Peroperative Findings in Acute Appendicitis: Relationship with Neutrophil-to-Lymphocyte and Platelet-to-Lymphocyte Ratios

By Faran Hamid¹, Saeed Bin Ayaz², Muhammad Asif¹, Muhammad Nabeel Imran¹, Adnan Mehraj¹, Naheed Akhtar¹

Affiliations

1. Department of General and Laparoscopic Surgery, Sheikh Khalifa Bin Zayed Al Nahyan Hospital, Muzaffarabad, Pakistan
2. Department of Rehabilitation Medicine, Sheikh Khalifa Bin Zayed Al Nahyan Hospital, Muzaffarabad, Pakistan

doi: 10.29271/jcpsp.2025.10.1325

ABSTRACT
Objective: To ascertain whether the platelet-to-lymphocyte ratio (PLR) and neutrophil-to-lymphocyte ratio (NLR) are reliable diagnostic tools for acute appendicitis.
Study Design: An analytical study.
Place and Duration of the Study: Department of General and Laparoscopic Surgery, Sheikh Khalifa Bin Zayed Al Nahyan Hospital, Muzaffarabad, Pakistan, from January to June 2022.
Methodology: This study was conducted using consecutive sampling of patients aged ≥16 years. Admission haemogram was used to calculate the NLR and PLR. These ratios were compared with peroperative findings regarding the stage of inflammation in the appendix. Sensitivity, specificity, and accuracy rates were compared and evaluated using a non-parametric (empirical) method for receiver operating characteristic curve analysis.
Results: The median age of patients was 26 years, with a male-to-female ratio of 1:1.03. NLR had a sensitivity of 76.9%, a specificity of 93.3%, a negative predictive value (NPV) of 94.2%, and an accuracy of 70.2% in separating complicated from uncomplicated appendicitis. Moreover, it had a sensitivity of 73%, a specificity of 100%, an NPV of 98%, and an accuracy of 73.03% in separating non-inflamed appendix from uncomplicated appendicitis. PLR did not show any significant differentiation between non-inflamed appendix and uncomplicated appendicitis (p = 0.8), and its accuracy for differentiating complicated from uncomplicated appendicitis was also low, that is, 48.2%.
Conclusion: NLR is a helpful diagnostic tool that can predict uncomplicated and complicated appendicitis and differentiate between them. However, relying solely on NLR for diagnosing appendicitis is not advisable. PLR does not have similar predictability. More research needs to be done to find additional biomarkers for NLR and PLR to improve their predictability as a diagnostic tool.

Key Words: Appendicitis, Biomarker, Negative appendectomy, Neutrophil-to-lymphocyte ratio, Perforation, Platelet-to-lymphocyte ratio, Sensitivity, Specificity.

INTRODUCTION

The most common cause of acute abdominal discomfort is acute appendicitis, accounting for as much as 25–30% of cases.¹ This disease has a lifetime occurrence of about 7%, and the usual presenting symptoms are anorexia, vomiting, nausea, and lower abdominal discomfort.² However, these classical symptoms are absent in about 40% of people. When acute appendicitis is complicated by an abscess, phlegmon, or perforation,  it  is  called  a  complicated  appendicitis.

Nearly one-third of individuals with acute appendicitis develop these complications and have a higher incidence of mortality and morbidity. In a recent Turkish study, 382 (66.3%) patients had non-complicated appendicitis, and 194 (33.7%) had associated complications.³

Although acute appendicitis is a common medical condition, diagnosing it can occasionally be quite difficult, particularly in patients who have complicated or severe appendicitis or who present atypically. Generally, the clinical characteristics, blood tests, and radiological evaluations are the primary diagnostic pillars. The Alvarado score, RIPASA score, and RIFT score are some of the screening and scoring instruments that have been used to diagnose acute appendicitis. However, these grading systems do not accurately predict the severity of acute appendicitis and have low sensitivity and specificity.⁴ While computed tomographic (CT) scans have the potential to lower the negative appendectomy rate from 24% to 7.6%,⁵ these invaluable diagnostic modalities are costly and not easily accessible in many locations. Therefore, it is imperative to adopt low-cost, user-friendly, and easily interpretable simple diagnostic modalities to diagnose acute appendicitis and lower the over- all  rate  of negative  appendectomies.

