Diagnostic accuracy of the c-reactive protein to albumin ratio for identifying complicated appendicitis in adults: a retrospective study

Abstract

Background

Acute appendicitis (AA) is one of the most common causes of surgical abdominal emergency. Based on the hypothesis that the C-reactive protein (CRP) to albumin ratio can differentiate the diagnosis of uncomplicated and complicated AA, we aimed to investigate the diagnostic value of the CRP to albumin ratio in the diagnosis of complicated AA in adults.

Methods

This study was a single-center retrospective. Patients who were admitted to the academic ED in Turkey, who were considered to have suspected AA based on clinical, laboratory, and imaging methods, evaluated by the general surgeon, admitted to the general surgery clinic, underwent laparoscopic or open surgery, and who did not meet the exclusion criteria were included in the study. A receiver operating characteristic (ROC) curve was constructed to differentiate between complicated and uncomplicated AA. Finally, sensitivity, specificity, likelihood ratios, and positive and negative predictive values were calculated.

Results

The study population comprised 232 patients, meeting the inclusion criteria. Of these, 90 had complicated AA and 142 had uncomplicated AA. One hundred fifty-one (65.1%) patients were men and 81 (34.9%) women. The Alvarado score, CRP to albumin ratio, and computed tomography (CT) or ultrasonography (US) measurement cut-off values were calculated to predict complicated AA. The Area Under the Curve (AUC) value for the Alvarado score was 0.771, and the cut-off value for complicated AA was 6, exhibiting 72.2% (95% Confidence Interval (CI), 61.8–81.2) sensitivity and 53.5% (95% CI, 45.0-61.9) specificity. The AUC value for the CRP to albumin ratio was 0.962, and the cut-off value for complicated AA was 0.43, exhibiting 94.4% (95% CI, 87.5–98.2) sensitivity and 90.1% (95% CI, 84.0-94.5) specificity. The AUC value for CT or US measurement was 0.664, and the cut-off value for complicated AA was 9.5, exhibiting 63.3% (95% CI, 52.5–73.3) sensitivity and 83.1% (95% CI, 75.9–88.9) specificity.

Conclusions

The CRP to albumin ratio appears to have high sensitivity and specificity in distinguishing complicated from uncomplicated AA. This suggests that the CRP-to-albumin ratio may be used to distinguish complicated from uncomplicated AA. To validate and apply our findings, testing across multiple centers and diverse cohorts is necessary.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12876-026-05197-3.

Background

Among patients presenting to the Emergency Department (ED) with abdominal pain, acute appendicitis (AA) is one of the most common causes of surgical abdominal emergency [1]. Medical history, physical examination, elevation of inflammatory parameters in the blood, and clinical experience all play an important role in the diagnosis of AA [2]. In addition, clinical scoring systems, including physical examination findings and various laboratory markers, may be used to aid in the diagnostic evaluation [3]. However, the usefulness of these alone is controversial [4, 5]. Ultrasonography (US) and computed tomography (CT) continue to play an essential role in diagnosing AA [6]. However, the availability of these imaging tests at all levels of the health care system and in different geographical areas is limited. Despite the use of all diagnostic modalities, negative pathology results can occur in 3% to 25% of patients with a diagnosis of AA [7, 8].

Clinical examination, Alvarado score, CT, US, and blood tests can be helpful in the diagnosis of AA. However, they are difficult to use to confirm the type of AA (uncomplicated or complicated) [9]. The ability to distinguish uncomplicated from complicated AA allows the surgeon to choose the best surgical approach, which can range from antibiotics and delayed appendectomy to a laparotomy [10]. Determining the optimal algorithm for diagnosing complicated AA may not only reduce the number of unnecessary surgeries, but also reduce the incidence of complications and may contribute significantly to reducing the cost of treating patients with acute abdominal disease.

Serum C-reactive protein (CRP) is a positive acute-phase reactant. It increases in the blood within hours in response to inflammation and infection [11]. Albumin is a negative acute phase reactant, and its level in the blood decreases during inflammation, which is associated with inflammation severity, disease prognosis, and mortality [12]. The ratio of CRP to albumin is a new inflammation-based prognostic score. It correlates with the severity of inflammation [13]. Based on the hypothesis that the CRP to albumin ratio can differentiate the diagnosis of uncomplicated and complicated AA, we aimed to investigate the diagnostic value of the CRP to albumin ratio in the diagnosis of complicated AA in adults.

