and blood agar plates. Proprietary reagents were added to samples, causing bacterial ATP to generate bioluminescence that is detected by the luminometer. Bioluminescence values (relative light units [RLUs]) were recorded and compared with the presence of bacterial growth on the culture plates. Nucleated cell counts in native and filtered effusion samples were recorded.

RESULTS

Twenty-one samples were septic based on positive culture. RLUs were higher in septic effusions for filtered and native effusions compared with sterile effusions. The use of a filter reduced cell counts. In filtered samples incubated for 30 minutes before testing, the sensitivity and specificity of the luminometer for diagnosis of infection in cavitary effusions were 81% and 82%, respectively, using a cutoff of 12,202 RLUs.

CONCLUSIONS

The luminometer kit evaluated in this study represents a viable screening tool for diagnosis of septic cavitary effusions and could be used in conjunction with other POC diagnostics to support the rapid diagnosis of infection.