When a patient experiences pain in the right iliac fossa, basic blood tests such as complete blood count (CBC) are performed as a baseline study. CBC can be used as a diagnostic tool to detect acute appendicitis. It is an economical and easily accessible test that measures differential count, platelet count, total leucocyte count, and haemoglobin level. Most people with appendicitis have elevated white blood cell (WBC) count; however, a raised WBC count does not discriminate between simple and severe appendicitis. Elevated serum bilirubin levels may serve as a signal for appendix perforation; however, they are not sensitive or specific enough.⁶

The CBC can be used to calculate the neutrophil-to-lymphocyte ratio (NLR), with a reference value of 1.9 ± 0.6,⁷ an easy-to-use and reasonably priced indicator of inflammation. According to a recent meta-analysis, NLR can aid in the diagnosis of appendicitis and help assess its severity.⁸ Similarly, the platelet-to- lymphocyte ratio (PLR) with a reference value of 91.77 ± 26.95,⁷ has similar implications in predicting the diagnosis of uncomplicated and complicated acute appendicitis. This can help in prioritising surgical cases and identifying the patients who can be monitored for conservative treatment. This study aimed to assess the capacity of NLR and/or PLR to distinguish among a non-inflamed appendix, uncomplicated appendicitis, and complicated appendicitis.

METHODOLOGY

A case series was conducted at the Department of General and Laparoscopic Surgery, Sheikh Khalifa Bin Zayed Al Nahyan Hospital, Muzaffarabad, Pakistan, from January to December 2022. From the previous area under the receiver operating characteristic (ROC) curve (AUC) values of 0.715² for uncomplicated and 0.727² for complicated appendicitis, as observed in an earlier study, a minimum sample size of 73 was determined using MedCalc version 19.1.3 (MedCalc Software, Ostend, Belgium). For the calculation, the null hypothesis value was set at 0.5, the needed significance level was set at 0.05, and power of the test was set at 90%. The minimum sample size estimated for uncomplicated appendicitis was 45, and for complicated appendicitis, it was 22. In this investigation, a non-probability consecutive sampling strategy was employed for sampling. All patients (age ≥16 years) of both genders presenting with pain in the abdomen (generalised pain in the abdomen, pain in the right iliac fossa, or peri-umbilical pain), nausea, vomiting, anorexia, and fever were included in the study. This study did not include patients with pregnancies or those with other significant comorbidities.

Informed consent was obtained from each patient, and the details were recorded. All patients had a preoperative clinical diagnosis based on patient history, clinical examination, and laboratory tests (primarily blood tests). The NLR and PLR were calculated from the admission haemograms evaluated using an automated haematology analyzer, and the ratios were compared with the peroperative findings on the stage of appendiceal inflammation. A differentiation methodology was adopted for the peroperative findings of acute appendicitis, which were later confirmed through histopathological evaluation taken as the gold standard.^2,9,10 The appendix retrieved after operation and histopathological evaluation was differentiated into non-inflamed appendix, uncomplicated appendicitis, and complicated appendicitis. Uncomplicated appendicitis was defined as an appendix with inflammation but without pus, phlegmon, gangrene, or perforation, while complicated appendicitis was defined as phlegmonous, purulent, gangrenous, or perforated appendicitis.