Methods

Study design, setting, and aim

This was a single-center retrospective study. Approval was obtained from the local ethics committee before data collection (decision no. 2022/207). This study was designed and reported in accordance with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines, with the aim of ensuring transparency and completeness in the reporting of observational studies.

Patients who were admitted to the academic ED in Turkey between January 1, 2021, and July 1, 2022, with complaints of abdominal pain, nausea, vomiting, etc. who were considered to have suspected AA based on clinical, laboratory, and imaging methods (CT or US) by an emergency medicine specialist, subsequently consulted by a general surgeon, evaluated by the general surgeon and considered to have AA, admitted to the general surgery clinic, underwent laparoscopic or open surgery, and who did not meet the exclusion criteria were included in the study.

The aim of our study was to investigate the usefulness of the CRP to albumin ratio in the diagnosis of complicated AA. For this purpose, the use of the CRP to albumin ratio in differentiating the diagnosis of uncomplicated AA and complicated AA according to histopathologic classification was determined as the primary endpoint.

Characteristics of participants

Patients under 18 years of age, patients who received treatment with antibiotics or other anti-inflammatory drugs before presentation to the ED, patients for whom medical treatment methods were preferred in the treatment of AA, patients who were referred to another institution, patients who voluntarily refused diagnosis and treatment, patients with missing information in the hospital information management system, patients with hematological and bone marrow disorders who are taking immunosuppressive drugs, and patients with a history of diseases that could affect albumin and CRP values (chronic inflammatory disease, liver disease, malnutrition (according to GLIM criteria [14]), malignancy or nephrotic syndrome) were excluded. The study population (N:232) was formed considering the inclusion and exclusion criteria (Total N:273). The patient flow chart is shown in Fig. 1.

Fig. 1.

The patient flow chart

Description of processes

The study population was formed after applying the inclusion and exclusion criteria. Demographic data, laboratory parameters, CT or US findings, Alvarado score, and clinical outcomes of the patients included in the study were analyzed. All these patient data were obtained from the hospital information management system.

White Blood Cell (WBC) (10³/µL) (Reference range: 4–10 × 10³/µL), Neutrophil (10³/µL) (Reference range: 2–7 × 10³/µL), Lymphocyte (10³/µL) (Reference range: 0.8-4 × 10³/µL), Platelet (10³/µL) (Reference range: 100–400 × 10³/µL), CRP (mg/L) (Reference range: 0–5 mg/L), and Albumin (g/L) (Reference range: 35–52 g/L), were analyzed among the laboratory parameters at the time of presentation to the ED. Additionally, the CRP to albumin ratio was calculated based on the laboratory parameters examined at the time of ED presentation. The Alvarado score was also calculated based on vital signs, laboratory parameters, and clinical findings. The Alvarado score, with a total score ranging from 0 to 10. It includes: Symptoms: migration of pain to the right lower abdomen, anorexia, nausea/vomiting: Signs: tenderness in the right lower quadrant, rebound tenderness, fever. Lab findings: leukocytosis and neutrophilia. 0–4: appendicitis unlikely, 5–6: possible appendicitis (observation recommended), 7–10: high probability of appendicitis (surgical evaluation needed) [15].

CT and US evaluations were assessed and reported by a single radiologist with two years of experience. The appendix diameter was used for reporting, and the maximum diameter measurement was taken. CT scans were performed using a multi-detector CT scanner (Toshiba Alexion™; Toshiba Medical Systems Corporation, Nashua, Japan) with 1 mm thick slices and 16 slices obtained at 120 kVp. For CT scans, images with or without oral/intravenous contrast were obtained. Sonographic examinations were performed using a Fujifilm-SonoSite-FC1 (FUJIFILM SonoSite Inc., Bothell, WA, USA, 2015) model ultrasound device. Measurements were performed using a 3.5–5 MHz convex (abdominal) probe or a 7–15 MHz linear probe. Due to the uneven distribution of the number of patients assessed by CT and US, the small number of patients in one group, and the fact that only the diameter of the appendix was assessed, these two imaging methods were subjected to a joint assessment following the diameter measurement.

