Procalcitonin, Erythrocyte Sedimentation Rate and C-Reactive Protein Index as A Predictor for Spontaneous Bacterial Peritonitis in Decompensated Cirrhotic Patients

ABSTRACT


Spontaneous bacterial peritonitis [SBP]
represents the most prevalent and perilous infection observed in individuals affected with cirrhosis, specifically those who exhibit ascites.It is responsible for over 50% of all infections.The global prevalence of SBP was determined to be 17.12%.It was observed that the highest prevalence was recorded in the African region, with a rate of 68.20%.Conversely, the lowest prevalence was noted in North America, with a rate of 10.81% [1] .The immune dysfunction observed in individuals with decompensated cirrhosis, commonly referred to as DCPs, in conjunction with the susceptibility of the gut mucosa, plays a significant role in the development of SBP.This condition is characterized by the migration of bacteria and bacterial endotoxins from the intestinal lumen into the ascitic fluid [AF], thereby contributing to the underlying mechanisms involved in the pathogenesis of SBP [2] .
The occurrence of SBP is known to trigger a cascade of additional complications associated with cirrhosis.These complications include but are not limited to hepatic impairment, hepatic encephalopathy, exacerbation of coagulopathy, variceal bleeding, renal failure, and potentially fatal outcomes [3] .
It has been reported that SBP was linked to a mortality rate of over 90%, but with the advancement of timely diagnosis and effective treatment, that rate has now dropped to less than 20% [4] .SBP typically manifests as fever-related abdominal pain and tenderness.SBP may also be asymptomatic in 10% of cases.Nevertheless, it can also present with other local symptoms and signs of peritonitis, such as vomiting and ileus; other manifestations of systemic inflammation, such as hypothermia, chills, tachycardia, tachypnea, and shock; worsening of liver or kidney functions; or hepatic encephalopathy [5] .
The most reliable way to diagnose SBP is with a positive ascitic fluid culture for a pathogen.However, this is not always the case; in fact, negative cultures are found in approximately 60% of cases with SBP-like symptoms and an elevated PMNL count in the ascitic fluid [6] .
Procalcitonin [PCT] is a polypeptide consisting of 116 amino acids.It serves as a precursor to calcitonin and has a molecular weight of 13 KDa.PCT is synthesized by cells outside of the thyroid, such as monocytes.Highly cited studies have suggested that it could be a valuable serum biomarker for diagnosing bacterial infections in general, and specifically for SBP [8] .
Typically, the PCT level is not measurable [< 0.01 ng/mL], but it quickly rises in the presence of an infection.Despite the relatively high reported average estimates of sensitivity and specificity [83% and 92%, respectively] for serum PCT in diagnosing SBP in various clinical trials, this level of performance was inadequate for achieving a reliable and accurate diagnosis [9] .So, the aim of the study is to evaluate the predictive value of PEC index in diagnosis of spontaneous Bacterial Peritonitis, which made by measurement of procalcitonin, ESR and CRP, which we called the PEC index as a predictive value in Decompensated liver disease ascites.Peritoneal fluid examination: Sterile bedside diagnostic paracentesis was done.A 23-G needle was attached to a 20-cc syringe after application of local anesthesia.Then, aspirated ascitic fluid was collected into two tubes and analyzed within 2 h of aspiration.The first tube for culture and sensitivity and second tube with ethylene diamine tetraacetic acid were to be analyzed for biochemistry and leukocyte [PMNL] counts.

PCT measurement: This was done by the electrochemiluminescence immunoassay [ECLIA]
[Cobas e 411 immunoassay analyzers, Roch, Germany], acting via the sandwich principle.It calculates the analyte concentration of each sample in ng/ml in an automatic fashion with a measuring range of 0.02 to 100 ng/ml and the coefficient of variability of 8%.

PEC index: This is a serum bioscore, calculated by the formula; PEC index = PCT × [ESR + CRP].
Statistical analysis: All data analysis was done using the SPSS version 25.Categorical data were presented as numbers and percentages and were compared using the Chi-Square Test.The normality of continuous data was initially checked by the Shapiro-Wilk test.All continuous data were not parametric, so we present it as Interquartile range and median [IQR].Within-group comparison was done using the Kruskal-Wallis test, and every 2 groups were compared using the Mann-Whitney U-test.