During the selection process, a total of 164 patients were included. MedCalc version 19.1.3 and SPSS version 24.0 (IBM Corp., Armonk, NY) were used to analyse all the data. The quantitative variables of interest were analysed for normality using the Shapiro-Wilk test in SPSS before statistical analysis. Age, length of stay at the hospital, NLR, and PLR did not follow a normal distribution. Therefore, the median and interquartile range (IQR) were observed for these variables. Categorical variables were expressed as frequencies and percentages. The Kruskal-Wallis and the Pearson's Chi-square goodness-of-fit tests were used for initial calculations (Table I). The sensitivity, specificity, and accuracy of haematological ratios were compared and evaluated using a non-parametric (empirical) method for ROC curve analysis. The method of DeLong et al.¹¹ was used to calculate the standard error of the AUC, and the binomial confidence interval was also calculated for the AUC. The AUC indicated how well the marker distinguished between an uninflamed appendix, uncomplicated appendicitis, and complicated appendicitis. For every biomarker, cut-off values, accuracy rates, positive and negative predictive values, and sensitivity and specificity with 95% confidence intervals were calculated. The cut-off values were defined at the point where Youden’s statistic (J) reached its maximum.¹² These cut-off values were used to determine the NLR and PLR values that differentiated patients with a normal appendix from those with uncomplicated appendicitis, and those with uncomplicated appendicitis from those with complicated appendicitis. Combining NLR and PLR with clinical evaluation and imaging enhances diagnostic accuracy in distinguishing uncomplicated from complicated appendicitis. The sensitivity and specificity of NLR and PLR were assessed to identify patients with appendicitis, thereby reducing the risk of missed diagnoses (sensitivity) and minimising the likelihood of misdiagnosing patients without appendicitis, thus preventing unnecessary surgeries (specificity). The efficient use of these markers can reduce unnecessary imaging and surgeries, optimising resource utilisation in healthcare settings. A p-value of ≤0.05 was necessary to determine statistical significance.

Table I: Frequencies and percentages for qualitative variables, and median and IQR for quantitative variables.

Variables	Normal appendix (n = 10)	Uncomplicated appendicitis (n = 89)	Complicated appendicitis (n = 65)	p-values
Age in years (Median, IQR)	27 (17)	26 (11)	26 (10)	0.240
Length of hospital stay in days (Median, IQR)	2 (1)	2 (2)	2 (2)	0.886
Male	3 (30%)	40 (44.9%)	34 (52.3%)	<0.001
Female	7 (70%)	49 (55.1%)	31 (47.7%)	<0.001
NLR* (Median, IQR)	1.34 (0.76)	2.79 (2.15)	8.3 (7.18)	<0.001
PLR** (Median, IQR)	106.8 (82.48)	113.1 (73.61)	205 (149.65)	<0.001
*Neutrophil-to-lymphocyte ratio, **Platelet-to-lymphocyte ratio.

Table II: Diagnostic accuracy, predictive values, and P-values of NLR and PLR in uncomplicated versus complicated appendicitis.

Parameters	Cut-off values	Sensitivity	Specificity	NPV	PPV	Accuracy	CI	AUC	p-values
Uncomplicated appendicitis
NLR€	>0.192	73	100	98.0	100.0	73.03%	0.786 to 0.928	0.869	<0.001*
PLR£	≤110.38	47.19	40.00	91	5.6	12.81%	0.422 to 0.626	0.525	0.8*
Complicated appendicitis
NLR	>5.6	76.92	93.26	94.2	74	70.18%	0.833 to 0.937	0.893	<0.001*
PLR	>189	53.85	94.38	89.1	70.6	48.23%	0.691 to 0.831	0.766	<0.001*
€Neutrophil-to-Lymphocyte Ratio £Platelet-to-Lymphocyte Ratio *ROC curve analysis using method of DeLong et al.11

Figure 1: The ROC curve analysis of NLR and PLR for both uncompli-cated and complicated appendicitis.

RESULTS

A total of 164 patients, with a median age and IQR of 26 (10) years who were operated upon for appendicitis, were analysed. There were 87 (53%) females and 77 (47%) males. Table I presents patients’ demographics and related results. Sixty-five patients had complicated appendicitis, eighty-nine had uncomplicated appendicitis, and ten had a normal appendix.

Table II provides comprehensive information using the non-parametric (empirical) method for the ROC curve analysis using DeLong et al.’s,¹¹ recommendations on the cut-offs, sensitivity and specificity with 95% confidence intervals, positive predictive value (PPV), negative predictive value (NPV), and accuracy rates for uncomplicated and complicated appendicitis. These were computed using the NLR and PLR ROC curves for both uncomplicated and complicated appendicitis (Figure 1).