The diagnosis determined after the combined evaluation of patients’ surgical notes, surgical specimens, and histopathological examination of surgical material was accepted as the gold standard. Based on this combined assessment, patients were classified into two groups: those with uncomplicated AA and those with complicated AA. Gorter and colleagues’ study was used as a reference for this determination [16].

Statistical analysis

All analyses were performed on Jamovi version 1.6 statistical software (The Jamovi Project (2021) Computer Software, version 1.6. Sidney, Australia). Categorical data were expressed as frequency (n) and percentage. Normally distributed continuous variables were presented as mean plus standard deviation (SD) and non-normally distributed data as median and interquartile range (IQR). Normality of distribution was evaluated using the Shapiro-Wilk test.

In comparing the continuous variables, groups with normal distribution were compared with the student’s t-test, and those lacking such a distribution were compared with the Mann-Whitney U test. The Chi-squared test was used to compare the categorical variables between groups. A receiver operating curve (ROC) was constructed to determine the cut-off levels of CRP to albumin ratio, measurements (CT or US), and the Alvarado score for differentiation of complicated and uncomplicated. In ROC analysis, Youden’s index (maximum value) was used to select the cut-off value. Finally, sensitivity, specificity, likelihood ratios (+ LR and -LR), and positive and negative predictive values were calculated for the CRP to albumin ratio, measurements (CT or US), and Alvarado score. In all analyses, a p-value of < 0.05 was considered statistically significant.

Results

The study population (N:232) was formed considering the inclusion and exclusion criteria (Total N:273). Of these, 90 had complicated AA and 142 had uncomplicated AA. One hundred fifty-one (65.1%) patients were men and 81 (34.9%) women. The patients’ median age was 34 (IQR 23–49). The median value of the patients’ Alvarado score was 7 (IQR 6–8). The median days of hospitalization were 2 (IQR 1–3). Complications developed in 18 (7.8%) patients and 214 (92.2%) patients did not developed complications. Laboratory parameters were analyzed: The mean value of the WBC and neutrophil were 13.7 ± 4.5 × 10³/µL; and 10.8 ± 4.4 × 10³/µL respectively; the median value of the Lymphocyte, platelet, CRP, albumin and CRP to albumin ratio were 1.8 × 10³/µL, with an IQR 1.2–2.4 × 10³/µL; 234 × 10³/µL, with an IQR 204–280 × 10³/µL; 12.7 mg/L, with an IQR 3-62.4 mg/L; 42 g/L, with an IQR 40–45 g/L; 0.3, with an IQR 0.1–1.5 respectively. Furthermore, the median US or CT measurement value was 10 mm, with an IQR 8–12 mm. Demographic data, laboratory values, duration of hospitalization and US or CT measurement values are summarized in Table 1.

Table 1.

