Introduction

Spontaneous bacterial peritonitis (SBP) is a life-threatening complication of decompensated liver cirrhosis. The 1-year mortality is up to 93%. Pathophysiologically, bacterial translocation from the intestine to the mesenteric lymph nodes is the key event in the development of SBP. State of the art diagnosis of SBP is established by the detection of >250 polymorphonuclear cells (PMN) per µl of ascitic fluid. Since antibiotic treatment is crucial at the very onset of SBP, innovative novel biomarkers for early diagnosis are the key to improving the clinical management of SBP.

Aims & Methods

To identify novel potential biomarkers for early detection of SBP, ascitic fluid was collected from patients with liver cirrhosis treated at a German University Hospital. Ascitic calprotectin and lactoferrin levels were determined by ELISA. Total protein in the ascitic fluid was measured by a bicinchoninic acid (BCA) assay. In addition, calprotectin- and lactoferrin-total-protein-ratios were calculated.

Results

190 ascitic fluid samples from 128 individual patients were analyzed. SBP was diagnosed in 29 (15%) of the samples. The amount of ascitic lactoferrin was considerably higher in samples with SBP (median 831 ng/ml) compared to non-infectious samples (median 48 ng/ml). However, a correlation between lactoferrin and the PMN count was not observed. In contrast, ascitic calprotectin (r=0.7; p < 0.001; cut off: 4.4 mg/ml; sensitivity 83%; specificity 98%) and calprotectin-total-protein-ratio (r=0.7; p < 0.001; cut-off 208x10^-6; sensitivity 79%; specificity 93%) significantly correlated with the ascitic PMN cell count. Moreover, ascites samples from patients with SBP displayed higher calprotectin levels (median 8999 ng/ml; range 27 ng/ml-163.59 µg/ml) and calprotectin-total-protein-ratios (median 5x10^-4) compared with samples without infection (median 539 ng/ml; ratio: median 3x10^-5). Remarkably, time course analyses in follow-up paracentesis revealed an association with the development of SBP and recovery from the disease with a coinciding increase or decrease of calprotectin-total-protein-ratios. Furthermore, even the very early phase of the development of an SBP was associated with an increase of calprotectin-total-protein-ratio in follow-up paracentesis of individual patients, which was detectable before PMN count exceeded 250. Likewise, lactoferrin-total-protein-ratios increased during the development of SBP and decreased with the recovery. Also, the lactoferrin-total-protein-ratio was elevated in early SBP. Thus, especially total protein ratios of the two analyzed parameters appear to be valuable markers for early diagnosis of SBP.

Conclusion

An appropriate novel biomarker for diagnosis of SBP needs to detect SBP at a very early stage and also monitor disease progression and response to therapy. Ascitic calprotectin and ascitic calprotectin-total-protein-ratios not only correlated with state of the art diagnostic criteria but were also associated with the development of and recovery from SBP. Furthermore, ascitic calprotectin-total-protein-ratio and lactoferrin-total-protein-ratio were revealed to be predictive markers for early SBP. In summary, our findings show the potential of calprotectin-/ lactoferrin-total-protein-ratios as potential diagnostic and prognostic markers of SBP, allowing earlier diagnosis and thus more effective treatment of a SBP.

Clinical Case Summary

Although liver involvement is common in leukemia, acute hepatitis as its initial presentation is rare. This case highlights the diagnostic challenge of distinguishing reactive hematological changes from underlying malignancies in patients with unexplained hepatitis.
A 35-year-old woman presented in February 2024 with myalgias, fever with chills (38°C), jaundice, and right upper quadrant discomfort. Relevant history included recent intake of herbal supplements (vitamin C, zinc, echinacea, elderberry).
Initial laboratory findings showed leukocytosis, lymphocytosis (25%), monocytosis (12%), blasts (3%), thrombocytopenia (136×10⁹/L), and abnormal liver tests (AST 448 U/L, ALT 686 U/L, ALP 242 U/L, GGT 147 U/L, total bilirubin 4.14 mg/dL, direct bilirubin 2.9 mg/dL), with normal INR. Peripheral blood smear revealed mononuclear pleomorphism and lymphocytes with prominent nucleoli. Abdominal computed tomography showed moderate hepatomegaly without biliary or vascular abnormalities. Comprehensive testing for infeccious, autoimmune and metabolic causes was negative.
Liver tests improved and leukocytosis turned into leukopenia. Repeat blood smear was deemed reactive by Hematology. She was discharged and in early March re-evaluation, liver parameters normalized and leukopenia improved.
Later that month, she returned with fever, night sweats, and abdominal pain. Laboratory findings showed recurrent cytopenias and cytocholestasis. Blood smear revealed increasing blast count, and immunophenotyping suggested monoclonality. Bone marrow and liver biopsy confirmed B-cell acute lymphoblastic leukemia (ALL) with hepatic infiltration.
This case illustrates an unusual presentation of ALL as relapsing acute hepatitis. It reinforces the need to consider hematological malignancy in cryptogenic hepatitis, particularly when associated with evolving hematological changes. Serial blood smears, immunophenotyping, and timely bone marrow evaluation are essential to avoid diagnostic delay.

References

1. Hepatic biopsy: clusters of intermediate to large cells expressing TdT, CD20, PAX5, CD10, BCL6, CD43.
2. Bone marrow aspirate: 64% blasts, CD10+, CD20+ (strong homogeneous expression).
3. Bone marrow biopsy: increased cellularity due to diffuse interstitial infiltration by intermediate cells with blast-like morphology and lymphoid immunophenotype (TdT+, CD34+, MPO-, CD20+).