Evaluation of Neutrophil-to-Lymphocyte and Platelet-to-Lymphocyte Ratios as Reliable Biomarkers for the Diagnosis of Perforated Acute Appendicitis: A Retrospective case control study

Background To investigate the relationship among neutrophil to lymphocyte ratio (NLR),platelet to lymphocyte ratio (PLR) of patients with perforated acute appendicitis and its clinical signicance (cid:0) Methods The present study selected 243 patients who underwent appendectomy presented with acute appendicitis from January 2013 and December 2015 (cid:0) All patients were conrmed by pathology (cid:0) AA patients were divided into Perforated acute appendicitis(PAA)group and Non-perforated acute appendicitis (cid:0) NPAA (cid:0) group (cid:0) The routine blood test results were collected pre-operation and calculated the NLR and PLR (cid:0) To analyze the relationship among the NLR,PLR, Age, Gender, WBC count, Operation approach in PAA group and NPAA group.


Results
The NLR and PLR of PAA group were signi cantly higher than that of the NPAA group (P < 0.0001 and P = 0.039);Cut-off value NLR (≥ 8.96) and PLR (≥ 173.03) of were PAA group were signi cantly higher than that of the NPAA group (P < 0.0001 and P = 0.012). Multiple logistic regression analysis identi ed NLR as independent variables.

Conclusions
We suggest that the preoperative NLR and PLR are useful parameters to differentiate among PAA and NPAA.

Background
Acute appendicitis (AA) is almost a daily occurrence in the general surgery department. Despite being just so common, but the mechanism of AA remains poorly understood in the past few decades. It still requires early diagnosis and prompt management to avoid complications such as perforation, subsequent peritonitis and appendiceal abscess nowadays 1 . In the development of in ammation of the appendix vermiformis, the direct luminal obstruction is the major pathophysiological mechanism. And recent theories associated with appendicitis focus on genetic factors, environmental in uences and infection.
The diagnosis of acute appendicitis is clinical symptoms, scoring systems and imaging methods. There are few methods for evaluating the severity of appendicitis itself before surgery. In many surgical centers, it is attempt to delay appendectomy for 12-24 hours due to decrease the operative risk during the night.
And it not seems to increase complications 2 . Biomarker re ect the severity of acute appendicitis may be correlated with data for in ammatory markers such as white blood cell count (WBC), neutrophil count, platelet count and C-reactive protein (CRP) 3,4 . Neutrophils regulate mast cells, epithelial cells and macrophages, and play an important role in in ammatory events. NLR is a marker of in ammation in various diseases and Changes in the NLR can be an early sign of bacterial and viral infections. Another parameter that has been used for the diagnosis of infection is the PLR. Platelets are cells that help in modulating various in ammatory conditions; therefore, changes in PLR may be a useful indicator of acute infection, including AA. NLR, PLR, in particular, is regarded as an in ammatory marker not only in acute in ammatory diseases, but also in several chronic in ammatory diseases 5 , including cancer 6 . The aims of this study were to determine the value of NLR and PLR in diagnosing AA and predicting its severity.

Materials And Methods
This retrospective study included 243 patients (150 men, 93 women), for whom su cient data were valuable. They had undergone appendectomy for AA, operated by the same trained surgical team at the Department of General Surgery, Wuhan Third Hospital, between January 2013 and December 2015. All patients involved in this study gave their informed consent. The institutional review board and Ethics Committee of The Third Hospital of Wuhan approved this study. All patients have given their informed consent. To divide the patients into two groups depended upon whether perforated or not, we calculated the cutoff values of Demographic characteristics such as Age, WBC count, NLR, PLR using receive operating characteristic curve (ROC) analyses. Exclusion criteria included the following: hematological disorders; chronic liver or kidney disease; chronic obstructive pulmonary disease; asthma; any viral, bacterial or parasitic infection; cancer or autoimmune disease. Patients with incomplete records were also excluded.

Statistical analysis
Data are presented as mean ± SD. Differences between the groups were analyzed using the x 2 test or Student's t test. Odds ratios (OR) with 95% con dence interval (CI) were calculated on the basis of multivariate analysis, performed using logistic regression. Recommended cut-off values of NLR, PLR, WBC were determined using ROC analysis. Statistical analyses were performed using the SPSS 22.0 (SPSS Inc, Chicago, Illinois) at a signi cance level of P < 0.05.