The patients’ demographic data and baseline characteristics

Characteristics	All Patients (N = 232)	Uncomplicated Appendicitis (N = 142)	Complicated Appendicitis (N = 90)	P Value
Gender
Male, n (%)	151 (65.1%)	93 (40.1%)	58 (25.0%)	0.870*
Female, n (%)	81 (34.9%)	49 (21.1%)	32 (13.8%)
Age (years), median (IQR)	34 (IQR 23–49)	28 (IQR 21–43)	41 (IQR 30.3–55)	0.001”
Laboratory Indices
WBC (×103/µL), mean ± sd	13.7 ± 4.5	13.6 ± 4.3	13.8 ± 4.8	0.742+
Neutrophil (×103/µL), mean ± sd	10.8 ± 4.4	10.6 ± 4.6	10.9 ± 4.6	0.561+
Lymphocyte (×103/µL), median (IQR)	1.8 (IQR 1.2–2.4)	2.0 (IQR 1.4–2.6)	1.6 (IQR 1.2–2.2)	0.005”
Platelet (×103/µL), median (IQR)	234 (IQR 204–280)	229 (IQR 205–272)	237 (IQR 203–292)	0.506”
CRP (mg/L), median (IQR)	12.7 (IQR 3-62.4)	5 (IQR 2-11.4)	79.7 (IQR 49.3–131)	0.001”
Albumin (g/L), median (IQR)	42 (IQR 40–45)	44 (IQR 41–46)	40 (IQR 37–43)	0.001”
CRP to Albumin ratio (%), median (IQR)	0.3 (IQR 0.1–1.5)	0.1 (0.1–0.3)	2.0 (IQR 1.2–3.2)	0.001”
CT or US Measurements (mm), median (IQR)	10 (IQR 8–12)	9 (IQR 7.1–11.8)	11 (IQR 9-12.8)	0.001”
Alvarado Score, median (IQR)	7 (IQR 6–8)	6 (IQR 5–7)	8 (IQR 7–9)	0.001”
Post-operative Complications, n (%)
No	214 (92.2%)	142 (61.2%)	72 (31.0%)	0.001*
Yes	18 (7.8%)	0 (0.0%)	18 (7.8%)
Hospitalization (Days), median (IQR)	2 (IQR 1–3)	2 (IQR 1–2)	3 (IQR 2–5)	0.001”

IQR Interquartile Range (25p, 75p), sd standard deviation, WBC White Blood Cell, CRP C-reactive protein, CT Computed Tomography, US Ultrasonography

WBC Reference range: 4–10 10^3/uL, Neutrophil Reference range: 2–7 10^3/uL, Lymphocyte Reference range: 0.8-4 10^3/uL, Platelet Reference range: 100–400 10^3/uL, CRP Reference range: 0–5 mg/L, Albumin Reference range: 35–52 g/L

*: Chi-squared test, ⁺: Student’s t-test, ”: Mann-Whitney U test

When the mean or median values of age, Lymphocytes, CRP, Albumin, CRP to albumin ratio, CT or US measurements, Alvarado score, and days of hospitalization were examined, a statistically significant difference was found between uncomplicated AA and complicated AA (p = 0.001 for age, p = 0.005 for lymphocytes, p = 0.001 for CRP, p = 0.001 for albumin, p = 0.001 for CRP to albumin ratio, p = 0.001 for CT or US measurements, p = 0.001 for Alvarado score and p = 0.001 for days of hospitalization). A statistical summary is shown in Table 1.

The Alvarado score, CRP to albumin ratio, and CT or US measurement cut-off values were calculated to predict complicated AA. The Area Under the Curve (AUC) value for the Alvarado score was 0.771 (95% Confidence Interval (CI), 0.712–0.835), and the cut-off value for complicated AA was 6, exhibiting 72.2% (95% CI, 61.8–81.2) sensitivity and 53.5% (95% CI, 45.0-61.9) specificity. The AUC value for CRP to albumin ratio was 0.962 (95% CI, 0.932–0.986), and the cut-off value for complicated AA was 0.43, exhibiting 94.4% (95% CI, 87.5–98.2) sensitivity and 90.1% (95% CI, 84.0-94.5) specificity. The AUC value for CT or US measurement was 0.664 (95% CI, 0.595–0.731), and the cut-off value for complicated AA was 9.5, exhibiting 63.3% (95% CI, 52.5–73.3) sensitivity and 83.1% (95% CI, 75.9–88.9) specificity. The ROC analysis is shown in Table 2; Fig. 2.

Table 2.

The cut-off values of ROC curve analysis

	Alvarado Score	CRP to Albumin Ratio	CT or US Measurements
AUC, (95% CI)	0.771 (0.712–0.835)	0.962 (0.932–0.986)	0.664 (0.595–0.731)
Cutoff	6	0.43	9.5
Sensitivity (%), (95% CI)	72.2 (61.8–81.2)	94.4 (87.5–98.2)	63.3 (52.5–73.3)
Specificity (%), (95% CI)	53.5 (45.0-61.9)	90.1 (84.0-94.5)	83.1 (75.9–88.9)
+ LR, (95% CI)	1.60 (1.3–1.9)	9.60 (5.8–15.8)	3.80 (2.5–5.6)
- LR, (95% CI)	0.52 (0.4–0.8)	0.06 (0.03–0.1)	0.40 (0.3–0.6)
PPV (%), (95% CI)	49.6 (44.2–55.1)	85.9 (78.7–90.9)	70.4 (61.5–77.9)
NPV (%), (95% CI)	75.3 (67.8–81.4)	96.2 (91.6–98.4)	78.2 (73.0-82.6)
Accuracy (%), (95% CI)	60.8 (54.2–67.1)	91.8 (87.5–95.0)	75.4 (69.4–80.8)

