Spontaneous Bacterial Peritonitis (SBP) stands as a critical and frequently lethal complication for individuals with cirrhosis. When left unaddressed, SBP carries a significant mortality risk, emphasizing the urgency for rapid and accurate diagnosis. The cornerstone of SBP diagnosis is often the analysis of ascitic fluid, specifically focusing on the cell count. Traditionally, a neutrophil count exceeding 250 cells/mm3 in ascites fluid has been the diagnostic threshold for SBP. However, some studies suggest that a total cell count greater than 500 cells/mm3 can offer improved sensitivity in detecting SBP. In settings where advanced techniques like flow cytometry for neutrophil quantification are not readily available or validated, the overall cell count, coupled with microscopic examination of the cell population, becomes even more vital.
A recent study conducted at Aberdeen Royal Infirmary’s Digestive Disease Unit investigated the diagnostic precision and management strategies for SBP within their facility. This retrospective analysis encompassed all diagnostic paracentesis procedures performed over a six-month period in 2019. The study meticulously gathered data from electronic health records, including details on the underlying causes of liver disease, prior SBP episodes, antibiotic usage, mortality rates, and 30-day readmission occurrences. The primary objective was to evaluate the effectiveness of cell count-based SBP diagnosis in their clinical setting.
The study encompassed 106 paracentesis procedures across 48 patients. Among the analyzed samples, a cell count surpassing 0.25 × 10^9 cells/L (equivalent to 250/mm3) was observed in 40% of cases, while 23.5% exhibited a cell count exceeding 0.5 × 10^9 cells/L (500/mm3). Notably, SBP was diagnosed and subsequently treated in 44% of patients with cell counts above the lower threshold and in a significantly higher 83% of those exceeding the higher threshold. Cytospin analysis, a microscopic examination technique, revealed marked neutrophilia in 20% of all samples. Interestingly, neutrophilia was more prevalent in samples with elevated cell counts, observed in 50% and 63% of samples with cell counts >0.25 and >0.5 × 10^9 cells/L, respectively. It is noteworthy that a considerable proportion (18.6%) of samples with elevated cell counts were not initially diagnosed as SBP, despite 6.8% of these exhibiting cytospin findings suggestive of infection. Conversely, a noteworthy 21.5% of samples with cell counts below the diagnostic threshold were still diagnosed and treated for SBP, highlighting the complexities in relying solely on cell count. Culture analysis, performed in 80% of cases, yielded a low positivity rate of only 7%. All patients diagnosed with SBP received antibiotic treatment and human albumin, adhering to established care protocols for decompensated cirrhosis. The study reported a 30-day mortality rate of 18.75% across all patients, with a slightly lower mortality rate of 13.3% specifically in patients diagnosed with SBP. Alarmingly, all patients with positive ascitic fluid cultures succumbed during their hospital admission.
The findings of this study underscore the significant mortality associated with SBP and highlight the challenges in its diagnosis, particularly when relying on cell count in the absence of validated flow cytometry for neutrophil counts. The variability in SBP diagnosis within the unit, as indicated by discrepancies between cell count thresholds and clinical diagnosis, emphasizes the need for standardized diagnostic approaches. The study points out that relying primarily on cytospin comments for diagnosis might lead to missed SBP cases, potentially underdiagnosing up to 11.7% of cases with elevated cell counts but negative cytospin findings. This issue likely extends to other centers where automated cell counts may not be complemented by neutrophil-specific analysis. The study’s conclusion strongly advocates for the implementation of an agreed-upon protocol to ensure consistency and improve the accuracy of SBP diagnosis based on ascitic fluid cell count, ultimately aiming to enhance patient outcomes. Furthermore, the study calls for increased awareness regarding antibiotic prophylaxis in patients with a history of SBP to optimize management strategies.
References
- Piano S, Fasolato S, Salinas F, Romano A, Tonon M, Morando F, et al. The empirical antibiotic treatment of nosocomial spontaneous bacterial peritonitis: Results of a randomized, controlled clinical trial. Hepatology 2016;63:1299–1309.
- Rimola A, et al. Diagnosis, treatment and prophylaxis of spontaneous bacterial peritonitis: a consensus document. International Ascites Club. J Hepatol 2000;32:142–153
- https://www.bsg.org.uk/wp-content/uploads/2019/12/BSG-BASL-Decompensated-Cirrhosis-Care-Bundle-First-24-Hours.pdf
