Acute appendicitis (AA) is the most common cause of acute abdominal pain requiring urgent surgical intervention. The life-long risk of developing AA is 7%. The majority of the AA cases are simple appendicitis (SA) without any complication. Acute complicated appendicitis (CA) is a serious problem that delays the healing process of patients and causes prolonged length of hospital stay and increased medical costs. Increased time from onset of symptoms to surgical treatment is a risk factor for CA. A successful treatment depends on early diagnosis and treatment.
Many studies have been conducted for early diagnosis and treatment of AA and its complications. There are many studies indicating that increased white blood cell count (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) can be used as a biomarker to show CA. However, despite the use of these biomarkers, it is not easy to differentiate between SA and CA. Therefore, new and more specific biomarkers are needed.
Immature granulocytes are indicative of increased myeloid cell production and these have been shown to increase in infectious and inflammatory conditions. Immature granulocyte count (IGC) and immature granulocyte percentage (IG%) are new biomarkers indicative of inflammation that can be easily and rapidly measured from routine complete blood count. Studies have demonstrated the ability of IGC and IG% to predict infectious conditions. To the best of our knowledge, there are very few studies on IGC and IG% indicating the diagnosis and presence or absence of CA; however, there is no study on IGC/neutrophil (IG/N) ratio. Therefore, we aimed to investigate the usability of IGC, IG% and IGC/neutrophil ratio (N ratio), new inflammatory markers, both in the diagnosis of AA and in differentiating SA from CA.
The study was designed as a single-center, retrospective cohort. The patients were selected among patients admitted to a tertiary emergency department and diagnosed with AA between March and September 2019. Our hospital has a capacity of 2000 beds and approximately 360,000 patients are admitted to the emergency department annually. The study was conducted in accordance with the Declaration of Helsinki and was approved by the local ethics committee of the institute. The study protocol was reviewed and approved by the independent review board of our institution (IRB No. 2019-314 obtained on October 10, 2019), written informed consent was obtained from all the patients, who agreed to participate in the study.
All patients were retrospectively reviewed on the hospital information-record system. Our patient population consisted of patients diagnosed with AA according to the ICD-10 (International Classification of Diseases) coding system in the emergency department. The exclusion criteria of our study were patients under the age of 18 years, pregnant patients and those with any comorbid diseases that may affect inflammation. All patients underwent appendectomy and were categorized into two groups as positive appendectomy (PA) and negative appendectomy (NA) according to their histopathological diagnosis. Subsequently, the patients were categorized into the CA and SA subgroups. Catarrhal and phlegmonous appendicitis were considered as SA, while gangrenous and perforated appendicitis and abscess were considered as CA. The laboratory results including demographic data and complete blood count (CBC) results were recorded.
WBC, neutrophil, IGC, IGC%, and also CRP were recorded in the patients' CBC examined during the application to the emergency department. NLR, PLR, and lymphocyte-to-monocyte ratio (LMR) were calculated by proportioning these parameters. Samples were drawn prior to antibiotic administration and patients did not use of NSAIDs or other anti-inflammatory agent. Blood samples were studied from the peripheral vein in Sysmex XN-1000 (Sysmex Corp., Kobe, Japan) automated hematological analyzer using ethylene diamine tetraacetic acid tube and the flow cytometry method. Normal values were respectively considered as 4–10.5 × 103 mm3 for WBC, 0–0.6 × 103 mm3 for IG%, 0–0.09 × 103 mm3 for IGC and 0–5 mg/dl for CRP.
Standard deviation and mean values were calculated for the continuous variables. Each of the independent variables was compared using the Chi-square test and according to suitability, the independent t-test. The descriptive statistical analysis of all variables was carried out using SPSS 18.0. The optimal cutoff value of WBC, CRP, IGC, IG%, and IGC/N parameters as diagnostic biomarkers in AA diagnosis and differential diagnosis of CA/SA was analyzed by receiver operating characteristic (ROC) analysis.