ROC Receiver Operating Curve, AUC Area Under the Curve, LR Likelihood Ratio, PPV Positive Predictive Value, NPV Negative Predictive Value, CI Confidence Interval, CRP C-reactive protein, CT Computed Tomography, US: Ultrasonography

Fig. 2.

The ROC analysis. Abbreviations: ROC: Receiver Operating Curve, AUC: Area Under the Curve, CI: Confidence Interval, CRP: C-reactive protein, CT: Computed Tomography, US: Ultrasonography

Discussion

Although many algorithms have been developed to determine the type of AA (uncomplicated or complicated), it is still difficult to distinguish the type of AA. An algorithm that can differentiate uncomplicated appendicitis from complicated appendicitis can improve the surgeon’s choice of antibiotics and surgical approach. In this way, the number of unnecessary operations and the incidence of complications can be reduced. As a result, it can significantly contribute to reducing the cost of treatment of patients with acute abdominal disease. Based on the findings of our study, the CRP (positive acute phase reactant) to albumin (negative acute phase reactant) ratio may be a laboratory algorithm with high sensitivity and specificity to detect complicated AA. As this high diagnostic value may be related to the number of complicated cases, it needs to be supported by different cohorts.

Koyuncu et al. examined the value of laboratory parameters for perforated appendicitis (PA). ROC analysis showed that the CRP to lymphocyte ratio (CLR) had the highest area under the curve (AUC) value (0.83). They found that CLR is an important parameter in the differentiation of AA and PA patients [17]. Hou et al. reported that the CRP to albumin ratio is higher in children with complicated AA cases [18]. In the study by Doğan et al., the cut-off point for the CRP to albumin ratio for the diagnosis of complicated AA was found to be 4.4 [19]. Similarly, in the study by Yüksel et al., a CRP to albumin ratio greater than 7.1 was found to be a good indicator of perforation [20]. In our study, lymphocyte, CRP, albumin, and CRP to albumin ratio were statistically significant between the two groups. Also, the AUC value for the CRP to albumin ratio was 0.962, and the cut-off value for complicated AA was 0.43, exhibiting 94.4% sensitivity and 90.1% specificity. The cut-off value being lower than in other studies may be related to the documentation of albumin (g/L) and CRP (mg/L) units. Accordingly, we may state that the CRP to albumin ratio demonstrated high diagnostic performance. It is also conceivable that such high diagnostic performance may be due to the high number of complex cases.

Sengul et al. evaluated the role of serum laboratory biomarkers in complicated and uncomplicated appendicitis in adolescents. They found elevated WBC, Neutrophil, CRP and Neutrophil to Lymphocyte ratio to be acceptable as useful biomarkers that assist physical examination and other diagnostic methods in differentiating the severity of AA [21]. In the study by Erkent et al. they tried a new approach in the management of AA. They divided the patients into two groups as complicated and uncomplicated AA. Age, gender, Alvarado scores, WBC, neutrophil to lymphocyte ratios, CRP, albumin, and CRP to albumin ratio were analyzed in two groups. Age, gender, Alvarado score and CRP to albumin ratio were not significant in differentiating between complicated AA and uncomplicated AA [22]. In our study, when evaluating the relationship between complicated AA and uncomplicated AA, age was found to be statistically significant, while WBC was not found to be significant. The fact that we obtained different results from the articles in the literature suggests that these two factors may be relative factors in the distinction between complicated and uncomplicated AA. This highlights the need for further studies to examine these factors in detail. Furthermore, the excess of complex cases in our study cohort may have led to our results being evaluated differently from those in the literature.

