Beschreibung
To date, veterinarians have only been able to identify septic exudates (SE) by bacteriological or cytological examination of the effusion. However, there is a lack of laboratory diagnostic parameters that would allow a distinction to be made between non-septic exudates (NSE) and SE, even in routine practice, and could therefore provide a decision-making aid for or against the use of empirical antibiotics. Therefore, the aim of this study was to analyse various laboratory parameters from effusion and blood with regard to their ability to quickly identify SE or to differentiate between NSE and SE. A particular focus was placed on the measurement of adenosine triphosphate (ATP) from effusions.
For this prospective study, dogs and cats with pleural and peritoneal effusions were examined.
The routine examination of the effusions to classify them into the various effusion forms included the determination of cell count, total protein, specific gravity, lipids and haematocrit. All effusion forms were also examined cytologically and, with the exception of low-protein transudates (PAT), bacteriologically. Based on these examinations, the effusions were divided into the corresponding effusion forms: PAT, protein-rich transudate (PRT), chyle, haemorrhagic effusion, NSE and SE. The parameters cell count, glucose, lactate, lactate dehydrogenase (LDH), -reactive protein (CRP) or serum amyloid A (SAA) and ATP from effusion as well as glucose, lactate and CRP or SAA from blood were analysed separately according to species and body cavity with regard to their ability to differentiate SE from NSE. Particularly noteworthy is the innovative use of a rapid test known from food inspection to measure ATP and thus indirectly detect bacterial growth as a clinical diagnostic tool.
A total of 129 effusions from dogs and 69 effusions from cats were analysed for this study, of which 120 effusions from dogs (50 pleural effusions, 70 peritoneal effusions) and 61 effusions from cats (49 pleural effusions, 12 peritoneal effusions) were included. Seventeen exudates from dogs (14 %; 10 pleural effusions, 7 peritoneal effusions) and 15 from cats (24 %; 11 pleural effusions, 4 peritoneal effusions) were classified as SE. Due to the small number of feline peritoneal effusions (n=12), a statistical analysis was not possible, which is why the parameters from peritoneal effusions were only analysed in dogs.
In the thoracic effusions of the dogs, SE showed significantly higher cell counts, LDH, CRP and ATP values compared to NSE. There was no significant difference between SE and NSE for glucose from effusion. In the blood, only the CRP value was significantly different and higher in SE than NSE.
Similar results were obtained for the cats. Feline SE had significantly higher cell count, lactate, LDH and ATP values and significantly lower glucose values. In the blood, cats with SE in the thorax also showed significantly higher SAA values. In dogs and cats with thoracic effusion, these parameters can be used as additional parameters for clinical diagnostics after identification of an exudate in order to make a suspected diagnosis of SE with a certain degree of certainty and to administer an antibiotic empirically until the results of the bacteriological examination are obtained. In dogs with ascites, significantly lower glucose and significantly higher lactate values were found in SE compared to NSE.
Cytological examination and bacteriological culture of effusion fluid with resistance testing cannot and should not be replaced by the aforementioned tests in effusion diagnostics. However, the additive use of the above parameters could provide a prompt and cost-effective clinical decision-making aid to confirm the suspected clinical diagnosis of a septic body cavity effusion and to justify the use or non-administration of empirical antibiotics until bacteriological findings are obtained. For the dog with thoracic effusion, in addition to cell count, the parameters LDH, CRP and ATP from the effusion or CRP from the blood and, in the case of ascites, glucose and lactate from the effusion are particularly important. In cats with pleural effusion, the following parameters can facilitate the decision: cell count, glucose, lactate, LDH and ATP from the effusion and SAA measured from the blood. With regard to the use of the rapid test from food hygiene used in the study as a medical diagnostic tool, it can be said that not only is sample handling simple and inexpensive, but ATP assessment also allows NSE and SE in the thorax of dogs and cats to be differentiated quickly, easily and inexpensively. Although a relatively high CV was determined for the Kikkoman test system and individual measurements, as well as the use for peritoneal effusions, do not appear to make sense, the purchase of the ATP measuring device could also be worthwhile for a smaller private practice.