RESULTS
In the current work, patients were mainly in the sixth decade of life and majority were males [85.3%].Hypertension reported for 52% of all patients and diabetes for 47.5%.the causes of liver diseases were hepatitis C-virus infection, bilharziasis, concomitant HCV and bilharziasis, then NAFLD and finally hepatitis B and autoimmune diseases.Groups were comparable regarding patient demographics, except for significant differences regarding cause of liver disease [Table 1].
Table [2] presented the laboratory data among study groups.There were no significant differences between groups regarding liver enzymes [ALT and AST] and serum albumin.In addition, there was no significant differences were recorded regarding hemoglobin concentration.Otherwise, there were significant differences regarding INR, total and direct bilirubin, serum urea and creatinine, TLC, platelets, ESR, CP, PCT, PMNL and PEC.The PCT was significantly increased in group B than group A than group C [0.945 ± 0.732, 0.546 ± 0.650 and 0.126± 0.12, respectively].The PMNL was absent in Cgroup and significantly increased in B than A groups [2185± 1850.8 vs 55± 49, respectively].Finally, the PEC was significantly higher in B, than A and C groups [96± 32 vs 32.9± 18 and 2.4± 1.6, successively].
Table [3] presented comparison between groups A and C regarding laboratory investigations.Results showed that, both groups were comparable regarding serum albumin, INR, AST, ALT, TLC, hemoglobin, and platelet count.Otherwise, total and direct bilirubin, creatinine and urea, ESR, CRP, PCT, and PEC were significantly higher among A than C group.
In addition, there was a statistically significant increase of total and direct bilirubin, INR, AST, urea and creatinine, TLC, ESR, CRP, PCT and PEC, but significant decrease of platelets in B than C groups [Table 4].
Comparing A and B groups, revealed significant reduction of platelets and significant increase of total and direct bilirubin, INR, urea and creatinine, TLC, ESR, CRP, PCT, PMNL, and PEC in B than A group [Table 5].
Table [6] and figure [1] revealed the sensitivity and best cutoff of different markers.For example, PCT at 0.48 had sensitivity of 86% and specificity of 92.20%.However, the best sensitivity was recorded for PEC [92.0%] followed by CRP [88.0%].In addition, the best specificity was recorded for PEC [97.8%] followed by PCT [92.20%].