DISCUSSION

Among the most prevalent illnesses needing immediate surgery is acute appendicitis. Primarily, it is a clinical diagnosis, but in some situations, complications can arise from a delayed diagnosis. Cheap and user-friendly biomarkers with excellent diagnostic accuracy have long been the focus of research, especially in low- and middle-income countries with overburdened healthcare systems. NLR has been shown in numerous studies to be a reliable indicator of the severity of appendicitis.^{1,2,5,8,13,14} Some studies have reported the usefulness of PLR as a predictor of complicated, but not of uncomplicated appendicitis.^2,10,15-17

In this study, postoperative histology confirmed 6.1% (n = 10) normal appendix specimens. In another Pakistani study, the appendices removed were non-inflamed in 20% (n = 60) cases.¹⁴ Rajalingam et al. found normal appendix in 255 (31.9%) out of 799 patients who were operated for appen-dicitis.² Chaochankit et al. reported a negative appendectomy rate of 8.6% (n = 77) in patients diagnosed with acute appendicitis.¹⁸ Henriksen et al. estimated an overall negative appendectomy rate of 13% after laparoscopic surgery, with moderate certainty of evidence, noting considerable variation across studies.¹⁹ A systematic review by Kumar and Soma concluded that the negative appendectomy rate varied between 10% to 25% and recommended better use of clinical scoring systems, blood investigations and imaging, which had contributed to improved rates.²⁰

These findings showed a statistically significant difference between complicated and uncomplicated acute appendicitis, which could be partially identified with both NLR and PLR. However, to differentiate between a non-inflamed appendix and uncomplicated appendicitis, only the NLR tool was helpful. Based on the present analysis, NLR had a sensitivity of 76.9%, a specificity of 93.3%, a PPV of 74%, an NPV of 94.2%, and an accuracy of 70.2% in separating complicated from uncomplicated appendicitis. Moreover, it had a sensitivity of 73% and a specificity of 100%, with a PPV of 100%, an NPV of 98%, and an accuracy of 73.03% in separating a non-inflamed appendix from uncomplicated appendicitis. On the other hand, PLR could not show signifi-cant differentiation between non-inflamed appendix and uncomplicated appendicitis (p = 0.8), and its accuracy for differentiating complicated from uncomplicated appendicitis was also poor, that is 48.2%. Notably, with a sensitivity of 73-76.9% and an NPV that does not reach 100%, sole reliance on NLR for diagnosing appendicitis is not advisable. Instead, it should be used as an adjunct to other clinical assessments and diagnostic tools to improve overall diagnostic accuracy. Nevertheless, it is a valuable test to rule out alternative reasons for right iliac fossa discomfort, which helps to prevent needless appendectomies.

The ability of NLR tools to diagnose at various cut-off values has been highlighted by numerous studies. Based on recent studies by Rajalingam et al.,² Hajibandeh et al.,⁸ Sengul et al.,¹³ and Ahmad et al.,⁵ NLR had cut-off values of >4.7, >4.7, 4.1, and 3.11, respectively, for uncomplicated appendicitis, whereas in this study the cut-off value for uncomplicated appendicitis was >0.19, which was lower than the reported values. For complicated appendicitis, the values quoted in the literature were NLR >6.96, 7.32, and 6.17, respectively, whereas this study’s reported cut-off value of >5.65 for complicated appendicitis was slightly lower. Kelly et al. reported a cut-off value of 6.35 to discriminate complicated appendicitis.²¹ Shimizu et al. reported an NLR cut-off value of 8.0 for gangrenous appendicitis.²² This discrepancy can be potentially explained by the ethnic and regional variations in haemograms as well as the effect of pooled results in meta-analysis. Ethnic and regional differences in haemograms are well-documented. Studies have shown that blood test results, including haemoglobin, mean corpuscular volume (MCV), and platelet counts, vary significantly among different ethnic groups.²³ For instance, Black populations tend to have lower average haemoglobin and albumin levels, while Asian populations have lower average C-reactive protein values compared to White populations. These variations can influence the baseline values of neutrophils, lymphocytes, and platelets, thereby affecting the calculation of NLR and PLR.²³ Meta-analyses combine data from multiple studies to provide a more comprehensive understanding of a particular topic. However, pooling results from diverse populations can introduce heterogeneity, leading to discrepancies in the calculated NLR and PLR values. The fixed-effect and random-effects models used in meta-analyses assume different levels of between-study variability, which can impact the pooled estimates. Additionally, variations in study design, patient populations, and laboratory methods may contribute to the observed discrepancies. Nevertheless, it is noteworthy that this study’s cut-off values remain statistically signifi-cant, with a p-value of <0.001.