In the study by Yüksel et al. laboratory indices and appendix diameter were evaluated to predict perforation in AA. Appendix diameter, CRP level and CRP to albumin ratio were found to have similar sensitivity in predicting perforated appendicitis (89%). However, the CRP to albumin ratio was the most specific biomarker for perforation (87.8%). They conclude that CRP to albumin ratio, CRP and appendix diameter can be used to predict perforation in patients with AA [20]. Hou et al. evaluated the use of CRP to albumin ratio for the diagnosis of complicated appendicitis in children. The CRP to albumin ratio ≥ 1.39 was found to be a significant marker in the prediction of complicated AA, with 86.61% sensitivity and 84.62% specificity. They thought that CRP to albumin ratio may be a new but promising hematologic marker to help differentiate acute complicated and uncomplicated AA [18]. In our study, we evaluated the usefulness of CRP to albumin ratio, Alvarado score and CT or US measurements in the differentiation of complicated and uncomplicated AA. It was observed that CRP to albumin ratio was more sensitive (94.4%) and more specific (90.1%) than other evaluated factors. With our current findings, we think that the CRP to albumin ratio can be used in the differentiation of complicated and uncomplicated AA. This idea of ours shows a linear correlation with many studies and an inverse correlation with very few studies.

The results of our study suggest that the CRP to albumin ratio is a useful method for distinguishing between complicated and uncomplicated AA. However, several points must be highlighted regarding the generalizability of our findings. Firstly, in accordance with our study design, only surgical patients were included in the study, which may have led to an overestimation of our results. Furthermore, as our hospital is an academic hospital, the high proportion of complicated cases may have contributed to our results appearing exaggerated. Additionally, the fact that the distinction between complicated and uncomplicated AA was interpreted based solely on the CRP to albumin ratio, without accounting for confounding factors such as age—which differed between the two groups in the statistical analysis—limits the generalizability of our results.

Akçiçek et al. evaluated the differentiation of complicated and uncomplicated AA with CT. In CT evaluation, moderate or severe peri-appendiceal fat stratification (77.9%) and increased appendiceal wall thickness (69.4%) showed high sensitivity for differentiation of complicated and uncomplicated AA. Furthermore, abscess, phlegmon and peri-appendiceal air had the highest specificity (100%) for differentiating complicated from uncomplicated AA, but these findings showed low sensitivity [23]. In the study by Tong et al., the usefulness of sonographic findings in the diagnosis of uncomplicated and complicated AA in children was examined. According to sonographic findings, an appendix diameter > 10.1 mm was more suggestive of complicated appendicitis than uncomplicated AA (AUC 0.63, [95% CI: 0.57–0.69]). They concluded that the presence of specific sonographic findings may help in the diagnosis and differentiation of uncomplicated and complicated AA in children [24]. In our study, appendix diameter was evaluated by CT or US. It was found that an appendix diameter > 9.5 showed 63.3% sensitivity and 83.1% specificity in the differentiation of complicated and uncomplicated AA. The fact that our measurements were performed by CT in some patients and US in others suggests that appendix diameter does not affect the ability to differentiate complicated and uncomplicated AA, and that we have reached similar conclusions with many studies in the literature.

Al-Tarakji et al. evaluated the role of the Alvarado scoring system in predicting the histopathologic severity of AA. It was found that the Alvarado scoring system alone was not sufficient to diagnose AA with insufficient sensitivity and specificity. However, the Alvarado scoring system was found to be a good indicator of the severity of AA [25]. Haak et al. aimed to predict complicated AA based on clinical findings. An Alvarado score ≧ 5 was found to have 95% sensitivity and 8.99% specificity for detecting complicated AA. It was concluded that the Alvarado score showed limited ability to distinguish between complicated and uncomplicated AA [26]. In our study, the usability of the Alvarado score in differentiating complicated and uncomplicated AA was evaluated. It was found that even high Alvarado score was not sufficiently sensitive and specific enough. In line with our findings, we think that the Alvarado score alone is not useful in the differentiation of complicated and uncomplicated AA.