Our study included 262 patients who underwent appendectomy with the diagnosis of AA preoperatively. One hundred and fifty-nine patients were male (60.7%) and the mean age was 34.5 years. According to the pathology results, there were 20 patients (7.6%) in the NA group and 242 patients (92.4%) in the PA group. The rate of NA was statistically significantly higher in females than in males (60% vs. 37.7%, respectively, P = 0.043). The mean WBC, IGC, and CRP values were significantly higher in the PA group than in those with NA (P < 0.001 in each parameter). In addition, the mean NLR, IG% and IGC/N values were significantly higher, while the mean LMR was significantly lower in the PA group than in those with NA. The comparison between the PA and NA groups is shown in Table 1.
According to the pathology results of the patients with AA, there were 206 patients (85.1%) in the SA group and 36 patients (14.9%) in the CA group. According to gender, male patients were the majority in both the SA group and the CA group. The mean age of the CA group was significantly higher than that of the SA group (46.11 ± 16.68 vs. 35.14 ± 13.8, respectively, P < 0.001). The mean IGC, IGC/N and CRP values were significantly higher in the CA group than in the SA group (P < 0.001 in each parameter). In addition, the mean WBC, NLR, PLR, IG% values were significantly higher in the CA group than in the SA group. The comparison between the CA and SA groups is shown in Table 2.
The effectiveness of WBC, CRP, IGC, IG%, and IGC/N parameters in diagnosing AA and in differentiating CA from SA was calculated by plotting ROC curves [Figures 1 and 2]. The ability of IGC to predict AA was greater than that of other parameters. At a cutoff value of 15, which is the optimum cutoff value for IGC, the sensitivity was 98.3% and the specificity was 80%. Moreover, this showed that the sensitivity was higher than CRP and the specificity was close to CRP [Table 3]. At a cutoff value of 0.085, which is the optimum cutoff value for IGC/N, the sensitivity was 63.9% and the specificity was 72.3%. The sensitivity and specificity for the optimum cutoff value of IGC/N ratio in showing CA were similar to CRP [Table 4].
AA is a disease which is most commonly suspected and may require urgent surgical intervention in patients presenting to the emergency department with abdominal pain. In the initial evaluation of these patients, a comprehensive anamnesis and physical examination are followed by blood tests. Despite advanced imaging and laboratory tests, it is complicated by perforation in 18%–34% of AA cases. As CA rates increase, the mortality, morbidity, length of hospital stay, and medical cost will increase. Therefore, biomarkers that can be used both in the diagnosis of AA and in the early diagnosis of complications are needed.
In the diagnosis of AA, increased WBC count, CRP, and ESR are important, but not diagnostic. NLR and PLR are inexpensive, simple parameters that can be studied in almost any center and have recently been used in many diseases, including inflammatory conditions. In a recent study, NLR was found to be a useful parameter in the diagnosis of AA and in the differentiation between CA and SA. In this study, it was demonstrated that NLR is a useful parameter in the diagnosis of AA with a sensitivity of 73.3% and a specificity of 69.2% at a cutoff value of 3.5 and in the differentiation between CA and SA with a sensitivity of 79.1% and a specificity of 61.1% at a cutoff value of 5.6. In a study of 102 patients by Kim et al., it was indicated that only CRP was statistically significant, although WBC and CRP were found to be higher in the CA group than in the SA group. Moreover, in this study, serum delta neutrophil and myeloperoxidase index helped differentiate acute CA from uncomplicated appendicitis. The studies by Aydin et al. and Beecher et al. showed increased probability of CA in cases where NLR and CRP levels were high. In our study, a NLR of >3.62 supported the diagnosis of AA and a NLR of >5.08 supported the diagnosis of CA. We suggest that WBC, NLR, and PLR are more suitable because they are more sensitive in showing AA complications.