Notably, the literature varies greatly in the reported levels of PLR and the units of its measurement. Phelivanli et al.²⁴ reported that a PLR >163.27 had a sensitivity of 64.3% and a specificity of 67.5% for distinguishing complicated appendicitis from uncomplicated appendicitis, while a PLR >140.45 had a sensitivity of 71.4% and a specificity of 88.9% for distinguishing uncomplicated appendicitis from a normal appendix. Rajalingam et al.² reported that the sensitivity and specificity of PLR >154.98 and PLR >180.5 were 75.9% and 40.8%, respectively, for simple appendicitis and 22.4% and 89%, respectively, for complicated appendicitis. Yildirim et al. reported the cut-off value of PLR as 169.7, with a sensitivity of 74.4% and a specificity of 73.5% for differentiation between uncomplicated and complicated appendicitis.¹⁶ According to Celik et al., the cut-off value of PLR was 284, with a sensitivity of 42% and a specificity of 86% for the same distinction.¹⁰ This study concluded a sensitivity of 53.9% and a specificity of 94.4% for a cut-off value of >189 for PLR. This discrepancy, due to the variability in regional, ethnic, and research population, can affect laboratory results and alter the body’s reaction to appendicitis.

Appendectomy is one of the most common surgical procedures worldwide. It is often considered the first learning procedure for postgraduate surgical trainees, and the ability to perform it independently is regarded as an important milestone in surgical training. Consequently, this procedure is routinely performed by junior surgeons under direct or indirect supervision. The COVID-19 pandemic stressed the healthcare system to its limits, and the elective surgery theatres were restricted to emergency and lifesaving surgeries only. Even cases such as appendicitis were conservatively managed, but the point of concern was that no reliable method or tool was available for differentiating uncomplicated from complicated appendicitis preoperatively. Both PLR and NLR are indicators of inflammation and do not require any specialised equipment for calculation, as they can be derived from a CBC test. When combined with other laboratory and radiology features, these indicators serve as a robust tool. Properly calculated, NLR and PLR may assist surgeons in selecting and prioritising cases according to severity. Early identification of complex patients allows for prioritisation in management, such as assigning senior surgeons to perform the procedure in emergency operation theatres. This approach will facilitate quicker recovery in patients, thereby lessening the overall burden on the healthcare system, especially in resource-limited settings such as Pakistan.

This study is limited by a small sample size and the exclusion of children, who represent the most significantly affected population in cases of acute appendicitis. Thus, the results do not represent the general population. Furthermore, only the surgical department of a single hospital was chosen as the recruitment area; thus, there was a high probability of selection bias, as only the willing participants from a relatively smaller population locality were included.

CONCLUSION

NLR is an economically helpful diagnostic tool that can be used to predict and differentiate between uncomplicated and complicated appendicitis; however, reliance solely on NLR for diagnosing appendicitis is not advisable. PLR, on the other hand, did not prove to have similar predictability. Further research is warranted for the identification of additional biomarkers other than NLR and PLR to improve their predictability as a diagnostic tool.

ETHICAL APPROVAL:
The study protocol was approved by the Ethical Review Committee of Sheikh Khalifa Bin Zayed Al Nahyan Hospital, Muzaffarabad, Azad Jammu and Kashmir (ERC Approval Number: Ethical Committee/DME-825; dated: 10 November 2021).

PATIENTS’ CONSENT:
Informed consent was taken from all patients.

COMPETING INTEREST:
The authors declared no conflict of interest.

AUTHORS’ CONTRIBUTION:
FH, MNI: Conception of study, acquisition of data, and manuscript writing.
MA, SBA: Manuscript drafting, literature search, and critical revision.
AM, NA: Conception and critical revision.
All authors approved the final version of the manuscript to be published.

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