The results of our study (CRP to albumin ratio and appendix diameter) present findings similar to many studies in the literature regarding the prediction of complicated AA. However, this does not prove that laboratory tests are superior to CT or US in distinguishing complicated AA. This is because our results may have been influenced by numerous factors, including case selectivity in our cohort, the limitations of imaging methods to diameter measurement alone, and the radiologist’s experience. These factors suggest that the superior diagnostic value should be proven in prospective studies.

Limitations of the study

This study has some limitations. Firstly, the study was small, conducted in a single center, and was retrospective. Patient data cannot be adequately assessed because of the retrospective design. This raises concerns about selection bias, similar to other retrospective studies. However, the study population was designed to address this concern by excluding situations that may cause bias. In this regard, to prevent bias in patient selection, exclusion criteria included conditions that could compromise clinical evaluation (such as antibiotic and anti-inflammatory drug use prior to emergency presentation) and conditions that could compromise laboratory parameters (such as malnutrition and liver disease). However, as the hospital is the academic healthcare center (one that accepts all complex cases), the number of critical and complex patients was higher than usual. This situation may have led to the occurrence of more complicated AA cases than expected. Diagnostic sensitivity was increased by adding histopathological findings to the surgical findings. Again, symptom onset times are also effective in high diagnostic performance, but symptom onset times could not be evaluated in our study. All these reasons that make up our cohort may have affected our results.

Secondly, the sample size for the study was not calculated. In accordance with the study design, all patients who met the criteria on the relevant dates were included in the study. This has limited our ability to assess selection bias and has raised doubts regarding the generalizability of our findings.

Thirdly, in accordance with the study design, patients who had undergone surgery were included in the study. This aspect of our patient selection calls into question the generalizability of the findings and may have led to our results being overstated.

Fourthly, the statistical analysis we carried out to determine the cutoff is a “Youden’s index”; this may have led us to present the statistical results in an exaggerated manner. Again, the difference in group sizes (complicated AA and uncomplicated AA) may have influenced our statistical results. Additionally, the fact that the distinction between the groups was interpreted based solely on the CRP to albumin ratio, without accounting for confounding factors such as age—which differed between the two groups in the statistical analysis—limits the generalizability of our results.

Fifthly, the imaging procedures were performed by a single radiologist. Furthermore, the CT and US assessments were subject to a joint review, which may have contributed to the heterogeneity of our results.

Sixthly, the available data are limited due to the study design. Consequently, the analysis was conducted using limited demographic data, necessitating an assessment that did not include demographic variables such as hospital admission times, the duration of the existing clinic’s operation, or perioperative ASA class. The time difference may affect the study’s results.

Finally, radiological measurements only include the diameter of the appendix and have been assessed by a single radiologist. This may have affected my results.

Conclusions

The CRP to albumin ratio appears to have high sensitivity and specificity in distinguishing complicated from uncomplicated AA. This suggests that the CRP-to-albumin ratio may be used to distinguish complicated from uncomplicated AA. The results of our study may be specific to our cohort. To support and validate our findings, testing across multiple centers and diverse cohorts is required.

Abbreviations

ED

Emergency department

AA

Acute appendicitis

US

Ultrasonography

CT

Computed tomography

CRP

C-reactive protein

WBC

White blood cell

SD

Standard deviation

IQR

Interquartile range

ROC

Receiver operating curve

LR

Likelihood ratios

AUC

Area under the curve

CI

Confidence interval

Authors’ contributions

Initials of the contributing authors were listed in brackets after the relevant parts of the research: Literature search (GA, MMY), study design (GA, MMY), legislative applications (GD, GA), data collection (MMY, GD, GA), supervision and quality control (GA, GD), statistical data analysis (MMY), data interpretation (GA), drafting the manuscript (MMY, GA). All authors were involved in the writing and critical revision of the manuscript and approved the final version. GA and MMY take the whole responsibility for the paper.

Funding

No funding was received from any organization for this study.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

This study was approved by the institutional review board and ethics committee (T.C. Recep Tayyip Erdoğan University, Non-Interventional Clinical Research Ethics Committee, number: E-40465587-050.01.04-537 and ID: 2022/207). Patients’ consents were obtained from the patients before starting the study. The principles outlined in the Declaration of Helsinki were followed.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.