IG is a routine CBC parameter that is automatically measured by an automated blood cell analyzer and is recently begun to be used as a new inflammatory biomarker. This measures the fraction of immature circulating granulocytes or, in other words, the increase in myeloid cell production. These cells are an indicator of inflammation. In a study by Kim et al., it was reported that IG% had a sensitivity of 25% and a specificity of 96.7% in predicting CA at a cut-off value of 5%. In a study by Mathews et al., the mean IG% was significantly higher in CAs than in SAs (0.34 ± 0.14 vs. 0.29 ± 0.19, respectively, P = 0.02). In a study by Shin et al., it was reported that IG% showed a sensitivity of 67.7% and a specificity of 90% in predicting CA at a cutoff value of 1.4. In a study of 412 patients conducted in 2018, WBC, NLR, IGC, IG% were reported to be a parameter that can be used both in the diagnosis of AA and to show complication. In this study, it was shown that IGC was more specific in the diagnosis of AA compared to other parameters area under the receiver operating characteristic curve (AUC): 0.795, sensitivity: 55.5%, specificity: 96.1%), and IG% could predict CA better than other parameters (AUC: 0.979, sensitivity: 94.4%, specificity: 97.9%). However, the role of CRP in diagnosing AA and showing complication was not indicated in this study. In our study, we demonstrated the effectiveness of WBC, CRP, IGC, IG%, and IGC/N parameters in diagnosing AA and differentiating between CA and SA. To the best of our knowledge, there is no study including IGC/N ratio in the literature. In our study, we found that the ability of IGC to predict AA was greater than that of other parameters. At a cutoff value of 15, which is the optimum cutoff value for IGC, the sensitivity was 98.3% and the specificity was 80%. CRP and IGC/N ratio had the highest predictive values in differentiating between SA and CA. At a cutoff value of 0.085, which is the optimum cutoff value for IGC/N 0.085, the sensitivity was 63.9%, and the specificity was 72.3%.
Our study had some limitations. The first is the retrospective design of our study. The second is that it was not possible to include the time from onset of symptoms to the collection of samples, which is an important limitation as it may affect inflammation. Since the measurement of the IG parameter in the CBC was not available before March 2019, this study included cases after that date. Thus, the number of patients was limited. In addition, clinical symptoms and physical examination other than laboratory findings were not analyzed in this study.
IG is a routine CBC parameter that is rapid and does not incur additional cost to the patient. Based on the results of our study, we can speculate that IGC is a reliable marker in the diagnosis of AA. An IGC value of >15 in routine CBC is an important and early indicator in the diagnosis of AA but immature granulocytes and derivatives (IGC, IG%, and IGC/N) cannot be used for predicting CA because of low sensitivity and specificity.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
1. Dhillon NK, Barmparas G, Lin TL, Alban RF, Melo N, Yang AR, et al Unexpected complicated appendicitis in the elderly diagnosed with acute appendicitis Am J Surg. 2019;218:1219–22
2. Storm-Dickerson TL, Horattas MC. What have we learned over the past 20 years about appendicitis in the elderly? Am J Surg. 2003;185:198–201
3. Papandria D, Goldstein SD, Rhee D, Salazar JH, Arlikar J, Gorgy A, et al Risk of perforation increases with delay in recognition and surgery for acute appendicitis J Surg Res. 2013;184:723–9
4. Parekh D, Jain D, Mohite S, Phalgune D. Comparison of outer diameter of appendix, c-reactive protein, and serum bilirubin levels in complicated versus uncomplicated appendicitis Indian J Surg. 2019;4:1–5