DISCUSSION
In our study, we included 120 Egyptian patients with cirrhosis, 40 of them had an SBP, and other 40 had clear ascites and the last 40 are without ascites.The most prevalent cause of liver cirrhosis in our study was HCV, which represent 68% of the participants, followed by Bilharziasis [15%], followed by mixed HCV and Bilharziasis [8.3%], followed by nonalcoholic fatty liver disease [5%], followed by HBV [1.6%] and Autoimmune hepatitis [1.6%].This is in agreement with the previous study done by Elbahrawy et al. [10] , who reported that viral hepatitis [HCV] is the main cause of chronic hepatitis and liver cirrhosis in Egypt.The cause of liver cirrhosis was significantly different between the study groups [P value < 0.04].
In our study, the mean and SD age of the patients was around 60 years old, which is in line with the results of Popoiag et al. [11] who found that the mean and SD of the patients with SBP was 59.29±11.30.
As regard the age in our study there is no significant difference between the 3 groups.
In terms of the gender distribution of the participants, we found that male with SBP was more prevalent than females, which agreed with the findings of Popoiag et al. [11] who found that 66.7% of the patients with SBP were male.This male predominance may be explained by that, estrogen in females may have a protective role against fibrosis in chronic liver disease patients by inhibiting stellate cells, which are responsible for fibrogenesis in the liver [12] .
Regarding Billirubin, we found that the total and direct billirubin were significantly higher in group the SBP patients [P value = 0.001] which is in line with Elsadek et al. [13] .
In terms of renal functions, we found a significant elevation in the level of urea and creatinine in the group of SBP [group B] in comparison with group A and C.This renal impairment in patients with SBP occurred due to that, the bacterial endotoxins and inflammatory cytokines in patients with SBP will increase the nitric oxide production in the systemic circulation via bacterial translocation, impairing the hepatic clearance and portosystemic shunting.This arterial and splanchenic vasodilation, causing decreased effective perfusion of the kidneys [14] .
In terms of cytological examination of ascetic fluid aspiration, Patients in group B had ascetic fluid inflammatory response due to bacterial infection which was identified by AF PMNL count ≥ 250/HPF, which is similar to the results of Elsadek et al. [13] .Also, other serum levels of acute phase reactants; ESR, CRP, and PCT were significantly higher in group B than in groups A, and C [P value < 0.001 for all].This is in line with previous studies [13,15,16] .This could be explained by SBP results in the activation of cytokine synthesis and innate immunity in response to circulating bacterial endotoxins [17] .
As regard to PCT in our study there is significant increase in group B [0.945 ± 0.732] in comparison with group A [0.546 ± 0.650] and C [0.126± 0.12] with P value=0.00.
PCT elevation in group B confirms the fact that PCT is elevated in acute bacterial infections and reaches the highest serum level in severe infections and sepsis as it is enhanced by a systemic inflammatory response.However, is not elevated by a viral infection or autoimmune inflammation.So, it can be used for the differentiation between viral, and bacterial infections [18,19] .
Procalcitonin has been considered as a novel index of inflammation marker of bacterial infection [20] .
In our study the area under the curve for procalcitonin in predicting SBP [0.82], are in accordance with the diagnostic capacity of procalcitonin reported in the cirrhotic population [AUC: 0.68-0.89] [21].
In Yang et al. [22] 's meta-analysis, procalcitonin was found to have a sensitivity of 0.82 and specificity of 0.86 with AUROC of 0.92 for diagnosis of SBP, which agree with our findings.
El Hasafy et al. [23] data showed a significantly raised PCT in cirrhotic patients with infected ascites than those with sterile ascites, which is in line with our study results.Despite that, other studies reported that the serum PCT was not a beneficial marker for predicting SBP [30% sensitivity] [24] .The small sample size [n = 32] of their study could explain this contradictory result.
As regards the CRP, our study showed that the CRP increased significantly in Group B in comparison with group A and C.This is in line with the results of two studies [13,23] who showed that CRP levels in the patients with SBP were more elevated than those in sterile ascites.
In our study CRP at the optimal Cutoff was 23.5 mg/L and 88% sensitivity and 75.6% specificity, AUC [0.85], which agree with the findings of Yuan et al. [25] , but disagree with Papp et al. [26] who reported a cutoff of 10 mg/L for CRP [AUC: 0.93] in a large study of patients with cirrhosis associated bacterial infections.
The diagnosis of SBP has been examined in several studies that investigated the combination of procalcitonin and CRP.These studies have been comprehensively summarized in the metaanalysis conducted by Lin et al. [27] .The pooled sensitivity and specificity for procalcitonin were reported to be 79% and 89% respectively.The combined sensitivity and specificity for CRP was 77% and 85%, respectively, which aligns with our findings.
Although CRP was more sensitive than PCT in this study [88%% vs. 86%], the sensitivity and specificity of serum PCT at a cutoff value of 0.48 for SBP diagnosis were relatively higher than those of ESR at a cutoff value of 30.5 mm/h [86% vs. 84%].PCT appears to be more effective than other pro-inflammatory indicators like ESR and CRP for diagnosing septic illnesses because it rises more quickly and with more specificity than other markers.This is in line with previous studies [13,19] , and disagrees with the results of Lesińska et al. [24] , who reported that serum PCT could not distinguish patients with and without SBP.The small sample size [n = 32] of their study could explain this difference.
As regards the ESR, we found that it was significantly higher in group B than in groups A, and C [P value < 0.001].This agree previous studies [13,15,16] .The ESR elevation in our patients could be explained by SBP results in the activation of cytokine synthesis and innate immunity in response to circulating bacterial endotoxins as reported by Deschênes and Villeneuve [17] .
The current work reports the value of the PEC index in the diagnosis of spontaneous Bacterial Peritonitis, which is made by measurement of procalcitonin, ESR, and CRP.

PEC index = [PCT × [ESR + CRP]].
As regards the PEC index, in our study the PEC index is significantly increase in group B [96± 32] in comparison with group A [32. 9± 18]  and group C [2.4± 1.6] with [P value < 0.001], and the sensitivity and specificity in diagnosis of SBP was [92% and 97.8%] at cut-off value 25.This was in agreement with Elsadek et al. [13]   , who found a cutoff value of 20, the sensitivity and specificity of serum PEC index for SBP diagnosis [98.33% and 96.67%, respectively] Our study found that the peritoneal fluid epithelial cell [PEC] was more effective than the serum markers procalcitonin [PCT], erythrocyte sedimentation rate [ESR], and C-reactive protein [CRP] in diagnosing spontaneous bacterial peritonitis [SBP].The PEC index is superior to any of its individual components for diagnosing SBP due to its ability to mathematically compensate for the varying degrees of sensitivity and specificity of each marker.This combination helps to minimize false positive and false negative results.

Conclusion:
PEC index is effective in diagnosis of spontaneous Bacterial Peritonitis, which made by measurement of procalcitonin, ESR and CRP, which we called the PEC index as a predictive value in Decompensated liver disease ascites.

Figure 1 :
Figure 1: ROC curve of Sensitivity and specificity of serum marker cutoff point

Table [ 1
]: Demographic Data among study groups NB: Percentages in groups were calculated from the total of each variable [not from the groups].HTN: hypertension; DM: Diabetes Mellitus; HCV: Hepatitis -C virus; HBV: Hepatitis B virus; NAFLD: non-alcoholic fatty liver disease.* Indicate significant differences.

Table [ 3
]: Comparison of Laboratory test between Group C and A