Result
A total of 263 patients were enrolled in the study, after the exclusion of 20 patients owing to multiple missing values or non-operation. The data of 243 patients were retained (Table 1) There was no signi cant difference in Gender, WBC count.  (Table 3).  The results of the multiple logistic regression analysis are presented in Table 4. The Age, NLR was signi cant independent predictors of a diagnosis of PAA. Discussion AA is part of the most common surgical emergencies 7 . Diagnosis of AA largely depends on a clinical diagnosis supported by laboratory and imaging studies. AA is a well-known entity with remarkable signs and symptoms, but there is not a single parameter to diagnose it easily. Complicated appendicitis occurs once the appendix has become gangrenous and/or has perforated with numerous degrees of peritonitis.
The rate of complicated appendicitis is slowly increasing and has been reported at an incidence of 12-30% 8,9 . A recent study suggests that perforation is not necessarily the inevitable result of appendiceal obstruction. PAA may occur more commonly in patients with altered in ammatory responses or alterations in the colonic microbiome 10 . In the elderly people, the morbidity rate and mortality rate are higher in the presence of PAA 11,12 . In our study, the mean age of PAA group obviously older than NPAA group. Appendectomy is the gold standard for the management of AA since the late 1800s. And subsequent technological advances and improvement in the 1990s, the LA has gradually become a mainstay of treatment for AA. Some studies indicate that LA provides advantages in terms of shorter length of stay, less postoperative pain and faster recovery time, but there is a controversy with the application of LA in PAA 12 . A range of novel biomarkers has been suggested during the past decade, including WBC and CRP, some studies have shown that increase in CRP and WBC are associated with the severity of AA, but these do not have external validity. In this study, we also found that NLR, PLR are reliable predictors of PAA, and NLR is signi cant independent predictors of diagnosis of PAA.
NLR is a novel in ammatory marker and the determination of NLR is a simple test can be easily ascertained using blood parameters involved in the complete blood count. Goodman 13 rst suggested that the use of NLR in the diagnosis of AA. Then a number of studies showed that NLR played a useful role in the diagnosis of AA and was different between non-complicated AA and complicated AA. Markar SR 14 has demonstrated that NLR is greater diagnostic accuracy than either WBC or CRP alone in AA and is an independent predictor of positive appendicitis histology. Takayuki Shimizu 15 demonstrated that a higher NLR is closely associated with severe appendicitis. In a retrospective study by Kahramanca 16 reported that an NLR cutoff value of 5.74 was found to be critical for complicated Acute Appendicitis.
Furthermore, Ishizuka 17 demonstrated that NLR above 8 was signi cant for gangrenous appendicitis.
Khan A 18 con rmed that an NLR > 6.36 or CRP > 28 were statistically associated with complicated acute appendicitis, and NLR had a better area under the ROC curve compared to CRP for predicting severe appendicitis. Similarly, in our study, the higher NLR was observed in the perforated appendectomy group (16.08 ± 10.48) and a cutoff value of 8.96 was found to be critical for PAA. Multiple logistic regression analysis determined that the examination of NLR is a signi cant screening test for the diagnosis of PAA. This conclusion supports the consequence of our present study that NLR is signi cant independent predictors of diagnosis of PAA.
PLR is a combination of the PLT and lymphocyte counts. The research of PLR is focused on cancers and in ammation. In a recent study, NLR, and PLR were evaluated in patients treated for familial Mediterranean fever 19 ; PLR was deemed increased in patients with the condition compared with the control group. In another study by Nazik 20 , use of NLR, PLR, IMA, and ESR values may be helpful in the diagnosis of appendicitis. In our study, PLR was increased with in ammation and was higher in the perforated appendectomy group (237.51 ± 149.98). However, multiple logistic regression analysis determined that the examination of PLR is not an independent factor for the diagnosis of PAA.
Our study has several limitations. Firstly, this retrospective study was carried out without estimating adequate sample size, so it is di cult to fully ascertain if there are unknown confounding variables that affect NLR and PLR validity. And only patients who underwent appendectomy were included. Secondly, symptom onset to blood test time interval was not included in this study. Lastly, other clinical data such as symptoms and physical examinations were not investigated in this study. This is a study showing promising role of NLR, PLR at PAA.

Conclusion
From the above discussion, the conclusion can be reached that NLR, PLR are a good predictor of PAA. And NLR is signi cant independent predictors of a diagnosis of PAA.

Declarations
Ethics approval and consent to participate The consent was obtained from the patients for publication of this paper. The ethics committee of the Wuhan Third Hospital has approved this study.

Consent for publication
Written informed consent was obtained from the patients for publication.

Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
HZ and JLX contributed to the conception of the study. HZ contributed signi cantly to analysis and manuscript preparation; HZ performed the data analyses and wrote the manuscript; JTH, XWX and HBX helped perform the analysis with constructive discussions.