5. Celik B, Nalcacioglu H, Ozcatal M, Altuner TY. Role of neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio in identifying complicated appendicitis in the pediatric emergency department Turk J Trauma Emerg Surg. 2019;25:222–8
6. Shin DH, Cho YS, Cho GC, Ahn HC, Park SM, Lim SW, et al Delta neutrophil index as an early predictor of acute appendicitis and acute complicated appendicitis in adults World J Emerg Surg. 2017;12:32
7. Ünal Y. A new and early marker in the diagnosis of acute complicated appendicitis: Immature granulocytes Ulus Travma Acil Cerrahi Derg. 2018;24:434–9
8. Nahm CH, Choi JW, Lee J. Delta neutrophil index in automated immature granulocyte counts for assessing disease severity of patients with sepsis Ann Clin Lab Sci. 2008;38:241–6
9. Seok Y, Choi JR, Kim J, Kim YK, Lee J, Song J, et al Delta neutrophil index: A promising diagnostic and prognostic marker for sepsis Shock. 2012;37:242–6
10. Gaitini D, Beck-Razi N, Mor-Yosef D, Fischer D, Ben Itzhak O, Krausz MM, et al Diagnosing acute appendicitis in adults: Accuracy of color Doppler sonography and MDCT compared with surgery and clinical follow-up AJR Am J Roentgenol. 2008;190:1300–6
11. Shahbazipar M, Seyedhosseini J, Vahidi E, Motahar Vahedi HS, Jahanshir A. Accuracy of ultrasound exam performed by emergency medicine versus radiology residents in the diagnosis of acute appendicitis Eur J Emerg Med. 2019;26:272–6
12. McGowan DR, Sims HM, Zia K, Uheba M, Shaikh IA. The value of biochemical markers in predicting a perforation in acute appendicitis ANZ J Surg. 2013;83:79–83
13. Hallan S, Asberg A. The accuracy of C-reactive protein in diagnosing acute appendicitis – A meta-analysis Scand J Clin Lab Invest. 1997;57:373–80
14. Yazar FM, Urfalioglu A, Bakacak M, Boran ÖF, Bülbüloǧlu E. Efficacy of the evaluation of inflammatory markers for the reduction of negative appendectomy rates Indian J Surg. 2018;80:61–7
15. Günay Y, Taşdöven I, Kozan R, Koca S, Caǧlar E. Investigation of predictive value of complete blood count in the diagnosis of acute complicated appendicitis Med Bull Haseki. 2019;57:26–31
16. Kim OH, Cha YS, Hwang SO, Jang JY, Choi EH, Kim HI, et al The use of delta neutrophil index and myeloperoxidase index for predicting acute complicated appendicitis in children PLoS One. 2016;11:e0148799
17. Aydin OU, Soylu L, Dandin O, Uysal Aydin E, Karademir S. Laboratory in complicated appendicitis prediction and predictive value of monitoring Bratisl Lek Listy. 2016;117:697–701
18. Beecher SM, Hogan J, O”Leary DP, McLaughlin R. An appraisal of inflammatory markers in distinguishing acute uncomplicated and complicated appendicitis Dig Surg. 2016;33:177–81
19. Kratz A, Maloum K, O'Malley C, Zini G, Rocco V, Zelmanovic D, et al Enumeration of nucleated red blood cells with the ADVIA 2120 Hematology System: An International Multicenter Clinical Trial Lab Hematol. 2006;12:63–70
20. Harris N, Jou JM, Devoto G, Lotz J, Pappas J, Wranovics D, et al Performance evaluation of the ADVIA 2120 hematology analyzer: An international multicenter clinical trial Lab Hematol. 2005;11:62–70
21. Kim HW, Ku S, Jeong SJ, Jin SJ, Han SH, Choi JY, et al Delta neutrophil index: Could it predict mortality in patients with bacteraemia? Scand J Infect Dis. 2012;44:475–80
22. Rhee NG, Kim MJ, Kim HJ, Chung SP, Lee HS, Lee JW. Assessment of perforation of acute appendicitis using the delta neutrophil index reflecting peripheral immature granulocyte count J Korean Soc Emerg Med. 2012;23:389–93
23. Mathews EK, Griffin RL, Mortellaro V, Beierle EA, Harmon CM, Chen MK, et al Utility of immature granulocyte percentage in pediatric appendicitis J Surg Res. 2014;190:230–4
24. Shin DH, Cho YS, Kim YS, Ahn HC, Oh YT, Park SO, et al Delta neutrophil index: A reliable marker to differentiate perforated appendicitis from non-perforated appendicitis in the elderly J Clin Lab Anal. 2018;32:22177